Charging in series - help

Hello. I’m standing in a situation were I have 4 2S batteries. I have these batteries because they are the only ones that fit in my design. I just don’t know how I am going to charge them. I can do it individually, but it would be annoying. That’s why I need a solution on how to charge them in series. If I connected them by 2 4S, I wouldn’t mind charging those 2 individually. I could imagine that I could use a parallel board charger, but I don’t think that would be possible because the all of the main wires are welted in series.

The batteries

I hope somebody can help me with explaining how I can do it, or with a diagram of some sort.


Some options:

  1. 8S BMS
  2. 8S charger (not that common, believe me, I was looking for one for a long time)
  3. Make 2x 4S packs, connect in series while riding, parallel when charging (4S charger)

I have 2x 4S Zippy Compact batteries and use option 3 :slight_smile:

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BMSs are really common on eBay

Hey guys, im in London im 14 and i have built my own electric skateboard but its not great i used to be able to go 20mph but now i can only go 16.4. Anyone can help? Maybe i stored my batteries at a two high voltage or i lost one magnet in my motor? Highly recommend skating in hide park, its great! Im going to change to chain drive in the coming days and I’m planning on using a bms but i don’t want to mess up my batteries. thanks

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I would suggest creating a new post for this one…you’ll get a lot more visibility.

Yeah, you don’t want to hijack someones post.

I’m not very used to BMS… I only know that they protect the battery when charging and such. How would you connect the 12 balancing cables, and the 2 main cables on a BMS? Is that even possible?


check out my thread on using 2s Lipos with a bms. includes wiring diagram.

Oh sweet. Thanks!

It’s a crazy good build. Much respect

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Thanks, Yes I have been running this setup for a while now and have been very happy with it.


I have been looking at this for my batteries

Do you think this would work? Im just not quite sure the discharge of 10A is enough?

Hope you can enlighten me

I would not recommend that bms. I would suggest spending more and getting either a Bestech or Battery Supports BMS capable of handling discharge as well as charge cycles. It’s well worth the extra investment.

As for the batteries, assuming you are in Australia These would be much better for almost the same price. 60C cont. 120C for 20 seconds

Hello again. Thanks for your reply.

The problem is just that I live in EU, and it’s hard to get stuff sent without paying a fortune in taxes.

I only chose these batteries because they at the only ones that fit in my design… They are only 14mm thick. I hope these work, because I don’t have much of a choice.

I’ll try to find a better a better BMS. Thanks again

Ok, 14mm is really thin. Not many packs that thin. Still 140a continuous, you should be fine with that.

Okay, I’m glad you said that.

I’ll go hunting for a better BMS. Thanks again for you help

Since no one said it yet : bulk charge at 8s w a “regulated power supply”, either linear or switching, and balance on the side w one or two of these. I think I’ve seen an 8s version too but u could use the 6s

A bulk charger is cheap and super powerful/fast, but I highly recommend adding a wattmeter in-line so u know what’s going on

Hello again my knowledgeable friend. I have been searching the whole Internet to find an 8S BMS. This is the only one that I think would be able to work. Would you believe it could work with 8S Lipo?

Also. I have an 25V lithium ion charger at home. Can’t I just use that instead of finding a 30V Lipo charger?

Regards Mikael

Hey Mikael,

That BMS is a bit low at only 30a discharge. You would do better with this one which is rated 60a

Or this one which is rated 80a and has a built in anti-spark E-switch.

Either one of these will work with Lithium Ion (Li-ion) or Lithium polymer (Lipo) cells.

You will need a charger that outputs 4.2v per cell so for 8s that would be 33.6v Like this one:

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That’s perfect. I think I’m ready to order now. Thank you (again) for your help. It worth a lot.

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