1. How can I tell if my battery
is charged or not?
2. How long will it take to charge a battery?
3. How can I tell if my battery needs to be replaced?
4. How is the Battery Fighter battery charger different from a trickle charger?
5. How is the Battery Fighter Junior battery charger different from a trickle
charger?
6. What makes the Battery Fighter battery charger different from other automatic
battery chargers?
7. Is the Battery Fighter battery charger more expensive than a trickle charger?
8. Is the Battery Fighter Junior battery charger more expensive than a trickle
charger?
9. How long can I leave the Battery Fighter battery charger connected to a
battery?
10. How can the Battery Fighter battery charger that is rated at 1.25 amperes
recharge a battery as fast as another charger that is rated at 3 amperes?
11. Can I leave the Battery Fighter battery charger connected to a battery while
I.m using the battery to power another appliance like a radio?
12. Is there any danger that the Battery Fighter battery charger can cause any
damage to other automotive electronic systems while it is connected to the
battery in my automobile?
13. Can the Battery Fighter battery charger be used to charge more than 1
battery simultaneously if the batteries are connected in parallel?
14. Can I charge more than one battery at a time with a
single charger?
15. Can I charge batteries with different voltages on a single charger, either a
12-volt or a 6-volt charger?
16. What happens if the AC power is removed from the Battery Fighter battery
charger while it is connected to a fully charged battery?
17. What is Temperature Compensation and how important is it?
18. What is Float / Maintenance Charging? Is it really necessary?
19. Can the Battery Fighter successfully perform the initial charge on a new,
flooded, motorcycle battery?
1. How can I tell if my battery is charged or not?
Lead acid batteries are made up of cells. Each cell is approximately 2 volts, so
a 12-volt battery has 6 individual cells. It turns out that a fully charged
2-volt cell has a voltage of approximately 2.15 volts. Oddly enough, a fully
discharged 2-volt cell has a voltage of 1.9 volts. That.s only a difference of
0.25 volts on each cell from fully charged to fully discharge. So a 12-volt
battery will measure at about 12.9 volts when it.s fully charged and about 11.4
volts when it is fully discharged. That.s a total of 1.5 volts that represents
the full range of charge on a 12-volt battery. To make a good guess at how much
charge your battery has left, you can assign a percentage of charge remaining
that is directly proportional to the battery voltage. Let.s see how we can do
that.
If the battery voltage is 12.15 volts, how much charge is left? Beginning with
11.4 volts representing no charge or 0% charge available, subtract 11.4 volts
from the voltage that you read. So 12.15 . 11.4 = 0.75 volts. Since there are
only 1.5 volts above 11.4 volts that represents the full range of charge, we can
divide the difference that we just calculated by 1.5 volts to get the percentage
of charge remaining. 0.75 volts/1.5 volts = 0.5 or when expressed as a
percentage, multiply by 100 and get 50%.
Here.s the procedure written as a formula that is applicable to 12 Volt
Batteries:
OPEN CIRCUIT BATTERY STATE OF CHARGE CALCULATION % Charge = SOC
% Charge = ((Measured Battery Voltage . 11.4 volts) / 1.5 volts) x 100
Equation 1
That seems easy enough. So what.s the catch? In order for this formula to work,
the battery must be in a rest state. In other words, the battery should not be
supplying power to any type of load. The experts say that the battery should
remain at rest for at least 24 hours to get an accurate measurement, but in a
pinch a couple of hours is good enough to make a reasonable guess. Even if the
battery is connected to a load, as long as the load current is less than 1% of
the battery capacity in amp-hours, then this method is probably good enough in
most cases. It.s all a matter of how accurate you want to be. If you.re a
scientist or engineer trying to develop a battery powered product, then you
probably want a more accurate measurement than if you.re going fishing for the
weekend and you just want to know if you need to take the time to charge your
battery before you use it.
There is one more thing to keep in mind. The only way to be absolutely sure that
your battery is fully charged is to do a load test. It is best to have the
battery dealer do this for you. We only mention it here because it is possible
for a battery to indicate a good voltage, but then immediately when you try to
use it, it acts like it.s dead. This doesn.t happen very often, but it.s good to
know that it is a possibility.
2. How long will it take to charge a battery?
We can make a pretty good guess by just dividing two numbers:
Approximate Recharge Time Calculations
(Battery Capacity) / (Charger Current) = Hours
(Amp-Hours) / (Amps) = Hours
Equation 2
Suppose I have a 50 Amp-Hour battery. That.s a fairly typical size for an
automotive engine start type battery. Now let.s say I have a 10 Amp charger.
(50 Amp-Hours) divided by (10 Amps) = 5 Hours.
So we would estimate that it will take a good 10 Amp charger about 5 Hours to
recharge a 50 Amp-Hour battery. Actually this rough estimate usually tells us
how long it takes to recharge the battery to about 80% of its capacity.
To complete the recharge of a battery to 100% with a 3-step charger, it turns
out that it will probably take an equal amount of time, or another 5 hours to
recharge the last 20% of the battery capacity.
To complete the recharge of a battery to 100% with a 4 step charger, in most
cases it will take less time than with a 3 Step Charger to recharge the last 20%
of the battery capacity. These times are different for all of the software
versions.
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3. How can I tell if my battery needs to be replaced?
Referring back to the discussion of how you can calculate the charge level of
your battery, we know that about 1.5 volts represent the full range of charge on
a 12-volt battery. Now it is possible to over discharge a battery, well beyond
its intended design. It is possible to take the battery voltage on a 12-volt
battery down to 3 or 4 volts under load. That would constitute a severe
over-discharge. Many lead acid batteries will not respond kindly to such abuse.
Although if this only happens a few times, the battery voltage may recover to 8
or 9 volts without recharging. There is also a good chance that the battery can
be restored to full health provided that it is recharged with a few hours of
experiencing the severe over-discharge.
Now we said that 11.4 volts represents 0% state of charge. So the battery is
sitting at a negative state of charge relative to its normal use. We usually
don.t talk about negative state of charge, but rather that the battery was
discharged 120% to 150% of rated capacity. Without knowledge of very recent
severe over-discharge conditions, we could make a judgment about the condition
of the battery by a voltage measurement. If the battery voltage on a 12-volt
battery is only 8 or 9 volts, when measured in a rest state, then there is a
very good chance, in fact a very, very good chance that battery is defective. At
the very least it is safe to say that the battery has been severely
over-discharged.
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4. How is the Battery Fighter battery charger different from a trickle
charger?
The Battery Fighter battery charger delivers 1.25 amperes during bulk charge
mode, holds the battery charge voltage constant at 14.4 VDC during absorption
charge mode until the battery charge current drops to 0.1 amperes at which time
it then automatically switches to a float charge mode. During float charge mode,
the output voltage of the Battery Fighter battery charger is 13.2 VDC, which is
well below the gassing voltage of a lead acid battery. This keeps the battery
topped off, while minimizing any detrimental effects to do gassing. The Battery
Fighter battery charger is able to perform these complex switching functions
because its electronic circuitry is controlled by an on board microprocessor.
Although they often appear to be a better economic choice for the typical
consumer, trickle chargers do not have the advantage of sophisticated electronic
control. Therefore, as they allow the value of charge current to trickle down to
what appears to be safe levels, the output voltage of the charger rises well
above 15 VDC, sometimes even going higher that 16 VDC depending on the charger
type and the battery that is connected to it. Either voltage is well above the
gassing voltage of a lead acid battery. If the battery remains connected to this
high level of voltage for an extended period of time, even less than 1 day,
extreme damage can be done to the battery. What appears to be a cost savings for
the charger may actually cost several times the charger price in replacement
batteries.
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5. How is the Battery Fighter Junior battery charger different from a trickle
charger?
In a fashion similar to the Battery Fighter, the Battery Fighter Junior employs
a higher level of sophistication in its use of electronic control to maintain a
battery in a full state of charge over extended periods of time. Although its
power output is less than the Battery Fighter, the Battery Fighter Junior
employs a similar charge control method to keep the battery at full charge while
minimizing the long-term risk of overcharge and premature capacity loss. Trickle
chargers are simply not capable of regulating the output voltage applied to a
battery as the battery ages, or if a different battery with different
characteristics is connected to the trickle charger's output terminals. The
Battery Fighter Junior is capable of charge maintenance on all lead acid battery
types, including both AGM and GEL cells.
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6. What makes the Battery Fighter battery charger different from other
automatic battery chargers?
Many automatic battery chargers turn off when the battery voltage rises or the
charge current falls to a preset level. Then after a period of time, when the
battery self discharge characteristics have reduced its terminal voltage
significantly, sometimes to the point where the battery has given up almost 90%
of its stored charge, the charger will turn on and recharge the battery. This
type of cycling will dramatically reduce battery life. The Battery Fighter
battery charger does not turn off. It automatically switches to a safe float
voltage level that keeps the battery charged and yet does not do any harm to the
battery or cause any reduction in its useful life.
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7. Is the Battery Fighter battery charger more expensive than a trickle
charger?
In simple terms, comparing only the .off-the-shelf., retail price dollars,
probably yes. However, in terms of the total cost of ownership, including the
likely dramatic reduction in battery life resulting from using a trickle
charger, then the answer is ABSOLUTELY NO. The Battery Fighter will more than
make up the difference in price by extending the useful life of only one engine
start battery. Multiply this savings over the 3 years warranty period and you
will save enough in battery cost to more than pay for the Battery Fighter
battery charger.
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8. Is the Battery Fighter Junior battery charger more expensive than a
trickle charger?
The Battery Fighter Junior will do a much better job in maintaining the charge
on a battery than a typical trickle charger. Just like the Battery Fighter, the
Battery Fighter Junior will provide more long-term value and hence a significant
improvement in the total cost of ownership. The initial price may be higher than
trickle chargers with comparable output power capability, but like the ad says,
"The Battery Fighter Junior is like a trickle charger with a brain." That added
measure of on-board intelligence provides the means for the Battery Fighter
Junior to more safely and effectively maintains the charge on a battery much
larger than its competitor's in the same power range. A trickle charger simply
cannot regulate its output voltage to consistently safe levels over extended
periods of time as the battery characteristics change.
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9. How long can I leave the Battery Fighter battery charger connected to a
battery?
In theory, you can leave the Battery Fighter battery charger connected to a
battery forever. Like they say, .Just plug it in and forget about it!.
Practically speaking, it is a good idea to check on the battery at least once a
week. Strange things can happen. Sometimes a battery can have a weak cell that
won.t show up until the worst possible time. Of course, that time is usually
when the battery is connected to a charger. If something goes wrong, then you
have to deal with the question of the chicken and the egg. Which came first? Did
the battery fail because it was connected to the charger or did the charger fail
because it was connected to the battery?
No matter how good a product is, anything can break. With a battery and a
charger connected together, it.s a much better idea to be proactive and
anticipate problems, however unlikely they may be. In more than 99.9% of cases,
nothing will go wrong. That still leaves about 0.1% where something might. Learn
to respect electricity. A little common sense can go a long way.
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10. How can the Battery Fighter battery charger that is rated at 1.25 amperes
recharge a battery as fast as another charger that is rated at 3 amperes?
To recharge a battery, it is necessary to replace the charge that the battery
delivered during the last time that it was used. The dimensions or units
describing electrical charge are the Coulomb or, more conveniently in the
context of battery charging, the Amp-Hour. The abbreviation for amp hour is Ah.
A battery charger delivers charge (amp-hours) to the battery by using an
electrical current (Amps) at its output over a period of time (Hours). The
numerical product of the electrical current and time period is the amount of
charge delivered. This is true in a general sense for any charger.
What is not obvious is that for the calculation of charge returned to be valid
is that the electrical current at the output of the battery charger must be
constant during the period of the calculation. This, and the amplitude of the
charge current are the critical features of a battery charger that determine how
fast it will recharge a battery.
Because of the many different ways that a battery charger can be constructed and
electronically controlled, there are many cases where one charger can have a
higher numerical charge current rating and yet not charge a battery as fast as
some other charger with a lower current rating. This is unfortunate for the
consumer because there is really no way to tell based on industry standards
because the standards define construction and fault protection methods to ensure
safety. Those standards do not define a framework that limits how a battery
charger.s numerical charge current rating is determined.
This is not unlike some of the confusion that exists when attempting to compare
a battery.s performance based on its ratings, although the Battery Council
International (BCI) clearly defines the tests that must be performed on a
battery for it to be rated at a specific number of cranking amps. No such
governing body exists to define a similar testing process to control how
manufacturers rate the charge current output of a battery charger.
The confusion with batteries is application specific. For example, .How long
will a 950 Amp battery run the trolling motor in my bass boat?. The 950-amp
rating tells the consumer how many amps the battery will deliver for 30 seconds,
when starting an engine, at a specific temperature before the battery terminal
voltage drops to 7.2 volts. The 950-amp rating says absolutely nothing about the
capacity of the battery, which is what you really need to know to estimate the
answer to the trolling motor question. However, the BCI does define a different
rating that is more appropriate for that application. That rating is the
.Reserve Capacity.. The reserve capacity is the number of minutes that the
battery will deliver 25 amps while the battery terminal voltage remains above
7.2 volts.
With battery chargers the electrical current rating alone cannot ensure an
accurate estimate of recharge time. Only by looking at the charge current time
profiles of two chargers connected to the same size battery, in the same state
of charge, can one accurately compare recharge time.
We claim that the 1.25 amp Battery Fighter battery charger will charge a battery
in the same amount of time as a typical 3 amp charger is based on the fact that
the Battery Fighter charge current is very nearly constant during the bulk
charge period, while a typical 3 amp charger, configured like so many chargers
on the market, is not.
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11. Can I leave the Battery Fighter battery charger connected to a battery
while I.m using the battery to power another appliance like a radio?
Yes, you can leave the Battery Fighter battery charger connected to a battery
even when the battery is being used. As far as the Battery Fighter battery
charger is concerned, the appliance just makes the battery look like it.s not
fully charged. The Battery Fighter battery charger can supply up to its full
1.25 amp current output even while its output voltage is at the lower, float
level of 13.2 volts. It is only when the battery voltage drops below somewhere
between 12.0 and 12.5 volts that the Battery Fighter battery charger will reset
and begin the full charger cycle. All that means is that when the appliance is
no longer being used by the battery, the battery voltage will rise normally and
there will be an absorption period of a few hours where the Battery Fighter
battery charger holds the battery voltage at 14.4 volts until the charger
current drops to below 0.1 amp, or until 8 hours has elapsed during the
absorption charge period. Then the Battery Fighter battery charger goes back
into float mode where its output voltage is constant at only 13.2 volts.
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12. Is there any danger that the Battery Fighter battery charger can cause
any damage to other automotive electronic systems while it is connected to the
battery in my automobile?
No. As long as the automotive electronics system is functioning properly, there
should be no problem. Typical automotive electronic systems run between 14 and
15 volts with the alternator running. The maximum voltage output of the Battery
Fighter battery charger is 14.4 to 14.5 volts.
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13. Can the Battery Fighter battery charger be used to charge more than 1
battery simultaneously if the batteries are connected in parallel?
Yes, the Battery Fighter battery charger can be used to charge more than 1
battery simultaneously when those batteries are connected in parallel.
Theoretically, there is no reason that you cannot recharge your batteries in
parallel, or that you can't use a larger battery. HOWEVER, you must recognize
that the amount of time required to recharge may be much longer than you would
normally expect. Effectively, by charging more than 1 battery in parallel, the
charger behaves as if one larger battery is connected to its output terminals.
The Battery Fighter only puts out 1.25 Amperes. That means it will take over 24
hours to recharge a 32 Ah battery to 80%, assuming that is fully discharged. It
will take another 12 to 24 hours on top of that to recharge the last 20%. If you
put an even larger battery in parallel with it, then the total times may double
or triple. That is not a reason for concern.
The real concern is that the Battery Fighter will only switch over from 14.4 VDC
absorption voltage when the current draw from the battery drops below 0.1 amps
or after an 8-hour period in absorption mode. Under normal circumstances, with
battery capacities up to 32 Ah, this is a good thing and the Battery Fighter
will switch over to the long-term storage voltage of 13.2 VDC with no problem.
In fact, it usually turns out that the amount of time spent at the constant
voltage of 14.4 VDC, typically a few hours, is good for the battery, especially
the newer AGM style batteries. There is a maximum time limit of 8 hours at 14.4
VDC. As long as the charger switches over to 13.2 VDC before the 8-hour timeout,
then the battery will be 100% recharged.
However, the larger the battery that you try to recharge, the higher likelihood
that the charger current will never drop below 0.1 amps with 14.4 VDC applied,
no matter how long the charger is connected. That means that the charger output
will remain at 14.4 VDC for the maximum time period of 8 hours. This is also not
a problem for the battery in terms of "dry-out", but again with the larger
batteries if the charge current has not been reduced to a maximum of a few
tenths of amps, then there is a good possibility that the battery will not be
100% recharged before the switchover to 13.2 VDC. This will result in even more
time required before 100% recharge is achieved.
Our recommendation is that you not charge batteries in parallel, again assuming
that the batteries are 100% discharged. If the batteries are only partially
discharged, then it is probably OK to charge them in parallel.
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14. Can I charge more than one battery at a time with a single charger?
This is a very general question and its answer will cover many aspects of both
battery and battery charger characteristics.
And the answer is both YES and NO, depending on several circumstances. Here are
8 items to consider:
A. Are the batteries connected in series or parallel?
B. Are the batteries the same type, that is, are they flooded, sealed, GEL, AGM,
etc.?
C. Are the batteries the same size, that is, do they have the same amp hour
capacity?
D. And are the batteries used for deep cycle applications, like large marine
batteries that are used to run trolling motors, or are they engine start
batteries used for automobiles, motorcycles, sports watercraft, or all terrain
vehicles? (This latter type of battery is referred to as SLI, which stands for
Starting, Lighting, & Ignition.)
E. Are the batteries discharged to the same level before recharging?
F. What is the nominal output voltage rating of the charger?
G. What is the nominal output current rating of the charger?
H. What type of battery is the charger designed to recharge? What this means is
what type of charging algorithm is used? In other words, what voltage levels,
current levels, and timing does the charger employ as it recharges the battery?
This seems like an awful lot of questions to ask before we can say .YES. or .NO.
to charging more than one battery with a single charger. The short answers are
given first, and then a more detailed discussion follows.
SERIES CONNECTIONS: If the answer to question 15.A) is that the batteries are
connected in series, where the battery voltages add to make a larger voltage,
then for optimum recharging, the answers to questions 15.B), C), D), and E) must
be yes. The batteries must be the same type, the same size, used in the same
application, and they must be discharged to the same level before they are
connected to a battery charger. The answer to question 15.F) is that the nominal
output voltage of the charger must equal the total nominal voltage of all of the
series connected batteries added together. The answer to question 15.G) is that
the nominal output current rating of the charger must match the battery
manufacturer.s recommendation
PARALLEL CONNECTIONS: If the answer to question 15.A) is that the batteries are
connected in parallel, where the battery voltages must be the same and the
battery capacities add, so that the charger behaves as if it is charging a
larger battery, then for optimum recharging, the answers to questions 15.B) and
D) must be yes. The batteries must be the same type and used in the same
application. For question 15.C), although desirable, it is not essential that
the batteries be the same size if they are connected in parallel when
recharging. Similarly for question 15.E), it is not absolutely necessary that
they must be discharged to the same level before they are connected to a battery
charger.
The answer to question 15.F) is that the nominal output voltage of the charger
must equal the nominal voltage of the batteries connected in parallel. Remember,
that all of the battery voltages must be the same or they can.t be connected in
parallel. The answer to question 15.G) is that the nominal output current rating
of the charger must match the battery manufacturer.s recommendation. This gets a
little complicated because it affects the maximum size difference, the amp hour
capacity difference between the largest and smallest battery connected in
parallel. It also affects the limit on the total amp hour capacity of all the
batteries connected in parallel.
BATTERY CHARGER DESIGN: SERIES and PARALLEL CONNECTIONS: Whether the batteries
are connected in series or parallel, the answer to question 15.H) is that the
charger must be designed to provide the output electrical power and timing
control for the type of battery being recharged. This includes the output
voltage and current discussed in questions 15.F) and G).
DETAILED DISCUSSION to support SERIES and PARALLEL Battery Charging: Let.s start
by saying that for the purpose of this discussion, most batteries fall into
three categories based on their use or application. These groups are: deep cycle
(marine), SLI, or standby power. Within these three application groups we can
now consider the type of battery. Flooded and sealed lead acid batteries have
different charging requirements. There are also several different types of
flooded and sealed batteries. But again, let.s limit the discussion to 3
categories: flooded, sealed GEL, and sealed AGM.
COMPARISION of GENERAL BATTERY CHARGING REQUIREMENTS by TYPE: The maximum
recharge voltage is the highest for sealed AGM, and the lowest for sealed GEL,
with flooded batteries falling somewhere in between. The exception to this rule
is flooded SLI batteries that have antimony added to their lead grids. The
highest voltage is delivered during the equalization charge period. Equalization
charging will be discussed later. The maximum recharge current is the highest
for sealed AGM and sealed GEL, and the lowest for flooded batteries. Most
battery manufacturers will specify the maximum recharge current to be a
percentage of the amp hour capacity.
For example, many flooded SLI batteries are limited to 10% to 20% of the amp
hour capacity. For more specific example, consider a 20 Ah, flooded SLI battery,
as you would find in a motorcycle, sports watercraft, or ATV. In this case, the
charger should only deliver a maximum charge current of 2 to 4 amps to the
battery. On the other hand, sealed AGM batteries are becoming very popular in
these SLI applications. Sealed AGM batteries do not usually have the same
maximum charge current limitations as flooded batteries. However, some AGM
battery manufacturers continue to prefer to make a more conservative
recommendation for the maximum charge current.
In this regard, with one more known fact about the majority of commercially
available battery chargers, the conservative approach to recommending a maximum
charge current is usually not necessary. That fact is that most commercially
available battery chargers are not true constant current chargers. What most
battery chargers do is one of two things. They either allow the charger output
current to immediately taper (reduce in amplitude) in response to an increase in
battery voltage, however slight that voltage increase may be, or they maintain a
regulated current limit until such time that the battery charger develops
sufficient voltage for the charger to switch to a true, constant voltage mode of
operation.
The initial period, prior to the constant voltage mode of operation is called
the bulk charge period. The constant voltage period is called the absorption
charge period. It is during the absorption charge period that the charging
requirements for AGM batteries differ most significantly from those for flooded
batteries and GEL cells. AGM batteries require a longer period of constant
voltage, so long in fact, that the current drawn by AGM batteries is virtually
nil for up to several hours at the end of the absorption period. Typically it
takes 1 to 2 hours for the battery charge current to drop to a few tenths of an
amp at the beginning of the absorption period. After the battery charge current
drops to this very low level the AGM battery still requires several more hours
with the constant absorption voltage being applied.
The precise electro-chemical requirements for this extended, essentially .zero.
current high constant voltage period are debatable. Suffice it to say that a
significant body of empirical evidence supports this claim. Without an extended,
.zero. current, constant voltage absorption period, the cycle life of AGM
batteries is dramatically reduced. The reduction may be by as much as a factor
of 2 or 3 to 1. In other words, an AGM battery designed to deliver 400 deep
cycles may only deliver 200 or as few as 125 deep cycles if the length of the
absorption period is not sufficient. One deep cycle is defined as a battery
discharge where the battery capacity is depleted to between zero and 20% of its
fully charged value. We could say that the State Of Charge (SOC) of the battery
is 0% to 20% after a deep cycle discharge. This is described as a Depth Of
Discharge (DOD) between 100% and 80%.
No such lengthy, .zero. current, constant voltage absorption period requirement
exits for either flooded SLI or GEL cells. However, both of these battery types
do benefit from extended float maintenance charge periods. This is usually
referred to a .topping off. the batteries. There is some debate amongst battery
and battery charger professionals about the benefits and risks of extended float
maintenance charging. The major difference between float maintenance charging
and absorption charging is that the float voltage is only a few tenths of a volt
above the fully charged, rest state voltage of the battery. This is typically
13.2 to 13.6 volts. This voltage range is below the gassing voltage of the
battery. The absorption voltage is about 1 volt higher, 14.2 to 15.0 volts. The
absorption voltage range is above the gassing voltage of the battery.
THINGS TO CONSIDER when CHARGING BATTERIES CONNECTED IN SERIES: The highest
charge voltage is delivered during the equalization period. For AGM batteries in
particular, this higher voltage, between 15.5 and 17 volts for an AGM battery
string has an interesting added benefit. For as few as 4 identically sized
batteries, discharged to the same DOD, after recharge without an equalization
period, the individual battery voltage may vary by as much as 1 volt across the
string.
EQUALIZATION VOLTAGE IMPACT on SERIES CHARGING: Let.s consider 4 AGM batteries
connected in series. The individual battery voltages would optimally be in the
14.5 to 15.0 volt range, while the charger delivers its absorption voltage.
Let.s say 14.7 volts per 12-volt battery for this discussion, or a total of 58.8
volts. Without high voltage equalization, it is possible, in fact even likely
after a few discharge / charge cycles, that the lowest battery voltage in the
string may be 14.2 volts and the highest battery voltage in the string may be
15.2 volts, with the other 2 battery voltages being 14.9 and 14.5 volts. Within
a matter of minutes after the charger applies an equalization voltage of 15.5
volts per 12-volt battery, or 62 volts total, each of the 4 batteries will
.snap. in line, varying by no more than 0.2 volts per 12-volt battery.
The optimal timing of this equalization voltage application, much like the
extended absorption period, is a subject of debate among industry professionals.
Again, the empirical evidence is clear pertaining to the result. If the
individual battery voltages in the string are not equally matched, with only a
few tenths of a volt per 12 volt battery, then the long term ability of the
battery string to deliver a significant percentage of its design deep cycle life
is dramatically reduced. An analogy can be drawn to the 6 individual cells
comprising a single 12-volt battery. If a single 2-volt cell is weaker than the
other 5, then the 12-volt battery will not consistently deliver its design deep
cycle capacity over time. This observed result is called .Premature Capacity
Loss. or PCL. There are other reasons for a battery to exhibit PCL, but
sub-optimal series string charging is certainly one of them.
CHARGING BATTERIES in SERIES that HAVE NOT BEEN DISCHARGED TO THE SAME DOD or
BATTERIES that ARE A DIFFERENT SIZE (AH Capacity): Just as a single, weak 2 volt
cell will degrade the performance of a 12 volt battery, recharging batteries
connected in series that have different beginning SOCs or have been discharged
to different DODs will have a similar result. The lowest SOC battery in the
string will most likely never recover fully, remaining undercharged, while the
highest SOC battery in the string will become overcharged. Either case situation
result in premature capacity loss.
Similarly, although at first glance the effect seems to be the opposite, the
smallest Ah capacity battery in the string will become overcharged, while the
largest Ah capacity battery will likely never be fully recharged. This assumes
that that both or all of the batteries have been discharged to the same DOD
prior to recharge. Different size, Ah capacity batteries is a more complicated
case than same size batteries discharged to different DODs.
An argument could be made that different size batteries could function and be
fully recharged, by exerting careful control over both the discharge and the
recharge. However, the smaller battery will experience a deeper discharge on
each cycle, thereby approaching the end of its cycle life sooner. Over time, the
smaller battery will not be able to be fully recovered and it will become the
weak .cell. in the single battery analogy.
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15. Can I charge batteries with different voltages on a single charger,
either a 12-volt or a 6-volt charger?
One of the answers to this question is a special case of the general question
asked earlier about charging more than one battery at a time. That specific
answer is that if the total nominal battery voltages of all of the batteries
connected in series equals the nominal voltage output of the battery charger
then you can use a single charger. For example, two 6-volt batteries connected
in series can be recharged with a single 12-volt charger. Of course, all of the
previous restrictions about charging batteries connected in series apply to this
case.
To this question answer more directly for single batteries, NEVER use a charger
on a single battery unless the nominal output voltage of the charger matches the
nominal battery voltage. For example, only use a 12-volt charger with a 12-volt
battery. Do not use a 12-volt charger on a 6-volt battery or a 6-volt charger on
a 12-volt battery. If the nominal charger voltage is larger than the nominal
battery voltage, then the situation can become dangerous.
The reason that this situation is dangerous is because the battery cannot
develop a voltage high enough to allow the charger to complete the different
phases of its charge cycle. That means that the charger will be .stuck. in the
bulk charge mode, continually delivering electrical current to the battery for
as long as AC power is applied to the charger, or until the charger safety
mechanisms engage. In this case, the only type of safety mechanism that would
work properly would be one designed to sense a battery voltage increase over a
specific period of time. Even then, depending on the specific design parameters,
that type of charger safety mechanism may not be sufficient to prevent serious
damage to the battery or even a potential fire hazard, or even worse, a risk of
explosion.
If the nominal charger voltage is smaller than the nominal battery voltage, then
one of two things will happen: nothing, or the battery will be discharged.
The reason that nothing may happen is that many chargers are protected from
reverse current. Usually a semiconductor-switching device called a diode
provides this protection. A diode only allows electrical current (charge) to
flow in one direction. For a battery charger that direction is out of the
charger and into the battery. If a 6-volt charger is connected to a 12-volt
battery, the 12 volt battery will try to deliver current to the 6 volt charger
because electrical charge always moves in the direction from the higher voltage
to the lower one. If the charger is protected from reverse current, then no
current will flow, and nothing will happen. Of course, the battery will not be
recharged, and if it is deeply discharged, then remaining in that condition may
result in permanent damage to the battery. If the charger is not protected from
reverse current, then the battery will be discharged. Likewise in this case, the
battery may be damaged severely from being over discharged.
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16. What happens if the AC power is removed from the Battery Fighter battery
charger while it is connected to a fully charged battery?
If the battery is fully charged, then the Battery Fighter battery charger.s
green light will be on. Once the AC power is removed from the Battery Fighter
battery charger, the green light will go out and the charger not has any effect
on the battery. The Battery Fighter battery charger is protected from reverse
current, so it will not discharge the battery. Of course, like we said earlier
when discussing nominal voltage mismatches between a battery and a charger, the
battery will not be recharged either.
When AC power is restored to the Battery Fighter battery charger, it will
restart its charge cycle. The sequence of events should go something like this.
The red light will come on for a few minutes. Then the green light will start
flashing while the red light stays on. The next thing that happens is what may
confuse some people who use the Battery Fighter battery charger. Remember, the
battery was fully charged, so you may ask, .Why doesn.t the green light just
come right back on?.
The reason that the green light doesn.t come on immediately is that when the
charger first comes on, the battery is sitting there, fully charged, at a
voltage of about 12.9 volts. The charger immediately tries to bring the battery
voltage up to about 14.5 volts. This takes a finite amount of time, although it
should only be a few minutes if the battery is fully charged. Then, when the
battery reaches 14.5 volts, the charger will hold it there until one of two
things happen. Either the battery charge current will drop to less than 0.1 amp
(from an initial value of 1.25 amps) or, if the current does not drop below 0.1
amp, then the charger will hold the battery voltage at 14.5 volts for 6 to 8
hours.
There are a couple of reasons why the battery current may not drop below 0.1
amp. First, on a larger battery, like an automotive SLI battery, the internal
losses of the battery may consume more than 0.1 amp. Second, if the vehicle or
the system that the battery is connected to has appliances that consume
electricity, then that consumption of electricity, coupled with the battery
internal losses may very likely exceed the 0.1 amp limit. This second cause is
very common and its result is that the Battery Fighter battery charger.s timer
circuits will be fully engaged. So it will take 6 to 8 hours for the green light
to come on. Fortunately, the Battery Fighter has the ability to continue to
supply its full current even after it has switched over to the lower, float,
maintenance charge voltage of 13.2 volts. When the charger turns the green light
back on, it also drops its output voltage to this float, maintenance charge
level of 13.2 volts.
Note: It only takes a momentary AC power outage to cause the Battery Fighter
battery charger to reset.
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17. What is Temperature Compensation and how important is it?
While a battery is being charged, it is important that the charger absorption
and float, maintenance voltages closely match the recommendations of the battery
manufacturer. The absorption voltage match is important for quick charging. The
float, maintenance voltage match is important for long term, storage charging.
Batteries are sensitive to temperature. Recall the number of TV ads showing how
tough a battery is when it can start a vehicle in sub-zero temperatures. Cold
temperatures tend to reduce a battery.s ability to deliver current to a load.
High temperatures not only increase a battery.s ability to deliver current to a
load, but also increase a battery.s internal losses.
Temperature compensation is a way to change a charger.s output voltage to
maintain optimum compatibility with the battery.s charging requirements. The way
it works is that the charger senses the ambient temperature. Then it increases
the charge voltage when it is cold and decreases the charge voltage when it is
hot. Typical values for temperature compensation for a lead acid battery are
minus 0.0025 to minus 0.004 volts per degree Centigrade per 2-volt cell. For a
12-volt battery, that would be minus 0.015 volts to minus 0.024 volts per °C.
The reference temperature requiring zero charge voltage compensation is 25 °C or
77 °F.
How important is temperature compensation? Like with most everything else about
batteries, it depends on the application. For industrial, critical load, standby
power applications, where the batteries may be connected to a live charger for a
number of years, then temperature compensation can have a significant influence
on battery life. In many consumer applications like SLI, deep cycle marine,
etc., temperature compensation will increase long-term battery performance, but
it is probably not essential in all applications. Where it is most beneficial is
in helping to minimize the negative impact of a battery's self-discharge
characteristics in high temperature environments.
Our Battery Fighter Battery Chargers Overcome the Negative Impact of High
Temperature on Battery Performance.
The self-discharge rate of a battery is directly dependent upon the ambient
temperature of the battery environment. At higher temperatures, the chemical
reaction rates that determine self-discharge will also increase.
When a battery sits idle, its self-discharge characteristics will reduce its
ability to deliver power on its next use. If the battery either sits long
enough, or if the ambient temperature rises high enough, then the battery may
become fully discharged. In fact, it is possible for the battery to be
over-discharged to the point where it cannot be recovered.
The Battery Fighter battery chargers overcome the negative impact of higher
ambient temperature and battery self-discharge in two ways. First, the Battery
Fighter battery charger applies a safe, float, maintenance voltage level to the
battery to overcome its internal losses and counteract the self-discharge
phenomena. Second, the Battery Fighter battery charger automatically compensates
the amplitude of its charge voltages for changes in ambient temperature. It
reduces the amplitude of the float, maintenance voltage as the ambient
temperature increases and it increases the amplitude of the charge voltages in
colder temperatures. In mathematical terms, this type of compensation scheme is
called a "Negative Temperature Coefficient".
The temperature compensation ratio employed by the Battery Fighter battery
chargers is approximately minus 3.67 mill volts per battery cell per degree
Centigrade of temperature rise above 25 °C. Stated another way, the output
voltage of the Battery Fighter battery charger will drop 0.022 volts, or 22 mill
volts, for every degree Centigrade temperature rise, when it is connected to a
12-volt battery.
In the event that the temperature would rise enough so that the Battery Fighter
battery charger voltage output drops below the what would be considered a normal
operating voltage for a 12 volt battery, then the Battery Fighter battery
charger automatically disconnects itself from the battery via an internal solid
state mechanism, affording an extra measure of safety in a very high temperature
environment.
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18. What is Float / Maintenance Charging? Is it really necessary?
Historical Background: Charging batteries in a float / maintenance mode has been
standard practice for decades when batteries have been used for standby power
applications, such as telecommunications, UPS (Uninterruptible Power Supply),
and emergency lighting. Also, the U.S. military has invested literally billions
of dollars in developing standby battery charger systems for uses in countless
weapon systems: ships, aircraft, ground vehicles, etc. The simple definition of
float / maintenance charging is that voltage is continuously applied to the
battery terminals. The amplitude of that voltage varies between 0.2 volts and
0.6 volts above the rest state voltage of the battery when it is fully charged.
The purpose of continuous float / maintenance mode charging is to maintain the
battery in a fully charged condition so that when it is called into service, it
will be able to deliver its full charge capacity. Until recently, the most
commonly used battery chemistry in sophisticated military weapons systems has
been NiCd, rather than lead acid. Nevertheless, the concept of continuous float
/ maintenance charging has been around for a long time.
Technical Discussion Categories: There are basically 2 categories of technical
issues that need to be discussed when debating the merits of float / maintenance
charging. 1) What observable characteristics of the battery support and detract
from using continuous, float / maintenance charging? 2) What observable
characteristics of battery chargers support and detract from using continuous,
float / maintenance charging?
1) A. Battery Voltage vs. SOC: In the first category, batteries develop a
voltage that indicates how much charge is available for use. The relationship
between battery terminal voltage and State Of Charge (SOC) is reasonably linear.
For a 12-volt, lead acid battery, that relationship is defined by a 1.5-volt
change in terminal voltage that represents the entire SOC range from 0% to 100%.
Also, that voltage must be measured when the battery is in a state of rest (the
battery terminals are open-circuited), neither being charged nor discharged. A
fully charged 12-volt battery will have a terminal voltage of approximately 12.9
volts and a fully discharged (0% SOC) battery will measure 11.4 volts at its
terminals. Therefore, a change of 0.15 volts represents a 10% SOC difference.
1) B. Internal Battery Losses: All lead-acid batteries develop and store charge
as a result of an internal chemical reaction. There are 2 primary internal loss
mechanisms. The first is a result of the chemical interaction between the
internal battery elements. That interaction is continuous and it is affected by
temperature. It is also affected by whether the battery is being charged,
discharged, or in a state of rest. In all 3 situations, the battery terminal
voltage will change. In one sense, the battery is never truly in a state of
rest, rather, its terminals are connected either to a charger (being charged),
or to a load (being discharged) or the battery terminals not connected to
anything (the terminals are open-circuited, or in a "state of rest").
The second primary internal loss mechanism is due to the physical
interconnections between the chemically interacting elements and the
electrically conductive paths to the battery terminals. This second loss
mechanism is usually called the internal resistance of the battery. When the
battery terminals are open-circuited, that is, not connected to either a battery
charger or a load, only the internal chemical losses influence the battery
terminal voltage. When the battery is being either charged or discharged, both
the chemical losses and the internal battery resistance influence the battery
terminal voltage.
The simplest battery model for electrical circuit analysis is an ideal battery
in series with a resistor. The voltage of the ideal battery is the open circuit
voltage that represents SOC. The value of the series resistance is the battery
internal resistance, typically measured on a fully charged battery at a
frequency of 1000 Hertz. That resistance value is usually in the 5 to 10
milliohm range. More sophisticated battery models account for the fact that the
internal resistance is not constant over the range of SOC. Even more
sophisticated models include a complex impedance (some combination of
resistance, inductance, and capacitance) in parallel with the ideal battery. For
example, because of the construction of lead acid batteries, the equivalent
electrical capacitance is in the range of several tens of thousands of Farads.
For this reason, specifying a ripple component of output voltage on a battery
charger when it is connected to a battery is somewhat futile because of the
tremendous voltage-filtering characteristic of the battery's equivalent
electrical capacitance.
Since the internal resistance of the battery is very small, its impact on the
value of voltage measured at the battery terminals is only significant during
high rate (lots of current) discharges and charges. When the battery is being
discharged, the battery terminal voltage is less than its open circuit value.
Conversely, when the battery is being charged, its terminal voltage is more than
its open circuit value. The difference between the voltages is calculated by the
product of the charge or discharge current and the internal resistance. In float
/ maintenance charging situations, the charge current is usually very small, so
that the difference between the open circuit voltage and the actual battery
terminal voltage is also small.
2) A. Battery Charger Output Voltage vs. AC Line Voltage (Output Voltage
Regulation): This one aspect of Power Supply (battery charger) Line Regulation
is very important because the output voltage of the battery charger must be in a
certain range, and it must not deviate significantly from that range, otherwise
a battery can be overcharged, or it can be undercharged. Fortunately, in the
Australia, the national AC power grid, the AC power distribution system, is very
stable. Therefore, battery charger line regulation characteristics have less
impact than they would when the AC power, particularly the AC line voltage
varies significantly. In general, one could say that the simpler the
construction of a battery charger, the more likely it is to have larger
percentage line regulation characteristics. The larger the percentage, the more
the output voltage will vary with the AC line voltage.
2) B. Battery Charger Output Voltage vs. Temperature (Temperature Compensation):
This battery charger characteristic probably has more influence on the battery
than line regulation. Even if a battery is kept at its ideal float voltage, and
it that ideal voltage is compensated properly for temperature, an increase of
only 7 °C to10 °C can cut the battery life in half, assuming that the higher
temperature remained for the entire observation period. Short-term fluctuations
in temperature have little impact on battery life, unless the temperatures are
extreme. In general, cold is good, hot is bad, very cold is better (but too cold
can be worse), and very hot is worse. At the extreme cold end, bad things can
happen as well, but those bad things are just dramatic reductions in the battery
performance. At the extreme hot end, while the battery is charging, it can emit
dangerous gasses. The ideal temperature compensation range for lead acid
batteries is typically in the range of 2.5 to 4.0 mill volts per 2-volt cell,
per degree Centigrade. The temperature compensation coefficient is also
negative, meaning that the change in charging voltage is in the opposite sense
as the change in temperature. If the temperature goes up, the charging voltage
comes down and vice-versa.
Arguments For and Against Continuous Float / Maintenance Charging: From the
preliminary background on batteries and chargers, positions can be taken for or
against continuous float charging. The main argument against continuous float
charging is that the battery will: a) be undercharged, or b) be overcharged, and
/ or c) be permanently damaged as a result of a) or b). The main argument for
continuous float charging one of convenience in that it is better to have the
battery fully charged when you need to use it. An automatic, well-regulated,
temperature-compensated charger can keep the battery fully charged and at the
same time minimize the risks of long-term damage to the battery due to either
under-charging or over-charging. The alternative is to let the battery internal
losses run their course, which for most batteries means that they are fully
discharged within a few months. If you forget to recharge them periodically, and
they become severely over-discharged, even due to only internal losses, the
plates will become severely sulfated. For many batteries, that means that they
are permanently damaged.
Recommendations for Using the Battery Fighter in Continuous Float Mode Charging:
The line regulation characteristics of the Battery Fighter are excellent; less
than 1% for line voltage between 230 VAC and 240 VAC. This charger is
temperature compensated and it has a special charging algorithm optimized for
sealed, gas-recombinant, AGM, lead acid batteries.
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19. Can the Battery Fighter successfully perform the initial charge on a new,
flooded, motorcycle battery?
Background: The motorcycle dealers receive batteries from the manufacturer in a
dry state. The plates are dried out, and there is no acid in the cell
compartments. (Do not confuse this with a dry-cell battery.) The dealer must
fill the individual battery cells with acid and then put them on a shop charger
to pre-charge prior to selling them to a customer. As the batteries arrive from
the manufacturer, the plates are approximately 80% "formed". The initial
pre-charge, post-formation charge, or more correctly, formation-finishing
charge, must be conducted at a specific power level and for a specific time
period. Each manufacturer has its own recommendations, for example one
manufacturer recommends that the charger deliver a constant current equal to 10%
to 15% of the battery amp-hour capacity and that the charge current be applied
to the battery for a period of 5 to 10 hours.
Answer 1) Certainly if the dealer has properly pre-charged the battery after
filling it with acid, then the answer is ABSOLUTELY YES.
Answer 2) If the dealer has not properly pre-charged the newly filled battery
prior to the sale, then the answer is YES, WITH SOME QUALIFICATIONS:
Qualification A) The Battery Fighter should be left on the new battery for a
minimum of 24 hours on float, in addition to whatever amount of time it takes
for the charger to get to the float stage. It is not clear how to correlate the
80% formed plates with a given state of charge once the cells are filled with
acid. To be safe, assume that the batteries require a full 100% charge after the
cells are filled.
For example, a 16 Ah battery will take about 13 hours to get to the absorption
voltage (constant 14.4 Volts). It may take another 6 to 8 hours to reach the
float voltage (constant 13.2 Volts). This may sound awkward; because what
happens is that the battery charge current drops while the absorption voltage is
held constant. When the battery current drops to 0.1 amp, or if 6 to 8 hours
have elapsed at the absorption voltage, the charger automatically switches its
output from 14.4 V to 13.2 V. So it may take the better part of 20 hours to
reach the float stage. Add another 24 hours to that and you are at 44 hours.
Throw in another 4 hours for good measure and you get a nice round, even 48
hours, or 2 days.
Qualification B) Although there are probably several charging methods that will
be equally effective, regardless of who manufactures the battery, in the
interests of technical consistency, they will not officially sanction any
initial charging method other than those published in their technical
applications literature.