I have an old 36v DC battery hydraulic indoor forklift.
The batteries are 23 years old, and no longer hold a charge for more than ten minutes, although they are a good counterweight. I have tried keeping them charged, but it just chews hundreds of dollars in power.
The forklift itself is quite useful as it's a compact reach truck with 4 metre high lift, in good complete condition. I only want to use it once a week in my small warehouse and front loading bay, about 30m long in total.
I priced new batteries, many thousands, or used batteries at least a thousand, and would still require frequent charging.
So I wondered about a DC rectifier supply, with a long mouse tail or catenary overhead wire feed.
The batteries are 2 units of 9 cells x 2v = 18v rated at 387amp hours, 5 hour rated.
Does that mean they can deliver approx 5kw continuous work per hour for a 5 hour shift?
I hooked up a medium size DC welder to the hoist, but it barely makes the hydraulic lift motor turn, and the drive motor won't start at all. It's rated at 135 amp 30% duty, or 74 amps continuous at 47vdc. 30% would be fine, use is very light.
I figured I could just look at the DC motor rating, but for the hydraulic motor I can't see any plate, and the drive motor is a wheel hub motor, and I can't see any plates on it. The DC feeds after the electro-mechanical relays are all about 1/2" diameter including jacket, which gives an idea of the draw.
My real question is how big a DC power supply or rectifier do I need to get this unit moving? Will some big old capacitors help by buffering the rectifier from the DC motor start current? Would capacitors with the medium welder work?
I was thinking a large old 3 phase DC welder, something that can deliver 200 to 300 amps ought to do the trick, but unfortunately isn't very compact. I was hoping to mount the welder to the roof of the forklift so the tail is AC, and doesn't suffer the low voltage power drop over a long cable.
If it's just not going to be mobile enough I suppose it would work as goods lift to a mezzanine floor.
The other option is give up and scrap it, wreck it or sell it, and get a manual or walk-behind unit.
TL;DR - Recycle or repurpose way of getting a few hundred amps DC @ 36v