The voltwatch drain is indiscernable or of no consequence.

v_twin1K: Yes, the voltwatch will technically reduce flying time becaue it is drawing current from the battery. I don't know the specs on the Voltwatch, but the current draw is probably squat. So in practice, it just won't be significant enough to matter. If you got 5 flights a pack (or whatever) before, I'd think it should be the same with the voltwatch.

Actually, you CAN calibrate a loaded field voltmeter with a regular voltmeter. Connect the loaded voltmeter to the battery pack and then connect the unloaded meter in parallel. The battery pack will still be loaded and you can then compare readings. Adjust the "hobby" voltmeter to match the "good" one. You'll now have the loaded voltage reading at the point where the two voltmeters came together. Usually, you do this at the battery connector.

I'm afraid some of you are needlessly worrying about how the meter was calibrated. If it was calibrated by both reading the same voltage (makes no difference if the battery was loaded or not--i.e. a volt is a volt is a volt no matter what the load on the voltage source).

The batt voltage measured by a loaded and unloaded meter will be different... batteries have internal resistance, they are not ideal voltage sources...

A loaded hobby meter will have a simple resistive load like what we have talked about. It is likely to be a high power resistor, say 5W+. The voltwatch as others have mentioned provides realtime indication and the RX etc acts as the load. Since on a voltwatch there is only ever one LED on at a time the current draw is probably in the order of about 10mA ie <5% of the load drawn by the RX and servos. Consider it this way, on a standard 600mAh pack the single LED drawing 10mA will take 6hrs to discharge the pack. Compare this to an hour or so that we normally get out of the pack during normal flying we can see that the LED will have little impact on the flight time.

When you calibrate a meter, you are not measuring battery voltage, you are comparing readings from a controlled source. The battery doesn't come into play during calibrations. That controlled source can be a battery though as long as both insturments (the standard and the unit being calibrated) are connected at the same time.

At 10 mA per LED, wouldn't it take 60 hours to completely discharge a 600 mAh battery? Insignificant either way... I think I might start mounting a VoltWatch in all of my planes. Is there a similar product for 6 V systems?

http://www2.towerhobbies.com/cgi-bin...&I=LXHDJ2&P=ML

Yeah you are quite right, damn fancy maths

Another thing is, that the hangar 9 might have been set like that, because that way your better safe then sorry. I know i wouldn't want to be responsible for planes..

Please see this newer post for a follow up to my original post that started this thread: http://www.rcuniverse.com/forum/Foll...3021170/tm.htm