Quote:
Originally Posted by Ether
|
The web site states that it uses internal resistance.
The auto industry has been using internal resistance for battery health (but not state of charge) for many years. In general, the higher the internal resistance, the worse the condition of the battery. You must properly characterize the battery (chemistry, capacity) for this to work properly.
The screen display shows three voltage readings at different current values, I
speculate that this is used in addition to internal resistance to measure battery condition. This is an even older (and some say more accurate) method for battery condition. In the auto industry, it is (or was) common to have a carbon pile load to test batteries, rule of thumb was 3x the Ah rating in amps, check the voltage at 15 seconds.
I will also
speculate that state of charge is calculated by measuring open circuit voltage after a small load (like 18A for 10 seconds) is used to remove any possible surface charge.
Assuming the designer knew what she was doing, using these three methods (none of which are technically challenging) should produce repeatable results that are accurate enough for our purposes.