That,s correct ,its hard to measure batt voltage under load without an oscilloscope or an analogue meter.
If you own a digital multimeter ,its not impossible for this task ,and it does try to capture the cylcing of up and down voltage during full auto , aired up .
I just went through this with my X-mag ( my particular problem ended up resulting in 2 failed battery's , under a load ! That's rite both of them !
I just kept telling myself " They are not that old " 1st one is 5yrs old , 2nd one is (?how ever many?) years old and gets hot when charging ,and never gets off the red ,full charge status . That one i suspected had a bad cell , set it aside ,called it bad for now . The 5 yr old KC battery held a charge 19.2 volts sitting around
This is what i did to test them under load , meaning aired up, in E-mode only .Set meter to DC volts
Put the red lead on one of the white solenoid wire soldered points on the board , Black on the board ground screw above the display ,hold down on the trigger on full auto ,
watch the numbers cycle . It happens very fast so watch for the lowest number during cycle ,trigger held,and highest number ,this was the data i got
5 yr old KC batt- 17.19v - resting Voltage / 11.57v trigger held down in full auto- garbage
old batt gets hot - 16.7v - resting Voltage / 8.26v trigger held down in full auto - garbage
brand new AGD batt- 20.01v - resting Voltage / 12.32v trigger held down in full auto -bingo ,never dropped below 12.32volt
this was the hard lessen that i learned. If batt voltage drops below 12.00volts , the solenoid is not going to be strong enough to pull plunger all the way down ! Until i checked these older batt's under load , i was convinced that a batt that holds a charge idle,sitting around if fine . Not true ,i would check battery if you own a multi-meter , to eliminate this and then move on if its not that .
solenoids do get weak after so many years ,but before you condemn one ,make sure battery is not to blame . that's what happened to me. Thought it was solenoid ,wound up just being a failing battery