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Brodjack
12-12-2005, 09:34 PM
Having not flown for about 3 weeks or so,waterlogged field, thought I'd cycle some of my bats.I go for the idea of 'keep em used,keep em'good'.
Anyway charged a couple of 3s2p 10-12c 3600,4000 and 5000mah lipos.
All stored and run in my large unheated shed,outside temp about freezing point or just above.
Connected each one up to a Projeti brushless,usually hitting in summer about 36 amps static full throttle. What a shock i got,with a wattmeter,seeing voltage at full thr. drop instantly to 9v.slowly dropping to about 8.25v.after about 30 seconds.Bats did start to warm up but never went back over 9v.Amps never went over 32 even with the 5000mah one.
Tried a 10 cell 3300 mah stick,fully charged,but left to go cold,to be fair.That also dropped to 8.5 v. but amps were in the 37-40 range.
All the lipos have never been discharged heavily,and never charged fast either. I balance them also,using the single-cell charge method,had none out by more than 0.1v about every 10 flights,all cells were checked and ok before the cycle.
Has to be the cold? Certainly hope so.Are my volt,amp readings about normal for 0C temps?
The biggest surprise was the 10 cell nimh?
I know bats.dont perform in the cold,but to this extent?

everydayflyer
12-12-2005, 10:17 PM
know bats.dont perform in the cold,but to this extent?
Afraid so. I prewarm my LiPolys to 80F and insulate them for flying in below 60F temps. LiPolys which provide 14 min. 3D flights durring the summer will drop to less than 10 minutes of so so flying in 50F temps.
LiPolys can be charged at 32F but do much better at 60F plus in my experience.

Charles

Red Scholefield
12-12-2005, 10:19 PM
Anyway charged a couple of 3s2p 10-12c 3600,4000 and 5000mah lipos.
All stored and run in my large unheated shed,outside temp about freezing point or just above.
Connected each one up to a Projeti brushless,usually hitting in summer about 36 amps static full throttle. What a shock i got,with a wattmeter,seeing voltage at full thr. drop instantly to 9v.slowly dropping to about 8.25v.after about 30 seconds.Bats did start to warm up but never went back over 9v.Amps never went over 32 even with the 5000mah one.
Tried a 10 cell 3300 mah stick,fully charged,but left to go cold,to be fair.That also dropped to 8.5 v. but amps were in the 37-40 range.
All the lipos have never been discharged heavily,and never charged fast either. I balance them also,using the single-cell charge method,had none out by more than 0.1v about every 10 flights,all cells were checked and ok before the cycle.
Has to be the cold? Certainly hope so.Are my volt,amp readings about normal for 0C temps?
The biggest surprise was the 10 cell nimh?
I know bats.dont perform in the cold,but to this extent?

1) Charging at low temperature can significantly damage a rechargable battery, Ni-Cd, Ni-Mh, Pb AND Lithium.

2) Dishcharge characteristircts are compromised significantly. Ni-Cd holds up the best, then Ni-Mh and Pb with Lithium being most impacted.

But your experience will do more to convince some people than my preaching. :rolleyes:

Brodjack
12-12-2005, 11:57 PM
Thanks for the reply,think i'll pack-up for the winter........

Red Scholefield
12-13-2005, 12:46 AM
Thanks for the reply,think i'll pack-up for the winter........

You don't have to do that, electric is great for winter flying. Just keep the plane and batteries in a warm place a few hours before using them. Once at the field it will take some time for the ambient temperature to cool the battery down to the point where you will notice a significant decrease in performance.

phat23
12-13-2005, 01:32 AM
Can't speak for LiPolys, but I always peak my Nimhs in the heated shop before flying in the winter. Even though winter around here means at least 40 degrees F, it does make a difference in performance.

Pushrod
12-13-2005, 04:58 AM
1) Charging at low temperature can significantly damage a rechargable battery, Ni-Cd, Ni-Mh, Pb AND Lithium.

2) Dishcharge characteristircts are compromised significantly. Ni-Cd holds up the best, then Ni-Mh and Pb with Lithium being most impacted.

But your experience will do more to convince some people than my preaching. :rolleyes:

:confused: Charging at low temps? While I'm new to the electric game, (in R/C)why is it I use to see the car guys charge there Ni-Cd in a cooler full of ice? I agree with the discharge statement just confused on keeping them cool while charging.

Matt Kirsch
12-13-2005, 01:38 PM
Car guys charge their packs in 15 minutes, at 4 or 5 C. Believe me, there's plenty of heat generated during the charge cycle such that the battery packs are not at all cold, even sitting in ice.

On top of that, have you ever felt a pack after a race? They are HOT. Again, the ice isn't chilling the packs, it's bringing them back to ambient temperature.

Red Scholefield
12-13-2005, 02:23 PM
:confused: Charging at low temps? While I'm new to the electric game, (in R/C)why is it I use to see the car guys charge there Ni-Cd in a cooler full of ice? I agree with the discharge statement just confused on keeping them cool while charging.

They do this to cool down the batteries after they get hot in use. It is unlikly the packs get anywhere near 32 degrees in the time they have them on ice. If they do then they are going to be real unhapppy hitting them with 4C.:eek: