DIY Electric Car Forums banner
1 - 20 of 30 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi, I'm doing research for a project where I would replace the gas engine on an old school bus to electric.

My questions are on pricing such a project. Ball park, with labor included, motor and batteries to provide a 120 miles reach for a vehicle that size what would it cost?

Thanks
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
The project is in research mode. The bus has not been purchased yet, and it will not be used as a school bus but rather converted into a motorhome.
 

·
Registered
Joined
·
6,523 Posts
I assume that we're talking about a full-sized school bus, which is a medium-duty truck chassis with a 30 to 40 foot long body on it.

Fitted out as a motorhome, this is likely a ten-ton vehicle. So, with that mass and the huge frontal area, it seems reasonable to me to assume that it will take about five times as much energy to move this vehicle as it would take to move a compact car the same distance.

So... 120 mile range will require five times the battery capacity of a typical battery-electric car with that range. The Nissan Leaf has somewhat less range than 120 miles with its 30 kW-h battery... so, perhaps 180 kW-h, or about double what a Tesla Model S has. You could use six complete Leaf batteries. :eek:

A small school bus is on a commercial van chassis, and could be substantially smaller, with correspondingly lower energy needs.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 ·
Thanks. I've heard of KWhours price dropping to $2 or less so a battery pack for a bus could be in the $36,000 or less range. That seems ok.

Now what type of motor would the bus require?
 

·
Registered
Joined
·
6,523 Posts
Now what type of motor would the bus require?
Huge! :D

But seriously, accelerating all that mass at an acceptable rate requires a lot of peak power. My motorhome is on the Ford F53 chassis, the only chassis available in North America for Class A motorhomes with a gasoline engine, and comparable in size and weight to a school bus - it has (like all current and recent F53) a 365 hp V10 engine, and while it performs well, it's not quick by car standards.

Keeping that big box moving through the air at highway speed requires a lot a continuous power... in my experience, about four times what my van takes, so about six times what a typical EV car takes. A typical electric car motor won't do the job.

Climbing grades while maintaining highway speed, and perhaps accelerating to pass slower trucks, takes at least half of my engine's 365 hp, so it looks to me like a continuous rating of over 150 hp or 120 kW would be suitable.... and a higher peak power is needed.

If you want to use a single motor (to work with the stock bus axle), then a motor from the rear of a Telsa, or some industrial motor, seems likely. None of the common motors sold for DIY conversions are big enough. There are various electric trucks and buses which have been made in limited production, and the motors from them might be usable. There are some Siemens motors made for Azure Dynamics which are still around; the largest of them might be adequate if run at the motor's maximum voltage, but that's only a guess.
 

·
Registered
Joined
·
6,523 Posts
Bus selection considerations

By far the easiest way to arrive at a large EV motorhome would be to start with a motorhome, not a bus; however, a cheap motorhome may have body issues that you would rather not deal with.

One difference between typical Class A motorhomes and the classic school bus configuration (called a "conventional" or "Type C") is that in the motorhomes the driver usually sits over the front wheels (cab-over-engine, with the engine under a hump between the driver and passenger seats), while the buses usually have a conventional hood with the driver behind the front wheels. The cab-over-engine layout provides more interior space for the same overall length, while the conventional layout provides easier engine access.

For an electric conversion, "engine" access seems like a non-issue, so cab-over-engine has an advantage... although the ride for the driver might not be quite as nice. School buses are available in a "flat front" configuration (which they often call a "transit" style or "Type D"), which is either cab-over-engine or rear-engined. The buses do that so the driver can see kids crossing in front of the bus, but it might also be the better choice for a motorhome. Some flat-front school buses have a rear engine (like an intercity coach, such as those run by Greyhound), but those are likely to be more expensive. And a final note - the front passenger seat setup might not be what you want in a flat-front bus (which normally doesn't have a seat beside the driver - just a entrance door and stair).

Some school buses have storage compartments underneath, which would be useful in a motorhome and could potentially house EV components. Even if there are no compartments, they can be added - all of these things have a very high floor so there's lots of room underneath... all of which you'll probably use between batteries, RV equipment, and storage.

Also - and this is unrelated to EV conversion - check the headroom on any school bus being considered. Kids are short, so ceiling height in some of them may not be comfortable.
 

·
Registered
Joined
·
171 Posts
A tesla setup could work, but you will probably need at least 3 Tesla battery packs and beefed up cooling capacity to deal with long uphill grades.
 

·
Registered
Joined
·
7 Posts
I'm looking to do something similar.
28ft Blue-bird motor home and ev conversion. The reason I want to use a bus is the structural supports throughout the sides of the bus for my workout equipment, muscle up bars, pegboards, grip trainers, etc.

I plan to keep the build to the lightest material possible.

My question is: If I were to buy 2 front end collision Model X performance editions, from one of the auction sites.
My math says those rear axles will be powerful enough to replace the stock diesel.

The question is it possible to mount those motors onto the bus? What garage would have that capacity?

Any word on 4680 battery sales, or Chinese knock-offs?
Bus selection considerations

By far the easiest way to arrive at a large EV motorhome would be to start with a motorhome, not a bus; however, a cheap motorhome may have body issues that you would rather not deal with.

One difference between typical Class A motorhomes and the classic school bus configuration (called a "conventional" or "Type C") is that in the motorhomes the driver usually sits over the front wheels (cab-over-engine, with the engine under a hump between the driver and passenger seats), while the buses usually have a conventional hood with the driver behind the front wheels. The cab-over-engine layout provides more interior space for the same overall length, while the conventional layout provides easier engine access.

For an electric conversion, "engine" access seems like a non-issue, so cab-over-engine has an advantage... although the ride for the driver might not be quite as nice. School buses are available in a "flat front" configuration (which they often call a "transit" style or "Type D"), which is either cab-over-engine or rear-engined. The buses do that so the driver can see kids crossing in front of the bus, but it might also be the better choice for a motorhome. Some flat-front school buses have a rear engine (like an intercity coach, such as those run by Greyhound), but those are likely to be more expensive. And a final note - the front passenger seat setup might not be what you want in a flat-front bus (which normally doesn't have a seat beside the driver - just a entrance door and stair).

Some school buses have storage compartments underneath, which would be useful in a motorhome and could potentially house EV components. Even if there are no compartments, they can be added - all of these things have a very high floor so there's lots of room underneath... all of which you'll probably use between batteries, RV equipment, and storage.

Also - and this is unrelated to EV conversion - check the headroom on any school bus being considered. Kids are short, so ceiling height in some of them may not be comfortable.
 

·
Registered
Joined
·
30 Posts
There are electric school buses Not sure if any have hit the surplus market yet.
https://www.blue-bird.com/images/brochures/SB-VIS-EV-0920.pdf full sized school bus specs

Later floyd
 

·
Registered
Joined
·
6,523 Posts
My question is: If I were to buy 2 front end collision Model X performance editions, from one of the auction sites.
My math says those rear axles will be powerful enough to replace the stock diesel.
Although I mentioned Tesla motors when this discussion was active four years ago, Tesla Model S induction motors have one major problem: they can't take sustained high power without overheating. They can produce lots of peak power, but keeping the rolling at highway speed, especially up a grade, might be a problem.

Another issue is that Tesla motors are not easily separated from the transaxle (gearbox and differential), although some aftermarket suppliers are now making housings to make that possible.

The question is it possible to mount those motors onto the bus? What garage would have that capacity?
How would you want salvaged EV motors (such as from Tesla... but any of them) to connect to the rear axle?

Tesla built custom axle housings and gearboxes to mount Model 3 motors onto a heavy truck axle for the Semi prototypes (who knows what they'll use if they ever actually put it in production), which is a somewhat common approach for heavy commercial vehicle propulsion, e.g.:
"e-Axle" products at Dana Electrified

Some of these (including the Tesla Semi) use one motor per wheel, mounted either out at the ends of the axle (as in buses) or near the middle of the axle (to fit with a typical truck - or school bus - frame and suspension).

The alternative is to mount a motor to the frame, and use a normal drive shaft. There's no need for the motor to sit where the engine did - it could be as close to the axle as the closest hanger for a multi-part shaft.
 

·
Registered
Joined
·
7 Posts
Although I mentioned Tesla motors when this discussion was active four years ago, Tesla Model S induction motors have one major problem: they can't take sustained high power without overheating. They can produce lots of peak power, but keeping the rolling at highway speed, especially up a grade, might be a problem.

Another issue is that Tesla motors are not easily separated from the transaxle (gearbox and differential), although some aftermarket suppliers are now making housings to make that possible.


How would you want salvaged EV motors (such as from Tesla... but any of them) to connect to the rear axle?

Tesla built custom axle housings and gearboxes to mount Model 3 motors onto a heavy truck axle for the Semi prototypes (who knows what they'll use if they ever actually put it in production), which is a somewhat common approach for heavy commercial vehicle propulsion, e.g.:
"e-Axle" products at Dana Electrified

Some of these (including the Tesla Semi) use one motor per wheel, mounted either out at the ends of the axle (as in buses) or near the middle of the axle (to fit with a typical truck - or school bus - frame and suspension).

The alternative is to mount a motor to the frame, and use a normal drive shaft. There's no need for the motor to sit where the engine did - it could be as close to the axle as the closest hanger for a multi-part shaft.
I thought the Model X performance addition had the most powerful motor they produce so far, with its towing capacity.

Does the Model 3 have that same rear axle power for towing?

My original thought was to buy at least 2 salvaged vehicles and place the motor a motor gearbox system directly in line with the tire.

Is there a more efficient method?

I'm budgeting 200k for this build. 32-48k to make it a house. Planning to cut up salvaged siding for all interior walls, sheep's wool, and salvaged phone books for most of the insulation. Get as much as possible off of craigslist free, use a family shop or military to work on it, and use my veterans status to bring down any other price possible.

That leaves 150k for the EV conversion. The same price as the 300mile Tesla Semi is supposed to be.

Not planning to start any build till next March, still deployed...

I built another discussion post.

Trying to figure out the right way to do this, as efficiently as possible.

EV with plenty of solar possibly additional charging from wind and/or water. Going from one Spartan, Savage, or Crossfit event to the next, doing medical support. Spending two weeks at a location for a charge, living on national parks sounds like the highest step for a great way to live.

I don't know enough about this so, please any aid. I'll be reading those links you added tomorrow or Monday.

Are there any shops I could speak to, that use the axle to tire method?

I can do most of the construction and welding for the motor home piece. I've never done electrical work.
 

·
Registered
Joined
·
6,523 Posts
I thought the Model X performance addition had the most powerful motor they produce so far, with its towing capacity.
Of the original series of Tesla induction motors (which are being discontinued), yes... but the difference is largely the inverter and its programming (not the motor itself), and peak power is irrelevant anyway. It is what the motor can handle for an extended period which matters with this heavy vehicle.

Does the Model 3 have that same rear axle power for towing?
The Model 3 motors (and the motors now in other models, derived from this one) are entirely new designs. The rated peak power of any single Model 3 motor is much lower than the old large Model S/X rear induction motor, but the continuous power is probably comparable. The Model 3 rear motor is a permanent magnet design, which doesn't have the rotor cooling problems of an induction motor.

The school bus, outfitted as an RV, will be much heavier than a Model X with the maximum allowed trailer.

My original thought was to buy at least 2 salvaged vehicles and place the motor a motor gearbox system directly in line with the tire.
...
Are there any shops I could speak to, that use the axle to tire method?
That is the approach taken by some of the commercially available "e-axles" that I link to; did you look at those? No one routinely does this as a custom service.

That leaves 150k for the EV conversion. The same price as the 300mile Tesla Semi is supposed to be.
The price of any unreleased Tesla model is entirely fiction, and the promised price of one that should have been built two years ago but is still nowhere in sight is particularly suspect. Real electric heavy duty trucks are much more expensive than that.
 

·
Registered
Joined
·
200 Posts
The price of any unreleased Tesla model is entirely fiction, and the promised price of one that should have been built two years ago but is still nowhere in sight is particularly suspect. Real electric heavy duty trucks are much more expensive than that.
I agree with this sentiment. Tesla, while performing great with their S through Y models, is acting very suspiciously with the Semi and Cybertruck. It is very different from their new Roadster, which has a total of two and a half buyers. Semi and pickup truck are intended for massive lucrative market segments which anyone would capture as soon as possible if they could.
 

·
Registered
1996 Toyota Land Cruiser
Joined
·
192 Posts
I thought the Model X performance addition had the most powerful motor they produce so far, with its towing capacity.

Does the Model 3 have that same rear axle power for towing?

My original thought was to buy at least 2 salvaged vehicles and place the motor a motor gearbox system directly in line with the tire.

Is there a more efficient method?

I'm budgeting 200k for this build. 32-48k to make it a house. Planning to cut up salvaged siding for all interior walls, sheep's wool, and salvaged phone books for most of the insulation. Get as much as possible off of craigslist free, use a family shop or military to work on it, and use my veterans status to bring down any other price possible.

That leaves 150k for the EV conversion. The same price as the 300mile Tesla Semi is supposed to be.

Not planning to start any build till next March, still deployed...

I built another discussion post.

Trying to figure out the right way to do this, as efficiently as possible.

EV with plenty of solar possibly additional charging from wind and/or water. Going from one Spartan, Savage, or Crossfit event to the next, doing medical support. Spending two weeks at a location for a charge, living on national parks sounds like the highest step for a great way to live.

I don't know enough about this so, please any aid. I'll be reading those links you added tomorrow or Monday.

Are there any shops I could speak to, that use the axle to tire method?

I can do most of the construction and welding for the motor home piece. I've never done electrical work.
I think it's a cool idea to drive around and live in a green EV bus like this. Especially with solar or wind or other green power to charge it.

There is another member here converting a coach style tour bus to EV. I forget who or other details but perhaps search and see what he's up to.

School buses are overly heavy compared to RVs or coach buses but if it's what you want then it's at least super strong and stout to hold the weight.

I would look into an electric propulsion system from an old city bus or something to adapt. Tesla stuff is for a 5000lbs car, a typical scool bus is around 33,000lbs. Oof.
 

·
Registered
Joined
·
2 Posts
For what its worth other than a trolly car. Disney ride or something like that the first real electric vehicle was an electric Bluebird full size school bus. That was 1982 in Mesa Verde National Park. They used electric bluebirds for several reasons. Among those: braking over the extreme grades, strudy chassis over the extreme roads, and they didn't stink up the place with diesel.
 

·
Registered
Joined
·
2 Posts
Honestly I really don't know. The runs were short (like maybe 3 or 4 miles at most as I remember) but very steep, narrow, and twisty. I was seated up front. The driver was pretty proud of his bus.
Gets me wondering if they still use the same buses.
 

·
Registered
Joined
·
2 Posts
Huge! :D
But seriously, accelerating all that mass at an acceptable rate requires a lot of peak power. My motorhome is on the Ford F53 chassis, the only chassis available in North America for Class A motorhomes with a gasoline engine, and comparable in size and weight to a school bus - it has (like all current and recent F53) a 365 hp V10 engine, and while it performs well, it's not quick by car standards.
I've seen a couple electric motors pushing 100Hp so I'm not sure that power is the issue here, but i could be doing the math wrong in my head, i feel like it'd be more the amount of wattage you'd need to carry (obviously could be wrong)
 

·
Registered
Joined
·
16 Posts
In my lifetime I have converted 5 school busses to rv's, two of which were mine with one being pure high performance diesel and as much as I wanted a full electric bus building it from scratch was over the top cost prohibitive and everyone just sit of told me it can't be done and shook their heads. So the second bus ended up being a "makeshift" hybrid in as much as I had an AC motor inline on the driveshaft, but no one had a controller that would integrate with the bus so it was me and a hand operated controller assisting the diesel and we traveled the world in them. It was novel, it was not a pain in the ass because I always had the diesel there in case the system went south. My last one was a client who wanted to convert a bus to electric and I told him it can be done but outside of the bus manufacturers we were in unkempt territory. I talked him into going with a bluebird ordered straight from the factory with no interior what so ever and highway gearing. We effectively doubled the battery and it works great but only about 170 miles per charge because the manufacturer designs and builds the bus for low speed stop and go, not long range and let me tell you the hills are a motherf***er on batteries and let me tell you, when you have an eye on charge remaining, you notice long uphill grades. My advice, do a hybrid it's much less expensive, a lot less guess work and self deception in regatta to "yeah, that should work" and somewhere out there is a company (person) that will custom build you a controller interface.

 
1 - 20 of 30 Posts
Top