Discussion About parallel charging of Lixx / PB packs.

[everydayflyer]

Doesn't it look like the balance connector of the blue pack is NOT connected?

Sure does !!!!

If you go back and read the last several post on the users problem he states how he has checked the balancinhg difference. At times multi packs connected to the balancing PCB only,sometimes to it and other pack directly connected to charger etc.

To add to the confusion there are several jumping into the discussion with their parallel balancing issues and I it is often difficult to follow one users problem much less two or three in the same discussion.

OP snip

I somewhat hessitated to put up this photo with all the wires everywhere as it might lead to more confusion about my setup, so I'll repeat that I have even eliminated the extensions and board, to just plug directly into the charger and got similar results. Point of the photo is to show the one pack unplugged, so charger is reading voltage of the other pack, which is extremely unbalance. The other pack was about the mirror image (voltages reverse order).

Charles

[chadr]

I charged 3 2s 500mah batteries today at 500mah. The charge time was 150 minutes with ~1000mah put back into the batteries. The final cell voltage reported on the 106b+ was 4.20 4.20.

I checked each of the packs individually on the charger.

pack 1: 4.20 4.20
pack 2: 4.20 4.19
pack 3: 4.19 4.23

Not that I am too worried about slight over voltage cell, but as others have suggested it may not be a bad idea to set the max voltage to 4.15 or less for extra cushion.

[maxmekker]

A quick question. Does it matter if one pack is 20-30c and one is 30-40 c ?
(both turnigy 6s 2600)
Thanks

[everydayflyer]

Have you read and studied the first post of this thread?

In very simple terms volts equals pressure. If the balancing leads are in parallel
Pack A cell #1 ,pack B cell #1 , pack A cell #2 pack b cell #2 etc.
then all the cells have to end up at the same volts (pressure) .

Cells which have lower IR (higher C rates) may charge a bit faster but during the CV (slow chare) stage they should all balance. A tired / worn cell will drop volatge more/ faster after the charge stops
Charles

[maxmekker]

Thanks everyday.

[vashon10]

Originally Posted by mrforsyth

Your IR's look pretty good and not far off from one another but still may be a contributing factor. My suspicion is that the imbalance may be caused by resistance differential in your balance leads in conjunction with the IR delta. Balance leads should be kept as short as practical with as few connector interfaces as possible. An oxidized or somewhat loose connection can cause uneven voltage drop and may induce the pack to pack imbalance that you're seeing.

thanks and informative. I do cover my bal plugs with a plastic and wire tie to keep them protected while in use (from dirt and water).

Originally Posted by mrforsyth

As your IR's are very low, your charger will spend very little time in CV mode so cells between packs do not have much time to equalize, especially if the balance leads are very long. Try making them shorter and reduce the number of connectors and I suspect that your imbalance will significantly improve. Leaving the balance leads connected for a period of time after charge termination will also accomplish the same end result.

In the pic, the bal leads are directly connected to the charger, and they're pretty short. Again, same results as with the full hardware setup.

Originally Posted by mrforsyth

You can also try to parallel charge in 'normal' mode without the balance leads attached since you have established that the packs are not prone to imbalance when charged individually.
Mark

I will try the other mode of charging that you mention. I think it allows monitoring the voltage for protection, just doesn't bal as I recall.

[mrforsyth]

Originally Posted by vashon10

I will try the other mode of charging that you mention. I think it allows monitoring the voltage for protection, just doesn't bal as I recall.

You might also give another shot at your full hardware setup and use the single connection to the charger. After charging completes, unplug the main discharge connector and balance lead from the charger and leave them plugged into both packs for about 10 minutes or so. That should be sufficient to bring all cells to equilibrium. I haven't poked around enough on my 106B's to determine the impedance between balance taps within the charger. If they have fet switches or other protection circuitry, I imagine that equalization through the charger would take longer than through hardwired harnesses.

Mark

[vashon10]

I did another parallel charge of the two 2s 5K packs, but this time with the bal turned off. Very revealing. Both packs started at identical voltage (all 4 cells). Charged at 8 amps and the blue pack sprinted ahead in voltage. It reached 4.20/4.20 while the other pack was 4.15/4.15 and the charger was showing 4.17/4.17. These were all observed while it was charging, by unplugging one lead and seeing the other pack's voltage. Of course after stopping the charger, all the voltages settled back about .02, but still retained the same type of divergence. Then while sitting still connected began equalizing rather quickly. Can't explain that change in behavior.

I'll have to do the same test on my 3s packs. They have identical gage leads. Note the blue pack has 8 gage wire while the red pack is 12 gage. Might account for some of current bias.

[mrforsyth]

Interesting results and exactly as expected given the IR tests that you performed earlier. The pack leads may be a very small contributor to this phenomenon but the main contributor is the internal resistance of the cells within each pack. Not necessarily a problem however as .05V differential is not significant and will vanish if packs are left connected for a period of time after charge has completed.

My standard procedure when parallel charging packs of different capacity or internal resistance is to leave packs connected for 10 minutes or so to allow them to level out. I also limit charge rate in these instances to ~1C. When parallel charging similar packs I will occasionally charge at up to 2C rates and have never had nor do I expect to have any problems.

Monitoring pack health by checking IR on occasion will go a long way in ensuring that you have no issues. In addition to being a phenomenal charger, the iCharger is an excellent tool to help monitor pack health.

Mark

[vashon10]

I manually stopped it when I noticed the one pack hitting 4.20. Now this was 4amps per pack, so less than 1C per pack. Are you saying if I kept it charging, the blue pack would not have continued to climb beyond 4.20 ? Seems that with the charger seeing the 4.17/4.17, it would keep rising. I said I had the bal off, but I actually set the bal option for CV phase (only). So I'm thinking it would keep rising until the charger hits 4.20 and I'd be concerned by then the blue pack would be at 4.23 or something. I guess I could drop the max voltage (CV trigger) down to 4.17, but then it might not work for the other packs.

[mrforsyth]

The blue pack may have continued to climb slightly above 4.20V / cell but it would have been very temporary and not a big problem as it would have continued to bleed current to the red pack during CV stage and after charge completion if left connected.

And yes, I recommend lowering the termination threshold to below 4.20 volts. It'll be easier on your packs in the long run. This was the first thing I did when I pulled my 106B's out of the box and another reason why I like them so much.

[Julez]

My settings are:

Balance speed slow
Balance trickle on
Li Balance CV phase

Vashon, I would recommend to make a very slow charge with both packs at this setting, with 500mA or so.
Then they will surely be balanced as good as possible.

Now make another experiment: When charging in parallel, check the individual cell voltages without removing any balance connections. I think that this might be responsible for some problems.
It might be difficult to do this. I recommend poking needles through the wires close to the pack.

[chadr]

Originally Posted by mrforsyth

And yes, I recommend lowering the termination threshold to below 4.20 volts. It'll be easier on your packs in the long run. This was the first thing I did when I pulled my 106B's out of the box and another reason why I like them so much.

What voltage do you use?

[mrforsyth]

Originally Posted by chadr

What voltage do you use?

Mine are set at 4.17 volts.

[mrforsyth]

Originally Posted by Julez

Vashon, I would recommend to make a very slow charge with both packs at this setting, with 500mA or so.

500mA charge on 2 5000mAh packs in parallel is a ~20 hour charge (depending on DOD, of course). There's little question that both packs will be in perfect balance after such an exercise but in my belief the same end result may be accomplished by simply leaving the main discharge and balance taps connected in parallel to one another for 10 minutes or so after charging completes.

As indicated previously, a few millivolts of variation is no cause for concern but can be eliminated by simply allowing the packs to reach equilibrium after completion of charge cycle.

Mark