Battery selection, please double check for me

Could you guys please double check my thought process before I mess something up. I want to build a 12S2P Lipo pack using 4 Turnigy 6s 500mAh 40C Lipos with a Bestech D140 BMS using 10awg cables for delivery. Does anyone see an issue with that?

Here are my specs. MBS ATOM mountain board 203mm inflatable wheels with - 84 tooth pully Dual 6374 BKB 190KV 3200watt max 70amp motors -10 tooth pully FOCBOX Unity on preorder 15mm wide belts

Thank you very much for your help!!!

40c is not going to be enough… You want at least 90c. Especially with your big wheels. The c ratings are massively overrated, you’l be luck if they are half that rating.

I think you’re going to need a bigger motor pulley bud


My thought was once I wire these 2 parrall and 2 series to get 12S2P would give me 10000mAh so at 40C would be 400 continuous amp draw?( I know the C rating is overstated) but is my math correct? wouldn’t I still have more then enough?

I have some bigger pulleys also, I actually miss wrote they are 12 teeth, probably still too small. if I rip the ridges off of the belts I also have 16 and 20 tooth pulleys.

Use the calculator to check your gearing, paying attention to loaded speeds.

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You mean 5000 mAh batteries to start I think was 500 in original post but assuming 5Ah battery in parallel with another then the math sounds good to me.

Like gummy said mfg ratings for this kind of thing are generally inflated though and not to be trusted if you want things to last for a good amount of time/cycles. Good to see third party reviews and discharge charts to compare cells.

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awesome advice thanks! yup your right I missed a ‘0’ in the original post…whoops

By experience I say that 14T is the minimum if you want your belts to last, 12T the radius is too small and bends the belt too much, at that size my belts lasted 100km tops, with 14T I never broke a belt so far

thanks @Pedrodemio , well i guess ill be putting the larger pulleys on before i thought.

You can get away with fewer teeth if you use an idler.

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The problem is not skipping, but fatiguing the strands inside the belt and they breaking without reason

The idler in this case would only make it worse since you bend it to one side a lot and then to the other

Yep, 15 tooth for the win.