Splicing BMS leads?

My BMS went tango uniform on me. It’s an original ANT-bms, getting a new one from @LithiumGods , but I believe the connectors are different on the new ones.

Any reason I should avoid splicing the individual cell wires?

connectors are different. The problem with splicing is that the bms is sensitive to wire resistance. You will have to make sure connections are good and don’t make any of the wires longer than needed.

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Thanks. Not what I was hoping to hear, but it makes perfect sense.

Here’s the failure info for the record, maybe it will be good for something someday.

  • GEM worked fine when parked.
  • plugged in to charge, got partway through charge and something failed.
  • Initial symptoms were that the GEM won’t turn on, and then the battery charger errors w/ code 2 “No battery detected or voltage too low to start”
  • BMS displays correct pack voltage, but no cell voltages.

Pack voltage is correct as measured with a handheld DVM.
Individual cells all measure 3.91v each at the connector going into the BMS.
No blown fuses I can find, including main pack fuse.

Not sure how a pin would have wiggled lose with the cart off and parked, and I was manually testing voltage at the pins, but I’ll double check the connectors when I get back. (@Inwo suggestion)

It’s an old ANT-bms. Maybe even one of the originals, not perfectly sure, but it’s got some years on it.

Can’t manually start the fets via the firmware, even after a full reset to defaults and reprogram.

Only board level anomaly I could see was a few partially corroded traces - Haven’t had a chance to ring these out yet. Be nice to know if this is the problem as I could jumper or patch them, but that would just be a temp fix, my experience with failures like this is that somewhere else on the coating will fail soon enough and be back to where we are today,

@LithiumGods @Inwo - Sorry I didn’t have time to review these closeup photos until this morning, I shot these a few days ago before I left on travel, but didn’t notice the damage on an unmagnified inspection.

Those didn’t happen overnight either, and, I’ve seen much worse.

@AssyRequired - any thoughts that maybe Dave and Michael and I haven’t already talked about?

To me, if this is the failure, a new BMS is still the right answer because, who knows what is going to go out next…

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Wow- That is interesting. Perhaps the board was not cleaned properly before the green coat was applied?

Nanites? Those are pesky little critters!

If LG has not shipped yet I have an unused ANT in my project box. It was bought earlier in this year so I may not fit your older harness either.

What has changed on the connectors? If it is just plug size and not the pins, It it worth swapping the little sockets out of one plug into the other?

Probably not without effort, but worth looking at. It seems like there is a reason swapping the wires out on the batts is a stumble.

Just thinking out of the box.

Old bms all used 2.54mm jst-xh connectors.
Now ant uses Chinese 2.0mm hy or jst-ph.
Never know which one. They sort of interchange, pin wise, plastic needs trimming.
Not a good idea, but it works.
There are generic pcb 2.54 to 2.0 pitch
Solder sockets to fit old xh bms wires.
Solder new bms leads to pads.

Very similar to how I adapt the HY samsung battery leads to the JK bms still using jst-xh.

@AssyRequired - thanks for the offer my friend, I suspect whatever model you have likely has the same connectors as the one I already purchased from Michael.

Until I’m back home and can look at everything, it’s hard to gauge how much work I got myself into.

The part that sucks is this is the only vehicle I own (besides a busted '02). So, I have to get it running soon.

Let me look at my little plug. If I can find the trip to get the pin out it sounds like its just a matter of a holder swap.

I have not used these JK active balancers much yet, but I would think that if you spliced the wires at the place where the old BMS connector was (cut it off), kept all the wire lengths the same and soldered them, not crimp that your additional wire resistance would be minimal and equal across all the leads…

Just my .02 - could be wrong

No, they are different.
Cut, strip, twist, and solder. It will be fine. Wire length is not critical in the short length we are doing. Using full 1 meter length of both might be pushing it.

@Inwo @MikeKC

I wasn’t planning on dry crimps, my bad I neglected to raise that point. I was thinking either manual soldered butt splices with heat shrink covering or giving something like these a try (they have been on my shelf for a year and have yet to use them).

I’d run the wires all the way to the cells, but I just don’t know how long it would take and if I can even access them / the connectors without either taking the pack out or lifting the bed off.

What is the base of your pack?
(What cells is your pack based on?)
(What are you packing under the seat?)
(What scoots your scooter?)

Don’t use those things from Amazon, been there done that - Fail…

Thanks Mike, I’ll skip them then. Save them for fixing xmas light strings and ■■■■.

AR, It’s a 2p22s chevy volt pack, like 120Ah/16kW. It’s massive because of the older technology. Runs the whole length of the battery tray on a '10 eL, not a lot of vertical clearance to get to the connectors,


Decided to use a JK bms to save the PITA of rewiring or splicing the balance leads to the larger plugs.

…neglected to check the balance amperage on the BMS though… stock setting is too high for this pack.

Talked to Dave, after… Looks like I blew a shitton of the individual cell fuses.

F… looks like I might have to take the pack out after all anyway to repair the fuses. Supposedly not hard, just tedious. Getting it out to work on… that’s another story
(the VOLT packs are huge and heavy…)


Ah, dude that sucks.
I would have never thought about the balance amperage either.
The JK uses 2amps by default correct?

1 amp by default. I didn’t know bolt packs had those small fuses.

Shyt happens. You’ve been a great help Michael, the volt packs seem far and few between because of the size and weight so how would you know.

@MikeKC apparently these blow at 0.2amp if I understood Dave correctly.