The battery builders club

I bypassed the bms during the 5v charge. I plugged the 1mm jst connector directly in the grd/b+ of the white connector.

Can i leave the solder of the 1st Serie/B- wire intact, cut the abraded wire and solder it again?
How do you recommend to inspect the pack? Is there a specific method?
Thank you

Yeah, you can just replace the damaged part with a short piece of wire, but if you can’t route the existing wire in a way that it won’t rub again, then replacing the whole thing might be a better option.

If the pack was built by a reputable builder that shows how their packs are built, then no real reason to open it up. But if it’s a mystery pack… it may be worth opening up.

I’d be curious to see what sort of amperage the series connections can handle, that way I could set the ESC to that max, or make those connections larger if I wanted to pull more amps. 4p 30Q can do 60A continuous, and 80A bursts, but if you only have a single narrow strip of nickel for a series connection, you may be limited to something anemic like 20A. I can see bulges on the sides of the pack which leads me to believe they soldered some wire on top of the nickel for the at least half of the series connections which is ideal… but the middle connections are unknown.

I’d also want to make sure that the P groups are isolated with more than just the cell shrink wrap. If that wrap wears through like the B- wire did, they will short and a fire is likely.

How hard is the silicone? You don’t want heat to get it off, moreso just pulling it off. It won’t be bonded THAT strongly to the metal and PCB, with tweezers (The ones which don’t go to a super sharp point) you should be able to kinda peel it away in 1 go or in chunks

also I can’t see which of the wires is cut in the image :frowning:

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I’ll keep poking and prodding then. I don’t have any cut wires, I was considering cutting the existing leads and soldering in the new bms’s lead wires.

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MAN THIS THREAD IS LONG

Im going to build my second esk8 battery and read pretty much the whole thing… pretty insteresting how the stardart has gotten better through the years!!
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I have a few questions that i might have missed the answer for:

How much amps per spotweld? (ill be using 0.2mm nickel)

Recommended Jules for stacking 0.2mm Nickel?(only 2 layers) (ive read somewhere that between 90j and 100j)

I´ve not seen how you guys solder the “S” cables on the nickel flaps without damaging/burning the fishpaper below it.

And if i understood correctly, the “S” connection “Takes” current away from the nickel. So with enough “S” connections between “P” packs I dont need to double stack nickel?
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I know everything else that its writen on here so ill CONDENSE THE MAIN SAFETY POINTS ive read:

-No welding in the center of the negative pole (Internal welds can be damaged) so weld arround it.

-Fispaper. Probably as important as the cells themselves, insulate all pgroups individually. Kapton tape on top to fix cables in place doesnt seem to have a sgnificant impact on abrassion resistance.

-Rounded nickel strip, If its round it cant pierce throught the fishpaper.

-Nickel flaps. If folding nickel over the cells (Recommended for “S” connections as it doesnt heat up the cells) fishpaper under the fold.

-No balance wire crossing if possible. If they rub and break, fire :frowning: If they have to cross, add fishpaper between them and fixate them with kapton tape.

-Flexible “S” connections are safer as they are more difficult to break. Copper braid isn´t ideal so if you have enough space use silicon insulated wire.(14awg-12awg seem to be the standart)

-Workspace. Work in a clean and metal free workspace, shorting
cells its no good.

-Plan ahead. How are you going to put the balance leads?(draw it), Draw cells layout.

-Check other designs from proffesionals!

I think this is about it, please correct if theres anything wrong and if you think i missed something!

@glyphiks @BenjaminF please guide me in my ignorance :heart:

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Stacking nickel is shit, don’t do it if you can avoid it. If not, 100J is minimum, as .3 nickel already requires around 100J. Also, if you make the series connections with copper wire you don’t need a stack.

If I remember correctly its 5A per spot weld. Could be wrong though.

You make “solder pools” before you weld the nickel on and then mush the pre-tinned wire into the pool, if you’re doing it correctly this should take under a second.

Yes. 12AWG runs cold till ~40A, so with 2x12AWG should cover most usecases. If not, adjust accordingly.

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This is very useful, thanks a lot man!

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Np. :slight_smile: I’m not an expert by any means though, so if you wanna make sure stick around some more and maybe one of the gurus will answer too.

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Imma tag two of the masters!

Ok thank you. And What do you recommend to adjust the voltage drift once and for all?

I’ve found a set of picks to be super useful with removing silicone. In my experience it comes off pretty easy once you get started.

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I started using a few picks but got worried I might short something

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Ceramic tweezers ftw, or tooth picks maybe.

tooth pick dipped in epoxy actually.

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Touching another mans white spooge :pensive:

Try hitting it with high % isopropyl at an edge? Once lifted it should peel if that method is gonna work well. Soak a q-tip or something in it

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Look at these sneaky fuckers!

“CREAMIC”

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Damn. I want creamic tools

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Welding a piece of 0.2mm nickel onto other 0.2mm nickel doesn’t take 100j, I don’t think.

Generally, a KWeld at 50-55j will do 0.2mm well. And for a piece on top, about 70-80j will do the job.

Stacking nickel isn’t inherently “shit”. It’s not ideal, and if it’s easily avoided, then absolutely it should be. But this is more so an effect of it being better to simplify a build as much as possible. More welds and layers add a more stringent requirement for attention and care in the execution and a real awareness of what the pack is going to do.

A newer builder is likely better off avoiding it, so I’d agree that this person should avoid it. But I felt compelled to add my perspective on stacking nickel in general.

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Ah the joys of creamics.

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Ebay/Ali there grate for holding cables as you solder them