Voltage Drop

[WanderIVth]

Hello everyone,

I'm having an issue with voltage drop at a high % of battery left. I'll get fine voltage at the top end, but when it hits about 75% capacity, I'll be down under 12v. The batteries charge and rest fine, but consistently drop voltage early.

Any thoughts?

AmpereTime 300ah x 2
Victron Solar Chargers
Magnum Inverter/charger.

[dougweibel]

Hello Wander,

More information would be helpful. What is the battery chemistry (LiFePO4 I'm assuming) and age? When you say the voltage drops below 12v is this at rest or under load? How much load? Have you pulled cables to separate the batteries and checked them individually?

[Corvidae]

It's a bad cell in one of the batteries. When you charge them that cell hits peak and stops passing current, so the rest won't charge completely.

Theoretically it could be an out of balance cell, but in a sealed battery it just means the whole battery is broken.

[WanderIVth]

Originally Posted by dougweibel

Hello Wander,

More information would be helpful. What is the battery chemistry (LiFePO4 I'm assuming) and age? When you say the voltage drops below 12v is this at rest or under load? How much load? Have you pulled cables to separate the batteries and checked them individually?

LiFePO4, yes.
Less than a year.
It's under load, but not much... maybe 5 amps. It's just the regular house stuff doing it's regular house stuff.

I've not hooked up the system with a single battery, no.

[WanderIVth]

Originally Posted by Corvidae

It's a bad cell in one of the batteries. When you charge them that cell hits peak and stops passing current, so the rest won't charge completely.

Theoretically it could be an out of balance cell, but in a sealed battery it just means the whole battery is broken.

Thanks.

[WanderIVth]

SOLVED:
This ended up being a settings issue on the charger. I purchased a new charge control unit with a lithium setting and the issue disappeared. Thank you all for your help.