Strats for recovering a battery that won't charge

I'm picking up a bike tomorrow that sat over the winter and now won't take a charge. At least I'm saving more money on it.
The pack is 72v 48ah, so I'd like to recover it if possible. Worst case is that I build/buy a new pack and be annoyed about it.

Anyhow, I'm considering options for recovering it. I figure I may need to shuck the battery cover and get my balance charger on it.
It's a 72v pack, so probably 20s. Dunno if it has balance leads, I figure I can add them and troubleshoot half the pack at a time.
My balance charger is good for 12 or 14s, I need to go look. I think I can whip up some 10s adapters and work with that.

I haven't had to test/troubleshoot packs before. Any tips are welcome!
I am open to buying a new balance charger, my current one has been on the shelf for a while.

You need to find a fire hall that takes batteries and give it to them. Tell them its non commercial, that its from an e-bike.

find out what cells are in it
ive been playing with desulfating

https://endless-sphere.com/forums/viewtopic.php?f=14&t=109601

and am starting think that cells with graphite-si anodes can be desulfated

markz said:

You need to find a fire hall that takes batteries and give it to them. Tell them its non commercial, that its from an e-bike.

Click to expand...

Really? It's not dead until I get into the bms leads. I have no issue with shucking the pack. And it could be a bad charger or just a triggered bms.

Anyhow, I've ordered a grin charger and figure I'll just have to go ahead and peel the thing once I go grab another multimeter from storage.

OK.
My Grin Satiator showed up a day early, and I spent a few minutes whipping up a XLR to XT60 adapter (lucky I had one in my old parts bin) I will say that the Satiator is a nice piece of kit. XLR is a bit of an odd choice for a charging connector but sure.

I programmed the Satiator for an 82V charge to be a bit gentle.
Hooked it up (yay I got the pinouts correct - no sparks)
Turned on the Satiator - no voltage.
Tried sending a charge down the discharge connector again - no voltage.

Broke out my knife and gently, oh so carefully removed the shrink wrap. Had to slice open several bits of fiberglass strapping tape and peeled back the fiberglass board until I located the BMS up top and exposed the connectors.

After some pondering, I finally grabbed some wire and bridged the main in/out wiring of the BMS.
Suddenly - Voltage! The pack was just below 42v. So, around 2.1V per cell.
Gave it a moment and let off the bridge - no joy.
So I connected it again, and realized the Satiator has a neat feature - trickle charge up to minimum voltage. (Saw the setting, just didn't realize what it did at first)
Held it closed for a minute and let off again - and it kept charging!

So...
I think I got lucky here - the BMS was performing as expected - LV cutoff protecting the pack.
2.1V/cell isn't ideal, but I believe it's quite recoverable.

After 25 minutes, the pack is up to 57v (so 2.85v per cell) I think this is a good sign.
I'm looking forward to keeping an eye on this thing as the evening progresses.

willo said:

XLR is a bit of an odd choice for a charging connector but sure.

Click to expand...

It's durable, easy to handle, and good for as many amps as the Satiator can source, and its' actually not all that uncommon to find on OEM scooters/bikes (at least it used to be that way).

They do sell adapters for most of the common charging ports, too. If you don't ask for something different, it typically comes with one for anderson powerpole PP45, along with the TRS-jack for serial-USB connection for programming, fw updates, etc.

THe XLR also has three pins, which means you can use the third pin for temperature sensing on NiMH / NiCd packs (though IIRC for some reason you can't enable it in anything else, though it would be a handy thing to be able to do for charge shutdown). Grin also uses that third pin as a data line for some OEM pack chargers so it wont' initiate charge without the right pack ID. (I suggested they enable DIYers to change a setting in the firmware to allow it to be used to detect a resistance on a pack's third pin to ID the pack and automaticlaly pick the right profile, but they don't trust this method enough to allow it's use).

Yeah, the pins are a decent size. I think my complaint would be that they've used the shield pin for positive - so my acutal XLR cable that I sacrificed for my adapter is using the outer copper shield of the cable for power transmission.

Standard XLR pinout:
Pin 1: Ground/Shield
Pin 2: Positive/Hot
Pin 3: Negative/Cold

Pinout of (I presume standard) ebike xlr chargers:
Pin 1: DC+
Pin 2: DC-
Pin 3: Signal

Well, whatever pin function they use is dictated by what was in common use at the time, so that it could be directly plugged into those packs.

The pin function in common use would be whatever evolved a long time ago from Chinese scooter and ebike manufacturers deciding to use whenever they began misusing these and the many other misused connectors out there, like the IEC AC plugs being used for battery connections (including some of them that use them on the battery charge port input, just inviting people to directly plug in the cord from the wall instead of a charger....thankfully nowadays most of them use the socket that won't let the wall cord plug in, but there *are* versions of the wall plug that *can* plug into them, still).

Even though almost nothing in ebikes and scooters has any real standards...those XLRs do, more often than not, end up wired that same way.