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

ESK8 Electronics
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That’s a beautiful battery @thisguyhere

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Ohh I commented as I thought the blue/green balance wires looked a little thick which might be a concern unless fused. And I thought I saw fuses where the balance wires join to the white balance plug wires. Like what @SkaterBoy58 did on his La Croix’s La Croix Long Range Cruiser Carving Machine - #65 by SkaterBoy58 - ESK8 Builds - Electric Skateboard Builders Forum | Learn How to Build your own E-board

In a pack built this solid its probably fine.

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20Awg silicone wires for the balance leads coming off the battery then spliced into jst connector that comes with bms.

No fuses

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So up for assessment is my first pack, 12s 6p 30q. I used 2 layers of 10mm x .15 nickel strip, central S connections are tinned braid, 10awg for the outer connections. Each pack is fishpapered and held also with kapton.

Let me know what I did wrong, I have a few days to correct it before the BMS turns up!

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That looks really nice

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I think you used 3/4 scale 30q cells, as that 12s 6p looks absolutely tiny next to your hand! :grin:

I stared at it for a while to try and find an issue but it’s pretty damn legit. :ok_hand:

The only thing that makes a little uncomfortable is the corners of the nickel strip on top of the positive insulation rings. Personally id like them to be longer or trimmed shorter so there is no chance of them going under the ring and touching the negative can if the battery was hit hard in a crash or something. Maybe they are already short enough not to be a problem but its hard to tell from the photo.

image

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Thanks for the feedback, much appreciated, I hadn’t considered that, it’s a good point I will take forward :slight_smile:

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have you tested your nickel to nickel welds? i find it surprisingly difficult to get it right.

but
good lookin pack, i got one very similar to it.

777Wh, gives me 35mi on pnumatics, 45mi+ on thanes.

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Thanks, that’s interesting, more miles than I thought I’d get :slight_smile:

I did a fair bit of testing, I used a malelectrics car battery version spotwelder, I found that as the voltage dropped the welds were affected quite a lot, so I kept the battery on charge while welding to keep the volts up, this helped a lot with weld consistency. I found that 18ms was good for the first layer and 35ms for the subsequent layers worked well.

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I use the malelectrics too
 with a 8000mAh nano tech battery the times are 8-10 to battery 14-16 nickel to nickel. I think the Li-Polymer puts out more amps instantaneously.

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I guess so, at one point I was at 65ms for a good nickel to nickel weld, that’s when I bust out the charger.

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2 nitpicks, and they’re pretty picky nitpicks.

  1. the series connection with the 180deg bend, those pairs of subpacks may benefit from being stabilized with respect to each other, to avoid wire breaking. Maybe tape/glue them to a small sheet of abs?

  2. for each subpack, you have the series connection going down the middle pair of cells, and only nickel to the left and right pairs of cells. That means the middle pair have a very low current series path, and the other pairs have a significantly higher resistance series path. So over time, the middle cells will see more wear, generate more heat (which is trapped in the middle of the pack).

Reference:

https://endless-sphere.com/forums/viewtopic.php?t=84412

I doubt these are going to really be issues though, nice build!

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Where’d you get the braided wiring?

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  1. I have kapton taped each pair of series pack pretty well, but a support board would be better, I’ll go have a look in the shed of dreams and see what I can find.

  2. Well I didn’t know that! I will employ this on my next pack in a couple of weeks time, thanks for the insight :slight_smile:

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This is what I used.

https://www.copperbraid.co.uk/product/flat-tinned-copper-braid-6-mm2-10-mm-wide-x-1-mm-thick-63-amps/

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Oh one more thing, I think for packs like this, it would make sense to use one wide piece of nickel that cover all 6 cells, rather than using 5 skinny pieces. It’ll be mechanically stronger, and the electrical paths will be more robust. Less work too. :slight_smile:

Like this

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Until you acccidentally weld in between two cells lol

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Have you seen my spotwelding jig on the 3d printables thread? :slight_smile: Would need a new one for 2x3 diagonal config, but the idea applies.

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I haven’t, I’ll have a look :slightly_smiling_face:

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