lol @ the logo for your LiPo batteries, "Mystery" .. and its in flames hehe

A bit disconcerting, to say the least.

im using 11.1v Li-Po batteries now and i love them.
im running a PGC M130 spring (430FPS) with insane ROF (had to reduce motor speed by 40% to prevent stripping thanks to the SW-computer from ExtremeFire). the batteries hardly get warm, they stay cooler then the NiCads and NiMH i used befor. that and they last longer then nicads and nimh of the same mAh rating. my 1200mAh Li-Po out lasts my 1650mAh nimh battery easy.
as long as you dont do anything "stupid" with the Li-Po batteries, they should be as safe as any other battery.

Guys you DO need the cutoff circuit to prevent a fire. The batteries can heat up way faster than NiCAD or NiMH and heat isn't a good pre-fire warning. Also if they do catch fire, the smoke that comes off of them is really nasty toxic stuff that you really don't want to be handling without proper training and equipment, not to mention the possibility of burns.

Buy the protection circuit.

ok
and what would a mosfet do ?

Mosfet isn't a LiPo protection circuit. The protection circuit is a very specific circuit. I would not run without one.

hum...where would we put that on a AUG ? inside?
pinching holes in the buttplate?

...a transparent buttplate would be good for that :)

You could also try something like this:

http://www.hobbycity.com/hobbycity/s...idProduct=2160

It's not that big, and makes a noise when your cells drop below 3v.

I built a modified one of these:
http://www.reuk.co.uk/12-Volt-Batter...ator-LM741.htm
And stuffed it in there. I stuck the LED out of the right side sling mount hole. It lights up when the battery's voltage goes below 7.0. It also flashes every time I pull the trigger. Makes my gun look high tech :p

I just ordered a couple of these from RSOV.com; we'll see how they work out. They plug right in to the JST port on the battery:

http://www.rsov.com/product/105_133/...rm-buzzer.html

http://www.rsov.com/images/bat_0045.jpg

http://www.rsov.com/images/bat_0045_1.jpg

Li-Polymer battery cells voltage monitor and alarm buzzer for 3-cells Polymer battery equipped with reverse-polarity protection.

- The green LED indicate the battery cell condition is good (3.8-4.2v).
- The red LED indicate the battery cell need to be charged to maintain the performance (3.5-3.8v).
- The red LED will turn on and alarm buzzer will sound when the battery cell is either under or over voltage ( <3.5v or >4.2v ).

The PCB is protected by heat-shrink insulation sleeve so you can stick the indicator to the Polymer battery on your AEG or RC plane for easy battery monitoring.