Max cell voltage differential?

[VOODOO]

What is the max differential between cell voltages that can still be considered a "balanced" battery? Also, to parallel charge, how much difference would be considered proper?

[Prowler901]

My voltage checker alarms when any cell is greater than 0.03 volts different.

[Skyboom]

Mine also alarms when any cell is greater than 0.03 volts. I'm wondering if it's the quality of battery were using. As for parallel charging, You mean wall charging vs charging from a car battery? Or charging multiple batteries at once? Which could dangerous. But my brother has a big scientific explanation of why using a wall charging outlet is better.

[fhhuber]

0.03 v differential between cells is a very picky standard...

The packs are generally safe to 0.2 v difference between highest and lowest cell.
when balancing chargers were rare and expensive, we used separate balancers only when the cells were greater than 0.1v difference from highest to lowest.

**************

Parallel charging is connecting 2 batteries in parallel to one charger output port. I works fine for charging many low capacity packs (especially the little 100 mah to 250 mah 1S "packs" used in micro RC such as the Parkzone/E-Flite uMX series.)

You want the pack voltages to start out reasonably close to each other when parallel charging. They will equalize in just a few minutes. The current of equalization will be related to difference between packs and internal resistance of the packs + resistance of the wring connecting the packs.
I connect the main power leads to the parallel charging board, then connect the balance leads, because the initial connection being by balance leads could burn out the traces on the board. The balance traces on the circuit board are very thin and can't handle much current.

[fhhuber]

Your brother's big explanation of how charging from a wall outlet instead of from a 12v source is probably full of fatal errors, since there is no difference as far as the battery being charged is concerned.

The modern chargers have very little power loss in changing voltage and changing from AC to DC.

But going from 12V nominal (appx 13.8 v full charge) car battery to 11.1 v (12.6 v full charge) LiPo is very low voltage change and virtually no loss due to the voltage regulation.
The change from 120VAC to 12.6VDC has more steps and more power loss to heating the charger's circuit board.

[VOODOO]

I never charge at the field from a 12vDC source. I use a eFuel converter which puts out 50amps @30vDC. I also use parallel charge boards that allow me to charge up to 8 batteries of the same cell count at once. I always limit parallel charges to batteries with total voltage no more than 0.10 differential. Each battery may have cells with 0.05 or less differential. My original question was trying to find out if there is a higher limit I have had no problems using these numbers, but sometimes a little more spread would be convenient, if safe. My chargers are SKYRC Dual output 1400watt and SKYRC 1000watt, which can both be plugged into the DC supply.

[VOODOO]

Mine also alarms when any cell is greater than 0.03 volts. I'm wondering if it's the quality of battery were using. As for parallel charging, You mean wall charging vs charging from a car battery? Or charging multiple batteries at once? Which could dangerous. But my brother has a big scientific explanation of why using a wall charging outlet is better.

I routinely balance charge 4 6s 5300mah simultaneously using a parallel charge board. The balancing keeps each battery within .01 v using this method. It sure saves a lot of time, and I have had no problems with this setup. I do always make sure all batteries are within 0.1v of each other.