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TAC

Jun 08

SOK 12V-206Ah LiFePO4 Won't Charge

in Questions & Answers

Setup: 4s 12-206Ah SOK LFPs. wired in series for 48V on an off-grid solar setup.

History: Used first in summer 2022, worked great. Batteries disconnected from system over winter.

Status: Spring 2023 individually charged each of 3 of the batteries full with the Victron BlueSmart 12V/15A IP65 charger

Problem: 1 of the batteries will not charge. While disconnected it reads at about 6.2V. When initially connected the charger reads about 7V/15A (via BT app) during "Test" phase but after a few seconds goes to "Absorbtion" at 14.4V/0.0A. I've repeated this several times with the same result.

Is there more I can do to wake-up this battery?

4 answers0 replies

4 Comments

sokbattery

Jun 08

when you connect batteries in series, there are 2 things very important.

the 1) do pre-charge before connect on inverter.

2) add the battery voltage balancer.

TAC

Jun 09

Replying to

Thanks, I always pre-charge with a resistor before connecting the inverter to the batteries (otherwise I think the batteries will shut down). Thanks for the pointer on the balancers, makes sense especially as the batteries age.

sokbattery

Jun 08

try this:

https://www.youtube.com/watch?v=9s2nw107oBY&t=120s

TAC

Jun 09

Replying to

Thank you for the very quick response. Bypassing the the BMS and charging the cells directly with a 10A current source worked great. After the voltage rose to around 12V or so I switched back to the main terminals.

Very nice build quality inside.