charging two 1cells as a two cell
 

So my charger over charges my single cells a bit, but it charges my 2cells just right. So could I simply make a harness that put them in series and attach a balance wire then charge as a two cell and go?

They are 4900mah 50c SMCs. Do I charge as a 2c at 4.9 amps?

--pakk

Yes, charge as a 2S at 4.9amps. Your balancer should show both cells if you've got balancing leads wired together correctly.

any draw backs to charging it like this if 1cell if fully charged and one cell is used up?

I wouldn't - as soon as you connect them the cells will try to equalize and that may cause overheating due to high current flow. I don't know that for sure, but I'd be concerned enough that I wouldn't.

I would charge the one thats down rather than disch the one thats up, but it prob doen't matter, I just don't like discharging a lipo for discharge sake, I'd rather run it to get it there.

Depending on what charger you use & how you balance, it could be a bad thing.

If you are putting out a high rate of charge & the balancer cant keep up, you will likely over charge the heck out of one pack...

Both packs should be fairly close, & if they are not... you can force a discharge separately on each one first to any voltage you like 3.7? 4.0? & then recharge them as a pair.

If your charger can auto discharge for you it is that much easier.

Most chargers don't care what cell is where as far as voltage, it will likely hard charge until near 8.4v & then roll back amperage until a full charge.

I ran all Summer with two 2s as a single 4s... I've had good results.

I like to see the outcome on a 1/2 & 3/4 pair, I'm not willing to try.
The amount of amperage isn't safe if you plug a dead pack into a 3/4 full one.
You could with NiMh or NiCd, they just get hot... :lol:
Don't do it with LiPos...

You may be able to do it in the future with LiFe packs... who knows yet...

Good info guys. How close would you guys be comfortable with when charging 2 1cells as 1 2cell?

I know my Blinkie discharges around 0.3amps...
If it were me I would aim for 0.02v cell imbalance or less.

I've seen my own junk packs with 0.02v difference after a run, & that's no problem recharging.

You could likely go higher, but with out testing & monitoring I couldn't tell you how much.

This little guy is quite handy...
http://www.hobbycity.com/hobbycity/s...rger_System_6S

I see they replaced it with their own...
http://www.hobbycity.com/hobbycity/s...edic_System_6S

other than having to push "balance" on startup every time, my MKS works great.

Depends somewhat on cell quality. My Neuenergy lipos balance down to a few mv. My oplder Neus show imbalance of 2-5mv, the newest ones right now are holding less than that. My IP lipos don't do as well, they show 5 to 10mv differences. I have some no brand 18th scale lipos I got as part of a trade and the worst among them shows 40-60mv imbalance.

My hyperion internal balancer is +/-5mv across the cells and its never had any prob doing that and has never needed more time than the regular time to complete a charge.

Try doing them in parallel instead. It may not overcharge them (as a single cell) No balancing required.

well the problem is my charger(s) don't charge my single cell packs to the voltage I want, but they charger my 2cell packs to exactly what I want. So your suggestion would work, but not get what I want done.

--pakk

Yes, understood. Doing both cells in parallel will probably give a different ending voltage than doing just one of them. It could also wind up being even higher than one single cell (which I understand is the opposite way that you want to go)

It may also be possible to increase the charge rate , vary the lead length and/or size affecting the termination point if the charger works that way. It might also be posible to use a 4.1 setting rather than the 4.2 setting.