I have a '97 Ameriquip Eagle 42 24V towable electric boom lift. Was working fine, and then the other day it started struggling to actuate the arms. The pump would cut out for 2-3 seconds, then start again. Eventually, that 2-3 seconds became 5-10, then 20-30. Now, if the pump turns at all, it turns VERY slowly. Batteries are fully charged, and I also am plugged into 110V. Is there anything else to check before calling the pump bad?
I'd check the motor, then the cable connections. put multimeter test leads on the terminals on the motor, and see what the voltage is when the motor is turning very slowly, then check battery voltage, then check the voltage drop of each battery terminal to the motor, all of these readings with the motor turning slowly. You should see a pattern soon enough. Or you could pull the motor off the pump and check the brushes, armature and whatever else is in there for obvious overheating, sticking, wear. Better yet, find a reputable auto electric place to rebuild the motor, or take it to an electric motor shop. Very unlikely the pump itself is the issue, unless you have evidence in the hydraulic filter that says otherwise.
Think you might be on to something. Put a DMM on the pump, and the voltage was varying between ~7-9V. Could hear the pump pick up RPM as the voltage increased. The whole lift is VERY simple (unless I'm missing something): it's just an industrial AC-DC 24V power inverter hooked to the pump and the battery bank (see pic). It appears maybe the inverter itself is failing? Without the pump running (so only charging the batteries), I watched the voltage climb from about 12-13V to 21V or so over the course of about a minute, which seemed strange. I turned the pump back on, and gave the inverter a couple hard smacks with the heel of my hand (very scientific!) as I watched the DMM, and the voltage dropped from ~8.5V to 7V or so for about ten seconds, then climbed back to 8.5V. The inverter itself seems pretty new (I just bought the lift a month ago), but I suppose it's possible it has failed?
I suspect the batteries and how you're measuring voltage. 12 volts from a set of "fully charged" batteries (12+12) = bad
Went out to give it another shot, turned it on, and boom: working perfectly. Steady 24.1V at the pump. Worked great for about 5 minutes...just long enough for me to climb in the bucket, raise myself up 30' off the ground, attach some window trim...and get stuck there when it would no longer move. Had to activate the emergency descent valve.
I suspect your charger is working, it's just seeing failed or failing batteries. In that case it will limit output to protect itself. I wager you have some failing batteries that would fall flat if you put a carbon pile load tester on them. On any battery operated electric motor, you need good batteries with good reserve capacity to prevent voltage drop. If you continue to run that motor under load (operating lift) with voltage anywhere below, say 18V, you're gonna make that motor go up in smoke because of the increase in amperage caused by low voltage.
how many bad connections can YOU see? I can't tell, that's why you need to keep using the voltmeter, that will give you the answer, all we can do is guess. The volt readings will tell you if it's a bad connection, battery, or motor. Did the motor run for five minutes? or was that the total time until it stalled again?
OK, I'm stumped now. Thought I had it figured out last weekend; it seemed like with the batteries only at ~50% charge it didn't want to work well. So if I left it on the charger for 1/2 hour or so, it would work perfectly at normal speed. Used it like this for almost an entire day. Left it charging since Sunday, went to use it yesterday, and nothing. Pump isn't even turning.