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Old Feb 15, 2013, 09:07 PM
Team Cobra USA/Team Blackout
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Joined Jan 2006
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Help!
question about using a lipo alarm

hello all, i am curious about what to trust. im running a 3s 2800mah 30c lipo. before i installed the alarm i was using the timer on my tx, which was set at 6minutes30 seconds. when using that timer i was putting roughly 1300-1400 back into the pack. today i used the lipo alarm and did some hovering and some slow forward flight and a few punch outs and got 13.5 minutes on the pack when the alarm sounded. i let the battery sit for about 30 minutes and then balance charged the pack. starting voltage was about 3.7 on all three cells but i put 2650mah back into the pack. that obviously exceeds the recommended 80%.

so should i use the alarm or should i set the timer on my tx to around 10 minutes?
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Old Feb 15, 2013, 09:48 PM
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If your alarm is adjustable, set it to 3.4V.

Concerning the 2650mAh charged capacity, it could be possible that your battery has a better capacity than expected.
Otherwise, your charger could be optimistic.

Buy this cellmeter, you will be able to measure remaining capacity: http://www.hobbyking.com/hobbyking/s...y_Checker.html
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Last edited by Mortimer; Feb 15, 2013 at 09:55 PM.
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Old Feb 15, 2013, 10:20 PM
Team Cobra USA/Team Blackout
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its not adjustable. just tested my second pack and starting voltage was 3.59, 3.65, 3.55 and i put 2600 back in
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Old Feb 15, 2013, 10:24 PM
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Joined Sep 2012
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Ive been using the hobbyking Lipo alarms, and they seem to go off at around 3.4 or so volts, been working more reliable than the on board one for some reason... And the LED is pretty hard to see a few hundred feet away in the daylight, so I really like the Buzzer that rings off as well as an LED.
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Old Feb 15, 2013, 10:30 PM
Team Cobra USA/Team Blackout
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so i guess my question then is should i worry more about voltage or amps?
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Old Feb 16, 2013, 10:01 AM
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"should i worry more about voltage or amps? "

Voltage. Never let it fall below 3V/cell under power or you will kill your battery.
That's why you have to set your alarm at 3.4V.

" im running a 3s 2800mah 30c lipo"
As your battery is 30C, there should be no problem with amps (2.8A x 30 = 84A max).
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Last edited by Mortimer; Feb 16, 2013 at 10:29 AM.
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Old Feb 16, 2013, 01:10 PM
Misfit Multirotor Monkey
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Joined Mar 2011
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A few comments about LiPo discharge from my experience.

I've been using the cheap HK low voltage buzzer and it works fine. I put a bit of tape over the buzzer horns as they were actually TOO loud and and annoying. The red LEDs trip around 3.6V and the audio alarm trips on around 3.4V per cell.

As to "killing your battery", from draining the LiPo completely, that is not necessarily true. I left my 3S 2200 battery plugged into my quad for several days and completely drained the battery to zero. Once you do this, you cannot simply charge it normally, you'll have to do a work around by CAREFULLY charging it as a NiCad for a short period (~15 minutes) under constant observation. There are several threads here with instructions on how to do this. Now, I will admit, I discharged mine very slowly with a phantom load and thus did next to no damage to it. (After I drained it and recharged it, it did puff a barely perceivable amount) So I may have reduced its lifespan somewhat. Draining a LiPo to around 2.0V per cell quickly could very well severely damage it.
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