How big is your pack? @Skyart had one one time that took days
If you’re above like 4p with p42a or something it will take a very long time
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The smart bms has an extremely low balance current, even on a 4p pack it may take a few hours to see any significant impact
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Depending on your pack and the BMS’s balance current, balancing a pack that’s that far out can take many hours or even days.
Most BMSs have a balance current in the order of <100 mA, usually less than 50. At 50mA, it would take 336 HOURS to fully drain a 4p P42A group.
Now obviously you’re not trying to fully drain the groups, but even a small mismatch will still take quite a while.
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Just 4P on Samsung 40T, I will leave it balancing supervised then.
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Hi, this is my first time building an esk8 battery so I’m looking for some feedback.
These P groups were welded by @Skyart . Due to the weird space inside my enclosures, these triangle groups are going to be put in a bunch of series packs of two, so each pair will be self-contained. I started by applying glue between the cells.
Then I wrapped them in fish paper with a bit of overlap, so that there are three layers in each spot the P groups touch each other.
The backside series connection is an 8 AWG wire with the ends split in half so that there are two independent solder joints. The balance lead is mechanically intertwined with the strands of the main connection and runs down the empty channel between the P groups, so nothing can put pressure on it.
Kapton tape over everything and fish paper over the solder joints, which are points that protrude the most so they will bump into things first.
Duct tape around everything for strength. There’s a bit of glue between the P groups as well, just to tack them in place.
The finished pack. Same strategy for everything applied to the front side where the main leads come out.
Hey! To start off, that’s a pretty small pack! What are you using it for? Looks like you could improve on your soldering. Seems to me like you should use more solder; There are some soldering experts on here so they can give you good advice. And I’m not sure about the use of duct tape when it comes to battery building. I haven’t seen a lot of people use it and I’m sure there’s a reason. A lot of people use fiberglass tape to provide some integrity to the pack.
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Soldering looks alright to me, as long as it passes the pull test I would say it’s fine
As for the duct tape, I think it makes packs look awful and it ages really badly, we prefer fiber tape like Aviator said, but it is kinda pricey.
Looks like a decent little pack, more precautions taken than many people so I think you’ll be perfectly fine
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It’s going to be a 16s3p, so there will be eight of these modules.
The actual connection point between the wire and nickel is sitting in a pool of extra solder, and nothing is dry. I figured that adding more solder than that would be mostly cosmetic, sink more heat into the cells, and let the solder wick further up into the wire and remove the joint’s flexibility. Think that’s the wrong call?
Yeah, I sanded and cleaned the nickel before soldering so the strength is great.
I know, I’m not a big fan of the tape either but all of the stores around me have stopped carrying fiberglass tape for some reason. 
Why are you soldering extra wire on there? Seems unnecessary. Why not just run the nickel all the way across?
Which wire do you mean? The smaller gauge ones?
No your thick gauge series connector
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If they are going to be together anyway just run the nickel to both p packs.
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Also, soldering on nickel like that isn’t really any better than just soldering to the cells directly
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Sorry, just saw your edit after hitting reply.
I guess it reduces strain on the welds and it let me do more of the build myself. It’s not a bad idea in hindsight though.
I have to disagree, while I still don’t recommend it, the heat is dissipated by much more nickel and many more cells.
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For balance wires, I agree, for 8AWG over only 3 cells, its going to heat the cell way past where i’d be comfortable
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Just glue or caulk all the cells together with fishy in between the p packs and weld em next time… easier quicker and better for the build.
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One of the reasons I split the ends in half. I only soldered half at a time and let it cool down before finishing the wire.
Try to never solder over cells…