[mortonc]

I'm trying to size up the conversion of a bus.

I don't yet have said bus but it's likely to be a double decker or single decker if it has to be. Think Leyland Olympian (bus) or Setra s328 (coach).

Average MPG of these jobbies (diesel) is 8MPG

HP for these busses seems to range from 300-500hp and torque around 700nm - 1500nm

Let's say that when it's loaded up I would expect total mass of between 10 and 15 tonnes

Now for my use I would be looking to achieve a range of around 60 miles between charges, used on mostly flat roads but with the capability to make it's way up a mountain once in a while (who wouldn't want to take their bus skiing!)

50mph would be more than sufficient.


So, where would you begin with finding a motor and batteries to carry out such a project?

 

[mortonc]

https://green-technology.org/gcsummit16/images/35-ZEV-School-Buses.pdf

page 18 of this PDF is quite interesting - it provides specs for an EV bus which includes:

motor: Permanent Magnet 3 Phase Electric 150kW Peak,
110 kW Cont.

torque: 530 @ 50 RPM

Battery capacity (kWH: 115.2 Total (92.1 usable)

Range(miles) : 70 (+/- 30)

 

[brian_]

Since lots of medium-duty trucks and similarly heavy buses have been converted or built as EVs, the obvious source is whatever components they used, perhaps salvaged from a vehicle which has been scrapped (usually because the battery is dead or the owner has given up on the idea of an EV for that application).

Typically, they use either a very large-diameter motor, or a motor with a fixed-ratio (single-speed) reduction gearbox, mounted where the transmission would normally be.

A lot of surplus electric drive hardware came from the bankruptcy of Azure Dynamics, but their only heavy enough vehicle was the Balance hybrid system for Ford chassis; it used a big induction motor and reduction gearbox, but I don't know if any of those are still available somewhere in the salvage market.

A few people have tried or at least considered projects with the components of the Smith Newton truck. It used a reduction gearbox.

TM4 (now a part of Dana) specializes in motors for large vehicles, but I doubt that it is practical (if it is even possible) to buy a single new motor from them. In their range, you would presumably want a Sumo MD. An alternative from another part of the same company's product ragne would be to replace the whole drive axle with one with an integrated TM4 motor, from Dana Electrified.

Most proposed DIY projects of this size don't get built, likely due to the high cost of the required enormous battery, but if you search in the forum for "bus", "RV", or "motorhome" you should be able to find some previous discussions.

 

[ConversionVirgin]

Why not do a tesla front and rear motor of and x or s. Their are a few controllers that will do it. My dream is to do one of these with solar on the roof too. You could use whatever batteries you wanted but most economical would buy a crashed dual motor S or X and part out what you don't need. You can get a wrecked chevy spark ev for under 3k and it comes with a decent 21kwh battery. You could then just plugin at rv parks and juice up and power both propulsion and the rv off the batteries.

 

[brian_]

Why not do a tesla front and rear motor of and x or s.

Even both drive units of a Model S or X Performance Dual-Motor might not handle the sustained power demand of a bus weighing 10 to 15 tons. These motors can put out a huge amount of power for few seconds, but then overheat if you try to sustain it.

You could use whatever batteries you wanted...
You can get a wrecked chevy spark ev for under 3k and it comes with a decent 21kwh battery.

That would not be nearly enough battery to be useful. The entire pack from one of the longest-range electric cars might work... certainly at least the 60+ kWh of a Bolt or Leaf Plus or Model 3, and better the 85+ kWh of a higher-capacity Model S or X or one of the very new other SUVs (Audi e-tron, etc).

You could then just plugin at rv parks and juice up and power both propulsion and the rv off the batteries.

I mentioned RVs because previous discussions in this forum dealt with RVs of similar weight, but this proposal is for a bus... no mention of RV use.

 

[Hollie Maea]

We're working on another project that needs a big torquey motor. We have a motor for it that would probably be just right for your bus project. It does 1530 Nm peak and 770 Nm continuous with a peak power speed of 2700 RPM and a maximum speed of 6000 RPM.

But we don't have an inverter solution yet. We're hoping to have something to pair with it later this year, but can't make any promises yet. It's not trivial to come up with a 700VDC/900Arms inverter.

But I'll try to come back and ping this thread when we are ready to release, if you haven't found another option.

 

[MattsAwesomeStuff]

Average MPG of these jobbies (diesel) is 8MPG

I'm skeptical of those numbers at 55mph. Maybe by double.

 

[remy_martian]

Wait for the CybrTrk as far as drive units go. In terms of homebrew projects, it's not that far off, lol. The premium model should be rated right around 10 tonnes continuous operation.

The Azure Dynamics van is a pipsqueak 3 tons and only has a 28kWh battery -- did they make a medium duty?

I'm lining up to do an F-450. The game here is torque at highway speed, not horsepower in terms of car-gearing....a Tesla, for example, is geared for double the top speed you need, which means you put down half the torque into the wheels as you could have...not good. Gear, if needed, your motor for a 2500-3000 RPM output and feed that into the bus transmission (hopefully a manual to make it easier) and you should be good.

You need to size cooling accordingly -- as was said, bolting on a Tesla cooling system could get you in trouble.

 

[lawrencerhodes]

Your project is quite ambitious. Sounds like you are in England. In the USA there was a 22 foot motorhome called the Ultravan which weighed about the same as a Nissan Leaf. It got 18mpg with a flat 6 boxer. You could restomod this using a Bolt or Leaf drivetrain including batteries and wiring harness. You would then have an OEM conversion which could be fast charged and have 50 to 150 mile range depending on the donor. The 22 x 8 foot roof would be capable of at least 3kw of solar panels. I don't know if a similar caravan was made in Brittan but it would be a better candidate for conversion. Also if it was aluminium like the Ultravan it would have less corrosion.

I'm trying to size up the conversion of a bus.

I don't yet have said bus but it's likely to be a double decker or single decker if it has to be. Think Leyland Olympian (bus) or Setra s328 (coach).

Average MPG of these jobbies (diesel) is 8MPG

HP for these busses seems to range from 300-500hp and torque around 700nm - 1500nm

Let's say that when it's loaded up I would expect total mass of between 10 and 15 tonnes

Now for my use I would be looking to achieve a range of around 60 miles between charges, used on mostly flat roads but with the capability to make it's way up a mountain once in a while (who wouldn't want to take their bus skiing!)

50mph would be more than sufficient.


So, where would you begin with finding a motor and batteries to carry out such a project?

 

[brian_]

The Azure Dynamics van is a pipsqueak 3 tons and only has a 28kWh battery -- did they make a medium duty?

The only medium-duty by AZD was the Balance hybrid powertrain in an F-450 (stripped chassis or chassis-cab). Because it was a hybrid, it still wouldn't have large battery, but the motor was inline in the propeller shaft of a loaded F-450... unfortunately with only enough power to slowly accelerate the vehicle by itself and only up to 22 mph. Good catch - it wouldn't be up to driving a ten-ton vehicle as a pure battery EV.

 

[olegil]

I'm trying to size up the conversion of a bus.

I don't yet have said bus but it's likely to be a double decker or single decker if it has to be. Think Leyland Olympian (bus) or Setra s328 (coach).

Average MPG of these jobbies (diesel) is 8MPG

HP for these busses seems to range from 300-500hp and torque around 700nm - 1500nm

Let's say that when it's loaded up I would expect total mass of between 10 and 15 tonnes

Now for my use I would be looking to achieve a range of around 60 miles between charges, used on mostly flat roads but with the capability to make it's way up a mountain once in a while (who wouldn't want to take their bus skiing!)

50mph would be more than sufficient.


So, where would you begin with finding a motor and batteries to carry out such a project?

The bad news, as everone here already pointed out, is that you're a bit out of spec for typical salvaged EV components. The good news is that you're into the range of industrial motors. You can probably afford the space and weight of a 400V/690V three phase induction motor (about a cubic meter and 1.5 tons for a 200kW 50Hz 4-pole motor).
The even better news is that if you run that 50Hz motor at 60Hz it's now a 240kW and at 70Hz it's a 280kW motor at about 2000 RPM. Allthough that might be a bit quick for direct drive, so a reduction gear or keeping the original gearbox would be essential. There are of course slower spinning 6 or 8 pole motors, but not as abundant as 4 pole.

So two Leaf packs, and a 690V 200kW motor, with a suitable industrial inverter (DC bus access, but this size usually does anyway, for external resistive braking) configured for torque control from accelerator pot.
Whether you'll be able to find this at an affordable price is a huge question, though.

 

[Tremelune]

Gearing could be your savior. What is the transmission in this bus? Final drive? Tire diameter? If you had 3+ gears designed to max out at 10k RPM at 50mph, even a puny Nissan Leaf motor putting out 280Nm might still be sufficient to get the thing moving. I feel like the "comparison" here is to calculate torque to the axles of the stock drivetrain (including transmission and diff), and see what that looks like if it were geared very tall for a lower top speed.

I dunno what factory BEVs are going for in your neighborhood, but buying one or two Leaf wrecks and salvaging the components is probably the cheapest way in. At 60mi range in a big ol' bus, the optimistic parts cost I would keep in mind is £10-15k just about any way you slice it.

 

[brian_]

Gearing could be your savior. What is the transmission in this bus? Final drive? Tire diameter? If you had 3+ gears designed to max out at 10k RPM at 50mph, even a puny Nissan Leaf motor putting out 280Nm might still be sufficient to get the thing moving. I feel like the "comparison" here is to calculate torque to the axles of the stock drivetrain (including transmission and diff), and see what that looks like if it were geared very tall for a lower top speed.

I agree that gearing needs to be considered, that suitable gearing is the solution to making available motor torque work for the load to be driven, and that multiple gear ratios can keep the motor in its full power output speed range... but that's probably not enough. Even with ideal gearing, a salvaged Leaf motor (with stock controller/inverter) is good for 80 kW, and that will mean slow acceleration and very limited grade climbing. Accelerating ten tons to highway speed would take minutes.

Solutions to the lack of power include

• using the latest Leaf motor and controller/inverter instead of the common 80 kW version
• bypassing the 80 kW power limit with an alternate controller (and probably inverter)
• using a motor salvaged from a different EV (most are now more powerful than the original Leaf)

 

[lawrencerhodes]

Gearing could be your savior. What is the transmission in this bus? Final drive? Tire diameter? If you had 3+ gears designed to max out at 10k RPM at 50mph, even a puny Nissan Leaf motor putting out 280Nm might still be sufficient to get the thing moving. I feel like the "comparison" here is to calculate torque to the axles of the stock drivetrain (including transmission and diff), and see what that looks like if it were geared very tall for a lower top speed.

I dunno what factory BEVs are going for in your neighborhood, but buying one or two Leaf wrecks and salvaging the components is probably the cheapest way in. At 60mi range in a big ol' bus, the optimistic parts cost I would keep in mind is £10-15k just about any way you slice it.

You can buy a running Leaf for 2k dollars if it has a degraded battery. More depending on condition of the battery. I bought my new Leaf in 2016 for $13,550. A wrecked Leaf that is newer might salvage for as much as 6k.

 

[piotrsko]

Out Barstow way there is a muni bus junkyard that may have bus powertrains from hybrid / full electric. Drove by the place many times.