Battery voltage question - higher volts at night

[crystalclear]

sorry for what is probably a simple question,

scenario:
when the panel is getting shaded/dusk - the battery reads 12.7 volts (as do the leads from the pv), but once it is night, the batt reads 12.9ish (odyssey agm)

am i to understand this as the batt will mirror the voltage being put out by the panels (until full dark)? this system is running a small pwm controller

i find this strange because on 2 of my rigs with mppt controllers, the batttery voltage will not drop below “full” during the daytime no matter how bad the light/shade (with no loads), even if the panels are producing less than 12.9 volts.

 

[john61ct]

There are three voltage levels on the circuit

1. what the SC would be putting out at its terminals if there were a tiny load device rather than a big thirst battery online

2. what the battery would measure at its posts, isolated and at rest - depends on its SoC

3. the "negotiated" voltage on the wire during charging, somewhere between 1&2

Huge amps output and/or small or Full battery, closer to 1, small amps big depleted battery, closer to 2.

And then active load devices also concurrently online will also have an impact, lowering voltage more at higher currents.

So with these principles, you should be closer to figuring out what's going on.

I would disconnect all loads, just the SC and battery.

Battery known good?

You should get to know how to tell its SoC aside from just voltage.