How to combine balance leads?

[wesnewell]

I've got two 5s packs and one 4s pack in series for a 14s pack. I need to combine the balance leads into two 7s balance connectors so i can charge the whole pack at once. These are Zippy packs with JST balance connectors. I'd prefer a ready made solution if you know of one. Otherwise I'd like to split the 4s balance connector and put 2 each with the 5s packs. I'm just not sure which wires to split out, and what to do with the extra wire from the 4s pack. Anyone?

 

[vanilla ice]

Wire all the main leads in series. Get two of the 7cell JST plugs and start swapping over one balance wire at a time. Use a meter to make sure they are in order before you solder the wires over to the new pins! Which chargers are you using? Its a PITA but you may have to feed out a couple of new fat main leads between the 7 and 8 cells (if your chargers cannot charge straight in to the balance plugs).

 

[snowranger]

I bought the jst-connectors from digikey and plan to parallel the male connectors on a breadboard. That way I can eliminate as much wire splicing as possible.

 

[vanilla ice]

Whats wrong with paralleling wires? I have a 6s pack cell level paralleled to two 3s packs. Works great, no breadboards required. Anyway the OP is talking series not parallel.

If your chargers do require the main leads in addition to the balance leads, I guess the easiest way way to go is to split the 4s pack in half and make two 7s packs that way.

 

[snowranger]

my bad. For my case, it turns out cheaper to buy the pcb rather than ready made pigtails.

 

[Alan B]

Here is my solution:

I sent this board in for manufacturing via BatchPCB. If it works we could make it available. If I release it into their "market" anyone can have a few made.

 

[nutnspecial]

I'm looking to combine two 3s balance leads into one 6s jst for easier monitoring.

The two 3s strings are in series with each other though which might be an issue?

Also, which wire to tie together or eliminate when combining 3s + 3s (8 wires) balance leads into a 6s (7wires)?

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I'll also keep searching and post a link if I find something before a reply. I'm sure it's pretty simple and in 'here' somewhere lol.

 

[dogman dan]

As you combine balance leads from whatever two small packs, to one large (in series) one, the last + wire on the plug of one pack, will be spliced with the negative lead of the next pack.

So for example, a 3s and a 4s, rewired to a 7s plug.

4 wires on one, 5 on the other, and 8 wires on a 7s plug. The "extra wire" is the negative wire on the second pack in the string.

The 3 s plug will have the negative wire on it. then 3 more positive. the last, usually red, positive wire on the 3s pack will be Y spliced with the black negative wire of the 4s pack.

Or the reverse, if you use the 4s pack for cell one.

Since those two cells do get connected in series anyway with the big discharge wire, you could also just snip off the extra negative wire. But leave enough wire to put it back the way it was, if you should want to later on.

Using the method to splice that extra wire would be a good choice if you are making up a harness with 3s and 4s plugs on one end, and 7s on the other.

 

[nutnspecial]

I just am confused by my meter only showing polarity change on the two end wires. The ones in the middle or from them to either end always shows positive voltage on the meter, no matter which way the tester leads are arranged for polarity. Maybe I didn't test enough.


But thankyou Dan that sounds so simple! Just arrange the two plugs with positives (red wire) on the same sides , plugs side by side, and transfer all the pins to a larger plug, just how they lay.

And overlap the last pin of first plug with the first pin of 2nd plug!

Since I'm putting an extension on anyway, I might mod the 3s plugs to jam into the female of the 6s extension, so there's no need to fart with those jst-sm pins!