# Electric skid steer conversion



## JeremyD (Apr 29, 2019)

Hi everyone, first post here.

I'm interested in converting my JCB robot skid steer from diesel to electric. I admit I have little experience with ev conversions (save for a simple 48v dc brushless conversion on a small david bradley walking tractor I use here on the farm). I'm also far from an expert when it comes to hydraulics. I'd like to brainstorm my thoughts and see if anything is off base. I welcome any and all feedback.

The target is this - my 2001 JCB Robot 165









She has a reliable 44hp peugot diesel powerplant. I've had her in and out of the JCB dealer several times over the last year though. At this point I'm convinced she needs a head gasket (no coolant in the oil, but she blows coolant out of the overflow and starts getting cranky after 20 minutes of operating). The thermostat, water pump and radiator all checked out, so this is my next target. Diesel engines are a bit above my head, so I'm looking at a likely $1500-$2000 job to have a head gasket done. At that price, I'm really pushed toward swapping the whole power plant for an electric one which is what I really want. I don't want to underestimate the size of the project, but being a simple direct hydraulic drive for everything makes it seem simple (at least on paper).

As far as I can tell from the service manual, with standard flow hydraulics its rated for 14.5gpm with a relief pressure of 2650psi. Banging around some quick engineering calculations (Hydraulic Pump Calculations - Womack Machine Supply Company) 14.5 gpm flow requires 27 mechanical hp at 2700 psi.

I'd like to stick with a 48v nominal system (I have other projects and a solar off grid system that run on 48v). This limits my choice of motor, but it seems like the curtis AC 9 would fit the ticket. It should deliver more than the required power at 48v (with 600A controller). The other obvious win is that it's available with an SAE A hydraulic pump mount, meaning I could bolt it directly to a hydraulic pump without any custom fabrication.

AC-9 motor kit w/ SAE A pump mount - AC-09 AC Induction Motor Drive Kit

Operating time is going to be limited by battery pack size. I'll be sacrificing run time for sure, but for my use on the farm, if I could get an hour of hard run time (an hour of operating without hearing protection and diesel fumes) that would be fantastic. I'm a fan of the bmw i3 modules (48v 60ah). I can get a salvaged battery pack from a local yard for a decent price. I'd be looking at 20kwh realistic for an 8 module pack.

BMW i3 60ah pack with 48v modules - 




Are there any glaring holes in my plan? Anything I haven't considered? I haven't seen anyone do a project like this. Does anyone have any links resources for other direct hydraulic ev builds or conversions?

Thanks!


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> I'd like to stick with a 48v nominal system (I have other projects and a solar off grid system that run on 48v). This limits my choice of motor, but it seems like the curtis AC 9 would fit the ticket. It should deliver more than the required power at 48v (with 600A controller). The other obvious win is that it's available with an SAE A hydraulic pump mount, meaning I could bolt it directly to a hydraulic pump without any custom fabrication.
> 
> AC-9 motor kit w/ SAE A pump mount - AC-09 AC Induction Motor Drive Kit


Listings like that one from Electric Motorsport tend to lead people to believe that Curtis motors exist - they don't. That's an HPEVS AC 9-06.06 motor plus a 1236SE-5621 controller from Curtis Instruments.


----------



## MattsAwesomeStuff (Aug 10, 2017)

I'd use a second-hand forklift motor, considering it's almost the same requirements and working conditions and voltages. Standard routine is that you can get them for scrap price, $100-200.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> I'm a fan of the bmw i3 modules (48v 60ah). I can get a salvaged battery pack from a local yard for a decent price. I'd be looking at 20kwh realistic for an 8 module pack.


The nominal voltage of those 12S modules is about 45 volts, but that's compatible with the motor and the nominally 48 volt controller. Many people seem to assume that all batteries are multiples of 12 volts, and that's only true for lead-acid.

These modules are used in series in the BMW. Using all eight of them in parallel would mean that you need to manage eight strings, all with their own battery management systems... that's still 96 BMS channels, despite being only 12S overall.

The 60 Ah BMW i3 modules are the earliest and lowest-capacity - the latest ones have twice the capacity, and appear to be the same physical size and likely even weight, although they would be more expensive. Weight may not be an issue (the battery pack will be the counterweight for this machine), but space might be an issue and four 120 Ah module or six 94 Ah modules (to get the same energy capacity) would require less mounting structure, less wiring, and less BMS.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> As far as I can tell from the service manual, with standard flow hydraulics its rated for 14.5gpm with a relief pressure of 2650psi. Banging around some quick engineering calculations (Hydraulic Pump Calculations - Womack Machine Supply Company) 14.5 gpm flow requires 27 mechanical hp at 2700 psi.
> 
> I'd like to stick with a 48v nominal system (I have other projects and a solar off grid system that run on 48v). This limits my choice of motor, but it seems like the curtis AC 9 would fit the ticket. It should deliver more than the required power at 48v (with 600A controller).


The peak hydraulic power calculation makes sense.

600 amps at 48 volts is a bit more than 27 horsepower, allowing for 80% efficiency; however, the AC 9 motor cannot use anything close to that current or produce that much power given 48 volts without overheating. 600 amps is just the controller's rated limit; the actual current will depend on the motor. This motor with a suitable controller can't use more than about 184 amps from the battery at 48 volts while staying at a tolerable temperature for continuous operation, and that's only at the motor's optimal point of about 6,000 RPM, where it can produce about 10 horsepower (from the 184 A * 48 V = 8.8 kW, at 85% efficiency). Down at the speed where it should run to match the engine, you might get five horsepower.

Of course you don't need the power corresponding to maximum hydraulic flow continuously, but my guess is that you need substantially more than 5 hp continuously. How fast does the engine turn that pump?

The peak power curve from HPEVS does show 27.75 hp at about 2200 RPM, but power falls off sharply with higher speed (voltage inadequate to maintain power) or lower speed (current limited), and that peak can't be sustained without overheating.

You can have more continuous power from the same motor by providing more voltage, but only at higher speed (the higher voltage makes higher speed at the same current and torque possible).


----------



## electro wrks (Mar 5, 2012)

JeremyD said:


> Are there any glaring holes in my plan? Anything I haven't considered? I haven't seen anyone do a project like this. Does anyone have any links resources for other direct hydraulic ev builds or conversions?


I think your calcs and assumptions are off. I could be incorrect, but the online formula must not figure in pump and motor efficiencies. For hydraulic pumps and motors, the efficiencies are not very good - at best, ~80% for each. So for a typical pump/motor set-up it's 0.8 X 0.8 = .64 or 64% overall efficiency. Applying this to the results from the calculations: 100% / 64% X 27HP =~ 42.2HP . This is close to the rated HP of your ICE: 44HP.

On the electric side, the ratings for the motor and controller are peak ratings. The continuous ratings are typically 1/3 to 1/2 of the peak ratings. Depending on the usage, the continuous ratings might be the better figures to use when calculating the HP available from a given motor/controller combination.

I always thought a skid steer's design lends itself to electric motors replacing the hydraulic drive motors. That is, if there is room. The hyd motors are much more compact. The electric motor set-up could be much more efficient. You would only need a small electric motor driven pump to run the hyd system. I suppose if you had large auxiliary hyd needs, a large drive pump would be good to have.


----------



## JeremyD (Apr 29, 2019)

MattsAwesomeStuff said:


> I'd use a second-hand forklift motor, considering it's almost the same requirements and working conditions and voltages. Standard routine is that you can get them for scrap price, $100-200.


 Anything you could recommend? I would think these would be much lower rated. An electric fork truck has a much smaller pump and lower demand. For reference, something like a front end loader with 2 lifting rams and single tipping ram uses a 5.5 gpm pump. The factory pump in this is 3x that capacity.


----------



## JeremyD (Apr 29, 2019)

electro wrks said:


> I think your calcs and assumptions are off. I could be incorrect, but the online formula must not figure in pump and motor efficiencies. For hydraulic pumps and motors, the efficiencies are not very good - at best, ~80% for each. So for a typical pump/motor set-up it's 0.8 X 0.8 = .64 or 64% overall efficiency. Applying this to the results from the calculations: 100% / 64% X 27HP =~ 42.2HP . This is close to the rated HP of your ICE: 44HP.
> 
> On the electric side, the ratings for the motor and controller are peak ratings. The continuous ratings are typically 1/3 to 1/2 of the peak ratings. Depending on the usage, the continuous ratings might be the better figures to use when calculating the HP available from a given motor/controller combination.
> 
> I always thought a skid steer's design lends itself to electric motors replacing the hydraulic drive motors. That is, if there is room. The hyd motors are much more compact. The electric motor set-up could be much more efficient. You would only need a small electric motor driven pump to run the hyd system. I suppose if you had large auxiliary hyd needs, a large drive pump would be good to have.


Yes, I'm trying to keep in consideration the idea of peak vs. normal rated power. I think your efficiency number look pretty close. The electric motor claims an efficiency on the order of ~90%. That compares to your calc for the ICE (probably 60-70% efficiency at best).Of course, the motor is never operating anywhere near it's peak hp output. The torque is what matters. Stock engine claims 80+ft-lbs. I'd be ok with less than maximal speed on the cylinders. They can operate scary fast at full throttle and I never operate over 3/4 throttle, 1/2 throttle most of the time to be honest.


----------



## JeremyD (Apr 29, 2019)

brian_ said:


> The nominal voltage of those 12S modules is about 45 volts, but that's compatible with the motor and the nominally 48 volt controller. Many people seem to assume that all batteries are multiples of 12 volts, and that's only true for lead-acid.
> 
> These modules are used in series in the BMW. Using all eight of them in parallel would mean that you need to manage eight strings, all with their own battery management systems... that's still 96 BMS channels, despite being only 12S overall.
> 
> The 60 Ah BMW i3 modules are the earliest and lowest-capacity - the latest ones have twice the capacity, and appear to be the same physical size and likely even weight, although they would be more expensive. Weight may not be an issue (the battery pack will be the counterweight for this machine), but space might be an issue and four 120 Ah module or six 94 Ah modules (to get the same energy capacity) would require less mounting structure, less wiring, and less BMS.


Yes, sorry, these are 12s, 44.4v nominal. Not as ideal as 13s, but should have good compatibility. These are about the best price per kw/hr I can get, and they are available locally.

I'd run the modules in parallel. Each would need BMS (if using). High quality cells like these rarely ever go out of balance when treated well. I think one could get away with cell by cell monitoring (cheap arduino circuit would do it) with a low cell voltage alarm/cut-off and manually rebalancing as needed. I'm not convinced these cheap chinese BMS modules alone should be trusted to protect expensive cells. And other BMS can add half as much cost to a battery. Another thought I have is cheap BMS for charging only, and draw from the batteries directly, bypassing BMS.


----------



## JeremyD (Apr 29, 2019)

brian_ said:


> The peak hydraulic power calculation makes sense.
> 
> 600 amps at 48 volts is a bit more than 27 horsepower, allowing for 80% efficiency; however, the AC 9 motor cannot use anything close to that current or produce that much power given 48 volts without overheating. 600 amps is just the controller's rated limit; the actual current will depend on the motor. This motor with a suitable controller can't use more than about 184 amps from the battery at 48 volts while staying at a tolerable temperature for continuous operation, and that's only at the motor's optimal point of about 6,000 RPM, where it can produce about 10 horsepower (from the 184 A * 48 V = 8.8 kW, at 85% efficiency). Down at the speed where it should run to match the engine, you might get five horsepower.
> 
> ...


I'm looking at curves on HPEVs website at 350, 450 and 650 A. I understand these are peak and not continuous duty, but I suppose so is our HP requirement of 27 hp and 14.5 gpm of flow. The 650 A curve looks like I would be in the sweet spot for both torque and hp around 2200 rpm. 450A curve shows a peak closer to 3000 rpmCoincidentally, most hydraulic pumps are rated for duty around 1800-2500 rpm. Am I misreading this graph?



https://www.hpevs.com/Site/images/torque-curves/ac-%209/48-volt/Imperial%20pdf%20graphs/AC9%2048%20volt%20650%20amp/Peak%20graphs/ac9%2048%20volt%20650%20amp%20imperial%20peak%20graph.pdf





https://www.hpevs.com/Site/images/torque-curves/ac-%209/48-volt/Imperial%20pdf%20graphs/AC9%2048%20volt%20450%20amp/Peak%20graphs/ac9%2048%20volt%20450%20amp%20imperial%20peak%20graph%2010-10-12.pdf



You mention 184 amps as a usable limit. Where is this coming from? I guess if I'm looking at 600A max, 1/3 or 200A should be a safe assumption for continuous rated duty?

I guess this begs an obvious question, is there a more powerful motor given the 48V limitation? I know the ME1004 dc motor is good for 200A continuous. If this AC-9 motor is limited to only 200A continuous, I guess it's no upgrade...


----------



## brian_ (Feb 7, 2017)

electro wrks said:


> I always thought a skid steer's design lends itself to electric motors replacing the hydraulic drive motors. That is, if there is room. The hyd motors are much more compact. The electric motor set-up could be much more efficient. You would only need a small electric motor driven pump to run the hyd system. I suppose if you had large auxiliary hyd needs, a large drive pump would be good to have.


I agree, but in a machine with working hydraulics I expect that the owner/builder would take the easier (but less efficient) route of keeping the existing system, replacing the engine directly. I see the same thing in projects to convert lawn mowers and small tractors, which usually keep the inefficient and indirect hydraulic system.

If anyone has a machine like this in which the hydraulic traction motors are shot, it would be a great target for a more thoroughly electric conversion.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> I would think these would be much lower rated. An electric fork truck has a much smaller pump and lower demand. For reference, something like a front end loader with 2 lifting rams and single tipping ram uses a 5.5 gpm pump. The factory pump in this is 3x that capacity.


Yes, a small forklift's pump motor would be way too small for the hydraulic demands of this skid-steer, even if the wheels were not driven hydraulically. The traction (wheel drive) motor of a forklift is larger.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> The electric motor claims an efficiency on the order of ~90%. That compares to your calc for the ICE (probably 60-70% efficiency at best).Of course, the motor is never operating anywhere near it's peak hp output. The torque is what matters. Stock engine claims 80+ft-lbs. I'd be ok with less than maximal speed on the cylinders. They can operate scary fast at full throttle and I never operate over 3/4 throttle, 1/2 throttle most of the time to be honest.


The HPEVS AC 9 probably never hits 90% even at the ideal speed and load, but 80% or better is plausible.



JeremyD said:


> That compares to your calc for the ICE (probably 60-70% efficiency at best).


What are you thinking has that efficiency? The engine will be substantially less than 50% efficient, but since we're not looking at fuel flow the engine's efficiency is irrelevant. The engine's mechanical output is converted to hydraulic power by the pump, at some efficiency unrelated to what is driving it... that's where the "probably 60-70% efficiency at best" would come in, and it will apply to the use of power from the electric motor as well.



JeremyD said:


> Of course, the motor is never operating anywhere near it's peak hp output. The torque is what matters. Stock engine claims 80+ft-lbs. I'd be ok with less than maximal speed on the cylinders. They can operate scary fast at full throttle and I never operate over 3/4 throttle, 1/2 throttle most of the time to be honest.


As always, torque by itself means nothing. The combination of torque and speed (which is power) is what matters. In driving a fixed-displacement pump, torque corresponds to pressure and speed corresponds to flow rate; you need both.

Do you mean the diesel engine is never operating anywhere near its peak power output? Yes, that's possible, although the engine is probably operating near its optimal speed, since it is designed for this sort of use (or at least this version is set up for this use) and chosen for this application. From other comments about JCB equipment of this era, it appears that the engine might be the XUD series, tuned for continuous lower-speed operation than the usual automotive application. 80 lb-ft (108 Nm) would be 44 horsepower (33 kW) at about 2900 RPM... is that about what it runs?


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> Another thought I have is cheap BMS for charging only, and draw from the batteries directly, bypassing BMS.


I hope you're not passing this sort of power through a BMS at any time. The BMS should monitor, control the charger, tell the controller to limit power if required, and balance cells; it doesn't need to have the input or output current go through it, like the cheap BMS units used in 12 volt lead-acid replacement units do.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> I'm looking at curves on HPEVs website at 350, 450 and 650 A. I understand these are peak and not continuous duty, but I suppose so is our HP requirement of 27 hp and 14.5 gpm of flow. The 650 A curve looks like I would be in the sweet spot for both torque and hp around 2200 rpm. 450A curve shows a peak closer to 3000 rpmCoincidentally, most hydraulic pumps are rated for duty around 1800-2500 rpm. Am I misreading this graph?
> 
> 
> 
> ...


No misreading, that's right... for short-term peak use which will overheat the motor if sustained.

The peak power comes at a higher speed with a lower current limit only because the lower current means lower torque. If you look at those two graphs, and recognize that their scales are different, they are the same data from 3000 RPM up (because they have the same voltage available), with a different torque limit being the difference below that speed. At any speed, the motor's power output is determined by torque and speed; at low speed the torque is limited by the current limit.



JeremyD said:


> You mention 184 amps as a usable limit. Where is this coming from? I guess if I'm looking at 600A max, 1/3 or 200A should be a safe assumption for continuous rated duty?


The 184 amps comes from the continuous power chart. That's as much as they could push through the motor in testing without the temperature continuing to climb.

I don't think a percentage rule of thumb is useful, because this is highly dependent on how well the motor cools.


----------



## electro wrks (Mar 5, 2012)

JeremyD said:


> Yes, I'm trying to keep in consideration the idea of peak vs. normal rated power. I think your efficiency number look pretty close. The electric motor claims an efficiency on the order of ~90%. That compares to your calc for the ICE (probably 60-70% efficiency at best).Of course, the motor is never operating anywhere near it's peak hp output. The torque is what matters. Stock engine claims 80+ft-lbs. I'd be ok with less than maximal speed on the cylinders. They can operate scary fast at full throttle and I never operate over 3/4 throttle, 1/2 throttle most of the time to be honest.


Backing up what brian says, torque is just a component of HP calculations. Also, with the skid steers I have and have operated, you run them at or near full throttle(and power output). It's how they are designed to operate. If you are moving the machine with a loaded bucket on level ground or up an incline, or digging into the ground, most of the engine's HP is used to drive the wheels(or tracks, as the case may be) through a large pump, control valves, and hyd motors. How do you know you are using all of the power from the engine? Because, even at full throttle you can usually stall the engine digging into the ground or a heavy pile of material, if you are not careful.

Simultaneously, usually through a much smaller pump, the cylinders of the boom and bucket are operated on a separate hyd circuit fed from an oil reservoir common with the drive system. This system has pressure relief valves built into the controls that usually activate long before the engine stalls.

As brian says, the efficiency of the ICE has no bearing in my calculations. Part of the confusion here is that diesel engines are usually designed for continuous use at their rated HP. Electric motors and controllers usually have a continuous rating and a peak rating.


----------



## JeremyD (Apr 29, 2019)

brian_ said:


> I agree, but in a machine with working hydraulics I expect that the owner/builder would take the easier (but less efficient) route of keeping the existing system, replacing the engine directly. I see the same thing in projects to convert lawn mowers and small tractors, which usually keep the inefficient and indirect hydraulic system.
> 
> If anyone has a machine like this in which the hydraulic traction motors are shot, it would be a great target for a more thoroughly electric conversion.


Yes, my intention would be to replace only the motor and hydraulic pump. I'd select the new pump based on the ideal operating range (in rpm) of the new motor. I'd select a pump with the right displacement to give me the flow rate I want at that rpm. There is only a single pump, delivering flow to both the drive motors, lifting and tipping rams, as well as the auxiliary hydraulic circuit.

Drive motors are a nightmare. I wouldn't dare try to swap them for direct electric motors. These use a pair of motors with an oil bath chain mechanism between the wheels. Not trying to re-engineer that 



brian_ said:


> As always, torque by itself means nothing. The combination of torque and speed (which is power) is what matters. In driving a fixed-displacement pump, torque corresponds to pressure and speed corresponds to flow rate; you need both.
> 
> Do you mean the diesel engine is never operating anywhere near its peak power output? Yes, that's possible, although the engine is probably operating near its optimal speed, since it is designed for this sort of use (or at least this version is set up for this use) and chosen for this application. From other comments about JCB equipment of this era, it appears that the engine might be the XUD series, tuned for continuous lower-speed operation than the usual automotive application. 80 lb-ft (108 Nm) would be 44 horsepower (33 kW) at about 2900 RPM... is that about what it runs?


I think that's a good way to think of it. Torque = pressure, power = flow - and both are important!

Yeah, I think that lines up with where I find the sweet spot for running. I'm guessing where I am just above half throttle is probably ~3000 rpm. Higher throttle makes more noise, but doesn't really deliver any more power. Coincidently, even in a modern mini ex (Kubota KX040 is what I have the most time in), I've never operated at full throttle. I only notice more speed over the ground when driving around, but no more digging power.


----------



## JeremyD (Apr 29, 2019)

electro wrks said:


> Backing up what brian says, torque is just a component of HP calculations. Also, with the skid steers I have and have operated, you run them at or near full throttle(and power output). It's how they are designed to operate. If you are moving the machine with a loaded bucket on level ground or up an incline, or digging into the ground, most of the engine's HP is used to drive the wheels(or tracks, as the case may be) through a large pump, control valves, and hyd motors. How do you know you are using all of the power from the engine? Because, even at full throttle you can usually stall the engine digging into the ground or a heavy pile of material, if you are not careful.
> 
> Simultaneously, usually through a much smaller pump, the cylinders of the boom and bucket are operated on a separate hyd circuit fed from an oil reservoir common with the drive system. This system has pressure relief valves built into the controls that usually activate long before the engine stalls.
> 
> As brian says, the efficiency of the ICE has no bearing in my calculations. Part of the confusion here is that diesel engines are usually designed for continuous use at their rated HP. Electric motors and controllers usually have a continuous rating and a peak rating.


I figured I could get away with some reduction in total pump flow to the boom and bucket circuits without issue. But the drive motors, especially climbing hills loaded, would really need that full flow from the pump. I even tried to do some calculations around duty cycle, but when I take the drive motors into consideration, that number moves up quite a bit.


----------



## JeremyD (Apr 29, 2019)

Are we coming to the conclusion that this particular motor (AC 9) is underpowered for my application? I have no experience with these motors but I had higher hopes. It seems a bit dishonest by the seller and manufacturer. Why sell a motor with a 600 A controller if it will set itself on fire with less than 1/3 that amount of current through it? The DC motors all seem capable of running at their rated current without issue (again, the ME1004 is rated at 200 amps, and will run 200 amps all day).

Can we squeeze more current with active cooling???


----------



## Tomdb (Jan 28, 2013)

For the BMS you could keep the BMW slaves and run one of these master units. SimpBMS (Battery Management System)


----------



## electro wrks (Mar 5, 2012)

JeremyD said:


> Yes, my intention would be to replace only the motor and hydraulic pump. I'd select the new pump based on the ideal operating range (in rpm) of the new motor. I'd select a pump with the right displacement to give me the flow rate I want at that rpm. There is only a single pump, delivering flow to both the drive motors, lifting and tipping rams, as well as the auxiliary hydraulic circuit.


Your machine may be different, but in this video @~4:18 there are 2 pumps driven in tandem off the end of the engine. They are in the long black cylinder, center lower picture frame. The one on the right, with the larger oil feed hose, is the drive pump. The one on the left, with the smaller feed hose, is the cylinders and aux pump(usually). The size of the feed hoses and the lengths of the pump sections correspond to the oil flow rates of the 2 pumps. The longer drive pump has a higher flow rate and needs more power to do this. This is a typical set-up: 






JeremyD said:


> . Coincidentally, even in a modern mini ex (Kubota KX040 is what I have the most time in), I've never operated at full throttle. I only notice more speed over the ground when driving around, but no more digging power.


All right, we're getting close here. Now, envision your mini ex moving forward and back at travel speed as the boom, arm, and bucket are being operated. In reality, this would never happen as the machine operates in a semi-fixed position. But, this is how a skid steer operates.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> Yes, my intention would be to replace only the motor and hydraulic pump. I'd select the new pump based on the ideal operating range (in rpm) of the new motor. I'd select a pump with the right displacement to give me the flow rate I want at that rpm. There is only a single pump, delivering flow to both the drive motors, lifting and tipping rams, as well as the auxiliary hydraulic circuit.


That works, but wouldn't the original pump work, too? With the original pump, a gearbox would help to match the pump speed to the (higher) motor speed; with a new pump, you could choose it to work at the best speed for the motor.



JeremyD said:


> Drive motors are a nightmare. I wouldn't dare try to swap them for direct electric motors. These use a pair of motors with an oil bath chain mechanism between the wheels. Not trying to re-engineer that


I assume that a conversion eliminating hydraulics from the wheel drive would keep that chain system, and replace only the hydraulic motors with electric motors. It still wouldn't be trivial, largely because a new control system would be needed.


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> Are we coming to the conclusion that this particular motor (AC 9) is underpowered for my application?


Yes, I think so, but that depends on how much power you actually need on average.



JeremyD said:


> It seems a bit dishonest by the seller and manufacturer. Why sell a motor with a 600 A controller if it will set itself on fire with less than 1/3 that amount of current through it?


The controller is spec'd to meet peak motor demand, and the motor can do that briefly. If they packaged the same motor with a 200 amp controller they would be accused of providing inadequate equipment for applications that briefly use the peak power.

The key is to understand that when a motor is listed as producing "up to 27 kW", there's a reason that it isn't listed as simply "27 kW".



JeremyD said:


> The DC motors all seem capable of running at their rated current without issue (again, the ME1004 is rated at 200 amps, and will run 200 amps all day).


Not really. Many DC motors are sold with output specs that they can only meet momentarily. Given the information that I've seen from Motenergy, I would be wary of any of their specs, but for the ME1004 specifically they say:


> Capable of 200 amps continuous, and 400 amps for 30 seconds.


... so 200 amps is the continuous rating, and they do claim higher.



JeremyD said:


> Can we squeeze more current with active cooling???


Better cooling is certainly the way to enable continuous operation at a higher power level. Retrofitting cooling might be practical, but generally doesn't work well. The AC 9 is designed to be cooled by its fan; there are other motor models from HPEVS which are available with liquid cooling, but only in larger sizes of motors intended for higher voltage (than 48 V).


----------



## JeremyD (Apr 29, 2019)

I was able to dig into the machine a bit, and as mentioned above, it may well be a tandem pump (why JCB oriented things with the pump buried all the way forward toward that cab I'll never understand). I have a service manual, but I'm on the lookout for a parts book ($90 on ebay right now...haha I'll wait). I'm having a hard time figuring what the specs (displacement) are for the stock pump without any part number.

This brings up a new consideration of splitting the system into two motor/pump combinations, one for the drive wheels and one for the lifting circuit. This would allow smaller motors, which might work with my self-imposed voltage limitation.

I guess some of the benefits of the above mentioned AC-9 setup might be lost on my application. The motor control for AC motor is much more expensive than dc motor. I don't need regenerative braking, or any kinds of acceleration control. The pump basically just needs to run at a constant RPM. Can I use a DC motor without motor control at all??? Voltage being the determinant of speed? I could use less expensive motors in multiples. Could even drive each drive motor with a separate pump. Decent quality gear pumps are relatively inexpensive in the context of AC motors, controllers and batteries.


----------



## electro wrks (Mar 5, 2012)

In a second look at the frame from the JCB video, the gray part of the pump set-up, to the far right, might be a variable displacement pump driving the wheels. In this case, there would be 3 pumps in tandem. Maybe, the auxiliary attachment pump is one of the black pumps.
A large DC shunt( preferably a sepex) motor from a larger forklift run with minimal speed control (constant speed) might work in this application. A series motor may not have sufficient load to prevent a runaway condition. I'm just not sure what size the motor needs to be. It maybe in the end you'll have to do some experimentation with motor sizes. Do some research on other conversions or talk to forklift people for their opinions. The nice thing about the existing tandem pump set-up is that there would be just one splined coupling(or possible a flange) needed to attach the motor to the pumps. You probably should be prepared to over-volt(to 60-72V?) the motor the have sufficient power. You may have to limit the RPM( and voltage) for motor safety/durability and possibly to prevent pump cavitation.


----------



## Windskier (May 14, 2017)

About four years ago I converted a 1983 Thomas skidsteer to electric drive.
The smokey old diesel engine (28.2 hp @ 2800 RPM) was replaced with a
Netgain WarP 9 72-156V 500amp motor 32 HP
Curtis 350 amp motor controller
Battery is 6-12V deep cycle
Onboard Quick charge battery charger
and a separate 72V solar charge controller with one 260 watt solar panel
The Netgain motor is connected to the 3 inline hydraulic pumps with a splined u-joint
I usually run about 30 min-small jobs around the property-enough for me


----------



## brian_ (Feb 7, 2017)

JeremyD said:


> The pump basically just needs to run at a constant RPM. Can I use a DC motor without motor control at all??? Voltage being the determinant of speed?


A motor's speed is not simply determined by voltage. If you supply constant voltage to a motor, it will run at the no-load speed determined by that voltage and back-EMF (which is turn depends on motor design), but will slow down as load is added. If the supplied constant voltage is high enough to keep the speed adequately high under high load, the speed without load may be excessive. Since the load when driving a hydraulic pump will vary greatly, my *guess* is that running without a controller wouldn't work well, but someone may have experience trying this.


----------



## cricketo (Oct 4, 2018)

In case nobody said it yet, those ~600A ratings for Curtis controllers is peak for 2 minutes or something. Most of their controllers that come with HPEVS motor kits are rated for 200-250A continuous. AC-9 is really not the motor for this application. I would go straight to AC-50, and then as a word of caution - don't expect HPEVS motor kits to integrate based on the specs/docs of the motor controller. HPEVS flashes their firmware to Curtis controllers and it can interfere with certain native capabilities.


----------



## Canadian Electric Vehicle (May 20, 2010)

You may have see the video of the Bobcats I converted and we learned a lot from them. We went on to apply that info to a number of Zamboni conversions. The one S570 Bobcat that we did had a run time of about 3 hrs with light work and 1 1/2hr with heavy work. The battery system was 300hr lithium cells at 96 volts. The motor was an AC50 with pump drive software. One of the big hurdles is heat. As a few have pointed out the continuous rating is much lower than peak power and that holds true on both AC and DC systems. Here is the E570: 



I'm a crappy operator and the machine was on low RPM setting, it really performed with a real operator and high RPM.


----------



## brian_ (Feb 7, 2017)

Canadian Electric Vehicle said:


> You may have see the video of the Bobcats I converted and we learned a lot from them. We went on to apply that info to a number of Zamboni conversions.


Thanks for sharing the experience and information 

Presumably, given the one motor, the motor directly replaces the engine, retaining all of the hydraulics including the traction drives. One online spec list that I found shows a 61 hp (45 kw) turbodiesel for the S570.



Canadian Electric Vehicle said:


> The one S570 Bobcat that we did had a run time of about 3 hrs with light work and 1 1/2hr with heavy work. The battery system was 300hr lithium cells at 96 volts.


One online spec list that I found shows a 61 hp (45 kw) turbodiesel for the S570.

300 Ah, rather than 300hr... presumably just a typo.

That would likely be 30 LFP cells in series, but could be 26 NMC or NCA... but regardless, it would be just under 30 kWh, so

light work would average under 10 kW (with higher peaks) and
heavy work would average under 20 kW (still with higher peaks)



Canadian Electric Vehicle said:


> The motor was an AC50 with pump drive software. One of the big hurdles is heat. As a few have pointed out the continuous rating is much lower than peak power and that holds true on both AC and DC systems.
> ...
> I'm a crappy operator and the machine was on low RPM setting, it really performed with a real operator and high RPM.


This suggests that the motor is controlled to a constant speed (although it audibly bogs down under load at the low speed), emulating the original engine, and higher speed would make more power available (seen as higher hydraulic flow at the same pressure).

The AC50/51 is the largest motor in the HPEVS line, which seems like a suitable choice.


----------



## Off the grid (Feb 10, 2017)

I want to do this to my mini skid steer its a ditch witch sk500 
It gives me a bad headache from how loud it is and the emissions are pretty bad smelling too it's a 24hp gas engine 
It has tandem pumps.
I have a 80v forklift that I put 4 tesla modules in to replace the lead acid and it does amazingly well.
It has a 16kw pump motor for the hydraulics 
Was wondering if I could replace the 2 pumps with one but not to sure 🤔.


----------



## Off the grid (Feb 10, 2017)




----------

