What gauge wire for paralleling Lipo at the cell level

[John in CR]

The time and effort required to balance charge 12 lipo packs is simply absurd. I've got one of those 4X chargers, and I'm willing to invest the couple of minutes occasionally to disco the series connections and program the 4 chargers to balance charge in one shot. I don't however want to do that 3 times, so I want to invest the time up front to essentially turn my 5ah packs into 15ah packs with 3 physical packs side by side. I believe this will also reduce my Lipo risk, since weak cells will be supported by 2 other cells.

What gauge wire should I use to tie the cells in each parallel pack together?

 

[EBJ]

I'd suggest you just buy a parallel harness from EPbuddy
They use the same wire-guage as the original (I want to say that's 24awg)

 

[E-bike4life]

What is the cell count in the 12 Lipo packs you will be charging? At what amp rate will you be charging? As suggusted EPBuddy has some nice harnesses with silicone wire to boot.

I use this set up for balance charging my 12 3s 5000mah Zippys at 12.5amps on one 206b iCharger

 

[neptronix]

Well, balancing current is about 1/2 an amp *at most*.

Thus, the stock 24/22awg is just fine.
Those balance boards are not so good because of the discharge lead. You don't want to use something like that on a permanent basis 12awg is just too small unless you are running something like a 15-20 amp kit.

progressiverc sells some balance lead parallel cables, anywhere from 2x to 6x.

As far as the discharge itself, you can use whatever is equivalent to a third of the main discharge diameter.
I don't care to calculate it myself, so i run 8awg to 12awg for each individual pack.

BTW before you turn them into a big parallel unit, make sure they are properly balanced to all the same voltages within about 0.02v.

 

[E-bike4life]

Well, balancing current is about 1/2 an amp *at most*.

Thus, the stock 24/22awg is just fine.
Those balance boards are not so good because of the discharge lead. You don't want to use something like that on a permanent basis 12awg is just too small unless you are running something like a 15-20 amp kit.

progressiverc sells some balance lead parallel cables, anywhere from 2x to 6x.

As far as the discharge itself, you can use whatever is equivalent to a third of the main discharge diameter.
I don't care to calculate it myself, so i run 8awg to 12awg for each individual pack.

BTW before you turn them into a big parallel unit, make sure they are properly balanced to all the same voltages within about 0.02v.

Just out of curiosity how are those 4mm bullets working out for you? I noticed mine were getting warm at 35 amps so I switched them out to 6.5mm on the discharge end.

The board has 14awg on the discharge wire and is only used for charging :lol: The board is rated at 30amps max, but the 14awg wire does get warm at 12.5 amps and even warmer at 22amps. My 12awg never even gets warm when pulling 35amps even thru a xt60 connector from hobbyking

John you are only reffering to charging for this harness correct?

 

[John in CR]

This isn't about the balance charging, which is low current. As a parallel connection of 3 cells that will see about 140A peak, small wires sounds like a fire hazard during discharge to me. Differences in IR or a weak cell could easily create significant currents through those parallel connections as the current winds its way through the pack. Put another way, even on a low power pack you'd never see 22-24ga wire for the parallel connections, and this is definitely no low power pack. I was hoping I could get away with 14ga.

Am I missing something?

 

[E-bike4life]

This isn't about the balance charging, which is low current. As a parallel connection of 3 cells that will see about 140A peak, small wires sounds like a fire hazard during discharge to me. Differences in IR or a weak cell could easily create significant currents through those parallel connections as the current winds its way through the pack. Put another way, even on a low power pack you'd never see 22-24ga wire for the parallel connections, and this is definitely no low power pack. I was hoping I could get away with 14ga.

Am I missing something?

I think WE are missing something :lol:

Just use what ever gauge wire you need to safely transfer the current at which the wires will see.

These are conservitive and safe values
14 gauge 15+amps continous 30a peak
12 40+ cont 80a peak
10 75+ cont 150a peak

If your wires are going to see 140a peak I would go with at least 10awg 8awg would be better.

 

[John in CR]

This isn't about the balance charging, which is low current. As a parallel connection of 3 cells that will see about 140A peak, small wires sounds like a fire hazard during discharge to me. Differences in IR or a weak cell could easily create significant currents through those parallel connections as the current winds its way through the pack. Put another way, even on a low power pack you'd never see 22-24ga wire for the parallel connections, and this is definitely no low power pack. I was hoping I could get away with 14ga.

Am I missing something?

I think WE are missing something :lol:

Just use what ever gauge wire you need to safely transfer the current at which the wires will see.

14 gauge 15+amps continous
12 40+ cont
10 75+ cont

If your wires are going to see 140a peak I would go with at least 10awg 8awg would be better.

I'm not talking about the series connections. I'll just use the factory series connections and parallel the leads, but I want to parallel the cells too. The wires I want to add will turn three 5ah 25c 1p6s packs into one 15ah 3p6s .

 

[E-bike4life]

Ahhh. Then yes, if you plan to parallel the 6 cells together then 14awg will be more than sufficient.

 

[dogman dan]

Even under heavy discharging, once paralelled at the balance wires, you'd see such small difference between the cells that the small balance wires are enough.
Be nice though, if HK started making packs of 2p, 3p etc. A 2p 5s pack would be popular with us I bet.

 

[NeilP]

Are you talking about removing the original balance leads all the way back to each cell or just tapping in to the balance wires that are already fitted.

If you are wiring all the way back to each cell, then I would go a gauge or two up from what is originally fitted. Not so much that the balancing will need it, but just for the ability to charge individual blocks of cells at a reasonable current direct from the balance wires.

if you are just coming off the wires that are already on he pack, then I would just go the same as what is already there

 

[auraslip]

I like this method. Solder really short 14 gauge to 4mm bullets or directly to the packs to ANL fuse. On the other end solder 8 gauge wire.

 

[NeilP]

Oooo i like the fusible links...can you replace the 'fuse' or do you have to unsolder. But those would be for the main harness right? not the balance leads?

 

[auraslip]

Correct. For main power. You'd have to unsolder them, but honestly if they do blow it'd be like a huge situation and probably something else would need to be fixed. They're more a last line of defense than the standard, "blow and replace" fuse.