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Old Mar 09, 2012, 08:13 PM
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smitty919's Avatar
manahawkin NJ
Joined Dec 2009
1,309 Posts
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can you dummy this up for me I'm lost

OK I'm using 1300 3s battery's whats my cut off level i should not fly after?
then when I'm recharging what amp do i charge at and how will i know its a full charge? whats the v reading per cell???

i have a ONYX 235 will it just charge till the battery is full and shut off even if the battery i am charging is say 3/4 full or will it try to over charge?

Oh god Oh god so many things for a silly battery
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Old Mar 09, 2012, 08:34 PM
CP heli ≠ 3D heli
Gedexas's Avatar
United States, NJ, Point Pleasant Beach
Joined Mar 2009
1,676 Posts
Charge at 1.3A, you should not fly after it reaches 3.6V/cell, for your battery it is 10.8V. When recharging, look at the amps going back in the battery, if you put 1A back, you're good, if you put less, extend your flying time, if you put more, reduce it. Make sure you don't charge a Li-Po with a Ni-Xx setting and choose 3.7V/Cell setting for lithium batteries ( I assume you have a 3.6 for Li-Ion ad one more for Li-Fe, don't use those).

The charger will cut off at 12.6V even if the battery is not discharged.

NEVER get your battery below 9V (3V/cell).
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Old Mar 09, 2012, 08:50 PM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,571 Posts
Lipos shouldn't be discharged lower than 3.7V/cell resting voltage. In flight they'll drop below this but then pop back up once you land and let them sit... Most ESCs have a low-voltage cutoff value around 3.0V/cell.

The best way to figure it out is to fly around with a timer running for, say, six minutes. Charge the pack up and watch to see how many mAhs the charger puts back in. You can safely use roughly 80% of a lipo's total capacity, so your 1300mAh packs should be taking in a maximum of about 1040mAh. Call it exactly 1000mAh to give yourself a bit of a buffer.

The cells should charge to about 4.2V/cell. You can extend their overall lifespans by stopping them at a bit less than that (4.1-4.15) but it will cost you some flight time. As for charge current, 1.3A will mean they're done in a little less than an hour depending on how empty they are. 2.6A is a 2C rate and will be twice as fast. Some newer ones can be charged at extremely high rates (up to 12C in some cases) but make sure you know what they're rated for before you go pumping that much current through them.

It's ok to top off slightly used lipos as long as you fly them again pretty soon. It's bad practice to leave them fully charged for more than a couple days. The charger pays attention to cell voltage, so it'll never just keep hammering current into the packs if they're full.
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