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Old May 08, 2004, 01:51 AM
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Tel Aviv
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On Orbit Charger - How do I balance LiPo packs ?

Hi

My quest continues..

I have Orbit microlader pro:
1. How do I balance LiPo packs like 4s4p ?
Do I have to balance it like People recommend ?

2. My Orbit is limit for 8 amper charge: can I still use
packs greater than 8000 Mah - by charging it less
then 1c ?

thank you !
Ido
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Old May 08, 2004, 03:00 AM
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on q1: you balance packs by bringing each indivdual cell to a full charge as determined by the charger. for cells above 4.2v, discharge the cell to below 4.2v and then charge it to full.

on q2: yes you can charge cells below 1C.

JT
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Old May 10, 2004, 02:47 AM
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q2 - yes no worries there, just takes longer.
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Old May 10, 2004, 04:56 AM
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"you balance packs by bringing each indivdual cell to a full charge"
In case I have 4s4p - I need to charge any of the 8 cells ??!
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Old May 10, 2004, 08:06 AM
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4s4p will be 16 cells, not 8. And as far as I'm aware, you need to charge each cell individually. I'm getting a 3s2p pack soon and I think I'll probably have to take the shrink wrap off to charge each cell, does anyone know if this is really necessary?
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Old May 10, 2004, 02:55 PM
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Quote:
Originally Posted by thermite
4s4p will be 16 cells, not 8. And as far as I'm aware, you need to charge each cell individually. I'm getting a 3s2p pack soon and I think I'll probably have to take the shrink wrap off to charge each cell, does anyone know if this is really necessary?
If you have a 4s4p pack, you must either charge each 4p block individually to 4.2V or add 4 LiPo-balancers to your pack.

For a 3s2p pack you either need 3 LiPo-balancers or you charge each of the three 2p packs individually.

Parallel cells are always balanced, nothing to worry about there.
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Old May 10, 2004, 03:05 PM
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I don't quite understand that, Suzanne.
Say I've got a 2p pack, the charger sees that as one
cell but just at a larger capacity. If they were unbalanced
to start with, it will see the peak voltage of the cell with more
of its capacity utilised first. (Please correct me if I'm wrong)
One cell could be at 4.2v and the other at 4.0 but the charger will
still see 4.2 volts so, as far as it's concerned, it's full.
The cell with less capacity used is in danger of approaching
deeper discharge than the other (and doesn't provide its full capability)
I hope this makes sense and please,
if I've got it wrong somebody explain.


Thermite.
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Old May 10, 2004, 03:15 PM
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And here is an answer

This is an answer I got today by email:



Hello Ido,

After a few years of extensive research, testing and development, we have found it not neccessary to balance our LiPo packs if they are properly cared for. Some of our top pilots have near 400 flights on multi "S" and multi "P" packs with no signs of imbalance. With our matched cell technology, building the pack right from the start is the best way to prevent imbalance.

In the future, we will add protection circuitry to all packs to prevent any problems during charging. This is the best way to prevent problems due to overcharging, wrong charger settings, etc which can damage or ruin LiPo packs of any size. These circuits will begin shipping in packs in less than 2 months.

Thank you,

Thunder Power Batteries
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Old May 10, 2004, 03:23 PM
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That would be nice.... in a perfect world.
But, there are still reports of bad cells without abuse or even use!
I'm a very careful person and unless I'm satisfied that something
is the way I want it (i.e, safe!) then I'm not happy.
TP may state this but there are other manufacturers with different
characteristics to their products.
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Old May 10, 2004, 03:43 PM
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I have 5 ETEC 1200 mah 3S1P packs. All made by me. None have required balancing until a week ago. I tested all packs and 1 pack came out with only 834 mah capacity.

Each cell's voltage was taken and came out with the following,

C1 - 4.3
C2 - 4.16
C3 - 3.88

C3 took in an incredible 580 mah after being fully charged. I will be cycling it today to see if I have gotten back the capacity from the pack.

As like some of you, I too did not believe cell imbalance until I saw it. Note that in two years of flying li-polys, not all of my packs required balancing as the rest of them are still pretty much up to spec.

JT
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Old May 11, 2004, 02:28 AM
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Imbalance slowly creeps in - without balancers or taps you don't notice it until it's too late. With balancers, the blinking lights show you what's going on with your pack during each charge. The balancers give you a certain comfort level, even if they have nothing to do for many cycles. You still know they are there and they will show you when things start to go wrong.

I agree with Charlie that his carefully matched packs have a lower risk of developing a substantial imbalance than unmatched cells. But it's not a perfect world, and even TP packs have gone bad in the past. Not knowing what's going on inside my pack would definitely make me nervous.

Also, I do not like the idea of a protection circuit in the pack, because putting something in series with the cells adds an additional point of failure. The balancers work in parallel with the cells. So if a balancer should ever fail, the pack will still work. All you lose is a balancer, not the power to your plane or helicopter.
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Old May 11, 2004, 06:41 AM
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1. “Imbalance slowly creeps in - without balancers or taps you don't notice it until it's too late.” – Suzanne, post #11.

2. “Parallel cells are always balanced, nothing to worry about there.” - Suzanne, post # 6.

Paragraph 1. is only true if you charge in series.

Paragraph 2. is always true.

So, why not always charge in parallel only?

http://www.rcgroups.com/forums/showt...+Configuration

Sorry, Suzanne, but means for coping with the imbalance problem inherent in series charging LiPos dominate the discussion on ezone. Newbies could get the impression that series charging is unavoidable, and I need to counter that false impression as best I can.

- RD
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Old May 11, 2004, 07:50 AM
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I think I've sorted my confusion now. If cells are in parallel, I guess they keep one anothers voltage balanced, is that correct?
So in a 3s2p pack, I would only need 3 taps? Would it be obvious if any one cell is behaving strangely or dying?
Is it best to check each individual cell periodically?
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Old May 11, 2004, 09:20 AM
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"I think I've sorted my confusion now. If cells are in parallel, I guess they keep one anothers voltage balanced, is that correct?"

Correct.

"So in a 3s2p pack, I would only need 3 taps? Would it be obvious if any one cell is behaving strangely or dying?"

The parallel pair containing the bad cell will be lower in voltage after the pack is discharged, just as though the parallel pair were a single cell.

The parallel pair can be thought of as a large cell with twice the capacity of a single cell. As one of the "large cell's" single cells goes bad, the "large cell" will drop in capacity and become unbalanced with respect to the other two "large cells".

Is it best to check each individual cell periodically?

Only if a parallel pair reads low, to find which one of the cells in the parallel pair is bad.

- RD
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Old May 11, 2004, 09:24 AM
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Thanks RD, that makes sense now.

Maybe you could help on my "adding taps" thread??
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