Lipo pack balancing...

[beto9]

http://www.pfmdistribution.com/images/TLC.jpghttp://www.pfmdistribution.com/images/TRC.jpg
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Read at bottom....


Update April 8th, 2009! Apogee LOA's (http://pfmdistribution.com/secure/shop/item.asp?itemid=203&catid=48) are back in stock!
Welcome to Apogee
Since 2003, Apogee has been an innovator of new technologies. Apogee has always been at the forefront of Lithium battery technology and product development.
Some industry firsts worth noting:
Utilization a commercial grade voltage port
Pack Matching for internal resistance and capacity, negating the need for balancing
Polycarbonate shielding to minimize damage due to rough handling
2C charge certification
No Fault lifetime replacement program

Our greatest achievement to date:
We are the innovators who brought Lithium Manganese (Li-Mn) to the R/C industry in 2005


http://www.pfmdistribution.com/secure/images/2S1000MNSmall.jpgSafety
In 2005, after nearly a year of testing varied chemistries of Lithium Manganese, we finally had a product we could be satisfied in knowing that it would not burn down someone's house. It was at this time that the Apogee "Magnum" series was released. Since then, we have not had any reports of any lithium fires using our chemistry. Safety is our top concern!
Product Diversity
http://www.pfmdistribution.com/secure/images/3S3800MNSmall.jpgApogee batteries are available in capacities ranging from 1000 through 6000 mAh, in cell counts from 2 to 6 cell packs. Packs are available and configurable for models from as small as 8 ounces up to 30 pounds, in aircraft, cars/trucks, and helicopters.
We are well versed in the R/C market, and can assist in helping consumers pick the appropriate pack for their model. We are also always available to help anyone, regardless of brand, become educated on the proper use of Lithium batteries.
OEM Capabilities
We have partnered with and invested in the best manufacturing facilities around the world and currently OEM products for several well known brand names. If your company needs a cost effective pack, whether standard Li-Po or Li-Mn, we're here to help. Please, however, understand that we are unable to build single packs that meet our matching criteria. In order to effectively match packs, very large batches of cells have to be manufactured.
No Gimmicks!
For years we have sat quietly aside watching the proponents of "pack balancing" spew forth misinformation. The truth is that a properly matched pack will not require balancing. Yes, we're sure this is a shock to many of you who have fallen for the balancing gimmick. Yes, Apogee was the first to put commercial grade plugs on all packs due to customer demand. We've had and seen enough.

Pack balancing is a gimmick perpetuated by companies who make balancers, and by other companies who do not match battery cells within the pack. A properly matched pack will not require balancing, and in fact will mask a failing cell. Balancing is a band aid for companies who lack the proper equipment to do cell matching. All Apogee packs have been cell matched since the day we started.
Due to misinformation, more packs have been damaged during balancing than have been helped. If you insist on balancing a pack (If it makes you feel warm and fuzzy inside, and you sleep better at night, have at it), please, please, only balance fully charged packs.
http://www.pfmdistribution.com/secure/images/2S2200MNSmall.jpg
Why only balance fully charged packs? All properly matched cells are mated together so that the high and low voltages will coincide. There may be mid-point voltage variances. Balancing a partially charged pack can cause the high and low voltages to become unbalanced. Again, please, if you insist on the balancing gimmick, please only balance fully charged packs.



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[AlixB]

Well,

Works fine when the cells are new and fresh.

As they age (or get abused by our extreme applications) internal resistance starts to vary from cell to cell.

I doubt there exists a (cheap)technology that will make them stay the same way after 100 cycles as fresh from the factory.
(a cell in the center of a pack will not age the same way as gracefully as a cell that is on the outside_because of temp_, rendering the matching argument heuuu ... irrelevant over time)

On the other hand most modern chargers balance cells while charging rendering obsolete the need for a SEPARATE balancer unit.

Isn't this a non issue to try to separate their Lipo cells from the pack...?
(I would do the same if I were them haha!)

Since as a bunch we are paranoids(!) Everyone will still do the same as they always have.


We still have a lot to learn about lipos.
My most recent experience was a two cell pack that I reported to the manuf as defective (see pict) (Totally unbalanced as it approached final charging voltage)

They sent me a replacement one.
After a few flights the so called BAD pack is now as good as the new one!!!!?????

Can someone explain?

[Andrew Fernie]

Good to hear from you Alix. Are you back in town for the summer? Will we see you out at the field sometime? Lots of area for helis now.

Andrew

[Xavier]

I was confuse by the first post and I agree with Alix about the way cells may not age the same, specially when abused in load and temperature.

The only explaination I could have for the behaviour of your 2S Alix is that it needed to be broken in and now it's set. When I get a new pack, I try to run it at low power and for short flights a few times before going all out. I now also do that in the spring or after the packs have been stored for a long period. It seems to work as I have a 10S pack for my pattern plane that has 3years and 186 flights, still going well. It's not as powerfull as a new pack but enough to give 10C while the new one give about 13C.

[AlixB]

Andrew

I am back since the 16 of April.

Did not attend the spring AGM not to take any risk (flu thing)

My season is seriously compromised

I am suffering from an elusive back ache.
I was in remission for two weeks and decided not to attend the field day to give my back a break.
Right now I am on pain killers.


Enough about me. Great jobs at the field guys.

Thanks Xavier (by the way nice foam bipe!)

Reminds me of the old nicads days when we had to cycle the packs.

This is precisely this kind of behaviour that makes me stay away from expensive packs.



The pack I returned is used in a Gaui 200


I bought two different no name brands on Ebay at $7 a pack
They claim 1000mah 2S for a mere 45g with 20C discharge rate

I routinely take 770 mah out of them.(<80% discharge rule)

All 6 packs are performing great (+the bonus BAD pack)



More expensive packs cost 5 times the price and show 800mah at 48g sometimes with as low as 15C discharge rate.

Here are the equivalent apogee pack for 27$ or 17$ on "special"

**********************************
LiPower Lites 750 mAh 18C 2S1P 7.4V
Continuous Discharge: 18.0C / 13.5 Amps
Burst Discharge (10 sec): 20C / 14.6 Amps
Pack Dimensions (LWH mm): 50 x 34 x 14
Weight (w/connector): 50 g
16 Guage 60 mm Leads
*********************************

Are lipos becoming a commodity ?


My figure of merit for the same configuration.

(claimed Capacity*claimed continous C rating)/(weight *cost)


mileage may vary :-)