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Lipo spark when plugging into balance board

Well this scared the beejezus out of me. I have an 8s lipo that has two 4s balance connectors to supposedly make charging easier. So I ordered a balance board with two 4s ports (and an 8s wore to the charger.

Excited that it finally came, I plugged the first 4s wire from my 8s pack into the board and it was a non issue. Then I started to plug the second 4s connector into the board and a pretty damn big spark and a bit of smoke followed. It happened on first contact and I immediately pulled them appart. (Tiny fraction of a second of contact. But it was enough to blacken the plastic on the balance wire and the balance board.

My questions are:

  1. Wtf was that about? Is that normal? I was certain that’s it was not plugged in backwards. And these batteries have never been used before. They are brand new.

  2. Do you think I fried anything beyond repair?

Pics attached.

So, this is what happened. The battery is wired in series @ 8s. And you tried to balance charge at 4s parallel. Unfortunately, I don’t think that’s possible.


Interesting… With two 4s balance plugs on the one 8s battery, how do you charge this thing?

If you wanted to balance it at 4s it would need to be taken apart and charged as two 4s batteries.
The only other way is if you have an 8s charger.

Thanks man. I do have an 8s charger but this battery doesn’t have an 8s balance plug… Just the two 4s ones. I’m just a little confused about what type of adapter I would need to connect it to the charger. (My first lipo)

Hmmm…someone else chime in here. Could he cut the one red wire on the negative side balance to pull this off?

I found the store listing for this board and it says it’s actually made for packs that are wired in series: So I think that should actually be the right thing. Just not sure why there was such a big spark.

It shouldn’t have sparked or melted the connection. Somethings crooked in Straightesville.

That’s what I was afraid of… The only place I could find one of these little boards was from a shop in India! I searched everywhere else in the world for one that allowed for this kind of use for an 8s pack.

You should order an 8s jst plug and wire it up 8s. Make sure the balance lead that sparked isn’t melted or needed. It might be the red lead that shouldn’t be used.

It was actually the ground wire.

That’s a good idea. I think I should just cut the two 4s plugs off and go with one 8s. That should be an interesting project for a newb though!

Did you see my diagram in the cable porn thread? Its for 6s but the theory remains the same for 8s. You need to cut the black wire off the balance lead of the positive pack. Not doing so or doing so incorrectly can actually blow your charger.

There you go! Thanks @lowGuido

ok so now that I’m out of bed, I’ll get a bit more detailed for you. here is how it works. … pictures say 1000 words so…

Left is what you have. Right is what you need.

the important thing to realize here is that the black wire on the left most pack is actually the same as the red wire on the right most pack. which is also the same as the thick red wire in the middle. so by connecting the small balance lead to that board (I can’t see how that board is wired I can only assume logic) if you have your left one and your right one mixed up, the black wire is basically just shorting straight across the positive and negative of one of your series batteries. make sense?

in saying that if you were to plug you 2 balance leads into the opposite ports, that board you have will still work assuming its not itself fried.

edit: in fact now that I have had time to look at your images in detail I can clearly see that you have plugged the negative balance lead into the positive side of the board. The damage doesn’t look too bad so you can probably still use that board. just make sure you connect the leads the correct way. (why would they even sell something so confusing)

TLDR: guessing which balance lead is the more positive and most negative is annoying and potentially dangerous. best solution is the right side of my diagram above with one 8S balance lead.

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im trying to make this as easy to understand as possible… sorry if I’m waffling on… so heres where you went wrong. (again I still don’t understand why they sell a product that’s so easy to confuse)

Thanks @lowGuido! Amazing detail and amazingly helpful. Last night I also contacted HobbyKing since this is the board that they actually recommended I get for this weirdo battery. They recommended that I cut off the two 4s connectors from the 8s battery and wire up a single 8s connector. I can’t imagine why in the world it wouldn’t come that way but I instead just initiated a refund process and I’m just going to simplify my life and get a different set of batteries with normal charging leads. That being said, your diagram still comes in handy for wiring the new batteries up together to balance charge down the road.

Thanks again!

I also connected my balance cables in series and had a massive spark. My batteries were connected in series. Did you have your batties connect in series?

I then speedster the batteries and connected them in series which much more caution and I didn’t get a spark. I then connected the batteries in series and had no spark.

I have not tested this while charging or using a BMS. However I am sure it’s just the process that the barriers must be separate at first then connect the balance cables and then connect the batteries in series.

Anyone else had a similar experience?

As it turned out, I had the wrong balance board for what I was trying to do and since went a different direction with different batteries. I was attempting to connect them in parallel at the time though. Lipo’s do spark when you connect them though, especially at the higher S’s

@siggs3000 @Paul There are a few ways to avoid the spark when connecting Lipos; I use a battery arming switch that has a small, temporary resistor. Kinda like this thing below. If the spark is just the normal “connection spark,” the danger is that it will wear out or melt your connectors. This thread is about something more complicated, but I thought I’d note that it is possible to mitigate the connection spark.

There are also xt90 antispark plugs, which are effective but giant:

@sl33py is working on builds of Vedder’s antispark switch