Trojan Flooded - Discharge Testing for Capacity

TROJAN BATTERY
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8.5 Discharge Testing
î Follow the procedure below to determine battery capacity.
î Connect and start discharger.
î Record the runtime (minutes) when discharge is complete.
î Correct runtime minutes for temperature using the following formula (valid between 75°F (24°C)
and 90°F (32°C):
M
c
= M
r
[1 – 0.005
*
(T
1
- 80
*
)]
*
(For Celsius, use 0.009 & 27°C)
Where M
c
= Discharge time corrected to 80°F (or 27°C)
M
r
= Actual discharge time
T
1
= Battery temperature at end of discharge (°F or °C)
î If the discharge runtime is greater than 50% of the batteries’ rated capacity at that discharge rate, then
all the batteries are operational.
î Restart the discharger to record the individual battery voltages while still under load
(current being drawn).
î If the discharge runtime is less than 50% of the batteries’ rated capacity, the battery with a voltage
that is 0.5V lower than the highest voltage may be a failed battery.
There are other methods of testing batteries including internal resistance (i.e. C.C.A. testers) and carbon
pile discharge testers. However these are not suitable testing methods for deep-cycle batteries.