Hello my fellow energy geeks!
We have a hybrid solar/wind system storing power at 48v in 12 deep cycle batteries, arranged in 3 sets of 4 batteries each.
Both the storage and the 10Kw inverter is designed for 48V. Meaning whenever i use 4 amps in 110VAC i will be draining nearly 10 amps from the batteries, having a 2.5 to 1 DC/AC conversion ratio.
Each battery is rated 150Ah and the whole set should last for 12 hours draining 30 amps permanently using less than 70% of the available charge.
Whenever we put a load to the inverter (air conditioning, fridge, etc) the battery voltage drops from 54 to 50 and slowly discharges.
We are confused on how to measure the idle charge, as when we reach 47.5 volts and release the load, the voltage goes back to 49.
Which reading should we trust to test for idle charge ? Measuring the voltage with full load ? Or with no load at all ?
Also, we noticed after 1 year of use without draining below 47.5V, the batteries are reaching this theshold faster, but they are practically new. According to the manufacturer if we never drain more than 30% of the batteries, they should last for 1200 cycles or so. Could you guys suggest a good way to test if a battery of the set is damaged or worn out?
Pedro