Hi Robert,
I have acquired a 1310Ahr (8hr rate) 24volt Unigy II AGM battery and am after comments re life in the following circumstance.
PV where Max daily load 130Ahrs
Input from 1500 watts of panels
Ave Temp ~ 20 degrees
Thus max daily cycle is 10 % but more likely closer to 5%
Charging regulated to Max 27Volts odd with occasional 27.4
Regards Rob Allen
Dear Rob,
You didn't say if the batteries are new or how old. Assuming new, you have 24v x 1310 AH .5-% = 15,720 watts of useable stored power, or about 16 kW/hrs.
At 130 A/h/ day load, at 24v, you are using 3kWhrs/day, or 1/5th your storage capacity. This is a really great ratio, about 18% of useable capacity! Your batteries should last a long time. Now, if you bought them used, you may actually have only half of that power available if they were damaged. If they were used in a telecomms system, then they were kept on float charge all the time and are usually a worthwhile buy. Also, keeping them at the 20C temp will give you a good life, as well.
You didn't say where you live, so I don’t know what an average solar day is for you. 1500 watts of PV at 24 volts should give you 64 amps of charging per hour in full sun when the batteries are really low. Because your demand is low, the batteries are mostly full all the time, so you can expect to see a charging current maybe of 25 to 30 amps first thing in the morning, with the charging current dropping off to probably 12 amps after the first hour of sun. Your charger setting at 27 volts is also a really good setting for sealed batteries, as they won’t last as long if you charge them too high.
In short, you have capacity for more loads in the summer, and maybe 5 days of not much sun in the winter. Sounds like a pretty good system to me. Congratulations.
Regards,
Robert Warren
