LiPo warners

[Balu]

I never really thought about LiPo warners, since I have telemetry on my transmitter. But now I'm building something for a friend who doesn't have that luxury, so I'm looking into LiPo alarms / warners to put on a multicopter.

Of course I need to make sure I get one for the right amount of cells, but other than that?

Just looking at the HK category, I get about 20 different options, some are missing an alarm, so they fall out of the list.

What else should I look for?

I've seen some start warning at 3.3 V which seems way too low?

Starting to limit the options this way I stop with these two:

http://www.hobbyking.com/hobbyking/...ll_Checker_with_Low_Voltage_Alarm_2S_8S_.html
http://www.hobbyking.com/hobbyking/store/__74024__HobbyKing_8482_Lipo_Voltage_Checker_2S_8S_.html

which seem to be exactly the same, just with / without the case...

Then there is the Turnigy one which doesn't have info on the warning level:
http://www.hobbyking.com/hobbyking/store/__13276__Turnigy_8482_Voltage_Monitor_3S_8S_.html

And this one which warns at 3.4 and 3.2 with different sounds, but I still think that's too low.
http://www.hobbyking.com/hobbyking/...ing_8482_Lipoly_Low_Voltage_Alarm_3s_8s_.html

Right now I'm thinking about the first one without the case. But I'd like to see what others use.

So which one did you get?

 

[RichB]

I think the tribal knowledge about what's too low for a lipo cell is subject to the game of telephone. According to manufacturers, 4.2-3.2V is the useable range for the cell. I don't think it's a coincidence that 3.7 is smack in the middle. They warn you not to go below 3.0V

People hear that 3.2 is the min and so they strive to stay above 3.3 just to be safe. Eventually it is known that 3.3 is the target for a dead battery, and so people are trying to get alarms at 3.4, just to be safe. And so on it goes until we are at the point we are at now, where if you ask 10 people what their min voltage is, at least a couple will tell you 3.7 (or higher!)

tl;dr: 3.3 and 3.2V alarms are perfectly fine.

 

[PHugger]

I've been using these -
http://www.amazon.com/gp/dp/B003Y6E...&tagbase=abba-metro&tbId=oPWS1NLOBNRuJGoOO*iV
Cheap and adjustable.



Best regards,
PCH

 

[nerdnic]

I have mine alarm at 3.4v. By the time I land and the battery cools they usually sit just about 3.65v per cell. If I set my alarm any higher I trigger it at WOT.

 

[Snarls]

I have the first one you linked too. It's nice that you can program what voltage to go off at. I think right now mine is at 3.7v , but I use to run it around 3.3v. The alarm is very high pitched and audible, which my dog does not enjoy. In retrospect I would by the case-less version because the case is too large to fit in some spaces, and if you break it it's cheap to replace.

 

[Ron B]

thanks huggar
You can't beat that deal as I spent more on my batt checker than this cost.

 

[JAG]

Yeah I have the first one listed as well. Very loud and does the job.

 

[Balu]

I guess I'm just too conservative with my batteries . I get Low Battery warnings from Telemetry when I go below 3.7V and critical at <3.6V. The 3.7V is mainly for informing me that it's going to be over soon, while the 3.6V is "get back and land". Yes, those are sometimes triggered when I open up the throttle, but I'm not that of an agressive flier and I know it's ok when the warning is not repeated.

The Amazon one from PCH is not delivered to Germany, but I've found some very similar to the HK ones on Amazon.de (design and writings on the back look identical), so I'll try one of those.