Battery teardown, seeking help to reset the battery


heikki

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My first post here, and not even sure if it should be on Builds -section or here :) Just got a hint to come the this forum to check if anyone can help.

So I have a build where I'm installing Stark motor to a small Suzuki moped from the 80's. Initially with a 1,5hp 50cc engine :)

I bought a Varg motor with VCU and wiring. According to the seller they are from a running bike. Then I got a battery from another person. He told the battery is broken and he's received another one on warranty. I work with Tesla batteries (repair them) so I though I could take a look inside the Varg battery and see if I could fix that too.

Before I started to open the battery I tested my setup. I had bought all the remaining electrical components form Stark (including the Android phone) and connected everything together. All I get is the red light on the power switch for couple of seconds. I've tried all the tricks I've found online to reboot the system (including holding the power button for a while, re-plugging the battery cables several times etc...) without any luck.

So I opened the pack and found four cells are shorted and completely empty. The pack is 100S4P split into two halves. Total of 400 21700 cells. There's a BMS board on both halves of the pack that monitors the voltages and balances the pack. I though the empty cells might prevent the pack from starting so I bypassed those and made a temporary fix to replace those dead cells with some Tesla cells I had and balanced the voltage to match the other cells of the pack.

I was hoping this would do the trick but I was no lucky, still getting the red light. Now I believe the battery may be in some sort of fault state and would require manual reset, perhaps with some service/diagnostic tool - similar to what car manufacturers use. Also Tesla packs need to be cleared from some latching alerts after repairing them.

I heard some people here have some background information on how these packs have been designed and perhaps could confirm if my assumption is correct? Also I suppose there are no tools available to diagnose and reset the pack/clear the possible alerts.

In my build I need to build my own pack with fewer cells to make them fit on the small moped frame. I was hoping I could have used the Stark BMS and VCU since they are the only ones that I know are able to control the Stark inverter.

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Both halves have their own BMS board

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Dead, shorted cells.

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Cells are glued to the case from the negative end of the cell. This will cool down the cells when the air cools the battery case. I assume the battery might overheat on a long ride under heavy load.
 

heikki

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Just saw the old post from 2019 regarding the Alta pack teardown - a lot of similarities on the pack design!

 

DaveAusNor

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Thanks for sharing! Good to start building some knowledge on some of these parts that may need some DIY fixing once bikes are out of warranty.
Seeing as you've ordered a phone, I assume you've spoken with Stark. My understanding is that the phones is locked to the bike via the VIN, so this probably includes the phones ability to power the system (motor+battery). Did you buy the motor and VCU from Stark or second hand? If second hand you may need the old owner to transfer ownership to you.
 

heikki

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A whole P group is shorted. That battery half is pretty much useless.
What do you mean with "whole P group"? You mean the four parallel cells? I have isolated those by cutting the cell wires and temporarily replaced with good working cells which are charged and balanced to the same voltage as others. Right now they are external to the battery and wired to the PCB. I'm not aiming to drive with this setup, just see if I can get the motor spinning.

DaveAusNor said:
My understanding is that the phones is locked to the bike via the VIN, so this probably includes the phones ability to power the system (motor+battery). Did you buy the motor and VCU from Stark or second hand? If second hand you may need the old owner to transfer ownership to you.
I bought the motor and VCU second hand and they've both been in the same bike and running with it. He had bike with two motors, VCUs and batteries. The previous owner has already sold the bike so he can't transfer ownership. I haven't been able to connect the new phone with the VCU, the phone can't even see Bluetooth of the VCU so I assume VCU is not starting properly.
 

fsfs

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What do you mean with "whole P group"? You mean the four parallel cells? I have isolated those by cutting the cell wires and temporarily replaced with good working cells which are charged and balanced to the same voltage as others. Right now they are external to the battery and wired to the PCB. I'm not aiming to drive with this setup, just see if I can get the motor spinning.


I bought the motor and VCU second hand and they've both been in the same bike and running with it. He had bike with two motors, VCUs and batteries. The previous owner has already sold the bike so he can't transfer ownership. I haven't been able to connect the new phone with the VCU, the phone can't even see Bluetooth of the VCU so I assume VCU is not starting properly.
OK, this time I read more carefully.

AFAIK (since i worked on the software which was a while ago) there is no fault storage or remembering. So if it was just the cells, replacing the P group should do it.

I cannot be sure, but my guess is something wrong the the BMS. That the BMS discharged the P group all the way to zero volts.
 

heikki

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I cannot be sure, but my guess is something wrong the the BMS. That the BMS discharged the P group all the way to zero volts.
I guess that's possible, if balancing is not working properly. I'll check if it keeps discharging the cells I connected.

Anyway I think my next plan is to try to connect everything to a fully functional pack to see if it starts with that. This way I'd know if the issue is with battery or something else. I don't have that pack myself but the guy who sold me this failed pack has one.
 

Beagle

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France
You could try to contact your crazy neighbors at critical.se, doing lots of wild stuff like go kart Varg, very complete videos from the setup and everything, they might be helpful.

 

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