My uncle has a 48V electric boom lift that sat for awhile and we're trying to get up and running again. We had a lot of stuff replaced and refurbished and we're almost there, but there's one last hurdle. There are two motors that drive the wheels. We sent these away to be refurbished. The brakes are part of these motors. The brakes are engaged by springs (I'm assuming). When you go to move the lift the brakes are energized and they release and as soon as you stop moving the springs once again stop the wheels. For whatever reason the wiring for the brakes is separate from the motors. There's two terminals with 16 AWG wire on each.
One of the two brakes won't release. I thought the two were separate, but I've discovered they're actually receiving 40v (the schematic says 48V) in series from the B+ wire (so going in). Power goes into the terminal on the right brake, a wire comes out the second terminal, into a loom and end up at one terminal at the second brake before coming out the second "return" wire. I've tried every configuration of hookup on these four terminals and the right brake is always the one that's working (I would have thought if I swapped it the left would be the only working one at some point, but that was not the case). If give the left brake 48V from battery power it works. I can get them both working by wiring them in parallel, but then they see 48V when I believe they should see 24v (if they're wired in series, right?). I don't know if that's going to damage them.
So that's where I am right now and I'm not sure how to proceed. Current flows through both, I'd expect them both to work. Maybe the resistance on the left one is higher? But I thought it'd still work, just maybe not as well. Maybe because it's only seeing 40v to begin with (as opposed to 48v) the voltage at the second one is too low to activate? This is pure speculation and it's probably flat out wrong.
There are two sets of four batteries. I believe each set it wired in parallel and then the two are wired in series for 48V input. My plan for if I can't figure this out would be to use two 48V relays to send 24V from one group of batteries to each brake and use the original 48V wire as the trigger.
Obviously my understanding of electricity is lackluster, but I know how to avoid getting zapped. If anyone can shed some light on what's going on I'd greatly appreciate it.
UPDATE: The schematic is on page 96 (3-20):
UPDATE 2: Left brake (the problematic one) measures 18.6 ohms, the right one measures 18.9 ohms.
I also forgot to mention I've tried swapping around the terminals to see if maybe they were reinstalled incorrectly, but it didn't make a difference. I tried AB-CD, AB-DC, BA-CD, BA-DC. On a related note, is there polarity? there's no markings. Obviously the original connectors had a wire in mind for each terminal, but those have been dismantled and it moves the same way no matter how its hooked up.