Balance lead singed help!

[Vapology]

Just bought a couple of zippy compact 8s 25c 5800 mah batteries and have used them both on my e mtn board. http://www.hobbyking.com/hobbyking/...t_5800mAh_8S_25C_Lipo_Pack_EU_Warehouse_.html
I've balanced charged these batteries a couple of times this week and once was earlier today. Tonight I went to run a discharge /charge cycle on one of the batteries that showed a little out of balance after today's ride even though it balanced out after being charged.
Here is the sequence of events:
1 I Turned on power supply set discharge/charge parameters.
2 Plugged up negative then positive,
3 then one balance lead,
4 then second and sparks!

Singed the black wire connector and the far negative pin on balance board. I know for a fact that i connected the balance lead in the right direction with positive wire on the far right side of plug. There are only two explanations I can come up with. 1) one of the cells was too far out of balance and the cells attempted to equalize each other overloading the tiny connector (unlikely since I balance charged earlier today, although I didn't check pack with cell checker before plugging up) . Or 2), the two 4s balance leads must be plugged up in a particular order and I plugged them up in the wrong order. If this is the case its a miracle ive plugged them up correctly this many times by chance. Why couldn't they just put a n 8s balance lead on this battery!? The pack seems fine, no puffing, but now I've got a balance lead that won't connect to cell checker unless you hold it just the right way, but when you do all cells read fine 4.10 4.09 4.10 and 4.10. I've also got a balance board with a singed pin.

I need advice before I plug anything else up.
Thanks

 

[Vapology]

In the meantime is there anyway to use the 5S balance plugs on the balance board to charge my other 8s battery that has 2 4s plugs?

 

[dogman dan]

That's a balance board, not a paralleling board.

When you plug in that second 4s plug, it was connected in series with the first.

So you get the usual KFF result when you plug in a pack in series on one lead, and parallel on another lead.

What they didn't make so clear on the board instructions, if any, was that some 8 s packs come with two 4s plugs. The board is wired to charge them.

 

[major]

8 cells in series in the battery. Call most negative cell = cell #1 and most positive cell #8. Two balance leads. Call them JSTA for cell#1 thru cell#4 and JSTB for cell#5 thru cell#8. Black wire (pin#1) on JSTA is neg cell#1 or zero volts. Red wire (pin#5) on JSTA is pos cell#4 or 16V. Black wire (pin#1) on JSTB is neg cell#5, BUT also positive cell#4 or 16V. Red wire on JSTB is pos cell#8 or 32V.

On the balance board, the sockets for the JST plugs have pin#5 on JSTA common to pin #1 on JSTB. When you plug A into A and B into B, those pins are at the same voltage, 16V. BUT, if you plug JSTB into socket A and then attempt to plug JSTA into socket B, you short circuit the 4 cells in B group drawing the big spark. Pin#5 on socket A was at 32V and pin#1 on socket B was at 16V, so 16V with very low resistance = very big current per Ohm's Law.

I have a similar set up on the Thunder 1220. So I tagged or labelled my two 6s JST balance leads off my 12s battery so I get them in the correct sockets.

 

[Vapology]

Major, thanks for the explanation that totally makes sense and that's exactly what I did!
Is it possible to use the 5s taps on the balance board with the 4s taps, if each is plugged in to the far left pin in the correct order this time, with the positive wire on the right?

 

[major]

Major, thanks for the explanation that totally makes sense and that's exactly what I did!
Is it possible to use the 5s taps on the balance board with the 4s taps, if each is plugged in to the far left pin in the correct order this time, with the positive wire on the right?

I don't know. I think those balance boards are real cheap. I'd just buy a replacement. I have some sockets for the JST plugs but no 5 pole plastic housings. I have a 9 pole housing. I'll mail you a few sockets and a housing which you might cut down if you want to try to repair the balance lead off the battery. Or you can buy a 4s extension and splice it to the battery balance lead for a new JST connector.