I just direct shorted my brand new 135amp LiFePO4 battery - is it toast?

If you cannot wake the bms up , cut the casing open with an oscillating saw and I would replace the bms with an external one. JBD will work great and you will have access to it in future via BT / RS232 / CanBus etc. a Lot of these sealed batteries contain very crappy and under rated bms’s. I have repaired a few for an importer friend of mine.

if you want to make sure the charger is dumb enough, just use jumper cables from running car to your battery. pos to pos/ neg to neg.

wild01 said:

if you want to make sure the charger is dumb enough, just use jumper cables from running car to your battery. pos to pos/ neg to neg.

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Good tip, I tried this just now and unfortunately had no luck. Before I hack the box open I will go back to the retailer where I purchased the battery and see if I have any joy there.

Crowz said:

Get a volt meter and measure volts at the battery lugs.

If volts are 0 then set the meter to measure resistance. If its showing open aka no resistance then something is wrong internally.

Blown fuse, Melted wire, dead bms etc.

Will require opening the battery up to repair it.

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Hi Crowz, Are you able to shed any light why the the little remaining voltage slowly disappeared when it was connected to the DC-DC charger?

And I guess it would be pointless trying again today?

EDIT: The battery before the short was at 95% SOC

To do the testing I mentioned the battery has to be disconnected from all of the existing stuff.

Otherwise you will have readings from those devices.

Also on charge controllers like you posted pics of they sample readings not live so its kind of an average thing on some of them so it doesn't go from x volts to 0 volts in one go. Some do some don't. So I wouldn't trust it.

Use a real volt meter and see if the volts drops instantly or not when you take away the other charger. Also if you simply unplug the charger from the wall or disconnect the chargers power cord it will slowly lose voltage going out not instantly. Again you have to disconnect the lead from the battery while checking it with a volt meter to know for sure.

Crowz said:

Use a real volt meter and see if the volts drops instantly or not when you take away the other charger. Also if you simply unplug the charger from the wall or disconnect the chargers power cord it will slowly lose voltage going out not instantly. Again you have to disconnect the lead from the battery while checking it with a volt meter to know for sure.

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Thanks for the quick reply. I can confirm that I was using a multimeter and testing the battery when not connected to anything. Before trying the DC-DC charger, the reading across the terminals was only 4V and after being on the DC-DC charger, it now reads 0V (again, just the naked battery)

What I was curious about is the loss of the 4V while being attached to the DC-DC charger. I know it is only nominal however having some voltage was slightly encouraging and now having zero is less so.

Doesn't sound good.
With it reading anything at all I would think it would respond to a wakeup charge though.

What all have you tried charging it with so far? When you say dc to dc what is that exactly?

Crowz said:

Doesn't sound good.
With it reading anything at all I would think it would respond to a wakeup charge though.
What all have you tried charging it with so far? When you say dc to dc what is that exactly?

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This post covers the methods that I've tried. As noted in that post, the DC-DC charger is meant to have a BMS wake function.

I thought I’d post an update and thank everybody who had replied. The supplier where I bought the battery was extremely helpful and provided me with a full refund immediately. He even offered a direct swap with a more expensive, however, lower amperage battery, which, with hindsight I regret not taking.

So I did this. I went back to the supplier and figured I'd make them an offer on the dead 135 Ah battery and see If I can performer Frankenstein and bring it back to life. They were happy to take $50 cash as I think it was just going to end up being be a door stop. I figured that if necessary I might be able to buy a new BMS and all would be good.

Now I've just cracked the case and first impressions it all looked neat. Then I noticed a bunch (5) 14-AWG cables going to each terminal. I thought that odd but put it down to an unusual BMS. (note that I'm a novice in this area, those with more knowledge will have picked up immediately what kind of battery this is!)

The cells were nicely wrapped and foam stand offs held the pack firmly in place inside the battery box. I carefully removed all the foam pieces and began to pry the pack out of the box. Let me tell you it was firmly held in place! I used a piece of timber to gently work around each side gradually applying pressure to realise the pack from the case. I figured they factory had just used a generous amount of adhesive to hold it in place as it was never intended to be taken out. It eventually started to seperate and I could begin slide the pack out from the enclosure.

Now when I peaked inside I was surprised to see that what appears to be a thin piece of aluminium was being left behind and tearing off the bottom of the cells. I put on some thick rubber gloves and carefully removed the aluminium from the enclosure and removed the battery pack.

Now it became evident what type of battery I have, it's a 12.8V 135Ah cylindrical cell pack. He comprises of 32 individual batteries each measuring approx 33mm x 140mm. From googling the dimensions, my best guess is that it's a 32140 cell. Using chatGPT it tells me my battery would be 4 sets of 8 batteries in series-parallel to create a 12.8V battery with a total capacity of 135Ah and 1728Wh.

Now that I can see what battery I have, can anyone kindly give some pointers to problem solve why after a very brief short, it is dead and how to diagnose the issue? I have attempted many times to kick start the BMS with various 12v supplies without success. My initial hope that I would was that I would be dealing with four 'normal' cells and I would just purchase a new BMS and hopefully be back up and running. Seeing this pack of cylindrical cells has thrown me a curveball and I don't know how to start trouble shooting.

One important piece of advice that I should seek in the beginning is apart from common sense what are the particular dangers of this type of battery configuration? Also, is the blue wrap holding the cells together or can I carefully remove it?

TLDR: I have what appears to be a dead battery consisting of 32 cylindrical cells. What steps should I take to diagnose why won't take a charge. (I've tried all the normal jumpstarting techniques)

As pictures paint 1000 words here is a gallery showing the guts of my battery.

Things I'd try at this point:
1) measure the voltage across the terminals of the cells them selves, both individually (no need to unhook them from the rest of the assembly) and as a group (from the most positive end to the most negative end of the string, "inside" any circuitry between them and the assembly's posts.)
2) I'd expect them to be close to fully charged. If they're way down, hook a low current charger to them and bring them up to something near fully charged (but stop before you overcharge the "hottest" cells). Do this outside and away from the house. Get back to us about how to deal with it if you have one or more cells that are substantially below the others.
3) If / once the group of cells is charged to a voltage corresponding to a decent state of charge: If the BMS doesn't wake up and turn it on, look at the cable(s) from the cells to the BMS: If they hooks up with, say, one or two plugs with a bunch of wires to them, unplug them (don't bother unhooking any heavy wires), wait a couple minutes, and plug them in again (as close to all at the same time as you can manage if there's more than one). Wait another minute and then check whether there's power at the main terminals.

If that fails, I suspect the BMS is toast and needs replacement. (But get back to us with more details in case somebody else has more ideas.)

Short circuit blues got your LiFePO4 feeling fried? Don't despair, sparky! Check for smoke, BMS whispers, and battle scars before declaring it battery-landfill bound. Safety first, then consult the experts (or mourn the crispy critter).

anthonydsouza said:

landfill bound

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Batteries should never end up in a landfill.

ULR said:

Things I'd try at this point:
1) measure the voltage across the terminals of the cells them selves, both individually

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All 32 cells measure 3.34V

ULR said:

If that fails, I suspect the BMS is toast and needs replacement. (But get back to us with more details in case somebody else has more ideas.)

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I took the heatsink off the BMS and a scorch mark is evident in the pad over one of the transistors. The diode and positive lead also look scorched as well.

anthonydsouza said:

Short circuit blues got your LiFePO4 feeling fried? Don't despair, sparky! Check for smoke, BMS whispers, and battle scars before declaring it battery-landfill bound. Safety first, then consult the experts (or mourn the crispy critter).

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HAHA -definitely short-circuit blues however I don't think all is lost. All cells appear to be fine, just the BMS is toast. Landfill will have to wait for another victim.