ORIGINAL: RysiuM
Fully charged NiMh can hold 1.5V per cell (for a very short period) that means you may start with much higher voltage than you wanted.
That over-voltage is of no practical concern, as it slides off the discharge curve very quickly. Most often, it is not even present by the time you switch on the system and apply a load to it. I have checked fully charged pack voltage with a loaded ESV, and I have never seen the fabled 7.5V (1.5V per cell). I use a field charger to top off every other flight or so, and I have not had any problem with the 5cell packs I use.
... I include small piezo buzzer (like this [link=http://www.kingstate.com.tw/product/kpe-242/kpe-242.gif]KPE-242[/link]) that costs and weights almost nothing. Thanks to that I can hear when ignition is 'hot'. Buzzer is on the 5V side so I know that battery, switch and regulator are working fine when I flip the switch. And after landing and killing the engine the beeping reminds me to tun the ignition off.
RysiuM
I use a super-bright LED instead. It draws less than 20mA and can be seen in direct sunlight. I use the same LED setup for on board glow drivers. At this point, I tend to trust my eyesight more than my hearing.
