Temperature compensation when testing battery banks
A battery’s capacity is dependent on the ambient temperature. If the ambient temperature is high the capacity increase, but it will at the same time shorten the battery life. In the opposite direction, when ambient temperature is low, the capacity of the battery is reduced. This must be considered
when performing a capacity test.
Nominal temperature for battery specifications is normally 20ºC/68F or 25ºC/77F. In order to compare the test result from a discharge test with the battery specification, the temperature must be considered. There are international standards that describe the temperature compensation procedure, IEEE 1188 (VRLA), IEEE 450 (vented) and IEC 60896-11/21(vented/VRLA).
TORKEL 900 has implemented all these temperature compensation methods according to the standards. To enable the temperature compensation, press the 
button. Select “Settings” and set to ON for temperature compensation. The
button coms up were temperature can be set, and IEEE or IEC standard can be selected.
- IEEE 450 and IEEE 1188
Tests longer than 1 hour
The most commonly used temperature compensation method in these international standards is to apply the temperature correction to the capacity calculation after completion of the test.
C = (ta / ts x Kt) x 100
Where
C is the % capacity at 25°C
ta is the actual time of test to specified terminal or cell/unit voltage
ts is the rated time to specified terminal or cell/unit voltage
Kt is the correction factor for the cell temperature before the start of the test
Simply run the test at rated current and time. When the desired voltage level has been reached the test is stopped. The temperature compensation is when performed according to the calculation above and the % Capacity is calculated.
In an earlier version of the IEEE standards there was a possibility to perform the temperature compensation prior to the test by adjusting the test time. This method is still valid and can be used.
Temperature compensation after performed discharge test.
Disable( if enabled ) the temperature compensation on the “SETTINGS” menu by clicking on the 
button and disable temp compensation. Go to the “RESULT” tab and select the 
button. Disable the temperature compensation. Set “Rated capacity” and temperature. Start the test from the “RESULT” tab. After test has been stopped, press the
button and save the test. Enable the temperature compensation in the “RESULT” tab. This gives the “%Capacity” value.
Temperature compensation before start of discharge test.
Click on the button. Below menu comes up.
Enable “Time correction”. And set temperature. When rated time is set on the start menu, compensated time is calculated for the specified temperature. The “Rated Capacity” on the “RESULT” tab shall also be set. The “%Capacity” are then calculated.
Tests shorter than 1 hour
For these tests a different method is used, current rate compensation which is made prior to the test. The discharge current for the test will then be compensated relative to the nominal rate. If the temperature is higher than 25°C, the current discharge rate is increased. If lower than 25°C, the current discharge rate is decreased.
% capacity at 25 °C = Xa x Kc / Xt x 100
where
Xa actual rate for the used test
Xt published rating for time t
t time of test to specified terminal voltage
Kc temperature correction factor