Hmm, as an electric flyer, who uses rx packs in some planes, I use a similar method. I can use my charger as it has a discharge capability of up to 10 amps, and I hook up my Astro meter in series between the pack and servos. Last attempt was 7 high torque servos Y'd all together to plug into the meter. That way I can see the draw, and any voltage drop as I work all the servos.

Funny thing about packs that die even though they check ok. I had one rx pack I was using to set up a plane. Hooked up the pack, and flipped the retracts on.

This is a pair of heavy retracts with 10 inch wheels, each uses a separate JR 791 servo to run them.

Anyhow, nothing from the retracts, not even a whimper. Check and all the other servos worked fine for the control surfaces. What the Heck?

So what do I do, spend close to an hour pulling the harnesses for the retracts, checking for a bad lead or two. Not fun on a 110" ws bird. I even unhooked the retracts and plugged them straight into the rx. Nothing, Nada, on either one.

Double what the heck?

I know they worked a couple of days ago . Ok let's try something else. Grab a spare esc, and lipo. Plug the esc into the lipo, and then plug the esc into the rx, using the built in bec to power everything. Zip/Zip both retracts go up and down.

Hmmm. Finally dawns on me to check the rx pack's voltage..................yep bout 4 1/2 volts.

Dang it. Playing with the plane the last couple of days, I had run the pack down to the point where if I activated the retracts it would draw down the pack and not run the retracts, yet it had enough power to run the smaller draw servos on the controls one at a time.

DUH!!!!!!