[electricbobcat]

Good morning from Michigan, US!

I've been looking to build an electric skid steer for about a year now. I've seen a few on YouTube, and there are a few commercial ones that use lead acid, so it has been done!

Here's what I have so far:
Complete Chevy Volt Gen 1 battery pack ~125k miles. Was working when pulled out.
Cat 246b Skid steer with blown motor here's a link to its specs. Of note it's an 80HP turbo diesel @ ~3400RPM

Here's what I need (high level):
Electric motor/controller
Charging system
BMS
DC/DC converter.

Here's some questions I need to answer that I'd love some thoughts from you all on:
What kind of equivalent HP electric motor do I need?

• These tend to run at a pretty constant RPM and I don't intend to use it for hard work all day
• I'm not sure whether to go AC/DC - I do have a limited budget. Which is better for value?
• Are there big enough forklift motors that would move over to skid steer land?

Depending on the motor I could run the battery pack as is (~360v) or split it up and run 48-96v packs.
It looks like some of the new from-the-factory electric skids run as low as 8kW motors @48v (see here). That would be way smaller than the diesel engine.

Charging also depends on how the battery ends up being configured - splitting it up to a lower voltage makes it less expensive I think.

I've browsed the BMS options available for the Volt batteries - there are some good discussions on this form regarding that. This will also depend on the final battery configuration.

DC/DC - again cheaper if I'm at 48v instead of 400.

Please let me know if anyone has a line on components that might work and you live in the Michigan/Indiana/Ohio area.

Thanks for anything!

 

[brian_]

A horsepower is a horsepower, whether the "horse" eats gasoline, diesel, or electricity. But due to the nature of the application, I suggest looking for a motor with a continuous power rating similar to what the original engine can produce at moderate speed; electric motors often have a rating for a peak power which can only be sustained for a short time before they overheat, and a lower "continuous" rating that they can work at indefinitely. If you're really lucky there will be a proper short-term "S2" rating which would be applicable.

In the linked article, the Avant Tecno machines with the tiny motors look like quick-and-dirty conversions that I wouldn't want to copy, but the Kovaco skid loader, JCB telehandler, and Schaffer wheel loader look like well-designed machines... and with 30 kW to 40 kW (peak) they're not very different in power from a diesel-powered machines of similar size. Those better machines all use separate motors for the driveline and the working hydraulics.

The Kovaco skid loader uses the driveline motor to drive a hydrostatic system, which is unnecessary complication and inefficiency (compared to just one electric motor per side), but it's apparently easier for the company to convert their existing design than to build a proper electric skid loader.

The Cat 246B has a Cat 3044C DIT engine, which is really a Mitsubishi S4S-DT. While it can produce 78 hp at peak, it is rated by Mitsubishi at 55 kW (74 hp) at 2500 RPM, and runs most efficiently at much lower speed and 40 to 47 hp... 30 to 35 kW.

 

[brian_]

A lower-voltage charger and DC-to-DC converter may be less expensive, but salvaged parts from EVs might be no more expensive than new 48 V stuff for the same power capability.

 

[electricbobcat]

Thanks for the reply - agreed about the HP ratings. The telehandler in particular seemed similar in weight and load capacity to the skid steer I have. With a 40ish Kw motor though that's still about 20 kW smaller than the ~60 kw (80HP) diesel.

I've got my eye on this which happens to be conveniently up the road from me. I think it would be over kill and also more than half of what I paid for the whole skid steer.

It would also require me to run the Volt battery pack as is which adds cost in chargers, DC/DC, etc.

My conversion would be most similar to the Kovaco - just run the motor straight into the input shaft of the hydraulic pump. I'm not up for complicating things more than that.

Thanks again for the thoughts.

 

[brian_]

Thanks for the reply - agreed about the HP ratings. The telehandler in particular seemed similar in weight and load capacity to the skid steer I have. With a 40ish Kw motor though that's still about 20 kW smaller than the ~60 kw (80HP) diesel.

Skid-steers probably use more power than wheeled telehandlers, but the Cat may have been somewhat overpowered so that it could normally operate at low engine speed (and less power) for efficiency and durability.

I've got my eye on this which happens to be conveniently up the road from me. I think it would be over kill and also more than half of what I paid for the whole skid steer.

The UQM PowerPhase motors are well-known and I think well-regarded. That one is more than you need, but not excessively large; the problem would be the cost of a suitable inverter for it.

My conversion would be most similar to the Kovaco - just run the motor straight into the input shaft of the hydraulic pump. I'm not up for complicating things more than that.

I understand the appeal of using this approach in a conversion. You're not avoiding complication - you're actually keeping a complex hydrostatic system that isn't needed - but you're avoiding changing the complicated parts by leaving them as-is and adding a simple fixed-speed motor... and that can certainly make sense.

 

[electricbobcat]

That UQM I linked has the inverter with it so that would get around that. It looks a little 'used' but supposedly works. Does their $2500 asking price seem reasonable for a motor/inverter pair?

Yes - avoiding changing the complicated bits - especially since this skid has joy stick controls that I'd have to replicate/replace somehow for the hydrostat system.

 

[brian_]

That UQM I linked has the inverter with it so that would get around that. It looks a little 'used' but supposedly works. Does their $2500 asking price seem reasonable for a motor/inverter pair?

I missed that. Complete with the inverter it looks like a good value to me, if it comes in a controllable form (with any required programming software and with workable methods to connected accelerator input, etc).

Yes - avoiding changing the complicated bits - especially since this skid has joy stick controls that I'd have to replicate/replace somehow for the hydrostat system.

 

[electricbobcat]

Thanks again!