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Battery module help!
Posted: Sat Jun 10, 2023 4:18 pm
by PatrcioEV-ATX
I have Tesla batteries out of a B250e, and they are working just fine, except that lately the voltage sense wires have been coming loose. This makes my BMS useless and I can't charge.
I tried soldering them back to the plates, but I'm just using regular electronic solder and it is NOT sticking to the metal that connects all the individual cells. Do I need a special kind of solder? Any other suggestions of how I can connect these sense wires? I don't want to have to take these battery boxes apart again.
Re: Battery module help!
Posted: Sat Jun 10, 2023 5:31 pm
by arber333
PatrcioEV-ATX wrote: ↑Sat Jun 10, 2023 4:18 pm
I have Tesla batteries out of a B250e, and they are working just fine, except that lately the voltage sense wires have been coming loose. This makes my BMS useless and I can't charge.
I tried soldering them back to the plates, but I'm just using regular electronic solder and it is NOT sticking to the metal that connects all the individual cells. Do I need a special kind of solder? Any other suggestions of how I can connect these sense wires? I don't want to have to take these battery boxes apart again.
Well you can try using plummers paste. When you put small ammount onto the nickel tabs and apply solder it will pull solder towards it and act as a catalyst. The problem is they have to be copper or nickel. If tabs are from aluminum you are out of luck...
Then you might solve the problem using alu wire with AC TIG welder.
Re: Battery module help!
Posted: Sun Jun 11, 2023 7:03 am
by Clanarn
A small blind rivet and cable lug might work.
Re: Battery module help!
Posted: Sat Jul 08, 2023 1:26 am
by leftcoast
Ive used copper tape with conductive adhesive. I put down about an inch of tape then quickly solder the wire onto it. a little hot glue on top for good measure..
Gadget
Re: Battery module help!
Posted: Sat Jul 08, 2023 9:23 am
by EV_Builder
Maybe somewhere on the edges threading M2/M3 hole/bolt?
Would go with something durable and have risk while you are at the job, not later something comes loose...
TIG on alloy is allot of heat and IMHO will end in disaster..
What ever you choose fixate it on multiple points.
Re: Battery module help!
Posted: Sat Jul 08, 2023 9:47 am
by muehlpower
how about a spot welder like this one? Could also solve the BMS cable problem with the M3 modules.
https://www.ebay.de/itm/354684344125?ha ... Sw9mVkJVss
Re: Battery module help!
Posted: Sat Jul 08, 2023 12:49 pm
by arber333
"Welding 0.1 to 0,12mm nickel strips..."
Clearly Tesla bus bars are much thicker than that.
Re: Battery module help!
Posted: Mon Jul 10, 2023 1:25 pm
by PatrcioEV-ATX
I fixed these by drilling and tapping very small holes right next to each wire and screwing in flat head screws that clamp the wire to the plate. Got the car all back together on Saturday and the BMS was happy. Was able to drive and charge. Fingers crossed!
Re: Battery module help!
Posted: Tue Jul 11, 2023 7:23 pm
by nubster
PatrcioEV-ATX wrote: ↑Mon Jul 10, 2023 1:25 pm
I fixed these by drilling and tapping very small holes right next to each wire and screwing in flat head screws that clamp the wire to the plate. Got the car all back together on Saturday and the BMS was happy. Was able to drive and charge. Fingers crossed!
Nice! Did you use anything to prevent the screws from coming loose over time? FWIW, you can get electrically conductive Loctite or epoxy. I think even a dab of non-conductive epoxy over the tops of the screws would go a long way. You could drill another small hole adjacent so the epoxy has something better to grab onto than just the smooth aluminum. I'm super paranoid about battery connections coming loose over time. Let's just say I have some experience with such things.
Re: Battery module help!
Posted: Wed Jul 12, 2023 4:22 pm
by PatrcioEV-ATX
nubster wrote: ↑Tue Jul 11, 2023 7:23 pm
Nice! Did you use anything to prevent the screws from coming loose over time? FWIW, you can get electrically conductive Loctite or epoxy. I think even a dab of non-conductive epoxy over the tops of the screws would go a long way. You could drill another small hole adjacent so the epoxy has something better to grab onto than just the smooth aluminum. I'm super paranoid about battery connections coming loose over time. Let's just say I have some experience with such things.
I didn't and I share your concern about the long term. But at this point, it's done and back together so I'll deal with it if it becomes an issue. Fortunately, I made several small installation changes because of this that will allow me to more easily access the front battery box in the future - should need arise.
Re: Battery module help!
Posted: Wed Jul 12, 2023 6:26 pm
by nubster
Right on. Glad you're back up and running!
If I may make one final suggestion: Simply adding some "witness marks" with a paint pen or the like would allow you to easily detect if any of them are coming loose just by visually inspecting. Would your changes to access the battery box allow you to add some marks quickly?
Either way, I'd suggest periodically checking on them just to be sure. The issue that may arise could be the car catching fire during the middle of the night. A garage down the street from me recently
caught fire due to a loose e-Bike BMS connection, which was only 48v (according to my neighbor who knows them). I don't mean to be a worry wart or annoy you about it, but I think it's important to stress the safety aspect.
Re: Battery module help!
Posted: Thu Jul 13, 2023 10:17 pm
by PatrcioEV-ATX
nubster wrote: ↑Wed Jul 12, 2023 6:26 pm
Right on. Glad you're back up and running!
If I may make one final suggestion: Simply adding some "witness marks" with a paint pen or the like would allow you to easily detect if any of them are coming loose just by visually inspecting. Would your changes to access the battery box allow you to add some marks quickly?
Either way, I'd suggest periodically checking on them just to be sure. The issue that may arise could be the car catching fire during the middle of the night. A garage down the street from me recently
caught fire due to a loose e-Bike BMS connection, which was only 48v (according to my neighbor who knows them). I don't mean to be a worry wart or annoy you about it, but I think it's important to stress the safety aspect.
Noted. While it's easier to get in, it's not easy.