Shorted 12v, 4 Lifepo4 (280aH) battery

YEP, majorly screwed-up. Shorted two cells. Now:
- Each individual cell shows 3.2 to 3.3, all four
- But instead of showing 13.6 volts (prior recording) it only shows 6.6V

??? Any hope? Do I just replace the two cells that were shorted? Confused because they both still show 3.3?

Check your wires. Maybe fried one. Also check your terminals and connections for carbon and pitting.

If each cell shows 3.2v-3.3v, then chances are they are fine. I would bet the BMS is toast if its only showing 6.6v.

No BMS at all. Just a charger with me watching it carefully. (Daly on order). The cells were all about 3.3 with total voltage at 13.5 when I shorted it. Snap, crackle pop. Slightly burned one side of a bus bar. I took the lower one off and moved it over to the #1 & 2 cells. DUH!
Totally baffled how they could all show fine individually now at 3.3 but 12 volt reading switched to 6???

To be blunt: Don’t fuck around with cells in series without a BMS. Just don’t. I’m guessing a BMS wouldn’t have helped with whatever happened, but still. Disassemble your battery until the BMS arrives.
If you measure each cell with a voltmeter individually and they all show 3.2 to 3.3, the cells are probably fine. While you wait for your BMS to arrive, do some reading through the forum. There’s lots of good info here.
When the BMS arrives, reassemble into a full pack, and if there are still funky readings, come on back and we’ll all try our very best to help you out.

Thank you. I will.

Wesubi said:

No BMS at all. Just a charger with me watching it carefully. (Daly on order). The cells were all about 3.3 with total voltage at 13.5 when I shorted it. Snap, crackle pop. Slightly burned one side of a bus bar. I took the lower one off and moved it over to the #1 & 2 cells. DUH!
Totally baffled how they could all show fine individually now at 3.3 but 12 volt reading switched to 6???

Click to expand...

That top left terminal looks like there is insulation between the bus bar and terminal. Can you check if it's making sufficient contact? Cut some back to be sure.

GOOD eye! Unfortunately, changing it didn't make a difference. I am so puzzled why the battery voltage reads 6.6. Tested tester on another 12v and it read fine. Seems like something must have broken inside one of the two shorted cells that somehow miscommunicates? But then why do each of them read 3.3? Over my head.

Can you step up through your cells with the multimeter to see where the problem is? Negative Cell #1 - > pos #1, 3.3v (presumably), then neg #1 to pos #2, should be 6.6v. Does neg #1 to pos #3 also read 6.6v? It should be 9.9v.