[Carlyle]

Hey Guys,

Quick (i hope) question for you. I have a plane which uses a SmartFly regulator with duel battery input. I am also using some 2400MAH 2S2P LiFe batteries with blinky ballancers installed right on the packs. Two batteries, two blinkys. I hope you're following.

My question is, can I build a charge lead that basically has a Y adaptor built into it, and charge both batteries at the same time, and just double my amps? Every time I charge the batteries, they take the same number of MAH (within 2 or 3%), so I can't see why this wouldn't work. They should both remain at the same voltage (much the same as when they are attached to the regulator), and should devide the amps up evenly.

Anyways, what's everyones thoughts?

Carlyle

[Terry Gauvin]

The quick answer is no, you can't do that. If the internal resistance of each cell in each pack was identical then, in theory, you could but that will never be the case. The charge current will never be divided equally between both packs. You may be able to get away with it if you charged at a rate below what the blinky balancers discharge at but then it would take days to charge your pack so you wouldn't be saving any time.

[hitechflyer]

I have charged 4 sets of li-polimers at the same time using a home made four branch Y harnes all packs are the same size. I never had any problems.

If I was in a hurry I would quaddrupel the charge rate, using a lower rate would help in ballancing.

[Billpilotca]

I agree with Terry's answer. Charge them separately. If you really have to charge them at the same time get two chargers and completely disconnect from the power expander or receiver as you don't want any common ground between the two when you are charging them. If you don't you will just end up with unbalanced charging and unbalanced cells.

[4wdmt]

I was also researching on how to charge 2 packs. I stubled in this youtube vid. I don't know if it is helpful.

http://www.youtube.com/watch?v=9d2uf...eature=related

[moo]

Originally Posted by Terry Gauvin

The quick answer is no, you can't do that.

I would have to disagree, you are charging all cells to 4.2 Volts and don't care if some get there first. It will all even out.

[MarkToo]

If your batteries are the same age and have seen the same use, and they discharge and charge in a similar fashion (as you've stated), I don't see a problem charging them in this manner either.

I would suggest however, that you do not leave the charging "y" connected after charging, as the SmartFly likely has isolated inputs to protect each battery from a possible failure of the other (you probably know this anyhow).

Another possible thing to consider, I've often left blinky's attached for extended periods myself with no ill effects but, one of the fellows at the field apparently had a blinky completely drain and kill his battery over time. I don't know if this is an isolated incident or not, and am not sure if Blinky's can be safely left connected for extended periods or not - just putting it out there.

[Jeff_D]

Moo is correct. You can parallel charge LiPo's and they can even have different capacities. Here is some more info.

http://www.rcgroups.com/forums/showthread.php?t=932319

[chris p]

Originally Posted by Carlyle

Hey Guys,

Quick (i hope) question for you. I have a plane which uses a SmartFly regulator with duel battery input. I am also using some 2400MAH 2S2P LiFe batteries with blinky ballancers installed right on the packs. Two batteries, two blinkys. I hope you're following.

My question is, can I build a charge lead that basically has a Y adaptor built into it, and charge both batteries at the same time, and just double my amps? Every time I charge the batteries, they take the same number of MAH (within 2 or 3%), so I can't see why this wouldn't work. They should both remain at the same voltage (much the same as when they are attached to the regulator), and should devide the amps up evenly.

Anyways, what's everyones thoughts?

Carlyle

hi, before i answer you say 2s2p life and not lipo right(not like it makes much difference)

since both batteries are connected to the smartfly and essently running the same electronics Right,not different ones.eg ,,one for the reciever and one for electric ign.

they are pretty much connected 4s2p (in my eyes, just connected through the smartfly for redundancy).
so therefore you can charge them togeather 4s2p.
I also would not leave the blinky on all the time, I would only use it when charging.

I the batteries are LiFe then charge whatever you want.
If they are LiPo than 1c is recomended but....

Now I am no expert on batteries and this is my own opinion,
I have charged this way for years and not had any problem with any of my batteries big and small.
BUT remember not to leave unattended when charging,thats when there will be a problem.

chris p

[Carlyle]

Chris, you're right, I would consider this a 4S2P set up.

I'm thinking it is possible (which is what I thought before), so I'm going to build a lead. However, I will make sure that when I have a chance, I will charge one at a time, and insure that both batteries are still taking the same MAH.