that looks familiar
Holy hell, it’s insane to me that someone was actually willing to sell something of that “quality”.
Joints look fine. Could be better could be worse. They’ll probably be functional enough if they passed the pull test. Only concern would be this wire here:
You stripped the wire a bit too long and you’ve got a live wire attached to a pos terminal hanging out right by the shoulder of a cell. I’d shove some fish paper in between the exposed wire and the cell if I were you.
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Can anyone tell from just this if the BMS is being bypassed for discharging? Or if it isn’t, if this BMS can handle high discharge?
I don’t want to tear it down further if I don’t need to since I don’t have any of the weird smelling yellow tape on hand to replace anything I have to cut through to open it up further. So far I cut through the very outside tape where it won’t matter which tape I close it back up with plus the heat shrink wrap alone can hold the plastic board in place if I decide to not tape it back.
I don’t really want to use painters or packaging tape on anything directly in contact with the battery though since they don’t have a high heat resistance
Looks like discharge is through the BMS
Just double checked some of the diagrams and you’re right. Thankfully the pack was built with the negative output facing the outside so it won’t require significant tear down to reach.
Is there any standard wire gauge for connecting the negative to the p- on the bms though? Since I know I’ll need to add that back.
I have 26awg wire and then 12 awg but the 12 is overkill and will be hard to fit in nicely. The balance wires all have larger 22awg on them though so I’m worried the 26 is too small
Here is this if it helps/matters:
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Looks like these wires could rub through eachother with vibration.
AFAIK this is a no-no in good pack building
This pack has been in use for a while already and there are 0 signs of any wear on any of them. This battery is used and 5 years old. Plus there isn’t really any way for them to move around on their own with how rigidly built it is. I can throw some liquid electrical tape on them before I close it up to be safe.
But that is only AFTER I’m done with all soldering. That shit is flammable when still wet 
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hot glue would probably be fine and much less of a pita to deal with
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No, that is a 20A BMS. For a small ebike that would be fine I guess.
https://de.aliexpress.com/item/1594873979.html
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It also doesn’t smell as bad. So I am going to use it instead.
I didn’t think it would be, but wanted to ask to make sure first. I’m working on bypassing it now
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Do you know if the cell groups can handle more than 20A? If not there’s no sense in bypassing it.
What cells are they?
Too late now. I’m not about to undo and redo stuff. Plus I’ve seen more than enough on here to know it is safer to bypass the bms so it can’t cut out on you
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It’s only safe to bypass if you have another way to cut off the discharge.
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I have a loop key that will be added as well. the XT 90 is already epoxied into my enclosure but just not wired up yet.
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A loop key is a good idea, but doesn’t prevent the battery from being over discharged. We use the VESC for that purpose, so bypassing the BMS is common around here. If you don’t use a programmable ESC though I strongly recommend to not bypass the BMS.
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This is for my 2nd board with a VESC. I wouldn’t even bother to bypass the BMS for an ESC since they can’t handle and won’t pull enough current for the BMS to shut itself off anyway.
Specifically for the standard Ling-yi ESCs. I have no idea if any company has bothered to make high current ESCs or not.\
Also my main board will eventually get a VESC (I have one ready for it currently) and only when I install it will I bypass that battery’s BMS
So I properly fixed the sensor wires, or at least fixed them as much as possible without fully taking it apart and soldering new wires on. So there ended up being some areas with overlap that couldn’t be fixed but there is now hotglue to stop them from ever shorting out.
Before:
After:
I might have added more hot glue then was needed but at least the sensor wires aren’t shoved between the cells anymore. Yes, some were wedged into that little gap. Also added some liquid electrical tape on the first group since the shrink wrap on the cells was a bit thin at the top of the cells. Soldering to that group melted it and made it worse so I coated the cells to make sure it was covered. The brush in the stuff is large so I just coated all the cells at the top. Only one cell really needed it though.
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gross, but proper
Hot glue is a bad idea for this, once the battery warms up it can undo your work. Some kind of cement or a construction adhesive is a better option
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