So my boss purchased a used Yale ERC030AG Forklift from a "friend", and it has fallen on me to try and sort out the issues. Here's the info from the Data Plates:

Model: ERC030AGN36TE084
Serial: A814V04167W

Battery: 18-85-17 (36V)
Capacity: 680Ah

Charger: Charter Power Systems FR18CE640A
Volts: 36
Amps: 135
Cells: 18

So, initially I plugged the battery into the charger and it would not charge. Checked the battery voltage and it was at ~7v, which I figured was too low for the charger to recognize, so I jumped the main relay to force the charger on to get some voltage into the batteries.

The charger is now recognizing the batteries and starting up automatically. However, I can't seem to get the battery voltage above about 36.6v. This voltage is right after disconnecting the charger, so it will probably be lower once it's had a chance to rest and cool down. I did check the voltage of the individual cells and they were all within.1v of each other. Also, it would seem that the plates are swelling pretty badly inside the batteries. I've had to remove electrolyte twice (about 2 gallons total) because it was overflowing out of the vent caps. Both times I've taken the fluid down to the bottom edge of the internal plastic neck.

When we hooked the batteries up to the forklift, we were able to get it to move forward and in reverse. The pump for the power steering appeared to be working, but the fork controls were unresponsive, no lift, tilt, or side-shift. This forklift does have a mechanical valve body, and the attached electrical switches are functional, but I don't appear to be getting any pressure to the valve body.

I believe the batteries are FUBAR and not supplying enough voltage to engage the main hydraulic pump, but was hoping to get some verification.

I was also informed that this forklift sat around unused for about 2 years.

I am new to electric forklifts, but have a decent amount of experience with older gasoline and propane systems, as well as pretty solid electrical fundamentals.

Let me know if any other information is needed, and thanks for your time in reading this...