Trying to replace BMS without welding something

So I’m trying to replace my old BMS

With a new LLT BMS

But the problem I have is the old BMS has more wires than the new BMS. Reading some others’ posts about replacing BMS I have more doubt now than confidence.I was planning on just replacing the BMS wire by wire until they were all soldered in place, however, it doesn’t sound like it’s that simple. For one, It sounds like there might be an order you must attack this is in lest you fry the BMS. Does anyone have some insight as to this?

I also have some pics for you guys to look at and let me know if I have bigger issues at hand. The following pic is where a burn hole has come through the top piece of fish paper. It’s not in the picture but it even burned through the plastic “cardboard” that they close up the battery pack with before shrink wrapping it, not to mention the shrink as well. It’s a small hole, about the size of a cigarette burn:

Same burn without the fish paper in the way. You can see over on the right where there is another burn but this one seems to be the “bus” bar that connects that segment of the pack

Finally, we have here another similar burn to the one just mentioned but on a different “bus” bar of a different cell pack.

Referring back to the pic of the old BMS in the upper left corner I see where there are three black wires soldered to a bus section of the BMS. It is labeled P-. The three black wires are the leads to the 1) main power xt connector 2) charge port, and 3) shitty meter than came with the battery - I removed the charge indicator and capped it with a JST connector that is unused. Moving over to the upper right side of the BMS again, there are three wires soldered to the bus bar of the BMS labeled B-. All three wires go from the BMS B- bus to the main negative battery bus, which doesn’t make sense - why not just use one wire?

I am aware that connecting wires in the wrong order of addition can result in a fried BMS immediately. Does anyone have some insight as to what order of replacement I should hit this with? Should I begin by removing the BMS starting with the negative leads and immediately capping each one with some tape or something (so I don’t accidentally short one while I’m working? Or should I start by removing the positive wires from the main battery bus? Or something else entirely???

Is there no way to edit your OP? The title is meant to say WITHOUT welding something…

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click the pencil next to the title
it looks like the pack was shorted while being built and patch jobs were done with solder

I must really be blind because I see no pencil near the title or anywhere else in the post. Even when I hover over it, still nothing.

If the battery shorted during build - or at any other time for that matter - wouldn’t the battery have been useless? Or more likely caught on fire?

no what happened was the nickel vaporised in some places because of the short circuit current burst
that nickel should’ve been removed and replaced or atleast more properly patched with additional nickel
also considering that looks like 4P 30Q, just that nickel is nowhere near enough for the series connections

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OI brosif…that pack :cold_face: why is it the way that it is, so many places where things look burned… you sure you want to mess with it? if you do please have a fire extinguisher on stand by


I think that falls into trust level “regular” maybe ?

Recategorize and rename topics

but maybe not. could be:

Edit their own posts

which you’d think he could do.

yeah you can always edit your own, thats why I had to take screenshot on mine :yum:


Is there an app for this site? I have only used it on my PC. The layout is not the same.

And I’m sorry, I don’t follow on the discussion about trust levels…

…Does anyone have some advice on what to do or not to do when connecting the BMS? Should certain leads be hooked up before others or just pull one wire, replace one wire and I’ll connect the extra’s to the bus bar as they are now? The battery is relatively new. Less than 10 charges on it. It’s been sitting for the past year while I used the other nearly identical battery on my board. But if I don’t do something with it then it useless to me anyways.