|05-21-2007, 07:42 AM||#1|
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I am slowly getting there.
I am now flying an electric airplane. I am using a 3 cell 2100mah Lithium battery. I have a Thunder Power charger. When new everything worked fine.
After my first flight I tried to recharge the battery. The charger displayed a message, "Incorrect voltage or reversed polarity". The battery was correct for the charger settings. In a wild guess I figured that maybe I had drained the battery to such a low voltage that the charger would not accept it. So, in an even more wild guess I gave the battery a five minute shot on a regular nicad fast charger in an attempt to bring the voltage up.
It actually worked. The lithium charger accepted the battery and went through the charging process quite normally. I have now done this several times.
My question is then, how do I prevent the flight battery from discharging to such a low voltage that the charger will not accept it.
Is the only way to not fly so long?
The speed control instructions seem to mention some programming capability. But as mentioned in another post, a total mystery.
Thanks for any help.
|05-21-2007, 08:19 AM||#2|
RCC Junior Contributor
I am: Leon L.
Join Date: Apr 2005
Location: Guelph, Ontario
Feedback: 2 / 100%
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There are a few important rules when it comes to using lipos and not letting the pack go down to less than 3 volts per cell under load is one of them.
If you go below this you will risk permantly damaging your cells. The result will be reduced capacity, lower operating voltages and/or a puffed cell. Once a cell puffs it should be disposed of.
Letting your pack go below 3v per cell and then using the nicad setting to bring it back up does work but is very risky and your pack will deteriorate very quickly, it will not charge back up to full capacity and the volts during discharge will be less. It's risky because if you forget it and leave it on the nicad mode you may overchage your lipos which could result in a fire.
I'd strongly suggest you figure out how to setup your ESC up to enable the appropriate low voltage cutoff (LVC) for your pack, 9v (or something close). If you're having problems figuring out how to do this perhaps you can take it into your local hobby shop, they may be able to give you a hand.
There is some good lipo information here: http://www.rcgroups.com/forums/showthread.php?t=209187
I hope this helps.
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