I have a scissor lift. 24 volt system that uses four 6 volt batteries. It was acting goofy a couple of weeks ago so I bought four new batteries. Still not working right so I investigated further and found a couple of wires that had worked loose from a terminal strip. Fixed that and all is well. Last Wednesday I used it on a job, at the end of the day I parked it and plugged the charger in. It did it’s test mode, and when the charger kicked in, it made a horrible racket and stopped. I unplugged the charger and tried again. Nothing. I was at a motorcycle shop, they didn’t have a charger, but did have battery tenders. I split the batteries so they were now two 12 volts, put the tenders on and went home thinking I had a bad charger. The next day I put a 12 volt charger on each set of two batteries. One charger, which was digital immediately went blank. The other charger started vibrating wildly and shut down. I then took the batteries completely apart so I had four six volts and tried to charge them individually with the charger I had left. The charger did the same thing on every battery, vibrated bad and shut down. I checked the charge voltage on that, 13 volts at the six volt setting and 18 at the 12 volt setting. Bad charger. Went across the street and bought another cheap 6/12 volt charger. Hooked it up to one six volt battery and it immediately let all of the smoke out. I then got mad, hooked all the batteries up to the lift and used it. It worked fantastic. I should add that I metered and load tested the batteries. 6.3 volts each, 12.5 with two hooked up in series and 25 with all four. The load tester showed fine, I flipped the switch to put 100 amps worth of load on and still fine. I load tested each battery separately, and in pairs. The tester doesn’t have the ability to test 24 volts, only six and 12. The next day I bought new cables and replaced them. I also brought the old batteries. Gotta back up, I forgot I found a blown fuse in the 24 volt onboard charger. Put on new cables and put the old batteries in. Plugged it in and it worked great. It was charging just like it was supposed to and showed the batteries to be at least 80% charged. I had parked it in front of an overhead door so I could take advantage of the daylight. I had to pull the lift forward so it wouldn’t be blocking the door. I unplugged the charger and drove the lift about 10 feet forward. Plugged the charger back in and bam! Same thing. Blew the fuse on the charger. I immediately took the cable off between batteries 2 and 3 to make it a couple of 12 volts again and tried a 12 volt charger. It kicked in and the screen went blank. jBy now I was really frustrated so I left for home with the new batteries in the back of my truck. On the way home I wondered about the AC voltage. I know I was plugged into the same receptacle for all the charger mishaps, I know I was plugged into a different recptacle while the two old batteries charged at 12 volts. (I forgot to add that I had them charging in pairs while I installed the new cables), I couldn’t remember where I was plugged into when the 24 volt charger worked before I moved the lift. When I got home, I took one of the batteries out and put in on my workbench and put a charger on it. The charger kicks in and immediately kicks out. Got another battery out hooked the two together. Put the charger on and it wont work. I load tested those two batteries and used a meter. Everything checks out perfect. I now have eight six volt batteries that test fine, but destroy every charger that touches them. The only thing that saved the expensive 24 volt charger is the fuse in it.
Does anyone have an idea where to start? I posted this on another forum and have got several shot in the dark suggestions that are things I have already done. I talked to a friend that is a 35 year heavy equipment mechanic, he has no clue. I talked to another friend who builds some kind of specialized concrete mixer. He has tons and tons of DC knowledge but is just as lost as I am with this.