July 28, 20224 yr Hello What is the general preferred method to capacity test a battery / battery bank ? Also is there any other way to determine the state of a battery / bank ? i.e those car battery Cold Cranking Amps machine or a similar sort of machine ? We can measure voltage and it shows full but then won't run a 100watts for 30 minutes, so curious to find out how batteries are tested and a agreed upon method if there is such a thing
July 30, 20224 yr Have you tried to put a "smallish" load on the battery while you test the V? A old incandescent 12v globe in either 20W or 50W might work.
July 30, 20224 yr On 2022/07/28 at 7:30 PM, Dylboy said: Hello What is the general preferred method to capacity test a battery / battery bank ? Also is there any other way to determine the state of a battery / bank ? i.e those car battery Cold Cranking Amps machine or a similar sort of machine ? We can measure voltage and it shows full but then won't run a 100watts for 30 minutes, so curious to find out how batteries are tested and a agreed upon method if there is such a thing The easy way is a car halogen 55W headlamp bulb. You can buy the double filament and test at 4.5A or 9A load. The 4.5A load is spot on for C/20 amps for a 100Ah battery. At fully charged and 100Ah capacity it could give 20hrs up to totally discharged but will never discharge that deep. Discharging down to 11.5V is a good enough indication for lead acid.
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