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Old Aug 24, 2012, 12:45 PM
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When Charging Lipo's At The Flying Field Do You Do A Fast Or Balance Charge?

I always balance or storage charge my Lipo's at home. I want to start charging at the field too and I'm tempted to fast charge rather than balance charge them at the field, is this a bad idea?

Thank you!
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Old Aug 24, 2012, 12:51 PM
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Go for it. A lot of guys only balance every 5 or 10 charges. Just make sure you still connect the balance wires for safety. It won't balance but it will monitor them and prevent overcharging individual cells.
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Old Aug 24, 2012, 01:54 PM
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'Bout roughly how long would it take to "fast charge" say, a 1000maH 7.4v, and how many amps should this be done at?
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Old Aug 24, 2012, 02:17 PM
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"fast charge" has nothing to do with the rate at which you charge but rather with when the charge terminates. When charging a lipo there's the constant current (CC) and constant voltage (CV) stages. First in the CC stage it puts in at the set current, once the cells reach 4.2V per cell it switches to CV and gradually reduces the current to maintain but not increase the voltage. A normal or balance charge terminates when the current drops to 1/10th of the original setting. A fast charge terminates when the current drops to 1/5th of the original setting. So you just put a few less mah in on fast charge because it terminates slightly earlier.

You can charge at as many amps as the battery label says you can.
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Old Aug 24, 2012, 02:32 PM
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I discharge balance my batteries EVERY time before charging, even at the field, and they have last a very long time and still going. You can charge most batteries at the rate equal to their capacity in amps (1000mah @ 1A and so on). There are some exceptions, as some batteries are made to accept higher charge rates. Be warned, you should charge a battery on a quality balance charger at a low rate and balance the pack before charging. I charge all my stuff at a max of 1A regardless of type, capacity etc... But then again, I have multiple packs and multiple chargers. If you must charge at a high rate, don't make a habit out of it and charge them slowly at home. Just my opinion
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Old Aug 24, 2012, 02:40 PM
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Originally Posted by erikc641 View Post
I discharge balance my batteries EVERY time before charging, even at the field, and they have last a very long time and still going. You can charge most batteries at the rate equal to their capacity in amps (1000mah @ 1A and so on). There are some exceptions, as some batteries are made to accept higher charge rates. Be warned, you should charge a battery on a quality balance charger at a low rate and balance the pack before charging. I charge all my stuff at a max of 1A regardless of type, capacity etc... But then again, I have multiple packs and multiple chargers. If you must charge at a high rate, don't make a habit out of it and charge them slowly at home. Just my opinion
There's no need to use an external balancer to discharge balance before charging unless you don't have a balancing charger. If you have good batteries charging at more then 1C does no damage to the long term life of them. You will get the exact same number of cycles charging at 1C as you do at say 3C.
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Old Aug 24, 2012, 03:32 PM
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I verify all cell voltages, just in case, and then fast charge when I need the speed..

Rick
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Old Aug 24, 2012, 03:36 PM
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Do what you want, it works for me. You should not begin charging an out of balance pack.
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Old Aug 24, 2012, 03:53 PM
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Got another question. I've got another LiPo that I'm afraid to use because while it's showing 8.4v, if I hook it up to the plane, it'll run for about 45 seconds, and then act like it's dead. Right now it's fluctuating between 8.4, and 8.37v, it's not puffed, it's not hot, doesn't get hot when I try to use it. The charger just stopped, and the final voltage is 8.39v. What's wrong with this battery?
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Old Aug 24, 2012, 04:08 PM
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How many cells? I will guess and say 3...?
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Old Aug 24, 2012, 04:44 PM
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2 cell, 1000maH 15c stock battery came with the plane(s). The other battery's fine, get about 8 minutes outta that one at 3/4 throttle...
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Old Aug 24, 2012, 05:01 PM
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Got another question. I've got another LiPo that I'm afraid to use because while it's showing 8.4v, if I hook it up to the plane, it'll run for about 45 seconds, and then act like it's dead. Right now it's fluctuating between 8.4, and 8.37v, it's not puffed, it's not hot, doesn't get hot when I try to use it. The charger just stopped, and the final voltage is 8.39v. What's wrong with this battery?
That's the definition of a worn out / bad lipo. Discharge and dispose of it. Either you've cycled enough times to wear it out or you discharged it too low (or charged too high) and damaged it.
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Old Aug 24, 2012, 05:03 PM
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I think it's old, because it was like that out of the box. I did charge it on my imax b6 charger before I tried to use it the first time...
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Old Aug 24, 2012, 05:32 PM
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Discharged LiPolys should not be balanced! The only time a LiPoly needs to be balanced is when it is charged. Slow (Normal ) Fast etc.., are terms which have different meanings for different chargers. Some will do a unblanced charge which may be fatser than a balanced charge , some have different terminaton points during a balanced charge as in 1/10 , 1/3 , 1/5 of set C in the CV stage , some have a Trickle balance which may be extremly low such as 40 mA rate.

I have charged at 3C and greater for many years and thousands of charges and have not seen any ill effects when used with decent LiPolys and quality balancing chargers.

FWIW I Balance Charge most of the time, from time to time I stop the charge before the balancing is completed if I want to fly the LiPoly . Not much point in waiting another 5 minutes to have 15 mAh capacitry added.

http://www.rcgroups.com/forums/showp...61&postcount=1

Charles
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Old Aug 24, 2012, 05:47 PM
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You have luck with yours, mine works too.
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