For my electric longboard I am using 2 3s 5000mAh batteries in series. This was an okay solution because it was affordable. But my biggest problem is that my voltage keeps dropping while riding. Then I heard you could install a voltage regulator to keep the voltage constant. I was wondering if anybody has any recommendations or requirements I need to be looking out for.
Yes the voltage drops. Thats normal. a voltage regulator that withstands 40-60 amps? You’d get better experience and less losses adding another two 3s in parallell. Alot better voltage curve as well.
1 Like
Sounds great, but how do I connect another two 3s batteries into the circuit? Do you have some kind of special connection parts for that?
A voltage regulator will just burn off the excess power as heat and won’t solve many problems without creating more. So if you feed it 32V and it outputs 24V, and you’re drawing 40A through it, then 320 Watts is being wasted – burnt off as heat from the regulator – which then has to be cooled with a HUGE heatsink
1 Like
Oh so it doesn’t help with undervoltage but only with overvoltage. Sounds quite useless then.
There are also buck converters and boost converters which don’t have that problem but have other problems. None of those will handle 50A. They will all waste power as heat.
1 Like
Then that isn’t a good solution. Do you maybe have any info about what @linsus said about adding another two 3s batteries in parallel?
yeah, you’ll get less voltage sag and larger capacity, if your cells are bit old i dont recommend mixing tho. They might discharge in an uneven rate. Sure theres many threads you can find to learn more about batteries
Don’t mix old and new cells in series. If you mix them in parallel it’s fine.
1 Like
@linsus @b264 Okay great! Is there some kind of connection part to make like a 5.5mm bullet connector turn into two?
Buy some male and female 5.5mm bullet connectors and some 10AWG super-stranded silicone-insulated tinned wire
Make your own adaptors with a soldering iron and heatshrink and kapton tape
1 Like
There are also sepic regulators that do boost or Buck depending on in vs out voltage. And there are for sure ones that could be used for these high currents… They probably cost more than a whole board though.
1 Like
Not really. But yes, its the better of the mixes.
@b264 @linsus Oh and I was wondering how I could charge these two extra batteries, because it technically is still a 6s battery, only with more capacity. Right now I have a 6s 12A BMS to charge my two 3s batteries.
if you use a BMS then the BMS will treat the parallell cells as one cell when charging. It will take longer to charge then your previous setup but it’ll work. Just make sure you buy the same battery when expanding your pack and it should be fine.
I sudgest doing a few trial runs where you can dissconnect the cells individually to see voltagelevels after a discharge cycle. Then connect the batteries as they’re s’posed to be during charging and see if they charge evenly. If they differ alot in internal resistance you might have some missmatch.
1 Like
@linsus Okay great, but if the BMS treats two cells like one, will the cells charge balanced? And how do I connect the balance wires of the two extra batteries to the BMS? Oh and can you tell if my picture could work, to make a parallel connection?
Make a complete wiring schematic and come back to us 
safest way.
Essentially, the wires to the BMS should be the same amount. Only more cables on the battery side to connect the parallell poles. (unless you plan to go higher in voltage)
