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Semi OT: Any Electric Forklift Experts Here? GE EV-100 Control Questions

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  • Semi OT: Any Electric Forklift Experts Here? GE EV-100 Control Questions

    As some of you may remember, I bought a ridiculously heavy electric forklift at an auction sort of by accident. It's a nifty machine but weighs a staggering 12,000 lbs+ with the battery but only has a 3k lift capacity.

    Anyway, back in August or September it went on the fritz. The pump motor and hydraulics all worked fine, the steering worked fine, but the traction motor was dead - no relay pickup, nothing. I turned it into a lawn ornament through the winter but I really need to move some junk so I started poking at the forklift again a few weeks ago. I've got a manual for the EV-100 control card and the service manual for the forklift itself, curtesy of Landoll, and I decided the problem was the oscillator card - a logic board that controls the SCRs and relays for all of the forklift functions.

    Thought briefly about trying to reverse engineer or repair the circuit board but then found I could buy a remanufactured unit for less than $200. I've got so many other projects now, I decided it was worth the money and the retailer's service department assured me that they had a direct drop in replacement for the card. My card was the first generation and was missing the "Y" plug for a handset or display (p/n IC3645EVS1 to be specific). They shipped me an IC3645LXCD1 SR card, a much newer version that has the Y-plug for a handset / display.

    I hooked everything up and tried it out. It sort of works but it has very little power. In fact, I got stuck because I couldn't reverse through a *very* slight dip in the driveway. I was able to limp it back to its resting spot by manually closing the 1A and REV relays (i.e. poking them with a screw driver and walking with the forklift - a funny sight indeed). Plenty of power when the relays are bypassing the SCRs, so I don't think there is a problem with the traction motor or super weak battery (although the battery is not great).

    Here's what I'm noticing with the new card:

    1) Slow to pick up: The pedal has to travel quite a bit before the SCRs start to hum. I don't think I'm getting the "full torque" start feature.
    2) I don't think I'm getting full 1A bypass, either. Particularly trying to reverse out of the dip, when I go all the way down on the pedal, I hear the microswitch close in the pedal sensor and there is a quick "clip clap" relay sound. For just a moment, I get a big lurch but then it goes back to a stall with SCR hum. I think the "clip clap" is actually the 1A bypass kicking in and immediately kicking out. I just get a momentary torque bump from the bypass.
    3) When in stall with the SCR hum and no 1A bypass, quite a bit of heat is generated in the electronics compartment; more than when I manually close 1A to provide full battery power to the traction motor. I'm not sure what the controller is doing, but the panel and the cables get very warm / hot.
    4) When driving (assuming I'm not stuck in a dip), the steering feels sort of gritty and weak. It feels fine when stationary - smooth and plenty of power to twist the rear wheel even though it's not rolling. Could be my imagination, though.
    5) My forklift is a 36V unit, somewhat less common these days. Based on the manual, it sounds like the card should auto-range for 36V or 48V trucks, but I haven't been able to confirm this. Maybe my current draw - particularly when 1A closes - exceeds the safe threshold for a 48V truck so it goes into some kind of limited power mode...??

    I'm guessing I'm going to need to buy ($550 YIKES!) or rent ($50, better) an LX handset to read status codes and change parameters on this card. Reading the manual, I haven't figured out exactly which settings could be causing the symptoms I'm experiencing, and that's what I'm hoping someone here can help me out with. The manuals are not super informative and, in some cases, they provide "helpful" information like "Listen to the SCR hum. If abnormal, do xyz" but I'm not experienced enough to know what it's supposed to sound like!
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    Last edited by Fasttrack; 04-06-2022, 10:22 AM.

  • #2
    The first thing to check is to put a volt meter on the battery and get a voltage under load.

    SW Mi


    • #3
      also verify that all the cells have the same or at least close, specific gravity.


      • #4
        I ended up with a controller similar to that, one time, back in 1995. It was an antique even then.
        SCRs were never all that high tech for DC.

        Gotta say, high current lower- voltage DC motor controllers are a LOT better now than they were then.
        My 2c would be to replace the controller- keep the reversing relays- and you'll be a lot happier in the long run.
        It probably won't cost that much for an import controller-

        even Curtis controllers aren't all that bad for lower voltages, and they're the expensive version.
        Found in a golf cart near you. A 48v version at whatever amps you want to draw (250 maybe?)
        oughta do fine.

        A quick google found

        and also that you can get a Curtis reman for a couple hundred.


        rusting in Seattle


        • #5
          I agree. A modern PWM motor controller will be more efficient and reliable. Using SCRs for a DC controller involved some voodoo to unlatch them - pretty clever, but that was before high power BJTs, MOSFETs, and IGBTs became ubiquitous and cheap.

          Many DIY electric car conversions have used forklift motors, most famously the "Forkenswift" project. Here is a link to some information about the EV-1 controller and the Curtis controller that he used instead:

          You may also find the following blog about the history of the forklift interesting.

          The forklift's establishment is one of the important events that have great influence on the world's industrial in the 20th century...

          There are some forklift schematics here:

          This website is for sale! is your first and best source for all of the information you’re looking for. From general topics to more of what you would expect to find here, has it all. We hope you find what you are searching for!

          Paul , P S Technology, Inc. and MrTibbs
          USA Maryland 21030


          • #6
            I have a stack of 48v alltrax controllers and will give you one if you cover shipping. PM me


            • #7
              Speed pot is not set properly. Needs to go close to 0 ohms for 1a contractor to time out and pull in. Pedal up speed pot should be around 5000 ohms and reduce to zero when fully depressed.
              If you can send me the make and model number of the truck I can probably help you out.



              • #8
                Thanks guys! I wonder how long those Chinese controllers last. they're amazingly cheap. The old GE controller looks like it's bullet proof and I suspect the reason my logic card failed had more to do with rodents and water than age. I also appreciate some of the features like full torque starts on ramps and plugging / ability to change direction lever while moving forward. That's especially important since my forklift doesn't have brakes at the moment... And there are a bunch of useful safeties built into the controller. I wonder how much of that is reproduceable with one of these cheap replacement controllers.

                Psomero - thank you for the offer! Let me do some research on the Alltrax controllers and then I'll send you a PM. That's very generous and I may take you up on it!

                Edit: Ray - just saw your post. Will do and thank you. I did check the speed pot and verified it was working properly. At full pedal travel, it actually has a microswitch that shorts the potentiometer to bring it to 0.
                Last edited by Fasttrack; 04-07-2022, 11:02 AM.


                • #9
                  I fixed an old Raymond electric forklift by replacing the controller with a Curtis controller. Unlike the old controller the Curtis can act like a transformer at lower speeds putting out as much as twice the current draw on the battery at half the voltage. We had a big hill on our driveway. Previously the only way to get back in the shop was to drive diagonally up the hill zig zagging back and forth. With the new controller no problem going straight up.


                  • #10
                    For the sake of posterity:

                    I tried renting an LX handset from MRK Sales Inc. but that was a fiasco. I ended up buying a used LX handset on eBay and verified that the problem was the current limits set on the replacement card. The factory default was for a 36/48V truck but the current limits were pretty low. My truck is massively heavy (12,500 lbs with no load) and operates at 36V, so it runs at the higher end of what the EV100 control card can handle current-wise.

                    The 1A over-current drop out was set to 540 amps out of 1260 amps max. I used the handset to set that to 910 amps, the setting recommended by Drexel. That corrected the 1A drop out problem and I've now got plenty of torque to get over bumps. Still need to tweak a few other settings but I'm relieved to have it driving again.