DIY 12S Battery help please

sorry in advance because I’m gonna sound really stupid.

Since I live in Australia, a big ass country with not many people, building an esk8 is slightly problematic. Even though I live in a relatively urban area of Melbourne, I still have to do, like, 40 kilometres (24.8 miles) just to work and back. I’m currently building an eboard to make my daily commutes. I’ve got 4 3s 5000 mAh 40C Li-pos ( that I originally thought I could wire together in series for a 12s 20,000 mAh battery unit. Apparently If i wired those in series I would only get 12s but still 5000 mAh. My question is that how would I get a battery to meet my specs? if I wanted 20,000 mAh and 44.4V (12s) I would have to have 2x 12s 10,000 mAh to wire in parallel, or 2x 12s 20,000 mAh li-pos in series right? And, as far as I know those don’t exist and even if they did they wouldn’t fit in an eboard. I’m open to suggestions guys but I generally don’t like putting together cells myself because of the extra equipment needed and various other reasons. Also, I would need a bms to charge via a single cable, so which one?

I’ve got a FOCBOX Unity and dual Torqueboards 6380 170kv Motors if that helps. ESC: Motors: https:///collections/electric-skateboard-motors/products/electric-skateboard-motor-6380-170kv

Any help would be appreciated, Thanks!

what wheels do you have?

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If you want a 12s4p pack of 3.7V 5000mAh lipo cells (which is what I think you are asking for, 44.4V 20,000mAh) then buy 2x of the 6s4p lipo packs from HobbyKing or something and put them in series…should go 60 miles on a single charge

TBH a 12s2p should be enough but won’t give much margin of error for range, I’d go 12s3p

A lipo shouldn’t have any issues with amperage if your wires don’t melt

For that much capacity I would go for a li-ion pack, a 12s4p or 12s5p would be lighter, but you need to weld cells or buy a pack and you’d get less max torque and acceleration

In theory you would need a 12s8p to max out the motors


hobby king do 6S lipos up to 20 Ah A pair of these in series would give you 12S 20Ah - approx. 840Wh battery - which on AT wheels at 14 Wh/km would give over 60km range

or a pair of 6S 16 Ah would give 48km range on AT wheels.

Street wheels are generally 8-10 Wh/km - so you can do the range calculation for that as well


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I’ve got caguamas

Those look low profile from the search page but once you click into them they become Turnigy instead, and there’s no way i’m fitting two of those onto a vanguard, but thanks nonetheless

Thanks dude but hobbyking dosn’t sell any 6s2p or 6s4p batteries. Google told me that those lipos are very very very rare and outdated

@stewie For such a huge capacity, I’d definitely recommend going with 18650 cells rather than lipos. The resulting pack will be much smaller than a lipo pack of the same specs.

Regarding your pack calculations, the key rule for figuring it out is, if you put stuff in series, you get more voltage, but no more capacity. If you put stuff in parallel, you will get more capacity, but no more voltage.

So for 3s 5000mah lipos, you’d need a total of (four in series) times (four in parallel), so sixteen packs. At the list price at that link, that’d be $580. For a 12s and >20k mAH 18650 pack, you’d need a 12s7p of 30Qs, which is worth about $260.

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uh, why 16 packs? dosn’t four plus 4 equal 8 or am I missing something? You said times (four time four) but why is that? And with custom batteries, will the discharge be enough? does the speed of the motor depend more on voltage or amperes? Thanks anyway dude,

It’s multiplicative. Four packs in series, times four.

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Think of the batteries making a box, height/series gives voltage and width/parallel gives amperage/capacity, but it needs to be a complete rectangle to work

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If you have a string of 4 packs of 3 cells in series and 5000mah capacity, that’s 12s. To get double the MAH, you need twice as many cells in parallel, so eight packs to get 10,000mah.

To get double the MAH again, you need twice the cells AGAIN, so 12 sets of four cells. If they’re in packs of three, that’s 16 packs.

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30Q cells are good for 20 amps, times 7 in parallel is 140 amps.

Speed is dependent on voltage. Acceleration and hill-climbing is dependent on current.

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Yeah thanks man your math definitely checks out

If I used a 12s7p of 18650 cells, voltage wouldn’t be a problem since 12*3.7= 44.4V (12S) right?

In the specs of my motor it says max amps is 80. The listings in the 30Q cells that I’ve seen are all rated at max 15 amps continuous discharge, 7*15=105, would both motors draw a combined 160 Amps or just 80?

Battery amps =/= motor amps. Generally you’ll pull less from the battery than is going to the motor. 50A in and 80A out is common.

30Q cells are factory rated at 15A, but they perform better at 20A than almost every 20A-rated cell.

Cool. Could you chuck me the link for those 30Q cells? Do I have to modify the cells to make them discharge 20A? Thanks

Nope, they’ll do it on their own.

Keep in mind, you’ll have to either get a spot welder, or get them welded together by someone else.

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After a bit of digging I’m about to buy them now. A friend of mine’s dad works at a University in mechatronics who’s willing to let me use his spot welder. Just checking, how many cells will I need to make a 12s7p or 12s8p?

Multiply the series count by the parallel count so 84 or 96 respectively…and buy some extra if a few cells go bad or get damaged somehow

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