Please review my battery pack so I don't make a šŸ”„

I used half inch ground strap: https://www.ebay.com/itm/1-2-BRAIDED-GROUND-STRAP-GROUNDING-TINNED-COPPER-FLAT-BRAID-MADE-IN-USA-PER-FT/302052799754?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

That wire was the smallest gauge wire I had, itā€™s almost as thin as the balance cables that came with the bms

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Never use duct tape or electrical tape for vibration insulation. Use fishpaper or plastic 2 liter soda bottle and polyimide tape if fishpaper isnā€™t available

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Oh, from the picture it looked like you just welded straight through kapton. Thanks for the correction!

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What if you did your square capton tape method then put a fishpaper ring on top of that? Your right that the rings donā€™t take well to the heat. You see some builds where it got carbonized. But capton is not as abrasion resistant as fishpaper.

@RHill051 At first I did not notice anything amiss. But after a second look I think it would be safer if you had some insulation between the P groups. Like one piece of fishpaper or something.

*Edit. Thought about this some more, its a little more complicated. If your glue never delaminated between the P groups it ā€œshouldā€ be fine as there is no movement. If you did go add some fishpaper between the P groups it would introduce more flex into the pack which could create other issues. Maybe just an extra layer of Kapton between the P groups then glue like you have now would be best for your pack design. Somewhat like what @jasonbhuynh has done.

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Yeah it sux that it makes the nickel bend down. I think button top versions are safer as it gives some additional serpation to the negative, but no one uses them as they cost more. :man_shrugging:

Just want to add @TowerCrisis 's diagram here of how P groups could short each other if the insulation between them became compromised. image

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Wow now I want to inspect my packs again :sweat_smile:

@legend27 iā€˜ll link your question here, maybe somebody of the experts can give you a feedback

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Do you know what @Kaly uses for the fuse? Also where could you get a PCB like that?

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If I remember right than 6mm 0.1 nickle stripes. The pcbs you can easy just let made by jlcpcb.

@Martinsp sold them too but not sure if they still in stock.

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Yeah 10 pcbs for $2 with them.

Guys Iā€™d like some feed back too, Iā€™ve just finished a battery, itā€™s a Lipo pack so a bit different but similar main issues. Itā€™s not as slim as I would like (13mm) due to the fish paper curving outwards at the fold. Hereā€™s some pics anyway

image image image image image image

Edit: I just realised there arenā€™t any pics of how the balance leads are wired. Basically they are soldered to the right point and then a piece of fish paper covers the connection, the balance leads do NOT run under each bit of fish paper. Instead they run over the top of each piece to reduce chances of shorts

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Did you need special aluminum solder for the tabs? Whatā€™s your technique?

As for feedback. Looks ok I would just like to see some more mechanical / physical protection for the pouches. Glass fiber tape for reinforcement and shrink wrap the whole thing.

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Nope just normal solder worked fine, I roughed up the tabs a little with some sandpaper then applied the soldering iron and made small circles while adding some solder. I tinned all tabs first and then when back adding the wire so the packs got time to cool off during soldering attempts. I also wrapped a wet facecloth around the lipos being soldered to keep them nice and cool, thanks @PatRocks. I also tried to keep soldering times under about 4secs

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Looking good @pat.speed !! I would just recommend that wet towel to be in full contact with the seams when heating the tabs! I guess those positive tabs have nickel attached? That makes it way easier to solder!

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You can actually see that thereā€™s a small fold on one tab for each cell. Thatā€™s a mechanically staked on nickel tab thatā€™s been soldered to, the aluminum is much shorter and folded back.

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You will NEED to adhesive tape the pack onto the deck or the enclosure. You cannot by any means have that free floating inside the cavity. Removing wiggle room is also not enough to keep it safe.

Connect it to something along the entire length of the pack with adhesive tape. If itā€™s just held or wedged in there and kind of forward or backwards impact is just going to squeeze (and severely damage over time) the first or last cell in the pack. Learn from my mistake.

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So I canā€™t just pack the inside of the deck with foam? I really wanted the packs to be easily removable and I think velcro is going to be too thick. Maybe Iā€™ll look for some reusable double sided tape

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Yeah, donā€™t try and just pack it in. Lipos can take compression against the flats, but side forces are really bad for them.

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If you donā€™t secure them, you will tear tabs over time at the very least. Ask me how I know

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