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.

 

[Bob Rooks]

Just throwing my two cents at you - seems you'll likely ignore it anyway.

A flywheel stores kinetic energy, and would be a good idea behind an electric motor to help in absorbing amperage spikes when operating the hydraulics and hydrostatic drive, particularly simultaneously. The main issue I see is the high amperage inrush needed to get the flywheel in motion from a static state. I believe this issue can be solved by eliminating the flywheel altogether and direct couple the electric motor to the hydraulic pump, and incorporate an adequately sized accumulator. The pump would only run when the pressure fell to a predetermined point.

 

[galstaf]

Just throwing my two cents at you - seems you'll likely ignore it anyway.

Oh contraire, everything is on the table right now.

Thanks for the input!

 

[/pine]

How long do you anticipate the charge will last on your battery pack ?...after what type of work ?

 

[Phil Timmons]

I have a shop manual of course. I realize it is not a simple project but was looking for leads on anyone that had done something similar that I could potentially collaborate with.

So how is this going so far? What are you finding and what are you needing?

Can help you on the design and details, if you like.

Sounds like you may do some stationary work? e.g., Backhoe, etc. If so, I would encourage you to consider a cord connection option, as well. So you move around on a smaller battery set up, and when you get in place, you can "plug in" and use line power for some hours without concern for battery life. You can even charge up the batteries while working. That is how we the BIG 1000HP + rigs.

 

[greenerdreams]

the main thing i am thinking is the batteries will be expensive and short lasting. Teslas(as well as most other all electric vehicles)have huge batteries that weigh a lot and take up a lot of space, this is in a car that is traveling pretty efficiently and only when needed. Since the tractor is hauling, lifting, driving over soft terrain etc. it is very inefficient and still needs a constant hydraulic supply as well unless you want the usefulness to be very low if you wait for hydraulics every time you move the bucket, it will use power very quickly. Even the electric mowers available don't last long and they are asking much less from a machine.

 

[Frogmore]

An HST tractor is a poor starting point choice for an electric conversion. But, let's just start with how much energy storage you need for all day usage. Let's use 10 hours for the day (to give you some reserve and room for degradation). At an average of 5HP (so 5:1 peak to average) that is about 35-40KWH. That is likely more than you will want to buy.

 

[Bob Rooks]

In my industry there are many success stories using electricity. On one of the vessels I worked on for years had a "power Island" propulsion system which consisted of a 4,160 volt buss and four 5,000 HP AC cycloconverter drive motors, and hotel load, all driven by four 3 mW diesel generators. The vessel is currently being reconfigured to full electric operation. Three of the diesel generators are being removed and replaced with battery banks. It's my understanding that the existing drive motors will be used. They are already using all electric tugboats. You can do this but I think the batteries will be the real challenge. Maybe you can find a used Prius battery to experiment with.

 

[Phil Timmons]

the main thing i am thinking is the batteries will be expensive and short lasting. Teslas(as well as most other all electric vehicles)have huge batteries that weigh a lot and take up a lot of space, this is in a car that is traveling pretty efficiently and only when needed. Since the tractor is hauling, lifting, driving over soft terrain etc. it is very inefficient and still needs a constant hydraulic supply as well unless you want the usefulness to be very low if you wait for hydraulics every time you move the bucket, it will use power very quickly. Even the electric mowers available don't last long and they are asking much less from a machine.

True. Part of why I am encouraging galstaf to consider a cord / cable option for this. Will also save a ton of money on the battery. Can build it with a little battery, and then add if he discovers he needs more. Covered part of this on this thread >>> Cord Management on Grid-Connected Electric Tractors and Mobile Equipment

 

[4570Man]

Do yourself a big favor and just fix the diesel. An electric tractor needs to be built electric from the ground up and even then the run times aren’t impressive. Trying to run all the hydraulics with battery is too much loss.

 

[shooterdon]

Being on the leading edge is always an expensive venture...but someone needs to do it or we would still be using oxen and horses.

Take a realistic inventory of you level of expertise, time to learn, time to get the work done and financial situation. On the money side, take your "reasonable" estimate and add a minimum of 100%. Time estimates are not as painful...if it takes you a year instead of 6 months it is not a big deal.

Good luck!