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HORNET FLYER
11-30-2005, 07:28 AM
is it critical to balance 2 or 3 cells packs??????

thanks
paul bingham

rocket_jim
12-01-2005, 02:59 AM
I'm looking for the same answer.

As far as I can tell, most 2S, 3S, 4S etc. packs at my LHS come with just one connector with two pins - there is no easy way to get into the pack to hook up a balancer, to measure the various voltages, etc. So clearly many or most (inexpensive) LiPos won't ever get balanced. So it must not be all that critical.....

Intuitively it would seem that very low current trickle-charging would eventually balance the cells out. But everywhere I read that overcharging LiPos, even at low current, above some voltage is detrimental to cell cycle life. So scratch that idea, at least for now. But perhaps a really low-rate trickle charge would never push the cell above that "bad" over voltage. Just thinking out loud here, not something to take to the (battery) bank.

So I'm not able to answer your question, but am sure hoping that someone can shed some light on this.

Matt Kirsch
12-01-2005, 04:08 PM
The short answer is, ALL packs must be periodlically checked for "balance," to see if the individual cells are within .01 volt of each other. Taps, or lack thereof, do not indicate whether or not the pack needs to balanced. All the lack of taps indicates is that the packs are older, or the manufacturer has not adopted a tap/balancing system yet.

You'd think that just trickle charging would balance the cells out, but to put it simply, LiPoly cells are "stubborn." They don't seek their own level like NiMH and NiCd; either of these will tend to balance under a trickle charge due to their high self-discharge rates. LiPolys have a very very low self-discharge rate, and remain at whatever voltage you charge them to for long periods of time.

everydayflyer
12-12-2005, 04:54 AM
HAve a look here.

http://www.wattflyer.com/forums/showpost.php?p=28058&postcount=2


Charles

Ron S
12-25-2005, 03:29 AM
Check this out! Ron http://www.commonsenserc.com/commonsenserc/index.php?cPath=29&osCsid=a4d6e40ac9eeb6c05a7c85700e7f6724

rcnerd
12-25-2005, 03:58 AM
So basically they work without, and you could get lucky, but at best it's unlikely that the pack will wear out as opposed to failing due to imbalance, and at worst it could result in a dangerous situation....

Ron S
12-25-2005, 03:09 PM
rcnerd,I've got 1 pack that has never needed balancing,in two years! Others have! It's kinda a crap shoot! The best way is to have a balancer and check them! Some packs last (almost) forever,some don't! I have two that are about shot,they show good balance,but the capacity is low. They fly about 2/3 the time of my other packs,but they still fly! They are over two years old,and keep on ticking away! They don't get hot,or swell up,during charging,or discharging. Ron;)

Vamooska
12-25-2005, 04:58 PM
What does help with those who choose not to balance their packs, is a manufacturer that matches cells for internal resistance and efficiency to build a pack, This allows for a pack to remain releatively balanced for a longer period of time. By balancing the packs you ensure that proper voltage cutoff is achieved. Charges not equipped with charge limiters cannot distinguish an unbalanced pack...only total voltage.
Balance those babies!!!!
Vammy