I’ve got an old 12S3P pack from Onsra. Original to my board. It died several months ago. Board just stopped charging or powering on. Swapped the battery out with a new one and the board worked fine.
Would like to test and possibly salvage this and use it for another build. Currently measuring 49.6V. Maybe the easiest thing to do would be to swap the BMS out? Please advise.
Thanks!
if you’re able to check each p group im willing to bet one of them is dead
How do I check each P group? There a good tutorial anywhere?
I’d start at the battery basics thread. But imo if you don’t know how to check the voltage of a p-group, salvaging the battery is not in the realm of possibility. It’s inherently dangerous even when you have the requisite knowledge.
Give the pack to a powerwaller for salvage.
Id recommend you send it to one of our pro’s to have it diagnosed and see what options there are for it, if anyone is willing. Better than spending money on tools for a possibly dangerous and possible useless job. If you do decide to do it yourself, read up plenty of tutorials.
Alright… I’ll go read up on battery construction… would I really need to buy anything just to swap out the BMS? Figured it was just soldered to the battery. Not sure if they are typically or required to be spot welded.
I dont know, i dont build batts, but i do know how easy it is to make a little mistake and almost burn my house down 
which is why i advise you make sure you know what youre doing first.
That said, dont be scared of the battery, just treat it with ita due respect. And if you do go on to start building them too, hell yeah!
I grounded on something in my board when working on it a little while ago and created a nice little blow torch and melt an x90 connector. Luckily I was able to pull the loopkey pretty quickly.
I’ve got some experience swapping an ESC out for a VESC, soldering, simp level experience of eletrical theory… lol. Was just thinking this would be the place for guidance. Guidance is: go read. Probably the right advice though…
Battery building is probably the steepest learning curve in Esk8. In order to even approach learning it, you have to start w the basics. Once you understand the foundational stuff then you can progress, ask questions, look at other battery builds etc… etc… walk before you run so to speak.
The reason for this is that it’s dangerous. Like reeeeally dangerous if you fuck up. Like burn down your house and hurt and maybe kill people dangerous. We don’t take it lightly and neither should you.
dont think a p group could be dead. 49.6v is almost full charge for a 12s pack.
I’d be willing to bet it’s either a) a broken weld or welds leading to an overvoltage shutdown or b) a problem w the bms.
My money is on this. Those BMS have a tendancy to fail so easily 
tho if one pack is dead and 11 are full, it probably wouldn’t pull the voltage down super far, but ya i did notice it’s pretty close to full full charge
where would one source this BMS anyway? it looks proprietary.
I understand they can be quite dangerous and have been storing it in the middle of a room in my basement with a concrete floor due to probably excessive paranoia. I will read up until I have a better understanding of battery building, standard configs, BMS’s, the “logic” of the flow of electrons, etc. so I can ask some more informed questions.
I frankly didn’t think it would be that complicated. If I could just swap this OEM BMS with a different one, that would confirm that’s the issue. And they are cheap. I’ll look at the voltage of the p-groups first… unless you think I should do something else?
With all the chatter, I would think someone here could point to some material that they learned with. Tutorials, books, YT videos, etc. Like… what are some good ones that are informative.
Thanks for the input. 
RTFM is the best advice in this case but that shit can be hard to find here (and often it rubs me the wrong way) so here’s the rundown:
do you have room for a larger BMS in your board? If so you can use something like a DALY or a xiaoxiang smart bms. Wiring one of those into your pack would be easy, you just need to replace the old balance leads with the new ones that come with the new BMS and attach the new BMS to the negative side of the pack.
On those types of BMSs, the PCB will be labeled with a 0 - 12 on the balance lead connector for 12S and 0 will attach to the negative pole of the first group starting from the negative side of the pack (group 1). wire 1 would then go to the positive side of group 1, then wire 2 would go to the positive side of group 2, etc all the way to 12.
then you would connect the wire from the BMS labelled B- to the battery’s negative side and the C- wire to the charge port.
Because you don’t want your brakes to fail and the general sentiment here is “burn the board to save the life”, we generally don’t use the discharge protections from the BMS for the main outputs. It will interfere with the brakes so the BMS B- wire and the pack’s main output wire on the negative side will both be soldered to the pack in the same place, putting them in parallel, or a “discharge bypassed” state.
yes obviously shorting will cause bad things but don’t let these guys scare you off. I set plenty of things on fire in the beginning. Keep an extinguisher handy for everything around the pack, because you’re not going to put a pack out with an extinguisher. It’s for everything else. But more than likely the worst that will happen is you’ll melt a wire or blow a hole in a tool and the cells will be fine.
for more reading, check out this category:
and this thread in particular is full of good clean battery porn going a ways back
I’m gonna respectfully disagree LHB on a couple of points @BallisticBullocks but first, I wanna clarify that I don’t think anyone is trying to scare you off. If anything, the community collectively tries to impress upon people who wanna jump into battery work that there are very real risks. Battery fires are a risk to life, limb and the hobby. If ur aware of the risks going in, then you can take steps to mitigate those risks. Going in blindly w assumptions that something is gonna be easy is not the right approach imo.
I don’t think swapping out a bms in easy at all for a beginner. It’s not modular, and requires that the individual knows how to identify cells 1 through 12, has to be able read and understand a wiring diagram and must know some tenets of battery safety (e.g. insulating groups, routing balancing leads safely). Plus, soldering. I think @BallisticBullocks said his soldering was a bit weak.
This is very true, unfortunately. We typically recommend people to read the battery builders thread in its entirety but it’s a fucking beast and you’ll go cross-eyed. It took me months of reading and taking notes and shit and the thread was half the size at the time.
We really do need a better battery wiki on here. Maybe I’ll take some of that on in the off season…
@Lee_Wright has a great video series detailing all the steps of a battery build. Check it out:
How To Build An Electric Mountain Board - Making The Battery Part 1 - YouTube Part 1
How to Build An Electric Mountain Board - Making The Battery Part 2 - YouTube Part 2
Last, I’m happy to help you troubleshoot the battery once you’ve familiarized yourself w the battery basics thread. You can also bring it to the battery builders thread and have a bunch of experienced builders (more experienced than me) give their $0.02. Share lots of pics. Ask lots of questions. Listen to advice. If ur unsure if something is safe or not, assume it isn’t until u hear otherwise.
Cover your connections when they’re not being worked on
Once u read the battery basics thread, I’d start by clearing your work station of anything metal, taking off al the insulation on the battery, taking lots of pics from all different angles, covering those connections again w some painters tape, and then posting the pics in the batt builders thread. We can help u sort out the p-groups and then guide u on where to measure voltages from to see if you’ve got a dead group, if one of your groups has broken welds, or to diagnose a potential bms issue. Cheers
You’re probably right on both points, it was 2 something in the morning and I had no business trying to help people in that state.
Thanks for the detailed response. I’ll watch those vids and familiarize myself with the basics. Probably take me a few days. I’ll order a new fire extinguisher as my current is 10 years old probably.
