Large Vehicle EV Conversion?

Discussion in 'Off Topic' started by zovc, May 20, 2018.

  1. zovc

    zovc King of Cable Management
    Thread Starter


    Something I've thought about a lot in the past was becoming a van-dwelling nomad. The more thought I gave that, the more I started to consider things like converting larger vehicles... buses, box trucks, that kind of thing. Traveling has made me feel even more like I'm suited to that kind of lifestyle, so again I find myself giving options thought and weighing them against others.

    Anyways, the title and that little blurb has probably given enough context: I've started learning about EV conversions and trying to figure out the practicality of converting something like a bus with a dead engine which can sometimes be had for like $100, but just staying under $1000 gives you quite a rich selection if you're patient.

    So, I've occasionally been asking about this in different places and trying to get better context to approach whether this idea is even plausible. Here are some things I have tried to get to the bottom of...

    • I like the look of transit/city buses a lot more than conventional school buses. But, besides that, I am under the impression that they are generally lighter (less durable) than typical school buses. They're generally lower to the ground which hypothetically allows for a higher (legal) roof height relative to the floor height if I wanted to raise the roof. I was under the impression that there are transit/city buses that are primarily made of aluminum--I haven't been able to verify that lately, but the lightness of aluminum compared to steel would be a huge advantage in this use case.
    • I asked on for people to share the weights of their buses, so far, the average weight I've had--combining both converted and stripped buses--is 21501 pounds.
    • It seems like there's a lot of options for how one could approach a DIY electric vehicle in terms of hardware. Lots of choices in terms of motor (AC, DC, Brushless DC), controllers, batteries, and so on. I'm still trying to get an understanding of the different elements here, but because this is a pretty out-of-the-ordinary pursuit, it's hard to figure out what's suitable for powering a vehicle that weighs more than 5 tons.
    • Frankly, the most interesting kind of battery cell I've heard of so far is the 18650 "Laptop" battery cell. I like the idea of recycling/re-purposing, and scouring Goodwills and the like for cheap cheap laptops to pull batteries from sounds like a lot of fun.
    Here are some questions I have, with what I've looked into so far:

    • What kind of vehicle do you think would be the best starting point for an EV conversion and a camper conversion?
      • Do you know if any aluminum-frame buses exist? Do you happen to know the manufacturers/models/years?
    • What kind of motor setup do you think would be necessary and/or suitable for such a heavy vehicle? Do I need to couple motors? Should I try to have a motor for each wheel, or the two stationary wheels?
      • Figuring out what kind of overall engine/controller power consumption I "might" be looking at would help me estimate how feasible scrapping batteries actually would be. For figuring out how many battery cells I need to connect in series and in parallel.
    • Do you have any recommended reading on this subject?
    Phuncz likes this.
  2. confusis

    confusis John Morrison. Writer, Editor, Awesome Person.
    Site Staff SFF Workshop

    From my knowledge of truck/bus chassis, EVs and general stuff;

    Urban buses are definitely lighter - unlike the US school bus, they are more designed as boxes on top of a bare truck chassis. The chassis, engine and drivetrain, and steering wheel position is supplied by a manufacturer (I.e. Scania) and then built into a bus by a coachbuilder.

    Eg, the above chassis is supplied as pictured, and is drive-able in that form (it's amusing watching them being unloaded from RO-RO car ships! The coachbuilder cuts and extends the chassis at the yellow points to the desired length, then a box is built on top.

    The above image gives you a good idea as to the layout of a modern bus in regards to drivetrain. Whilst a very modern bus may be out of the price range, the layout has been in use for years.

    In regards to powertrain installation, you have a few options. Since you'll be pushing a heavy chassis, use of an existing gearbox may be the best option - giving you the ability to have low end torque and highway speed. Alternatively, you could just connect to the driveshaft - but then you lose some of the speed range and performance.

    Don't bother with hub motors or similar - truck and bus chassis are designed to have solid drive axles, which support the weight of the rear of the bus.

    Mounting batteries will be relatively easy since the floor of a bus rides on top of the chassis rails - you have a tonne of room under the floor between the axles to mount batteries, controllers, etc.

    AC motor drive is the best option at this time - most new EVs I'm aware of use AC.

    In the long term, i have a couple of suggestions;
    -Use the massive roof space for solar panels. This will mean that you can be more self sufficient on power (especially if you set up all your interior amenities to run on 12v DC!), as well as trickle charge any excess into the vehicle batteries. Definitely not enough to drive the motors, but it could theoretically mean a week long stay at a location could mean you save $ on charging.
    -Replace any windows you can with polycarb or alu sheet where appropriate (behind storage units, bathroom). Glass is heavy!
    -Insulate - buses are designed to run with an engine and AC unit - you'll find being parked somewhere with these off will result in high heat in summer and freezing cold in winter. The average bus only has walls about 1-2 inches thick.
    VegetableStu, Phuncz and zovc like this.
  3. zovc

    zovc King of Cable Management
    Thread Starter

    Dang, @confusis, that's a lot of good info!

    Do you have any idea how integrating a new, different motor with an existing automatic transmission works?

    I'm not sure I understand what a hub motor is, but I'll look into that.

    So, when you say city buses are typically built on that kind of frame/drivetrain... what are they normally built out of on top of that? I've seen people raise the roof on school buses by just cutting the (steel) frame and patching it up with steel stock and panels. Doing that with fiberglass seems dubious, maybe even aluminum is sketchy.
    VegetableStu likes this.
  4. confusis

    confusis John Morrison. Writer, Editor, Awesome Person.
    Site Staff SFF Workshop

    Automatic transmissions would almost be ideal, but they do have a fair bit of parasitic loss. You may be able to find or have made a control module for the auto that works without the main engine ECU.

    Most buaes these days seem to have a mix of aluminium frame and aluminium panels or fibre glass panels. If done right, any mods can be as strong as the original structure.
    zovc and VegetableStu like this.
  5. zovc

    zovc King of Cable Management
    Thread Starter

    Hm. When you say "most buses these days", do you have any estimation of when that started to be the case?

    I asked on how much folks' buses weigh, and they all seem quite heavy. Much larger than the typical EV conversion, of course. (Weights in Pounds, mostly US folks on that forum.)

    Do you have any estimate for how much lighter a city bus would be than these (presumably steel) school buses from 2000 and before weigh? And do you have any idea what the process for a sturdy roof-raise on a fiberglass body would be like?
  6. confusis

    confusis John Morrison. Writer, Editor, Awesome Person.
    Site Staff SFF Workshop

    going by the NZ fleet, I'd say 20 years or newer. USA buses may be different though!

    Regarding transit buses, Google may help :)

    26400 lbs
    But that includes large glass windows, seating, etc. That site seems to have a good range of possible candidate buses to get an idea of what size you want, etc.

    Why the necessity for a roof raise? most transit buses are tall enough inside to walk upright :)
    zovc likes this.
  7. zovc

    zovc King of Cable Management
    Thread Starter

    I'm 6'0"/~183cm, a lot of (school) buses wouldn't let me stand upright after insulating the floor and ceiling with more than ~2" of insulation on both surfaces. Or, if they would, with any sort of decorative layer (tile/paneling/etc) it would be really cramped.

    In transit buses, this might not be a problem. But I just generally like tall spaces and have fantasies of being able to fit a comfortable loft bed in a camper conversion. :p
  8. confusis

    confusis John Morrison. Writer, Editor, Awesome Person.
    Site Staff SFF Workshop

    Damn tall people!

    To be honest, your biggest limitation will be your budget and access to donor vehicles. Whilst buses in one country may be primarily of one layout, other countries may vary. The majority of buses here are Scania/MAN based, or Japan made, with all being "cab forward" in style. I'd expect bonneted school buses to be much more common in the USA.
    zovc likes this.
  9. jØrd

    jØrd SCSI for life
    Moderator Gold Supporter Supporter of Efficiency LOSIAS Digital Seppuku

    The majority of transit busses in West Australia are Mercedes or Volvo w/ coachwork by Volgren. Whats available in your area is super region specific and somewhat affected by whats in the surrounding regions too. It would pay to spend some time just researching whats being used where your looking to buy.
    zovc likes this.
  10. zovc

    zovc King of Cable Management
    Thread Starter

    This would be once I get back to the US, not sure where in the US that would be.
  11. el01

    el01 King of Cable Management

    By the way (somewhat unrelated), I remember seeing this crazy project in a Make: The Best Of book of a Honda Accord modded to burn trash as fuel. Just a random tidbit.

    I would suggest looking at this:

    A Nissan Skyline, sure, but it's a good example.

    Finally, it would be super cool if someone modded a VW T1 minibus to be electric, defying all VW standards today ;)

    Or, live in one of those Chinese cargo tricycles ;)

    If only this was a real thing in real life:
    Electric, enough torque to tow a small tank, durable (Danish AND Swedish engineering), modular, and highly customizable. The plastic interior leaves something to be desired, though ;)

    Sorry for being the forum rambler who rambles about somewhat unrelated topics ;(