Batteries can be dangerous if handled or designed improperly. Nobody wants a fire at home or to lose a board because of a poorly built pack.
This thread is meant to be a collection of safe, reliable battery pack designs, as well as a place to ask questions about building your own or general battery related questions/discussions. Feel free to share progress photos and get feedback on layout, weld quality, or anything else you’re unsure about.
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@Linny, you may already know, but most issues that can come up with those BMSes are just with the Bluetooth modules, so if you’re still having trouble and have another somewhere, you could try swapping the modules out. You can also buy the Bluetooth modules themselves in some places.
@Linny the BLE on those things won’t show up for discovery if it thinks it’s attached to something already. makes for some weird situations… sometimes quitting the app and restarting clears it. sometimes there’s a second app that’s connected (probably not your case, ,you’d know). sometimes disabling bluetooth and reenabling clears it.
I could have the wrong idea, but for larger P count packs where I’d prefer to charge at 10A-15A it seems like this would help keep the pack better balanced if I’m not leaving the pack plugged in overnight.
So, I’m in the designing stages of building a 12s8p Bak 45D pack. While the cells should be able to handle something insane like 480 amps, the current plans for the build only require about 200 amps. I’m not sure how much I should overbuild it in case I decide to try to pull more power, though. I thought about going the precut nickel route, but something like 8P 21700 0.2mm Pure Nickel Strip — MBoards is only good for about 120 amps, from my estimation. Does that seem right? It only has about a 40 mm width for the series connections.
Are there any places with precut nickel with more area for series connections? I figure since I’m doing 8p double stacked, if I do the full ~80mm width of the groups for series connections that should handle ~240 amps, and if I did it top and bottom, it should handle about 480 amps, at least as far as 0.2 mm nickel. I guess I just need to decide if I want to have series connections on one side of the battery and be limited to ~240 amps, or go wild and do series connections on both sides and be able to fully use the cells if I somehow end up with the ESC and motors for it.
I guess I just wanted to check and see what people here think and sanity check myself.
This depends on BMS some BMS keep balancing also when charger is disconnected until they reach their setpoint. You do not need high balancing currents for fast charging.
Yeah, I’m still not fully decided, but I want at least one full-width tab. I’m considering doing full-width tabs on both sides because, at that point, if I build the rest of the battery out enough, it should be capable of fully utilizing the cells or close to it, even though, for now, my plan requires less than half that.
I’m more of a minimizing resistance mindset, rather than what can I get away with.
I recently found I can weld 0.35mm copper under 0.1mm stainless steel with my AwithZ P20b14.6kW welder at near max power, using brazing paste/welding flux, and will struggle to use anything less than 0.25mm forever after.
My 10s2p BAK45D currently in my enclosure is 0.1mm copper, 0.1mm nickel plated steel sandwich with dual 14awg series connections and 10awg to an XT90s, and my ESC is just a lingyi capable of 24 battery amps. So I like overkill, But can also easily feel voltage sag as I’m almost always accelerating at full throttle, and my old battery was difficult to keep under 60C when it was retired, and had nearly 6 volts of sag at full throttle. The BAK is about 0.8v of sag and has at least 20% more torque.
That BAK pack was done with a 21$ purple spot welder with a 36$ zee 3s 5.2 ah weld battery at about 85% max power.
The BAK Battery stays cool, but I wish I could have used 0.2mm copper. I want my parallel and series connections to be a heatsink, not another heat source.
The 45D is an impressive cell. I say find the maximum thickness of copper your welder can weld under 0.1mm stainless steel, even if you never approach the cell’s maximum temp limited rated current.
