Series and Parallel Skateboard Circuits

@Kaly one more thing. It’s probably a stupid question, but I noticed on your project you had two balance ports for 2 batteries that were wired together. When charging the board, how does that work? What do you plug into the charger? Just one of the balance cables or is there an adapter to connect to both?

You need to make a parallel adapter for the balance leads, you do this by soldering tougher balance lead extension. I’ll post a pic in a couple of min.

i am also planning on using this system on my build, @Kaly Your DPDT switch is the missing part for me but now i guess its all clear , i learned alot from this discussion , i also made a diagram of how the set up will be with the DPDT switch maybe it will make things clear for others as well , because your instructable tutorial uses motors instead of batteries i got a bit confused so can you please confirm if this is correct ,

This diagram is correct :slight_smile: Just to clarify the balance leads only will be connected in parallel when charging. In any other state or configuration have to be disconnected.

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Bottom line, The only way to run multiple Lipos in series and charge them conveniently is to use an onboard BMS and a laptop charger. Then you will not have to disconnect and reconnect anything. You won’t even have to open the enclosure. You just plug in the charger and wait. The bms will monitor each cell individually and stop when each cell is fully charged. and you won’t have to charge in parallel, which btw is not really recommended for Lipos. Check out my Lipo with bms build.

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For sure this the most safe way to charge.

I have the same layout as you, @AbdeTy here it is:

I was wondering if this was a good setup and if the battery voltage checkers were setup correctly. (They are the black boxes with the red volt inside)

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good , about the balance wires yes i will be using a 15 pin VGA adapter that will have both the balance wires and the charging one and they wont be connected from the charging cable end :slight_smile: thank you

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For the voltage meter you can use a lipo saver alarm connected to the balance lead with a small on/off switch on the negative wire of the balance lead.

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that’s true , but with all what i read about BMs i find it hard to trust them , do you have any recommendation for a good place to get good quality BMSs ?

@Namasaki @AbdeTy The only reason why I don’t do that (use BMS) is this: https://youtu.be/pljSZcEwc8Q The video explains how using hobby chargers are safer and more reliable than BMSs. I would eventually look into it for a v.2 of the board, but for now I’ll just stick with my hobby charger.

lol yep i did see that one , that’s when i decided not to use them as well , i would feel safer while riding my board if i am sure my battery is balanced after each charge and once there is a problem i will know right away, the BMS can fuck up and you wouldn’t know and if you dont monitor your batteries regularly that could cause a disaster

Until I can monitor the BMS easily, I will stick with the old-school system :wink:

yep they really need to develop an advanced BMS, maybe a display and live data bluetooth and a smart app that can let you know if something is wrong, maybe we should develop it ourselves lol

I googled doing this, but this requires the balance cord. Is there a way to permanently install the meters while still being able to balance charge? Would I use a parallel adapter?

First there was the VESC as an open sourced ESC, now the needs to be a VBMS!

yep i guess a parallel adapter is what you need for each cell.

yep hopefully we will see it soon

I don’t know what bms the guy in that video is talking about. I did not recognize any of the boards he was holding and for all I know they are some of the $15 dollar cheapies that you get on eBay. The Bms I’m using is by a reputable company and has overcharge protection, over discharge protection, over voltage protection, under voltage protection, short circuit protection(if there is a short anywhere in the entire system, it shuts off) and overheat protection. It monitors every cell individually during charge and discharge. And if anything goes wrong, it shuts off. It is important to use a quality BMS just like it’s important to use a quality balance charger for manual charging. And although you can charge lipos in parallel, you really shouldn’t For one thing, the internal resistance in each cell of a lipo pack varies. thats why they never discharge or charge at exactly the same rate. If you want to stick with a balance charger and don’t mind the hassle, the best and safest option would be a dual bank charger that can charge 2 6s Lipos separately and simultaneously. Edit: As far as monitoring battery voltage, you can use multiple cell alarms like the guy in the video. You can use them with a BMS if you don’t want to trust the protection circuits. The problem with them is that they constantly drain the battery unless you unplug them. I’m pretty sure that all the people in this community who are building battery packs for retail, are building them with bms’s So are all of the commercial manufactures of electric skateboards.