Thanks in advance for any help.

I am trying to wrap my mind around this. Discussion assumes Two 2S Lipos.

So I am going to solder up a parallel charge cable, this seems simple enough. Go from one male connector having a positive and negative and branch each wire to two female connectors, each with a positive and negative.

The balance portion is what confuses me. It seems balance boards and splitters tend to go from a 2S (3 wire) balance plug to two 2S balance plugs. My understanding is the idea of a balance plug is for the charger to check and adjust the voltage of each individual cell of each battery, to balance them.

Lets assume there is battery 1 and battery 2. Each battery having an A cell and B cell. In the method I have described above, cell 1A is connected in parallel to cell 2A and cell 1B in parallel with 2B, at least that is how I understand it. To me, it seems the charger then sees them as a single cell, how does it balance between them.

To me, I would think the proper way to do it would have a 4S balance plug branch off into two 2S balance plugs. that way... the charger would be balancing each individual cell, 1A, 1B, 2A, and 2B. Maybe someone could enlighten me?

If its important I have a Icharger 206B. This is my first foray into electric RC. I appreciate your patience.

Thank you!

Nope, you are escentually charging one big 2S battery. At least as far as your charger is concerned.

It will see 2 cells and the same voltage as if it were just one two cell battery. What will change is the charge current because you doubling the mAH.

It's only the, for lack of a better term, "volume" and hence charge current that will change. For example, assuming you don't have a charger that will do the math for you ( you should get a good charger and Para board if you intend to parallel charge); assume you charge two 2S 4100mAh batteries in parallel.

A 1C charge rate would be 8.2 amps at full charge voltage would still be 8.4 volts. The charger would charge the battery as if it were a 2S 8200mAH battery.

IMHO if you're going to do much parallel charging you should invest in a very good fuse and thermo protected parallel charge board and a high end charger. Especially given what seems seems to be prep city to abuse LiPo batteries in the the RC car hobby.

Something along the lines of a PL6 and FMA (or similar) board for instance.

Take a look at buddyrc.com or progressiverc.com for higher end chargers and para boards.

Each pair of paralleled cells essentially balance each other, as they are directly connected by the parallel balance connection. Any imbalance is quickly eliminated by this direct connection. In a sense they are shorted out against each other.

What the charger can't see is the balance condition of each pack. For parallel charging it is important to have reasonably healthy packs in good balance. Wise to check the cell voltages of each pack, at least occasionally anyway, before connecting in parallel to charge.

Just charge them one a a time or get a dual charger

You can parallel charge them (make a 2S2P battery) but there is a 50% chance you miswire and cause a short, which best case results in melted wires

Same for serial charging (make a 4S battery)

Serial charging is certainly riskier, switching the balance leads would be a problem, or the main leads with the jumper. Parallel not so much, mixing up the balance leads isn't an issue, just need to be plugged in with correct polarity same as single pack charging.

Although I agree a dual charger is simpler, and more flexible for many/most uses.

Thanks for the replies.

I don't have a strong electrical background, just the necessarry EE class during my Mechanical Engineering curriculum.What bothers me about the parallel balance cables, is that if there is a difference in voltage between say cell 1A and cell 2A, wouldn't there be a significant amount of current going through a tiny balance cable in order to balance them out?

Ideally the packs are at similar voltages - similar charge states before starting. And all in good balance as mentioned.

Notice how a pack voltage quickly rises when charging, and sags under load. This helps limit the equalization current. Unless the difference is fairly dramatic tests have shown that the packs equalize fairly quickly with minimal heating of the wires. Some have even tested very significant differences with little issue.

There are different opinions regarding hook up order. Some suggest the balance wires should be hooked up first, as then the voltage difference is limited to a one cell level. Others recommend the main pack wires first, as the main wires can handle more current. This is the way I would go, as the currents are actually similar for either approach, use the larger wires to achieve equalization.

Safest approach is to use one of the "safe" or "MPA" boards that have fuses on all connections as DWill mentioned.

Thanks!

I also found this article which is helpful. very similar to your explanation just fleshed out with an interesting test.

https://sites.google.com/site/tjingu...allel-charging

Yes, TJ's site is full of good info.

Sky the whole thing with parallel charging is that the to be charged battery's are close in voltage to each other to NOT have a sudden burst of voltage to the other cell.. so connect the main leads + pos and -Neg 1st.. then connect the balance leads..no matter what you are going to get some voltage transfer from one cell to the other...but that is the risks of charging this way..