question about using a lipo alarm - RC Groups
Thread Tools
Feb 15, 2013, 09:07 PM
Team cobra USA/ team n-armed
awdspider's Avatar

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?
Sign up now
to remove ads between posts
Feb 15, 2013, 09:48 PM
Registered User
Mortimer's Avatar
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:
Last edited by Mortimer; Feb 15, 2013 at 09:55 PM.
Feb 15, 2013, 10:20 PM
Team cobra USA/ team n-armed
awdspider's Avatar
its not adjustable. just tested my second pack and starting voltage was 3.59, 3.65, 3.55 and i put 2600 back in
Feb 15, 2013, 10:24 PM
Registered User
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.
Feb 15, 2013, 10:30 PM
Team cobra USA/ team n-armed
awdspider's Avatar
so i guess my question then is should i worry more about voltage or amps?
Feb 16, 2013, 10:01 AM
Registered User
Mortimer's Avatar
"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).
Last edited by Mortimer; Feb 16, 2013 at 10:29 AM.
Feb 16, 2013, 01:10 PM
Misfit Multirotor Monkey
Cyberdactyl's Avatar
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.
Last edited by Cyberdactyl; Feb 16, 2013 at 01:22 PM.

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Question about using computer monitors for FPV Koo FPV Talk 3 Oct 29, 2014 10:43 AM
Help! Question about quantity lipo cells. Gregorio Dunayev Power Systems 5 Jan 28, 2013 08:29 PM
Discussion Question about using LiPO for Rx power RickAvery Power Systems 3 Nov 17, 2007 08:19 PM
How about an audible low voltage alarm for LIPos? Doc Data DIY Electronics 1 Jul 11, 2004 09:53 PM
Question about using fireproof safe for charging LiPo's nadt770 Batteries and Chargers 1 Jan 12, 2004 10:03 PM