Battery: Bin or Keep?

How-Tos & Esk8 mechanics Esk8 Mechanics
1

Hey All,

To start with, i realise I’m asking a question I probably already know the answer to. But i want to ask it anyway.

Today I did something I’ve been meaning to do for over 12 months. I took a peak inside a battery I recieved as part of a part complete at the beginning of 2020. (12s4p VTC6)

I knew it wasn’t the greatest build from this balance lead birds nest but aside from that… It looks neat.

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IMG_20210814_1535463648×2736 1.81 MB

So, this battery has been stored for most of the time I’ve owned it but I have ridden with it a number of times. It charges to 50.4v and seems to take a relatively normal time to balance (Bestech d140 BMS, nothing smart), range is completely normal and generally speaking, electrically it functions perfectly well. I have verified cells are balanced ok.

However, it’s construction is…questionable. From the outside the pack is well wrapped and perfectly square but on the inside… I’ll let a picture do the talking. (All it took was trying to peel back one corner for me to sigh and have to make this post - which I knew I’d make before I even looked in the pack)

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(Unfortunately at this point I should habe taken more photos as I dug slightly further in, but I was concentrating and forgot - this photo tells you pretty much all you need to know! I didn’t go too far because the tape…oh the tape. )

The good:

  1. Cells look to be glued together as standard

  2. Whilst unconventional, it appears to be very well wrapped in Polyethylene Cloth Tape, I’m talking multiple layers. This stuff is waterproof :joy:

  3. Was shrunk wrapped well and had multiple layers of shrink…not that it’s particularly challenging… I’m clutching at straws

  4. Spot welding & Soldering looks… Not bad… Quality wires used and appropriate thicknesses

  5. The balance wires look to come out of the pack in a flat arrangement and then just be a birds nest outside the pack

  6. Fishpaper rings on positive terminals… That’s a solid +1 point

Aside from the non standard material choice and balance leads… The battery looks well put together… As well as it can do, considering.

The bad:

  1. Nickel corners are sharp (from what I have seen)

  2. I am pretty sure balance wires will be crossing (although they may be seperated… It’s hard to tell)

  3. The tape is so sticky…I couldn’t deconstruct the pack at any normal working pace… I was planning to redo it and put a smart bms in… Didn’t get that far.

  4. Lack of fishpaper by the looks of it… Although this battery builder clearly thought the tape was equivalent judging by how it was used

So the question is as follows.

Battery: Bin or Keep? Or more to the point, what would you do in this situation? Is it worth spending an entire day taking it to pieces and we wrapping with fish, smart bms etc etc etc

My brain says it’s dangerous, dispose. But then equally, logically it’s a perfectly working pack (and has been for a year or two) with very unconventional build methods that appears to have been put together… *methodically and with care *… Even if without top notch standards…strong text

Thanks for reading that mess!!

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any chance you could open it a bit more so we can see how the pgroups are isolated exactly? and also how they’re joined in series?

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Send all bad packs to @cfelzien for tear apart and recycle. Is that some kind of cushion tape?

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Sure, will post photos tomorrow, I have a feeling everything is isolated with glorious amounts of tape from what I have seen so far. :rofl: As for series connections, judging by the sides of the pack, I think they’re connected with wire, but will find out tomorrow during part 2 of the tape adventure, if it’s one long nickle strip that’ll be game over.

Tbh I have everythinf required to re work it on hand, by the time I get the tape off… I might as well re work the damn thing.

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Lol I’m across the pond man, I wouldn’t dare send this by any form of post…

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I would rework it … the send bad packs to cris is just in general…

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Touché

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8

do it. Meticulously. And reflow those solder joints while you’re at it.

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reflowing solder to nickel directly on a cell take some skill and no avoiding heating the cell. Hopes for the best.

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I’ll see how bad it actually is first. Lord only knows what horrors await

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looks like whoever built this pack was thoughtful enough to put at least one of the solder joints between the cells and not directly over them. maybe they were that thoughtful with the rest of it.

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I was gonna say, looking at what OP talked about, it sounds “OK” but not great

I build all of my packs with non-sharp corners on the cell positives, but there are many packs in the wild with sharp corners that run okay

Definitely take pics and look closely - tearing packs down is a royal pain

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I wouldnt bin the pack, i would redo w/ fish paper, snip the sharp edges(maybe put some foam around the back and sides of the pack when in an enclosure. The less it vibrates the less of a chance for the pack to go through the wires), redo the balance leads or at least repin it, reflow the soldered wires ( i recommend using a bit of flux just to keep the cells from heating up a lot, if ur comfortable using it around live packs).

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So… Worse than expected. All series connections apart from the end end are spot welded nickle (multiple layers) . P groups aren’t separated by fishpaper, just glue😩

Only upside is there appears to be fishpaper in the pack (you can see it on top of the far right cell ans far left), looks like it might be used for balance wire routing.

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pick it up by the corner like you would a dead rat and BIN IT.

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If you think the cells are OK I would dissaseble it cell by cell.
Grab a pair of plier and stars remove those nickel strips. For the remnants you could use a dremel to get terminals clean.

Once taken apart its quite easy to determine capacity per cell if you own a cell charger (litokala or alike).

I still have the cells from my first pack, they’re pretty shit by now and gives alot of sag. But I can make some cool stuff out of it that dsn’t need to draw that much current.

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needlenose pliers, and peel like it like a tuna can.

GENTLY. larger cutting wheels are good because you get more precision than say a sanding drum or grinding drum but apply no pressure. high speed, no pressure. veeeery careful.

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