How to discharge in series and charge in parallel [solved]

Hello guys, my question is regarding this 4s2p battery from hobbyking

According to the information I’ve gathered this battery is has 4 cells hooked up in series in 2 parallel groups (because its a 4s2p) Does this mean that I have 16000 mah x2 for a total of 32000 mah, or is it 16000 total.

Minimum Capacity: 16000mAh Configuration: 4S2P / 14.8V / 4Cell Constant Discharge: 10C Peak Discharge (10sec): 20C Pack Weight: 1290g Pack Size: 173 x 74 x 45mm Charge Plug: JST-XH Discharge Plug: XT90

These are the specs. This is what you’ll have.

Thanks for the quick reply.

I’ve already seen the specs. So it has 8000mah in series for 16000 mah total?

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16000 is the battery capacity, so yes, it two x 8000

It’s basically two 4s 8000 mah packs in parallel. All you have to worry about is the 4s part and the stated capacity.

Thanks a lot, can’t wait to receive them. :grinning:

I am planning to use two 6s2p batteries instead of the aforementioned 4s battery. and I am also planning to make a waterproof build to acommodate for the rainy danish weather. So I want to make a build that has a sealed enclosure that doesn’t require me to swap batteries or remove them for charging. Being 19 years old, makes you want to go faster all the time, to get that adrenaline pumping, therefore I am going to wire the 6s batteries in series.

I normally just try stuff and if it shorts out I know I did something wrong. I’ve shorted at least 3 batteries in the last month, that was all fun and harmless as I only ruined 3s or 6s batteries. Shorting the batteries also made me realize that I don’t know nearly enough about the electronics I am using as I thought I knew (damn :sweat_smile:, I also dont have any background at all in electronics so that might have something to do with it). And now that I am planning to upgrade from 6s to 12s I feel that working with 12s might require me to be a liiittle bit more careful. And that’s where you guys come in :smiley:

I made you a little sketch of how I am planning to wire stuff together and would love to get some feedback/suggestions.

My gut feeling tells me that unfortunately this will burn down my parents house. Do I have reason to believe that?

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Be careful. If you tend to “feel” your way around setting a board up, you’re in for some fireworks !

I think you may be over-complicating things by trying to parallel-charge and series-discharge in one setup. Too many things that can go wrong, it gets complicated fast. Keep it simple. If I were you I’d rig my board to discharge in series and charge is series as well. You’ll need less wires and less connectors plus there’s less that can go wrong. Here’s a quick sketch of what might work:

You’d remove the anti-spark loop key when charging and you’d need to rig your balance wires correctly into a series configuration, which is not difficult but needs to be done precisely in the correct order. I don’t know if you already own a charger, you’d need a 12S charger to pull this off.


As it is, you are trying to link x2 6s batteries in series to get 12s - and feed the VESC. Correct, You cannot then link the two same batteries in parallel to charge them, as you are trying to do. (that would short them out) You can only charge the pack as 1 x 12s pack - via the same leads the VESC uses. You could charge each 6s pack seperately with appropriate leads. OR, to charge them in parallel you’d have to have a switch on the link between the two packs’ (+ and - link) - but that would be very dangerous if you forgot to switch it each time you were charging. You’d have a fire on your hands.

Personally, I’d start with 6s - nothing wrong with 6s. You’ll get just the same top speed with 6s and the right gearing. The types of speed you can achieve with 10-12s if you want to, are completely dangerous and unusable. Trust me, I’ve got experience. You’ll end up gearing down your 12s setup to the point you might just as well have gone 6 or 8s and save lots of money on ESCs and chargers.

And yes, you run a very real risk of burning down your parents house. You’ve shorted three packs already… I’ve never shorted a pack. There is a LOT of energy in a 12s pack, let alone a 6s pack. Not only fire, but the ability to weld metal objects through your skin…


Sorry for late reply was out all day. Wow @trbt555 nice work on that sketch. It seems like that would work, but as you said I would need a 12s charger.

Seeing as I have already spent about 80$ + 50$ on 2 decent 6s chargers (both still work without complaints), I would much rather use one of these chargers to charge my batteries instead of spending another 230$ on a 12s charger even if that makes my setup more complicated. I would be happy to get myself a 12s charger if that is indeed the only way this will work, but does everyone here who run >6s setups really have those kind of chargers?

Thanks for the sketch, I’ll probably try wiring up my stuff like that if parallel charging is too big of a hassle. I’ve actually already ordered the xt90s because those would be useful in any case.

Man, to be honest, even with your nice input you kinda scare me. your idea of putting “a switch on the link between the two packs” I really like! Of course forgetting to turn it off would probably make my parents’ house suffer catasprophical consequences, but shouldn’t that be avoidable if I put a 50v capacitor in my circuit? I’ve never used a capacitor before, though I believe they can be used to avoid shorts right?

I also started out with 6s with enertion 83mm wheels and 14/36 configuration. I’ve since upgraded to heli 12s esc without brakes and I can do 45km/h, but my need for speed is making me want to go faster, which is why im looking into making myself a more permanent 12s solution along with 97mm flywheels to up my max speed. I wouldn’t say im a pro eboarder, but I’ve had a finished build for about 2½ or 3 months that I have a few 100 kms on, It almost completely replaced my need for a bike (and we usually bike a lot in Denmark).

you can hook up in series for discharge and then parallel to charge. its a little tricky but not impossible. you will need a loop key in between the 2 batteries and a parallel charge board to plug into the 2 balance leads once the loop is removed. discharge as one 12S and parallel charge as two 6S

in fact this is exactly how I intend to wire my next board

I actually run 12S on my board. I also have two 6S chargers. But I need to open up my box and connect my batteries manually. This also gives me the benefit of being able to swap packs on the go, which gives me more range than I ever use. I understand you want to avoid this but I think you’ll have a hard time not having to open your box for charging.

@mohammedex I’ve been giving this some more thought and here’s a schematic of how you could rig your setup to discharge in series as 12S (insert loop key) and charge both packs separately as 6S using your two chargers (remove loop key).

@lowGuido, it was your comment that got me thinking, is this what you were planning ? However I don’t see how you could rig this to charge both packs in parallel using only one charger and one charge port without adding additional connectors/loop keys. How would you do this ?

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Yeah you are on the right track. You just need a parallel charging board to allow your 2 chargers to be replaced with one. Other than that, spot on.

That’s actually really nice and simple. as lowGuido said it’s probably easier with a charging board and a single charger, but is there any danger to always having the balancers hooked up in parallel?

Having to “only” plug in 3 connectors when charging can’t hurt :smiley:

You can’t have your balance or charge leads connected in parallel while your batteries are connected in series. So basically you’ll need to parallel connect everything on the outside of your board so it can be removed for normal operation. Which means you’ll have two charge ports connected to one charger via a parallel harness and two balance ports connected to a parallel balance board. Plus one loop key port.

If you are going to use separate enclosures I think this way is the best way to change your connection between parallel and series. Also you don’t have to buy a new charger.

I am using two 5s2p Li-ion batteris. The xt60 connectors from batteries are glued together. When I am charging the board I connect the parallel connector and parallel balancing connector. When riding I use the series connector. Hope this helps!


Thanks alot guys, I dont know what I’d do without you. I’ll make sure to post lots of pics when I finish my build and receive the VESC’s in a months time :slight_smile:

You could of course save yourself a WHOLE lot of hassle and just grab a “brick” style 12s charger and charge in series.

I use a 6s variant for my board (I have proper 6s RC chargers but this makes it simple and neat)