Hey mrbass111... A expanded scale voltmeter is a great tool to assist
in keeping you out of battery problems with the onboard system..
It's a quick check of the receiver battery while at the field... I would
get in a habit of checking after 3 flights to keep tabs on the battery
then give it a quick charge if you fly more... On the Transmitter IMO
it's pretty much useless.. I just use the radio's battery monitoring
system built in the radio... I think it's on all radio systems, but may
be not.. They have a diode(think that's what it is) which will not let
the battery lose voltage in that direction, which also prevents a
reading on the voltmeter and or allow you yo cycle the battery while
it's in the transmitter... You need to remove the battery to read the
voltage and or cycle it..... Not sure about the rest of your questions
you could have a battery going bad... I do not believe you can hurt
the batteries by just flipping the correct plug over.. But if you use
the wrong plug it could cause a problem. Only thing I would do on the
trans battery is to pull it from the tranny and cycle it if you have a
cycler, than see what condition it's in Hope this helps..