Charging Large LiPoly Packs in Series? - RC Groups
Apr 23, 2005, 01:27 AM
Artillery! King of Battle!

# Charging Large LiPoly Packs in Series?

Hello All!

I have just finished putting the third charge on my 4S3P and 5S3P TP ProLite packs. They are the first large LiPoly packs I have owned. I have been charging them with an Astro Flight 109 charger at 4.2amps, one pack at a time.

The AF109 with charge up to 9S, is it safe for me to charge my 4S and 5S in series as a 9S pack? Would it be safer with the new Tp-205 balancers?

Thanks

Brian
 Apr 23, 2005, 02:36 AM Registered User Safe as long as neither pack exceeds 4.20v/cell. Ensuring this is impossible without a balancer. Even with a balancer, you have to guess which pack will peak first. With two balancers, it _might_ work. That is, it will work unless the balancer can't dissipate as fast as the charger is charging (the charger will still be going at full speed, remember). With or without balancer(s), if you are going to do this you must (imo) stop the charge before either packs hits 4.2v/cell. This might become an almost safe practice when done with the upcoming TP chargers. If you know which pack is going to peak first, put the balancer on that one, and connect the balancer to the charger. The charger should shut off when told to by the balancer. I say almost safe, because if that process fails or if the other pack peaks first (for any reason), you will likely have a balloon or explosion on your hands. Some quick math to see if the balancers could do it with the Astro 109: worst case is the 5cell peaks first. That is 5*4.2v = 21v, at 4.2A, which equals 88W. No way those balancers will dissipate 88W without melting away. Last edited by adamg; Apr 23, 2005 at 02:38 AM. Reason: added the math
 Apr 23, 2005, 02:59 AM Registered User I have no arguement with adamg's post. As I see it, without balancers, the more cells in series = the greater possibility of cell imbalance. I'd stick with your current practice. Bill
 Apr 23, 2005, 12:05 PM Artillery! King of Battle! OK, so it would be best to wait until the new TP balancers and chargers are available, the new TP charger will have 2 comm ports, so it can talk to 2 balancers at once. Just try to get the chrage time down at the field. Later Brian
Apr 23, 2005, 12:12 PM
Southern Pride
Quote:
 Originally Posted by bwillhite Hello All! I have just finished putting the third charge on my 4S3P and 5S3P TP ProLite packs. They are the first large LiPoly packs I have owned. I have been charging them with an Astro Flight 109 charger at 4.2amps, one pack at a time. The AF109 with charge up to 9S, is it safe for me to charge my 4S and 5S in series as a 9S pack? Would it be safer with the new Tp-205 balancers? Thanks Brian
Well if you were useing 3 each 3S3P packs in series then you could charge all three packs at once in parallel at 8 amps which would be much faster.

Charles
Apr 23, 2005, 12:17 PM
I'm here for the women..?
Quote:
 Originally Posted by adamg Some quick math to see if the balancers could do it with the Astro 109: worst case is the 5cell peaks first. That is 5*4.2v = 21v, at 4.2A, which equals 88W. No way those balancers will dissipate 88W without melting away.
Orbit defines their balancers to have a max draw of 550 mAh, and only with an aluminum heat sink of some sort mounted to them....

Each balancer only sees the 4.2V of a single cell or bank of parallel cells, so

4.2V @ .550A = 2.3W :-) So ya, 88W me thinks would not be good :-)
 Apr 23, 2005, 12:21 PM Southern Pride Li Po Balancer only need to handle the charge at at the end of the charge cycle. I use Li Po Balancers designed by Suzanne (user name here) and they will handel 300 mAh plus however I always reduce the charge rate to 200 mAh after the 4.15 volts per cell state as the cells will balance easier here, not as much charge is wasted driving the balancers. I have found that most packs after being balanced a few time will be very close to balanced as long as they are not discharged to deeply. Charles
Apr 23, 2005, 04:01 PM
know it all
You can only do this if both packs were used at the same time and were connected in series while flying.. other wise NO.. and I would not thrust a balancer to keep up with a high power charger like the Astro if the packs are at different levels of charge.

If they were flown in series then go ahead and charge it in series, as a big pack..

Herm

Quote:
 Originally Posted by bwillhite The AF109 with charge up to 9S, is it safe for me to charge my 4S and 5S in series as a 9S pack? Would it be safer with the new Tp-205 balancers? Thanks Brian
Apr 23, 2005, 04:14 PM
Southern Pride
Quote:
 Originally Posted by hermperez You can only do this if both packs were used at the same time and were connected in series while flying.. other wise NO.. and I would not thrust a balancer to keep up with a high power charger like the Astro if the packs are at different levels of charge. If they were flown in series then go ahead and charge it in series, as a big pack.. Herm
This has been debated to death and resent testing by RD B and others have once again proved that it is safe to do so even if the packs are not the same capacity or even not extremely close to the same resting voltage.
This user is using a 5S 3P and a 4S 3P battery in series to get 9C 3P.
The simple fact is that if he used 3 each 3S3P batteries, charged them in parallel ,connected and flew them in series then back to parallel to charge them there would be less issues to deal with than he has at present.

I am not going to get into a paralle charging of series batteries debate here. I know it works as do many other who use this means on a regular basic. Thiose that want to arrgue battery IR ,cell and battery voltage / capacities can do so with others.
I will only state once again that I have parallel charged up to 5 3S packs at a time on my Astro Flight 109 and these are packs which were flow as single packs.

For those who want to read the latest testing.
Charles
Last edited by everydayflyer; Apr 23, 2005 at 04:19 PM.
 Apr 23, 2005, 05:30 PM Artillery! King of Battle! Thanks everydayflyer, wish I would have thought of the 3S3P pack option before I bought my packs! Seems like a good idea, less cells in series, easier to keep in balance. hermperze, yes the packs are used in-flight as a 9S3P pack (4S and 5S packs connected in series). I will get a couple more cycles on them and try charging as a 9S pack. Maybe the TP balancers will be available then. Brian
Apr 23, 2005, 05:48 PM
know it all
nobody is debating parallel charging of packs with the same cell count, this is not a problem since the voltage will automatically equalize across all the packs in parallel. It is safe and smart to do.

You cant parallel a 3s and a 4s pack and charge them, you cant series two packs at different charge states and charge them.. what you can do is parallel charge packs of equal cell count, as you advocate.

Herm

Quote:
 Originally Posted by everydayflyer The simple fact is that if he used 3 each 3S3P batteries, charged them in parallel ,connected and flew them in series then back to parallel to charge them there would be less issues to deal with than he has at present. Charles
Apr 23, 2005, 05:52 PM
know it all
Brian, you can charge it as a 9s pack right now, you can even have 9 1 cell packs and charge them in series ... as long as they were discharged in series..many people do this.. the only thing to look for is that the astro 109 detects a 9s pack when you do this, there are some reports the 109 gets confused with 9s packs sometimes.

Balancer is a great idea when you spend this much money in a pack.. I worry about cell balance but I never have a pack go out of balance.

Herm

Quote:
 Originally Posted by bwillhite hermperze, yes the packs are used in-flight as a 9S3P pack (4S and 5S packs connected in series). I will get a couple more cycles on them and try charging as a 9S pack. Maybe the TP balancers will be available then. Brian
Apr 23, 2005, 06:31 PM
Southern Pride
Quote:
 Originally Posted by hermperez nobody is debating parallel charging of packs with the same cell count, this is not a problem since the voltage will automatically equalize across all the packs in parallel. It is safe and smart to do. You cant parallel a 3s and a 4s pack and charge them, you cant series two packs at different charge states and charge them.. what you can do is parallel charge packs of equal cell count, as you advocate. Herm
Sorry I mis read your first post bout only if in discharged series since I had already read in the first post that indeed they were. I guess one to many has questioned the safety of parallelcharging series packs. Good to see that we agree and sorry for the confusion on my part.

Charles