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Who am I???

 

I'm Peter Kirby and I have been flying model planes for 20 years, helis since late 2005.   I'm a Telecommuncation Tech / currently an IT geek for my "full-time" job.  I made my first alarm after trying to fly my Trex450 with a flat battery.  Well, it didn't work too well and I broke it.  After making an alarm, I shared my achievements to others on Helifreak.  Then someone else wanted one... now 40 per month go around the world.

I'm now experimenting with aerial photography using both my Trex450 and Trex600.  The alarms now protect a large investment.  Check out my early photo work here.

 

 Why use an alarm?

Lipoly packs do not like being over discharged.  I recommend limiting use to 80% of the packs capacity.  Testing has shown that repeated use over 80% may cause permanent damage.  3.33v per cell gives close to the 80% mark, depending on flying style, temperature etc.  I use 10v on my 3S packs.  21v on my Trex600 packs.   

The best way to assess how hard you push your battery is by recording how much current capacity your charger puts back in.  3.33v is a guideline and may be too high or low, depending on your flying style.  If you take too much out first flight, simply up the voltage sensor a little - at the field - without any tools.

 It is more than just protecting your pack.  I like to know when I have about 1 minute left.  These alarms let you do that.  I carry cameras on my helicopter - thats a big risk when you don't know how your battery is going!!!  Camera flying is often many small flights.  A stopwatch won't help you here.

  

How do they attach to the battery? 

 

All the alarms connect between the battery connector and the esc, or across the battery balance plug if you prefer.  They easily wire across the back of the battery/esc deans plugs.As my alarms monitor voltage not cell count, they work on any battery type.  
I have a variety of alarms to cover most uses.  If I don't have what you need, just ask.  I started with only one type, until someone asked for something different...