Charger cables: parallel vs series (with balance plug)

[RyanRC]

I have a charge cable that allows up to 6 batteries in parallel:
parallel charger lead

My batteries allow up to 2C charge (180mah Lectron 45C), but when charging 6 at 1.2A it hits 4.2V and the charger shuts off when they are actually 4.13-4.17V. If I charge them at a lower C rate or fewer batteries on the lead (3 or less) then I get 4.17 or higher.

I've seen these before and wonder if it might work better with my charger (that seems to shut off too soon).
6S balance cable

Also wondering the same for my yet to be flow mCPX BL and the batteries I have for that. Thought those only allow 3 battery charging if using a balance plug.

[Bimbo]

I think this is a pretty common thing to happen. While charging, the charger applies a voltage to the battery to charge it. When the charger stops charging, the voltage will drop a bit again. This is more pronounced with smaller batteries.

The reason you're getting higher voltage at a lower charge rate, is because (at least my iChargers) terminate charge when the charge current hits 10% of the set charge rate. So if you set the charge rate, say, at 10A, it will stop charging when it hits 1A. If you're charging at 1A, it will stop charging at 0.1A (don't put these kind of currents into your small batteries!)

My iCharger also has the 'fast charge' option, it will stop charging when the rate hits 20% of the set rate, so it'll cut off sooner, and charge a little less into the battery.

It doesn't really matter if you charge in series or parallel, although the series charge will allow for larger state-of-charge differences between batteries. I assume you know you can't mix near full and near depleted batteries when charging in parallel

[RyanRC]

Originally Posted by Bimbo

The reason you're getting higher voltage at a lower charge rate, is because (at least my iChargers) terminate charge when the charge current hits 10% of the set charge rate. So if you set the charge rate, say, at 10A, it will stop charging when it hits 1A. If you're charging at 1A, it will stop charging at 0.1A.

Thanks, I figured it was something like this but wasn't sure. That has helped me get better charging results. Lower A charge rate has allowed me to get more mah when I charged up today.

Originally Posted by Bimbo

It doesn't really matter if you charge in series or parallel, although the series charge will allow for larger state-of-charge differences between batteries. I assume you know you can't mix near full and near depleted batteries when charging in parallel

Yup, and being able to mix state-of-charge is something I hadn't considered. I will usually fly and use my TX's timer. My batteries are usually very close, but I do spend an annoying amount of time checking each's voltage before charging. Then I give them ~20 minutes to balance after I connect them to the charge lead. Being able to charge a wide range of voltages will definitely help me spend less time fiddling with batteries and more time flying.

Thanks for the help, very useful and just what I needed.

[Bimbo]

Originally Posted by RyanRC

Yup, and being able to mix state-of-charge is something I hadn't considered. I will usually fly and use my TX's timer. My batteries are usually very close, but I do spend an annoying amount of time checking each's voltage before charging. Then I give them ~20 minutes to balance after I connect them to the charge lead. Being able to charge a wide range of voltages will definitely help me spend less time fiddling with batteries and more time flying.

Thanks for the help, very useful and just what I needed.

No problem dude! I have find though, when I use a timer, the batteries are usually pretty close. As in the difference is less than 0.1V. (Pulse 860 mAh 3s, for trex 250). You can do the math with internal resistance of batteries (I=V/R) to see what the current will be when you connect them, I'm pretty sure it's low though. And since the SoC is similar, it'll only have that current for a couple of seconds. I'd say there's really no reason to not start charging right away when the SoC is similar.

Nowadays I don't even check my SoC when I charge my batteries... Yeah maybe I should...

Do notice though, that when charging in series and one of the batteries is seriously more depleted than others, the balancer is doing most part of the work. My balancer can only handle a current difference of 300 mA, so that means if one cell is full and the other depleted, it'll charge the depleted battery only at 300 mA... So it would be faster to charge them individually.

[D_Vail]

I have the one from astroid. Works great. Balance charge 6s at approx 2c which is about .3A same lectron 45c batteries. Charge all 6 in about 20 minutes all come off charger at 4.19~4.20v.

[D_Vail]

Came across this thread again and just happened to be charging the batts, so thought I would add pics..