Some sort of short on balance leads. What happened?

[ions82]

I've recently finished my first e-bike build. It turned out great. However, I've now run into a bit of a problem with a balance lead. I was going to balance charge a couple of the LiPo packs in my battery, but one of them created some sort of "short" when I tried to connect it to the balance board coming from the charger. I had hooked the battery up to a Cell Log before connecting it to the board, and everything seemed OK. However, once I put it on the board, it created a mini light show. The voltages on the charger seemed to be reading, but it sparked again when I tried to re-seat the plug. I decided to quit there and see if I can find out what in the heck went wrong.

I've attached a picture. As you can see, the parallel board is going to need some repair. And here I thought I had this whole LiPo game figured out! Maybe I'll be the next one to have a big fire. If anyone can tell me what in the heck I did wrong, please let me know. The main battery leads weren't even connected when it sparked. I was just connecting the balance leads. The negative lead going to the parallel board was connected, but I don't know how that would affect the issue since nothing was even connected to it. I thought I remember reading that it was the proper order (balance leads, battery leads, parallel board leads). Maybe I should go back and re-read the manual. The charger is a Thunder Power TP1430C. At first, I thought I may've put the plug in backward, but I had actually tried it again (the right way) and still got the same result.

If anyone knows what went wrong, please let me know. I had a fantastic time riding the e-bike around, and I was looking forward to riding it over the holiday. Thank you for taking a look at my post!

 

[amberwolf]

Unless there is something wrong with the board you are plugging the pack into (the one shown in the pic), or the device the board is plugged into, then if you did not have main leads for the pack hooked up to anything at all (another pack, another board, the main unit, etc), I don't see how it could spark like that, as there should be no current draw to cause that.

Note that if you have the packs still hooked in series via the main power leads, and then try to parallel your balance leads, then what you see there is exactly what I would expect.


Is the charger itself already plugged in to the wall?

Do you have a multimeter you can use to continuity test that connector on the board?

 

[ions82]

I think I may've figured out what I did wrong. You can't see it in the first picture, but the last pin on the right-side 6S receptacle is in series with the first pin on the one that is on the left. I've attached another one to illustrate what I'm guessing at. I would've assumed that they would be on completely different circuits. Before, I had only used the receptacle on the right. However, I was going to balance charge two packs this time. I'm fairly certain that the manual said that I can balance charge two 6S packs at the same time (without having them in parallel.) Hopefully, the picture will help determine if my uneducated guess is right. Would the last pin on the right (a positive lead from one battery) being tied to the first pin on the left (ground balance on the other battery) cause that short?)

 

[amberwolf]

I think I may've figured out what I did wrong. You can't see it in the first picture, but the last pin on the right-side 6S receptacle is in series with the first pin on the one that is on the left. I've attached another one to illustrate what I'm guessing at. I would've assumed that they would be on completely different circuits. Before, I had only used the receptacle on the right. However, I was going to balance charge two packs this time. I'm fairly certain that the manual said that I can balance charge two 6S packs at the same time (without having them in parallel.) Hopefully, the picture will help determine if my uneducated guess is right. Would the last pin on the right (a positive lead from one battery) being tied to the first pin on the left (ground balance on the other battery) cause that short?)

You say the balance plugs are in series? Seems odd-normally those are in parallel, or at least they are on the various balance plug adapters I have around here (but none like that one).

But if your charger is capable of higher voltages (like 14s) then it would make sense to have a pair of balance leads that are in series rather than parallel, and in that case you would get the short if your packs' main power leads are paralleled and then you plug the balance leads in series. (because series and parallel connections can never be made at the same time on the same pair or set of packs).



EDIT: I couldn't see it at first, but I zoomed in on the picture and now I can see the (breakable) series connection. So yes, your charger must be capable of series charging mulitple packs, and so you must make sure your packs' main power leads are not paralleled when you hook them up to the charger, unless you use something else to parallel the balance leads as well, and hook the output of that only to the most negative one of those two balance connectors on that board.

 

[dnmun]

using a voltmeter to measure the difference in voltage between the pin and the plug would help a lot when it is the first time to plug something in. especially if you build a battery and solder all the sense wires onto the cells. if you get them outa order it ruins the BMS, i got proof.

 

[ions82]

EDIT: I couldn't see it at first, but I zoomed in on the picture and now I can see the (breakable) series connection. So yes, your charger must be capable of series charging mulitple packs, and so you must make sure your packs' main power leads are not paralleled when you hook them up to the charger, unless you use something else to parallel the balance leads as well, and hook the output of that only to the most negative one of those two balance connectors on that board.

Upon checking the owner's manual, it does say that you can balance charge two packs in series. However, one then needs to put the main power leads in series, as well (which I failed to do.) There are so many possible mis-steps that one can make when dealing with LiPos. Although I've been trying to be as careful as possible, I'm still a bit surprised that I haven't already had some sort of catastrophic failure or meltdown. Just a couple burned connections thus far. These things pack some serious power.

 

[dogman dan]

I see what the designers inteneded with that, but it sure can be confusing since it looks so much like a paralelling balance board. I bet I'da made the same mistake too.

 

[TMaster]

You have it figured out right. Thats a series junction board. You can get on digikey and order a male header for like a buck and replace the one that you smelted. There are all kinds of different brands of parallel boards out there if you need to charge that way. I can't wait for the day when someone makes a real 24S balance charger The biggest I have seen is 16S.

 

[docnjoj]

You have it figured out right. Thats a series junction board. You can get on digikey and order a male header for like a buck and replace the one that you smelted. There are all kinds of different brands of parallel boards out there if you need to charge that way. I can't wait for the day when someone makes a real 24S balance charger The biggest I have seen is 16S.

Yeah and that 16S is about 600 euro. I agree that a good relatively low cost balance charger up to 24 S would be a really good thing. Especially if it were around 250USD.
otherDoc

 

[Laureloke]

I had the same problem.
Connect your two 6S in serial to 12S.
Then connect them to charger.
Afte that connect balance plugs to balance board. If you see sparks, then you mean mixed plugs on balance board. Then change their location with each other.

 

[Laureloke]

I connect 8S 5800 with 2 JST-XH plugs and 3S with 1 JST-XH plug in serial (11S) to balance board.

I asked ThinderPower support about right connection, but they told me, that 8S and 3S should be charged separated. I didn't belive them))
And charge them in one time.

There you can see some pics.