Electric conversion of a Kubota B26 / Similar

[Grandad4]

Kubotas all use "open center" type hydraulics, meaning the tractor supplies a constant pressurized flow of fluid to all hydraulic circuits whenever the tractor is running, whether it is in motion or not. When no hydraulic controls are activated, the fluid simply circulates through the supply lines and returns to the reservoir. In contrast, "closed center" circuits systems (such as used on John Deere tractors), are under pressure but there is no fluid flow until the control is activated.

I don't know enough about hydraulics to know if you can easily turn a circulating, open center system into an "on demand" one. If it ends up needing a constant feed of hydraulic fluid at, say 10 gpm and 2,500 psi, that could be a major energy draw and a challenge to how much battery storage you would need. If you were doing a backhoe project, for example, you might need to be working the tractor non-stop for 6-8 hours.

Maybe others have ideas about this. Repeating myself, I'm no expert.

B26 is maybe not the ideal starting point since almost everything on it is hydraulic. This does sound like an interesting project - as long as you don't need a working tractor in two weeks!

Good luck!

 

[galstaf]

Not directly related, but you might want to check out Jerry Rig Everything on YouTube, https://www.youtube.com/channel/UCWFKCr40YwOZQx8FHU_ZqqQ

He's doing an electric conversion on a retired HMMWV that might give you some ideas on the some of the problems you'll need to overcome.

Ha.. yeah, been watching this dude for a year or so now and developing the E-vehicles/wheelchairs for his girl.
I was holding off on watching the Hummer project til he got further into it, but just got upto date after you posted. I love how much room there is when all the ICE stuff comes out.
He is using a 3phase AC motor which is what I intended to do also. That is a very serious motor controller (inverter) he has there!

Makes you think that the hydrostatic tractor transmission is a lot less important when you drive it with electric where you can switch direction instantly and have all that torque available with none of the bllsht! It would be tempting to take out all that stuff!

 

[galstaf]

Kubotas all use "open center" type hydraulics, meaning the tractor supplies a constant pressurized flow of fluid to all hydraulic circuits whenever the tractor is running, whether it is in motion or not. When no hydraulic controls are activated, the fluid simply circulates through the supply lines and returns to the reservoir. In contrast, "closed center" circuits systems (such as used on John Deere tractors), are under pressure but there is no fluid flow until the control is activated.

I don't know enough about hydraulics to know if you can easily turn a circulating, open center system into an "on demand" one. If it ends up needing a constant feed of hydraulic fluid at, say 10 gpm and 2,500 psi, that could be a major energy draw and a challenge to how much battery storage you would need. If you were doing a backhoe project, for example, you might need to be working the tractor non-stop for 6-8 hours.

Maybe others have ideas about this. Repeating myself, I'm no expert.

B26 is maybe not the ideal starting point since almost everything on it is hydraulic. This does sound like an interesting project - as long as you don't need a working tractor in two weeks!

Good luck!

Thanks GD!



I did an online hydraulics course which was super helpful. This guy is a college professor and does a good job of putting all his courses online if anyone wants to brush up their skills.

https://www.youtube.com/playlist?list=PLdnqjKaksr8ruhw85YYSSO6EWLhVVmSKm

You are correct, the Kubota is open center and fluid is constantly circulated back into the tank. If I remember correctly, there are pressure accumulators (the hydraulic equivalent of an electrical capacitor) that could be used on the incoming pressure line to "smooth" out any start up lag from the electric hydraulic pump. But having used an electric scissor lift for a while, the hydraulic pressure from those pumps is pretty instantaneous.

So I am hoping that the hydraulic pump can be "on demand" and not having to run constantly to do the job.
However with enough batteries a full day's work is possible; especially if at least part of the pack is hot swappable.

 

[galstaf]

Don't worry about the loss of service.. this is definitely a background project for me and I have a great solid working noisy polluting diesel tractor in the meantime!


Having seen the comments and the HumVee conversion in progress, I am starting to think a hydrostatic transmission tractor may be an inferior choice and I would be better off with a traditional engine/ transmission machine that could be torn down and direct drive the axle transfer cases from an electric motor.
No mechanical gears / mechanical reverse would be needed. Electric allows an instant change in direction with no gearbox. Just needs a good quality motor controller.

 

[pmsmechanic]

My understanding that this tractor is a TLB and is only going to be used as such. If that is the case I would install the motor directly onto the transmission with an in/out dog type clutch on it. That way you can use the same motor to do hydraulic work and move the tractor around. You can disengage the in/out clutch when you just need hydraulics there by saving on the parasitic losses of the hydrostaic drive. With the motor directly coupled to the transmission you can use the hydrostaic drive as your motor speed controller saving the cost of the speed controller as you really only need it for the transmission.

I would also be interested in a motor with a shaft coming out of each end. That way the hydraulic pump can be run directly off of the front of the motor. No chains or belts adding to parasitic losses. Keep the open center hydraulics as closed center are always using energy to keep the oil at 2900 psi. Also an electric motor doesn't use as much energy idling along as it does to get up to speed. I would just leave the electric motor running all the time while using the hydraulics as starting and stopping it is wear and tare on the motor with minimal energy savings if at all.

These are just my thoughts. I have no experience in a project like yours. I'm looking forward to learning something here!

 

[CalG]

Forget the HST Use the electric motor as it is designed. That is it's best qualities.

Also change to a closed center hydraulic system with a dedicated auxiliary electric motor.

Cobbled together hybrid is nothing but a failure from the get go. (that is a constant running electric motor with a fly wheel and HST. = BAD IDEA)

 

[MossRoad]

Thanks GD!



I did an online hydraulics course which was super helpful. This guy is a college professor and does a good job of putting all his courses online if anyone wants to brush up their skills.

https://www.youtube.com/playlist?list=PLdnqjKaksr8ruhw85YYSSO6EWLhVVmSKm

You are correct, the Kubota is open center and fluid is constantly circulated back into the tank. If I remember correctly, there are pressure accumulators (the hydraulic equivalent of an electrical capacitor) that could be used on the incoming pressure line to "smooth" out any start up lag from the electric hydraulic pump. But having used an electric scissor lift for a while, the hydraulic pressure from those pumps is pretty instantaneous.

So I am hoping that the hydraulic pump can be "on demand" and not having to run constantly to do the job.
However with enough batteries a full day's work is possible; especially if at least part of the pack is hot swappable.

You're probably looking at more money in batteries than the machine is worth if you want to get that amount of time and hot swappable out of it.

 

[Smokeydog]

I saw where you have a B26 as well as I. Great machines! The engine is small and compact. Not much room for an electric motor(s), controls, pumps or batteries.

About half the noise comes from the engine the other half from the hydraulics. Nature of HST. 25hp electric motor driven hydraulic systems are noisy.

Hydraulic accumulators are big, $$$ and heavy.

Dangers of high current and hot oil don’t play well together.

In your conversion what percent loss of operability compared to your diesel is acceptable? 50%? Would you spend $25K to get there?

Someday we will have small electric tractors. It will not be because we run out of oil or be better for the environment.

Funny if we are moving to electric the old electric motor repair shops are closing.

 

[Williy]

By the time you get your tractor converted your
tractor will look like you been to a cobble shop
I don't believe all the parts will fit where the diesel
was so you will have to make brackets, shelves etc
to get all parts necessary for the switch to electric
and it will not be a quick fix & I hope you have a nice large bank account!
Golf cart electric motors are $450 would they work??? MHO

willy

 

[galstaf]

I saw where you have a B26 as well as I. Great machines! The engine is small and compact. Not much room for an electric motor(s), controls, pumps or batteries.

About half the noise comes from the engine the other half from the hydraulics. Nature of HST. 25hp electric motor driven hydraulic systems are noisy.

Hydraulic accumulators are big, $$$ and heavy.

Dangers of high current and hot oil don’t play well together.

In your conversion what percent loss of operability compared to your diesel is acceptable? 50%? Would you spend $25K to get there?

Someday we will have small electric tractors. It will not be because we run out of oil or be better for the environment.

Funny if we are moving to electric the old electric motor repair shops are closing.

I love getting input from the folks with much more tractor experience than I.

I am thinking the HST based tractors may not be the best choice and just direct drive the wheels with the motor.
The accumulator was just a thought. I think if I could just drive the existing hydraulic pumps with a suitable motor, that may well be a better choice. With the instant torque of electric, power on latency should be minimal.