Combining 3 cell batteries

[Pietros]

Hi Guys,

I would like to get a good discussion going on the batteries for the 500.

Combining 2, 3 cell 450 batteries is not the problem - charging and balancing them is.

What I am not clear on is the detail of what is possible - let's take 2 identical Flight Power batteries. If you connect them in a harness to make a 6s you need a 6s charger.

What is even worse is that I have the ability to charge 6 x 3 cell batteries at the same time (so that i can have 6 batts charged in an hour and go fly...). I really do not want to crawl along with one big, bad 6s charger but would prefer to charge them all as 3s and then wire them up to make 6s packs.

The question I have is this; would doing this be a bad idea? I realize ideal would probably be to charge (and balance) as a 6s but is charging (and balancing) as 3s going to be so much worse?

Also, if doing the 3s separate charging thing is not recommended, what about charging (and balancing) as a 3s2p pack (may need a balancing harness but that is not the end of the world - buying 4 or more TP 1010's does not sit so well with me...).

Anybody worked this out yet - any solutions?

[arclite5]

Charging and balancing as a 3s2p might actually work.. Ultimately I think that the only major thing is that you balance both of the batteries TOGETHER, regardless of how you charge them. Of course, balancing while you're charging is probably always the best idea, but in the end I think the only important thing is that you balance both batteries together, if even after you charge them separately.. I'll edit this post if someone corrects me for the sake of keeping the thread clean!

[Pietros]

Thanks for the reply - let's see what else comes back from the collective wisdom out there :)

[rhone]

if you charge a 3 cell on a balance charger and each cell stops @ 4.2
then a second pack the same I don't understand the difference if each cell is 4.2
when you connect them together each cell is still 4.2
please educate me

[Pinecone]

I agree, no reason to not charge them separately. We balance to make sure any single cell isn't over charged or discharged.

On charge, each pack will be balanced, so no big deal.

On discharge both packs will start at 4.2 volts per cell nominal, so also long as you don't push the pack to the bitter end, it will be fine.

Only real hazard would be hooking up a fully charged pack and a discharged pack and flying. Let's see 3 x 3.3 volt (discharged) = 9.9 volts. 3 x 4.2 = 12.6 9.9 + 12.6 = 22.5 volts. Fly to lipo alarm set at 20 volts (about 3.3 x 6) will be VERY bad on the one pack, down to about 2.9 volts per cell. And without a lipo alarm, even worse.

[rmuckley]

if you charge a 3 cell on a balance charger and each cell stops @ 4.2
then a second pack the same I don't understand the difference if each cell is 4.2
when you connect them together each cell is still 4.2
please educate me

I'm wondering the same thing.... Can you charge/balance two packs separately as you normally would?
I don't understand why it would matter....

[psindrup]

I see no reason why you can't charge and balance the two packs separately.
The only disadvantage is twice the charging time.

But combining a charged and a non-charged pack in series would spell trouble

Peter

[rmuckley]

Makes sense to me, thanks Peter.

[ke6d]

But combining a charged and a non-charged pack in series would spell trouble

Peter

Charging them in series with a different state of charge ( one half empty, one almost empty) would also spell big trouble.

There was a discussion about charging 2 3S packs in this forum a while back. The consensus seemed to be if you just want to fly around, using any old 2 450 packs would work just fine. If you want to optimize the performance of your power system, you should "match" your packs, then keep them charge/discharge/balance in series from that point on.

Dan

[psindrup]

Charging them in series with a different state of charge ( one half empty, one almost empty) would also spell big trouble.
Dan

Or, if the charger is "intelligent" enough, it would at least take ages to get the two packs balanced in relation to each other


There was a discussion about charging 2 3S packs in this forum a while back. The consensus seemed to be if you just want to fly around, using any old 2 450 packs would work just fine. If you want to optimize the performance of your power system, you should "match" your packs, then keep them charge/discharge/balance in series from that point on.

That would seem as the ideal solution (if your charger can handle 2x3s) :lol:

Peter

[Pinecone]

Discharging as a pair is good. Charging and balancing togther doesn't do that much versus charging separately. As long as you use two of the same charger.

They will both get charged to the same level, with all cells in balance.

[arclite5]

My idea was that sometimes you get a cell or two that seems to hold voltage differently. Sometimes you can end up with 3s packs that have different fully charged voltages.

For example, my resting 3s packs usually drop to 12.40-12.50v.. If you then balanced these batteries together, they'd both be mated at 12.4v. I guess the difference is ultimately very small and probably doesn't matter, since you'll be re-balancing these batteries when you charge anyway.

Finless, any input?

[invertmast]

You can always get the Flight Power V-balancer and still keep them as seperate packs and balance charge them as a 6s pack. This is what i'm planning on doing, unless they start making a 6s 2100-2500mah pack.

[Pinecone]

I guess the difference is ultimately very small and probably doesn't matter, since you'll be re-balancing these batteries when you charge anyway.


That's my point. No cell will be overcharged, which is the big thing we are trying to prevent when charging.

And unless you run your packs to the bitter end, you will not really over discharge any one cell.

And if you start with two new quality packs and run them as a pair, no cell should get THAT far off.

Basically during break in, I did this with the packs for my Hurricance 550.

[rmuckley]

All makes sense....thanks Pinecone.

[psindrup]

T
And if you start with two new quality packs and run them as a pair, no cell should get THAT far off.


Basically, what happens between the two packs, is no different from what goes on between the different cells in one pack - when it comes to discharging.

And charging is very much the same, that the cells charged are kept "within reach" of each other.

Peter

[rmuckley]

Can someone should how to make a "Y" connector to connect two packs together?

Would it be like the attached picture? Sorry for the crude drawing

[skeppley]

Here ya go:

[rmuckley]

Thanks skeppley!! :)

[skeppley]

No problem Rob.
You can buy those made up like that from most online shops, but if your soldering skills arent too bad, it only takes a few minutes to make one.
Shane

[rmuckley]

Yeah, it doesn't look too difficult to do. Did you make it or buy it?

[Pinecone]

Basically, what happens between the two packs, is different from what goes on between the different cells in one pack - when it comes to discharging.

And charging is very much the same, that the cells charged are kept "within reach" of each other.

Peter

Yes. The big thing in charging is to keep teh cells close enough such that no one cell goes above 4.2 volts. Charging them separately does that fine.

Discharging we are trying to keep any single cell from going below 3.0 volts at a bare minimum. Since I set my lipo alarm to 3.3 - 3.4 volts per cell, even if one pack is 0.6 volts lower (assuming even balance within the pack) at 3.3 volts per cell, that pack will stil be at no lower than 3.1 volts. And having one pack at 12.6 volts and the other at 12.0 volts is not likely, more like 0.1 to 0.2 volts per PACK.

[skeppley]

Just for shits and giggles, I took out two of my old TP 2100 Prolite packs with the date stamp of August 2005 (wow) that are pretty well abused, and have been sitting for a long time.
I hooked each one up seperately to the TP1010 charger and 210 balancer and juiced them up to full charge.
Then I let them sit from Saturday(12-8) until today(12-14)
I just now hooked them up in serial and hooked both balance tabs to the 210 and checked them out. They were only .035 out of balance between all 6 cells. I put them on charge as a 6 cell pack at 2.1 amps and they only needed 33mah to top off and balance all the cells within .005 of eachother.
These packs have never been flow as a 6S together for the entire time I had them since new.

So anyway, I dont really see anyone really having too many problems balance charging them seperately and then sticking them together to fly.

[rmuckley]

Nice job on the test....that's helpful info.

[spencer737]

OK i am having the same problem. here is what i want to do:)

Astro 109 charger
Flight Power V-Balancer
2x Flight Power 11.1v 2170's

can anyone tell me how to charge 2 packs with this setup???