HobbyCity Lipo Warranty - Important Information!

[simplechamp]

Originally Posted by KaztheMinotaur

I just looked up the Hobby City battery warranty myself.

I was charging my Zippy 5S, 5000mah, 30C batteries for the first time. I had 2 cells come up to 4.13 and the others were full, balance charges. I have it on the blinky now and then I will charge it at a lower amp rate.

Is that to much of a difference?

Personally I think anything more than 10mV difference is too much out of balance. So that would be having most cells at 4.20V and one or more other cells at 4.19V. Even a cell at 4.19V bugs me, and I want all my cells balanced to within 5mV or less.

Of course HC says it's acceptable for cells to be up to 245mV out of balance, which is ridiculous IMO. It would be nice if we could get some official recommendations from lipo manufacturers on what is acceptable as far as cell balancing.

I got the 4.09V cell to go back into balance by putting my charger into the slowest most accurate balance mode. BrianG also suggest just charging the individual cell as a 1s pack using the main charger leads directly into the balance taps of the low cell using some high-value resistors (see his post for more details). Hopefully you'll be able to get your cells back in balance too!

[KaztheMinotaur]

So the balance will be more accurate when balance charging at .5A instead of 5A?

After being on the blinky for a while (4) cells are 4.07 and the 5th. is 4.08. I'll balance charge it tomorrow.

[BrianG]

Originally Posted by KaztheMinotaur

So the balance will be more accurate when balance charging at .5A instead of 5A?

After being on the blinky for a while (4) cells are 4.07 and the 5th. is 4.08. I'll balance charge it tomorrow.

Not sure about "more accurate", but it will balance easier. If you are charging a 5Ah pack at 1C, that's 5A. Most balancers bleed off excess charge at a rate of 100mA-300mA. Normally this is fine for packs that are slightly imabalance. But a highly imbalanced pack may reach 4.2v/cell before the balancer has a chance to do its job.

Look at it another way: You are charging a 4s pack at 5A with a balancer capable of 100mA discharge rate. Let's say one cell is high, which means the balancer will bleed 100mA off the cell as it is getting the 5A charge, which results in a net charge level of 4.9A (5A-0.1A). Depending on how bad the imbalance is, that high cell could exceed 4.2v before the others catch up.

[KaztheMinotaur]

Yeah.

[Bondonutz]

Originally Posted by KaztheMinotaur

So the balance will be more accurate when balance charging at .5A instead of 5A?

After being on the blinky for a while (4) cells are 4.07 and the 5th. is 4.08. I'll balance charge it tomorrow.

Not being arguementive but I've found that with my charger/balancer Venom Pro that with a 5amp setting the charger finishes the charge /balance process much faster and with a higher finishing amperage IE 0.4 volts. When I set the charge rate at 2.5amps the charger takes much longer at the last part of the charge by finishing at 0.1 and really is much more thorough at balancing each cell. You can see the way is bleeds off the higher cells voltage while the lower ones are catching up.
What I've elected to start doing is I'll charge my packs at 5amps to acquire 75% charge and then drop the charge voltage down to 2.5 and let it finish that way (I can change charge rate while charging) it finishes more precisely.
I also use my seperate balancer prior and after charging, ben doing that for years and have had great luck with Lipos.