Guide

TROJAN BATTERY

7. 3 Specific Gravity Testing (continue from pg 19)

î Correct specic gravity readings for temperature by adding 0.004 for every 10°F (5°C) above 80°F

(27°C) and subtract 0.004 for every 10°F (5°C) below 80°F (27°C).

î If every cell in the battery set is below 1.235 the batteries may be undercharged; recharge batteries.

î If any battery has a specic gravity variation of more than 0.030 between cells equalize the set.

î If there is still a variation there may be a failed battery.

7. 4 Open Circuit Voltage Testing

This is the least preferred method of evaluating the condition of a battery.

î For accurate voltage readings, batteries must remain idle at least 6 hours (but preferably up to

24 hours).

î Measure the individual battery voltages.

î If any battery voltage is greater than 0.3V from any other battery in set, equalize the set (deep-

cycle ooded/wet batteries ONLY). Refer to equalizing section 3.4.2.

î Re-measure the individual battery voltages.

î If any battery voltage is still greater than 0.3V from any other battery in set you may

have a failed battery.

7. 5 Discharge Testing

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): Mc = Mr [1 – 0.009 (T - 27)] where Mc is the corrected minutes, Mr is the minutes

recorded and T is the temperature at the end of discharge in °F or °C.

î If the discharge time is greater than 50% of the batteries’ rated capacity then all the batteries

are operational.

î Restart the discharger to record the individual battery voltage 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.