ORIGINAL: dick Hanson

If you really want to know if your battery setup is up to snuff -or if your servos are setup correctly---
purchase a simple little voltmeter by EXPERT.
available in 4.8 or 6 v.
weight is a few grams -plug it ANYWHERE into system which sees battery power with switch ON.
use a Y if needed to get there .
The little LCD display zips up to full when battery is full.
now move each servo full travel -watch the meter-

Basically-the meter sees actual voltage in entire circuit that the battery feeds.
So for example --if the battery reads high when nothing is moving - yet drops quickly when a certian servo moves - -you are seeing a "problem" with that servo or linkage.
Now - put a battery in the plane which is old or vey small or weak. and look at the meter - as you move the sticks - the meter will rapidly drop .
OR- stall a servo -again the meter drops .
The SIZE of a battery is important as is the IMPEDANCE--which is a fancy way of saying how easily the battry will release current.
Example a 2700ma pack with high impedance (these are common as fleas on a dog ) is a terrible choice for a model with 3D or active flying .
You would be better off with a 1400 ma pack with extremely low impedance .
tho the number of flights seemingly would be far less --in actual practice-the 2700ma pack would quickly be choking power (voltage)to low and very possibly below rx operating threshold.
This tiny readout will tell you more than a whole roomful of test equipment and $$chargers .
Why?
Simply because it shows what is happening AS it happens.

I use one of these a 6 v model-and a 2300 ma, A123 dual cell pack - NO reg -for my planes - until the cells hit under 3 volts - the current available will melt wires.
when ready to take off -I look into canopy at the meter - and move the sticks - IF for some reason the meter takes a dump- something is wrong - low cells stalled servo -whatever .
THAT kind of info simply is not available from stuff sitting on your shelf.