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Old Jul 24, 2006, 10:05 PM
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Need help with my 3s2p 8000 packs.

I have two questions for you guys about the TrueRC packs I just got:

a) So far I have only charged 3s1p 2100 packs with my Schulze Chameleon. And no problems at all. But now I realize that the Schulze will only go to 5500mAh in its settings. Is it still save to use it for those new 8000 packs I got or is there another charger I should get?

b) This is the tough one. I got the packs with Balancer leads. Sure enough, there are only 4. Meaning that the manufacturer obvioulsy went 2p on the balancer leads as well. What a bummer.


Any advice on either?

Dan is superb when it comes to service, but its late here on the westcoast and I dont want to call him that late....but still...I am curious...
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Old Jul 24, 2006, 10:24 PM
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NE Pa
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Some say that Lipo cells last longer if you charge them less than 1C, in your
case less than 8AH. I charge my 3AH cells at 1.5 rate. It's easier on my
power supply, charger and batteries. My charge time is under 2 hrs.

I haven't heard about anyone making a lipo cell in an 8AH rating. If they do,
it probably would be much more expensive than 2 4AH cells in parallel.
What you have is 3 sets of cells, each set has 2 cells in parallel to get your
8AH rating. The only way you would have a pack such as this and have
balance plugs for 6 cells is if they had an external wiring harness to
parallel 2 3s1p packs together. Then you would be charging 2 separate packs,
one at a time, and in the end balancing 6 individual cells.

This probably doesn't make sense, best I can do on the East Coast.
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Old Jul 24, 2006, 10:37 PM
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United States, WA, Puyallup
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Quote:
Originally Posted by DerGoetz
a) So far I have only charged 3s1p 2100 packs with my Schulze Chameleon. And no problems at all. But now I realize that the Schulze will only go to 5500mAh in its settings. Is it still save to use it for those new 8000 packs I got or is there another charger I should get?
Perfectly safe to charge at less than 1C. Believe your charger has a 3 hour safety time-out, and at 5.5 amps, the charge should complete in 2 hours or less.
Quote:
b) This is the tough one. I got the packs with Balancer leads. Sure enough, there are only 4. Meaning that the manufacturer obvioulsy went 2p on the balancer leads as well. What a bummer.
That is pretty much standard - supplying single tap leads to cells which are in parallel. By definition, the voltage of each cell in a parallel set will be the same.

Bill
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Old Jul 24, 2006, 10:56 PM
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Canada,Quebec
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a) Your charger is fine, 5.5A will be easier on the pack, charge time will be around 2 hour like ebill3 said.

b) No need for extra balance leads, the "P" cells balance by themselves.

-Hugo
TrueRC Canada
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Old Jul 25, 2006, 01:48 AM
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My Robbe Balancer does not accept the 2p setting.
And in order to balance every cell I DO need to tap them seperate.
That is what balancing is all about, after all, to equalize.

I will look into this, as of now I cannot balance at all.

But thanks everybody for their help, now I know that my Schulze at 5.5 will work.
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Old Jul 25, 2006, 02:40 AM
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If you connect 2 cells in parallel, as TrueRC has apparently done, they are balanced.
If one pair of parallel connected cells varies from the voltage of the other two parallel pairs, it is the job of the balancer to get the 3 pairs of paralleled cells to read the same voltage. Think of a paralleled pair as one cell.

Bill
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Old Jul 25, 2006, 11:14 AM
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Yeah, I understand absolutely what you mean.
I will give Dan a call this week and talk to him about his balancer. My Robbe, as I said, doesnt accept the 2P setup.
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Old Jul 25, 2006, 11:24 AM
phillyphly
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No, I think that you still don't understand...

Your balancer doesn't care that it's a 2P setup. It only sees it as one cell and will work just fine.

(this is just about how every large pack on the market is built so if you don't use this format, you're outta luck on pre-built packs!)
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Old Jul 25, 2006, 11:38 AM
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the af 109 can charge at 8000 ma
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Old Jul 25, 2006, 02:00 PM
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Quote:
Originally Posted by e-guru
No, I think that you still don't understand...

Your balancer doesn't care that it's a 2P setup. It only sees it as one cell and will work just fine.

(this is just about how every large pack on the market is built so if you don't use this format, you're outta luck on pre-built packs!)
Haha...Dear Guru.
Please dont try to tell me that balancing EACH cell seperate is inferior or even equal to balancing two inherently different cells in parallel.
I am willing to compromise and go this route for now until I have the time to open up the packs and attach two 4-prong balancer leads myself.

But think about it. The 2 p setup is NO DIFFERENT from me using an external 2p harness. Only difference is that it is shrinkwrapped into one pack and has shorter leads onboard. BUT, no more dedicated balancing.

We both understand what's going on in a 2p pack, its only that I am not satisfied with less when it comes to the quality of balancing.

BTW, Dymond understands this dilemma and fits their 2p packs with 2 balancer leads.
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Old Jul 25, 2006, 05:55 PM
phillyphly
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If you use a balancer and then check voltage of each individual cell with a DVM, you will get voltage deviations (how much difference depends on your balancer but I submit that no balancer will get cells to identical voltage). If the cells are connected in parallel, the voltage of the cells are identical by definition.

Which is inferior again?

The only issue is a masking issue where the healthy cell acts as a crutch to support paralleled weak cell during discharge... but that isn't entirely bad either...
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Old Jul 25, 2006, 10:09 PM
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I have had packs in the past where one out of the 3 cells (on a 3s) was completely off.
It bums me out and I see why it is worth spending more money on a pre-matched pack.

BTW, the Robbe is what all of Europe goes Ape over these days.

All in all, thank you very much for your great advice, I truly appreciate it.
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Old Jul 26, 2006, 12:36 AM
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Hi Guys, the "masking issue" e-guru mentions is the only real downside of packs built in parallel and then in series. If a cell is bad it will drag the other down with it so you loose 2 cells instead of one.

Building cells in Series and then installing them in parallel has some pluses when it comes to keeping track of each cell, but believe me its a total pain to mainatin and balance, also if there is a flaw in a build or an issue with one of the cells one of the 3S banks will be stressed even more then the other causing overheating and possibly even faster death of the pack.

Also, costs are involved (as always)

Building a 3S2p pack the way its built now its a little less expensive; You only need one balance connector connector and the cells dont have to be perfectly matched to still work good.

For example:
Our new Heli 6S1P 4000mAh stick packs that are coming out very soon for one of our distributors, cost $10 more to build then a 3S2P 8000mAh pack just because the cells are matched. Its the same amount of cells and similar time of build but the price is determined on the amount of cells they go through to pick 6 matching ones.

DerGoetz, the TrueRC 3S2P 8000mAh packs you purchased should work well with the Robbe balancer http://www.elektromodellflug.de/bala...ncer-robbe.htm

It looks like a standard schematic for a Series pin out, and should not have problems with balancing our pack as long as the correct adapter is used.

Would you be able to post a detail photo of robbe balancer adapters? both sides please.

Best Wishes,

Dan
TrueRC
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Old Jul 26, 2006, 07:14 AM
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Joined Sep 2002
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Quote:
Originally Posted by DerGoetz
Haha...Dear Guru.
Please dont try to tell me that balancing EACH cell seperate is inferior or even equal to balancing two inherently different cells in parallel.
Ok, then I will.

How can having two cells at precisely the same voltage (in balance) be any diferent whether they were connected together, or not, when that precise adjustment of their voltage was made?

Oh,...I see. The main downside is that it reduces the number of balancers that vendosr can sell to naive people..and makes it hard to justify sloppy vendors who buy in 1p packs and simply parallel them.

Fairy nuff..
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Old Jul 26, 2006, 07:14 PM
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Sorry to beat a dead horse, but perhaps what is going on here is as follows:

I, and most other posters, believe the 3S2P pack is constructed by connecting 2 cells in parallel, 2 more cells connected in parallel, and another 2 cells connected in parallel. Then the 3 parallel pairs are connected in series to make the 3S2P pack. The conventional method of making a 3S2P pack and pretty much confirmed by the pack manufacturer, Dan in post #13. If constructed as such, I, and others, believe trying to balance individual cells would be an exercise in futility.

Quote:
Originally Posted by DerGoetz
But think about it. The 2 p setup is NO DIFFERENT from me using an external 2p harness. Only difference is that it is shrinkwrapped into one pack and has shorter leads onboard. BUT, no more dedicated balancing.
Based on the above quote, perhaps DerGoetz believes the pack is constructed by connecting 3 cells in series, another 3 cells in series, and then connecting the 2 series strings in parallel. In that case, he may be justified in his disappointment at receiving only 4 tap leads. If indeed the pack were made in such a manner, I'm not sure I would know how to go about balancing the cells in the pack. I guess it would be necessary to break the parallel connection and charge each series string separately.

Bill
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Last edited by ebill3; Jul 26, 2006 at 07:42 PM.
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