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diy solar

battery voltage decreases then increases

ghostman

New Member
Joined
Apr 13, 2022
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18
Hi,
my off-grid system consists of 14 solar panels 410 W, Voltronic 48v 5300w Inverter and 12x 12v FLA batteries (Leader LDR INV TT 220AH/12v) set in 3 parallel banks of 4 batteries each.
I ran the 230V output from the inverter directly into my electrical panel.
when on battery mode, I noticed that battery voltage decreases on high consumption, then increase back up when consumption is lower.
For instance, at a certain time when load is ~700w battery is at 49.0v; when increasing the load to ~1200w (after turning on an AC), battery voltage drop to around 48.1v, then go back up to ~48.7v when load decreases back to 700w (when AC stabilizes).
Is this normal? My assumption was that battery voltage will keep decreasing as long as it's in use and not been charged up.
 
Normal. The fluctuation reflects the speed of the electrochemistry's ability to produce the electrons. Yes the voltage may recover some when the draw is reduced. Soon the steady drop in voltage will continue as long as the discharge continues.
 
Hi ghostman - what you are seeing is called the Peukert effect.

Basically, the larger the load you put on the batteries, the faster the voltage drops. Reduce the load, and the voltage rises again. Mostly seen with lead-acid batts, but not so with LiFeP04.
 
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