Solar Charge Controller and Battery Monitor Showing Different Voltages

[Marlz]

SCC: Epever Tracer4215BN
Battery: LiFePo4 12v 100Ah
Batt Monitor: AiLi type

So sometimes my solar charger sees my batteries as full (13.7v in the picture) but the battery monitor sees them as low (13v in picture). Measuring at the battery shows that the battery monitor is correct. So since the SCC is seeing the battery as full it is not charging the battery and it just continues to discharge.

Any idea what might be causing this?

 

[sunshine_eggo]

SOMETIMES?

Do you see it happen typically during the day with charging, but it's accurate at night?

Double check that all connections between the MPPT and battery are properly torqued and that any breaker/fuses do not have excessive voltage drop.

Check voltage at the MPPT terminals If it doesn't agree with the meter, then the MPPT is reading incorrectly.

If it does measure higher than the battery and the MPPT agrees with the meter, you have excessive resistance in your connection to the battery - thin wires, loose terminals/connections, etc.

 

[John Frum]

Do you have a reference meter that you trust?
Compare and see if one or both of devices mentioned are off.
Agree with @sunshine_eggo the "sometimes" raises eyebrows.

 

[Marlz]

Yeah, it's just "sometimes". Like, it will be fine for weeks then what I described starts happening. I appreciate the advice and will try the things you mentioned.