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parameters. The battery will be gassing and you will see an accumulation of a large number
of amp hours each day. This is a clear indication that you are destroying your battery by
overcharging. Check your
LINK 2000
before turning off a charging source to see that you
have not accumulated too many overcharge amp hours. When discharging begins,
overcharge amp hours are erased and the
LINK 2000
resets to zero.
Systems that have a Conditioning or Equalization cycle
will accumulate a few
overcharge amp hours during equalization. This is normal and ensures that the
LINK 2000
stays in sync with the battery state of charge.
BATTERY CAPACITY TESTING
Your
LINK 2000
can be used to conduct periodic capacity tests that tell you the
actual amount of energy your batteries can store. A capacity test should start with a battery
that has been properly charged and conditioned. The objective is to find the maximum
available capacity.
Deep-cycle battery capacity is usually based on a 20-hour discharge rate. A 100 Ah
battery will provide 5 amps for 20 hours. At discharge rates above 5 amps, the battery will
not supply 100 Ah. For example: If you are drawing 100 amps out of the battery it will last
less than one half hour. This was discovered in 1897 by a scientist named Peukert and is
discussed in detail later. You can see the effect in the following table listing approximate
capacities at different discharge rates.
CAPACITY AT VARIOUS DISCHARGE RATES
(percentage of 20-hour rate)
Hours to Discharge Capacity (percent of rating)
20
100%
10
89%
5
78%
3
66%
1
45%
To test battery capacity, turn on a load that draws approximately 5% of the declared
battery capacity. Measure the current using the Amps function of the
LINK 2000
. The load
should be constant, such as incandescent lighting. When the battery voltage reaches 10.5
volts, hopefully about 20 hours later, turn off the load and look at the A hrs display on your
LINK 2000.
The number displayed is the capacity at the test current. If less than 20 hours
passed before the battery voltage fell to 10.5 V you can still determine the capacity with
some arithmetic. For example: assume a 12 V battery rated at 100 Ah. Apply a 5-amp load.
Suppose it only took 10 hours for the voltage to reach 10.5 volts.
The
LINK 2000
would
display -50 Ah. This is the 10-hour capacity. Dividing 50 by 89% (10-hour rate) from the
table above, you determine that the actual 20-hour capacity is 56 amp hours. You could
repeat the test at 5% of the tested capacity (2.8A) to verify the actual capacity.
USING YOUR FREEDOM INVERTER
TO TEST BATTERY CAPACITY
Your inverter makes testing the battery capacity easy. First fully charge (and equalize
if necessary) the battery to be tested. Use a load like incandescent lights running on the
inverter whose amperage consumption is 5% or less of the battery capacity. Let the load
run until the inverter shuts down on low voltage (about 10.2 V). Read the number of amp
hours that have been consumed from the battery. If it is not close to the expected number,
use the procedure outlined above to estimate the capacity.
Caution! Be sure to completely recharge your battery after a discharge test.
