Please review my battery pack so I don't make a 🔥

I am creating this thread for anyone who has made their own battery pack, so we can all come together and help each other make safer boards that don’t spontaneously combust.

Noob or expert we can always improve our methods and designs.

I was inspired by one dude @RHill051 was humble enough to make such a thread and take on suggestions from the forum to improve his pack. It was really quite a beautiful thing.

And that there are good discussions on this topic but they are spread all over the place in peoples build threads etc. If it’s all in one place it will be a more useful reference.

Also to prevent people riding around with aBOMinations like this.

Include several close ups of how everything is connected, where the ballance wires are going so we can give detailed feedback.

Whether the pack is Lipo / Lion / Tiger / :tiger2: welded or soldered it don’t matter.

And always remember vibration is MUCH worse than you imagine, it will eat all your insulations and crack all your welds! :scream:

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Currently I like to take best practice inspiration from @Eboosted and @Kaly Packs. Thanks guys for the dedication to safety.

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A vigorous peer review of battery pack construction is a really good idea.

Roast me?

Here’s my p groups ready for welding…

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Looks good so far, you got ALL the insulations. What is the plan for connecting the cells to each other / the p groups to each other and the balance wires?

Is the shrink wrap just to hold the fish paper in place?

Small hot air gun fail. haha.
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The only potential downside of your design I think is if you push the cells amp limit really hard they will retain the heat for a while.

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30 posts were merged into an existing topic: Fishpaper and cell level fusing, USE IT!

The purpose of my first thread was to see what I did wrong (or not the best) so I could do it better when I make a pack for my friend. I started the new pack last night. Here is what I’ve got so far.

I rounded the ends of the nickel strips on the positive end of the batteries to prevent the corners from bending in and shorting out. I added the fish paper on the top so I can run the balance wires over them. There was some really good discussion about not crossing balance wires in my thread found here. Really glad to see more battery related discussion!

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Here’s my pack I made for my Evolve GTX. 40 miles so far without issue. First build with a lot of research.

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Looking really clean. :+1: What glue between the cells, hot or silicone? I prefer silicone for heat resistance and flexibility without coming off the cells. Are the ballance wires going to the negative side on the P groups?

The only thing that makes me nervous about your pack is balance wires down the side here. Id want to be 100% sure they can NOT move from vibration in this arrangement. Or add some extra insulation.

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Also it looks like 1 layer? Am i wrong?

Thanks :pray:, yes I used silicone and the balance wires are on the negative P groups. There’s kapton tape isolating and suporting the balance wires for while retaining flex along the p groups

Yeah, I think in the photo where it looks like a double layer, the series connections get folded in half, so the pack is opened out flat. Interesting, first time I’ve seen that.

That’s correct , each p group gets folded. It’s a popular method for the evolve replacement

Great! I think it looks legit so far :+1: No complaints. Maybe someone else can spot something?

On the subject of rounding the nickel strips on the positive end… @PickSix24 - possible area for improvement?

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I was just going to say that ! I recall seeing that before but didn’t do it. Next build for sure ! Glad I put those stick on isolaters :neutral_face:

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Here is mine, its a lipo 5000mah 60c / 12s1p, ballance charged. Been using it for about a year so far and I use in torrential rain pretty often. Tropical country.

It has four 6s ballance plugs as its designed to have battery monitors permanently attached. Which I had for a while and I like the extra safety it provided but there was some issues, they only take power from two cells and will drain them over several days if you just leave the board. Also I didn’t waterproof them and they died a couple months ago. Now I just double check all the cells before I un-plug my charger.

The other thing that I don’t like about is I used 18 AWG balance wires and it was too bulky. And maybe its better to have something thinner that can burn up before the batteries do in a short circuit situation.

I opened the hard cases and filled the inside with epoxy for better water resistance and vibration control.

The reason it has two loop keys is so I can parallel charge it as one 6s pack. I use the one on the side as on off switch but have to remove both to charge it as a one 6s pack or it shorts the ballance wires.

My main safety concern is shorting out the wires on the metal enclosure. I have 3 layers of duct tape on it for insulation. Is fish paper waterproof? If so I may switch to that instead.

After a year of use and plenty of water. :cloud_with_rain: :cloud_with_lightning_and_rain:

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I really only got the one response from @Battosaii and was wondering if there was some additional feedback from others. I think maybe my question got lost in the cell level fusing discussion.

I’ll admit that this has been my hope that with the super short lengths there is far less of an issue here but the last thing I want to do is kill my battery prematurely because the nickel strip is getting really hot during normal use. (when i ride I have a tendency to smash the throttle all the time lol really like the acceleration :grin:)

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Well that’s my understanding from doing my own reasearch.

On a side note I didn’t have any kapton tape and I found a local supplier in Miami :slight_smile: they specialize in tapes and have any tape any size it was pretty cool. I got 2 rolls of 3/8" tape

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This is my 10s4p battery rebuild for the build I posted a couple days ago. That battery used cell level fusing, but I was careless and didn’t check for faulty cells, two parallel packs won’t charge above 4.1 on two separate BMS’s (also when charging each pack individually with an 18650 charger. So, I built a new one with cells that I checked individually, and I will recycle the cells in the original pack for another build.

This one doesn’t use cell level fusing, as it requires a bit more room the way I did it than I prefer (my Hummie deck cutout is the older narrower one). My future packs will use cell level fusing and will take up less horizontal and vertical space than even this pack. I did my best to make sure that the nickel strips wouldn’t be able to make their way under the positive terminals. The series connections are flat braided copper for flexibility purposes. I’ve had bad experiences back when I used nickel strips for the series connections so I moved away from that.

This is a gluing jig I made from laser cut plywood when I had access to my uni’s laser cutter.

Gluing in action

via GIPHY

Repeated this for both sides.

All parallel packs glued up

Kapton tape insulation. I tried to mimic the way @Deckoz did his insulations on his 13s evo.

Top spot welds plus solder points (I scratched up the nickel under each solder point. How do these welds look? They seemed pretty strong, but I don’t have a frame of reference that isn’t my own. My other battery’s spot welds used the same settings or ever so slightly shorter pulses, and have held.

Negative terminal welds

Soldered the flat copper braid to each solder point. I wrapped the ends of each braid with kapton tape. I think the fraying would get worse with vibrations and make their way into the cells. Balance cables were then soldered, and connections were covered with adhesive back fish paper.

Here is the battery installed in the board. The cabling is messy, but balance cables are secured with kapton tape to the battery. Also I think soldering and heat shrinking balance cables to jst connectors is one of the worst parts about building batteries.

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Is there a reason why you used so big balance wires?
Could you say me the size of the copper mash you used? Want to use the same but not sure what to order.