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Discussion Starter #1
Hi,


I live in a small city in a low-population area in the central USA.



I've been interested in electric vehicles since before auto makers started releasing them a few years back. (Don't talk about the early days of autos, I'm talking like Chevy Volt)


My problem with typical EV projects is that they focus on some econobox car, which is impractical for me. I'm 6'4" (193 cm) and those cars just don't hold somebody my size. Not only that, I'm a foster parent and we have some variable number of kids, and then the people in my real family, and then a couple dogs, and whatever fishing/camping gear I want to take with me.


My current vehicle is a 15 passenger van. It's a 2010 Chevy Econoline 3500, extended. There are 4 bench seats and 2 buckets up front. 3 of the bench seats hold 3 people, the last one holds 4. Usually the back seat is out to make room for dogs, but I have literally had every other seat used. The van has a V8 in it, and it's adequate for acceleration but nothing to write home about. The most economic speed is 55-60 mph. My area generally has 2-lane blacktop roads at about 65 mph, and interstate speeds of 80 mph. The existing ICE gets terrible fuel economy in town, usually less than 10 mpg. On the highway it can get close to 20 mph depending on the wind and such.


My normal day involves driving around town a few miles, easy for an EV project. Most days the van just doesn't move at all. But when we take a trip, we use the van. When we take a trip, we WILL go more than 300 miles round trip.


So here's my question finally:
Consider a van conversion, set up for in-town driving. I can't sacrifice a whole lot of weight to batteries as I use the van to carry a lot of people. But they're little people usually, maybe as many as 5 adults but the rest are miniatures. I figure this is a do-able EV conversion and probably straightforward.


The van has an OEM trailer hitch, something like 7500 lbs weight rating.


What I'm thinking of is a trailer for trips. Probably double-axle. It would have:
1. An internal combustion engine, possibly the same one that's in the van now.
2. A big fuel tank.
3. A storage area for luggage.
4. More batteries.
5. Possibly motors to assist with driving force.


My idea is that, in town, the van is a pure EV. When I go on a trip, I hook up the trailer which converts it into a hybrid. I would obviously need a big high-voltage umbilical going up to the van, and a pretty good control unit.


Is this a feasible idea, or are there too many safety or legality concerns? AFAIK there are no laws forbidding a running engine on a trailer, but I haven't really researched it.


Thanks for your time.
 

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This was a somewhat common thing in the 90s-2010 or so. At least common enough that people knew about it. I don't know that more than a handful ever got built since most people just owned a second vehicle anyway.

You could make a generator trailer, but that means you need the whole engine on there, plus a generator large enough to power the vehicle at highway speeds (maybe 20hp for your van? 25? That's 15-18kw). Then you charge the batteries (or just drive) from the power cables. Meanwhile, you already have a big electric motor under the hood. Kinda redundant. Maybe you get away with a smaller generator, while the bigger motor under the hood can handle accelerating (dipping into battery use for short term as the smaller genny can't keep up), but still redundant.

So what people do is build a "push trailer". Meaning you drive the trailer wheels with the actual engine. The ghetto way of doing this is to just take the front end of a FWD car, stopping just after after the windshield. A little bit of hotwiring and you're done.

If your motor has regenerative breaking, you can still charge the batteries this way too by applying the brakes while being pushed, though your throttle and brake arrangement gets a bit sketchy that way unless you rig the regen on a second system (brakes should prevent engine from pushing, also brake lights will be on). All possible.

Under the hood the easiest and cheapest thing to use is an old forklift motor, maybe two in your case.
 

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Discussion Starter #3
I have serious doubts as to whether a 25hp engine could move this thing fully loaded (per my description above, plus trailer) at 65 mph for hours, and if I'm traveling from town to town it would be hours. Even if you're using the on-board electric drive to even out the high-power stretches. I'd go so far as to doubt that a 4-cylinder auto engine could do it without really stressing. I wouldn't mind a little 5L Cummins diesel though. I'm pretty sure you can get those buckled up to an appropriate generator already on a trailer, but the trailer would not be what I had in mind. And it might be expensive.



We have a second vehicle, but it's a little Toyota Corolla. My wife commutes with it. Usually if we travel we have more people than the Toyota can hold, and the van is much more comfortable for everyone anyway. Clearly if the Toyota is adequate for the job it's the vehicle we take, but usually it's not.



This is a more-than-one-ton capacity vehicle. It's not a minivan, it's at least two minivans in one. I figure It's frequently loaded to more than half weight capacity during trips, the way we do it right now. Limiting myself to less than 65 mph top speed would be counter-productive, I don't think I want extra nights in motels with 8 or more people just to accommodate a lower top speed. State law says no more than 4 people in a hotel room per night. If I'm going to do the conversion at all, it will need to perform like it does now. I will accept a 65 or 70 mph top speed, even though it does much better than that right now. But hill climbing and acceleration I would not want to sacrifice.



I could consider having the van's motors capable of pulling the loaded van and trailer combined at highway speed continuously, I can see where this might simplify things a bit and may even save money on build cost. But the pure push trailer idea does not have appeal for me. I'd like to arrive at the destination city fully charged, possibly find a place to drop the trailer off, drive around doing my business and then come back for the trailer. Possibly the trailer would run at night and charge the batteries, unless the place I drop the trailer has EV charging as a service. I haven't seen this at all in my area, at least at motels. At any rate I'd be looking at a pretty good (quiet) exhaust system for the trailer.



I know that typical DIY EV projects use DC motors, and that absolutely every commercial offering uses AC motors. I know that the DC motors can be had cheaper, especially if you look at an old forklift or something. While I can't say what I will actually choose to do at this point, I can say right now that an ACIM appeals much more to me than any DC option. The final decision would have to be left to a price estimate comparison on both options, and a comparison of features possible on each system.


There are lots of hills where the van coasts higher than the cruise speed, both in and out of town. Regenerative braking would be an appealing feature. I currently ride the brakes to keep the speed in check. I know that regen only gets about 10% of the energy back.
 

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What I'm thinking of is a trailer for trips. Probably double-axle. It would have:
1. An internal combustion engine, possibly the same one that's in the van now...

My idea is that, in town, the van is a pure EV. When I go on a trip, I hook up the trailer which converts it into a hybrid.
I get the idea of a hybrid spread between the van and trailer, but there's no reason to use the huge original van engine, because that engine is sized for peak load rather than average load.

You could make a generator trailer, but that means you need the whole engine on there, plus a generator large enough to power the vehicle at highway speeds (maybe 20hp for your van? 25? That's 15-18kw)...
The van with trailer will need more power than that. At the same time, there's no point in an 18 kW generator on a 200+ horsepower engine. The generator needs to have more capacity than the average load over the trip, and the engine needs to be sized to operate efficiently at that power level.

I have serious doubts as to whether a 25hp engine could move this thing fully loaded (per my description above, plus trailer) at 65 mph for hours, and if I'm traveling from town to town it would be hours. Even if you're using the on-board electric drive to even out the high-power stretches. I'd go so far as to doubt that a 4-cylinder auto engine could do it without really stressing. I wouldn't mind a little 5L Cummins diesel though.
Right, 25 hp isn't enough, but something much less than the van's current engine is suitable. If you're using up to a kilowatt-hour per mile, and averaging a mile a minute (60 mph), that's 60 kw or 80 hp.

A Cummins 5L (the V8 engine in the Nissan Titan XD diesel) is not "little" by any rational measurement. It would be heavier than the van's current engine. If you really like diesel, the GM "baby" Duramax 2.8 from the Colorado/Canyon, or the Ford small Powerstroke 5-cylinder from the Transit would be a better match, but I think an automotive 2-litre would be better.

I could consider having the van's motors capable of pulling the loaded van and trailer combined at highway speed continuously, I can see where this might simplify things a bit and may even save money on build cost.
Because this is a series hybrid, and even for pure EV operation without the trailer, the van's motors are going to need to be large.
 

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Push trailers

... So what people do is build a "push trailer". Meaning you drive the trailer wheels with the actual engine. The ghetto way of doing this is to just take the front end of a FWD car, stopping just after after the windshield. A little bit of hotwiring and you're done.

If your motor has regenerative breaking, you can still charge the batteries this way too by applying the brakes while being pushed, though your throttle and brake arrangement gets a bit sketchy that way...
It has been done, but a lot of unsound things have been done - that doesn't make it advisable. "Sketchy" is the nicest word that I can think of for this scheme.

There are actually articulated buses (essentially a bus towing a passenger-carrying trailer) with the engine in the back (so, the trailer) pushing the whole thing... but they are not nearly as crude as those "push trailers".

By the way, powering one axle with an engine while charging with a generator driven by another axle is called "through the road" hybrid charging. It is a bad idea with both axles on the same vehicle, but with the driver on the trailer and the drag on the tow vehicle it's really bad.
 

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Discussion Starter #7
If I'll need another engine for this, I think I'd rather get something designed for a generator than something designed for an automobile. Given a diesel's maintenance cycle and overall simplicity, I'd rather go that route than with gasoline.


I can see your point about average power. And I was thinking of the inline v6 diesel found in 90s Dodge trucks. My father had one, it would pull like a mule. You're probably right about it being bigger than the original van engine in terms of power and torque, but it was pretty small in terms of physical size per unit power. If there's a 4-liter version of that, or even 3-liter I'd be interested. Not sure if I want to design something that has to run flat out when being operated in the typical use case though, equipment wears out faster when you do that. And of course it would need a matching 3-phase generator on it.



Motors:
I was thinking that I could replace the rear suspension with independent suspension, run a shaft to the centerline to a gear box mounted on the frame of the van, and then power each wheel from a motor with a fixed gear ratio. Motors sticking out in front or behind the drive shaft. By my guess the van wheel will be turning about 780 rpm at 65 mph, so probably 4.6:1 or so ratio if I'm using 3600 rpm motors. I'd like to avoid shifting gears and clutches or any of that nonsense if possible. I was thinking 3-phase induction motors with a separate controller for each wheel, and some sort of sensor and controller to provide traction control to avoid spinning one wheel on slick roads. We get ice here, and snow.


It would be interesting to have 4wd, but I'm not sure I can find an adequate suspension and drive train for that size vehicle. And I don't want to sacrifice turning radius, it's already bad enough as it is.


I know most DIYers take off the engine and keep the transmission, putting the motor right where the engine was, but I think that will likely just add a lot of weight and complexity to the drive train and take up a lot of room. I see most people here seem to use just one gear most of the time anyway. I can see how it would be a much simpler conversion that way, just saying I don't like the compromise.
 

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Discussion Starter #8
It has been done, but a lot of unsound things have been done - that doesn't make it advisable. "Sketchy" is the nicest word that I can think of for this scheme.

There are actually articulated buses (essentially a bus towing a passenger-carrying trailer) with the engine in the back (so, the trailer) pushing the whole thing... but they are not nearly as crude as those "push trailers".

By the way, powering one axle with an engine while charging with a generator driven by another axle is called "through the road" hybrid charging. It is a bad idea with both axles on the same vehicle, but with the driver on the trailer and the drag on the tow vehicle it's really bad.

I don't like any of these ideas. The only "through the road" charging I was thinking of is regenerative braking.


I had originally thought to power the trailer wheels only because I was thinking that the van motors would be smaller and aimed at just carrying the van's weight. I've already been convinced not to do that. I have fairly extensive experience with trailers, they can get in enough trouble when they're not pushing anything. The more you guys talk about push trailers the more the hair on the back of my neck tickles me. Enough said on that.


Right now I'm focused on a generator on a trailer, with storage and power cables. And general ideas about driving the van itself.
 

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Engine options

If I'll need another engine for this, I think I'd rather get something designed for a generator than something designed for an automobile. Given a diesel's maintenance cycle and overall simplicity, I'd rather go that route than with gasoline.
Any modern diesel is certainly more complex than a gasoline engine. If you want an engine designed for optimal efficiency at the desired power level, that would be a gasoline engine from a Toyota hybrid.

I can see your point about average power. And I was thinking of the inline v6 diesel found in 90s Dodge trucks. My father had one, it would pull like a mule. You're probably right about it being bigger than the original van engine in terms of power and torque, but it was pretty small in terms of physical size per unit power. If there's a 4-liter version of that, or even 3-liter I'd be interested.
Inline and V are opposite things; I assume that you mean the Cummins B-series inline 6, originally called the 6B (then 6BT when turbocharged). The current version (called the ISB for commercial applications) is still used in 2500 and larger Ram trucks, but it is now much more complex and powerful. The B-series started as a 5.9 litre and has grown (to 6.7 litres). It is not small for its power, by comparison with anything other than an even larger diesel.

There is a 4-cylinder version of the B-series, called the 4B. With the same bore and stroke, it is a 4-litre. It is an enormous and heavy paint-shaker, used in many delivery vans and similar commercial vehicles. There is no version which meets modern emissions standards, but it might be suitable in power output.
 

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Transmission?

I know most DIYers take off the engine and keep the transmission, putting the motor right where the engine was, but I think that will likely just add a lot of weight and complexity to the drive train and take up a lot of room. I see most people here seem to use just one gear most of the time anyway. I can see how it would be a much simpler conversion that way, just saying I don't like the compromise.
All good reasoning, and especially valid with the weight and complexity and issues of an automatic transmission, but be sure that the overall drive ratio is right. Modern motors need to run faster to get enough power than they would with just the rear axle's final drive ratio for reduction.
 

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Discussion Starter #11
That tesla powered mercedes build looks like what I was thinking, only I don't think both of those sides are motors. Not sure what the other can is. But I thought I overbuilt when I weld crap together, this guy is outrageous.



Those are both much smaller vans than I have. I have seen another maxi van project here a couple years back, but it's not an extended van, and it was only built for a small amount of local driving. Small battery pack, small motors for only in-town driving.



I've read enough though to know that the bigger the vehicle the more it's worthwhile to convert it to an EV, even though the conversion cost is higher.





The main point of my query seems to hold water though, the idea of a generator on a trailer that converts a pure EV into a hybrid. Especially attractive is the idea of storing luggage on the trailer too. We always end up with 3 coolers, baby supplies, a couple pack-and-plays and pretty much an entire daycare in the van all folded up.


I'm thinking that the first step is to get a plan to convert the van itself, and price that out. There's a ton of room under the floor of the van, still protected by the frame. Not sure if I could swing actual EV battery packs, but there's lots of room for them if I can. I'd probably need some sort of cover under them to prevent damage from rocks and dirt though. Things have changed a bit since I first started researching this years back.
 

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That tesla powered mercedes build looks like what I was thinking, only I don't think both of those sides are motors. Not sure what the other can is. But I thought I overbuilt when I weld crap together, this guy is outrageous.
That's a typical Tesla drive unit. One side is the single motor (which drives a differential through two stages of reduction gearing); the other side is the inverter/controller, housed in a metal can.

Those are both much smaller vans than I have.
Yes, they are relatively small. That's a problem in finding a motor - even the large Tesla Model S motor would be marginal for the large loaded van pulling a trailer.

I've read enough though to know that the bigger the vehicle the more it's worthwhile to convert it to an EV, even though the conversion cost is higher.
If the benefit of conversion is saving money on fuel, or reducing fossil fuel consumption, then yes there is more to be saved.

The main point of my query seems to hold water though, the idea of a generator on a trailer that converts a pure EV into a hybrid. Especially attractive is the idea of storing luggage on the trailer too. We always end up with 3 coolers, baby supplies, a couple pack-and-plays and pretty much an entire daycare in the van all folded up.
One challenge is weight distribution, with the big fixed weight of the engine and variable cargo load. Where do you put things so that the weight distribution is suitable under all conditions?

I'm thinking that the first step is to get a plan to convert the van itself, and price that out. There's a ton of room under the floor of the van, still protected by the frame. Not sure if I could swing actual EV battery packs, but there's lots of room for them if I can. I'd probably need some sort of cover under them to prevent damage from rocks and dirt though. Things have changed a bit since I first started researching this years back.
A complete EV pack won't fit, but repackaged modules of production EVs is the current trend in conversions.
 

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Discussion Starter #13
Re: Engine options

Any modern diesel is certainly more complex than a gasoline engine. If you want an engine designed for optimal efficiency at the desired power level, that would be a gasoline engine from a Toyota hybrid.


Inline and V are opposite things; I assume that you mean the Cummins B-series inline 6, originally called the 6B (then 6BT when turbocharged). The current version (called the ISB for commercial applications) is still used in 2500 and larger Ram trucks, but it is now much more complex and powerful. The B-series started as a 5.9 litre and has grown (to 6.7 litres). It is not small for its power, by comparison with anything other than an even larger diesel.

There is a 4-cylinder version of the B-series, called the 4B. With the same bore and stroke, it is a 4-litre. It is an enormous and heavy paint-shaker, used in many delivery vans and similar commercial vehicles. There is no version which meets modern emissions standards, but it might be suitable in power output.

I don't know where that v came from. Inline 6 is what I was talking about, from a 90s Dodge Ram truck.


I can't say I've looked at a modern diesel, but the ones from the 90s are much simpler than a gas engine if you discount the mechanical injectors. I know that the newer injectors are computerized, with some sort of actuator instead of a mechanical pump. To me, that means simpler.


With respect to efficiency I'm going to have to ask for proof. My dad's truck frequently pulled a 40 foot trailer with 20+ tons on it, and it still got 15 to 17 mpg. He drove it until it had 300k miles on it with minimal maintenance.


If your claims about gas engines being more efficient were true, or even if the efficiency were close to true, the commercial haulers (big trucks and trains) would be switching over.



I don't mean to get into a pissing match here. If you show me real-world proof that your gas engine is more efficient and more reliable than a diesel generator then I'll pay attention.
 

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Discussion Starter #14
One challenge is weight distribution, with the big fixed weight of the engine and variable cargo load. Where do you put things so that the weight distribution is suitable under all conditions?

Put the engine at the desired center of gravity. Put the fuel roughly the same place, just like a commercial trailer generator. Luggage goes around the outside.


Correctly loading a trailer is not complicated, just necessary. The only post-loading variable here is fuel. You pack the trailer with the correct hitch weight, and if the fuel tank COG is right in front of the axle then the trailer maintains correct balance the whole trip.
 

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Put the engine at the desired center of gravity. Put the fuel roughly the same place, just like a commercial trailer generator. Luggage goes around the outside.

Correctly loading a trailer is not complicated, just necessary. The only post-loading variable here is fuel. You pack the trailer with the correct hitch weight, and if the fuel tank COG is right in front of the axle then the trailer maintains correct balance the whole trip.
If the fuel tank is at the centre of gravity, then the engine can't be behind the fuel tank (the trailer would have negative tongue weight without cargo), so it must be ahead of the fuel tank. That's pretty front-heavy. A more practical configuration would put the fuel at the axle, and the engine and generator immediately in front of that.

Of course the fuel could be on top or under the genset, but that's not reasonable for a large tank. It could also go in saddle tanks on each side, I suppose.

Even then, the cargo is all going in front and rear trunks on the trailer. That can work, but doesn't sound like a convenient thing to use, and requires attention to distribution between front and rear. On the other hand, if this is a simple build, the front and rear cargo compartments can just be off-the-shelf cargo boxes.
 

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Re: Engine options

I can't say I've looked at a modern diesel, but the ones from the 90s are much simpler than a gas engine if you discount the mechanical injectors. I know that the newer injectors are computerized, with some sort of actuator instead of a mechanical pump. To me, that means simpler.
The problem is that a mechanical injection pump is more complex than a complete gasoline injection system plus a complete ignition system. Modern diesels use electronic injection systems which are similar to gasoline injection systems but at much higher pressure; modern ignition systems have no moving parts and routinely go for the life of the vehicle without failure or repair... and a couple hundred thousand kilometres without even changing the plugs.

On top of that, modern diesels have both diesel particulate filter (DPF) and selective catalytic reduction (SCR) emissions control systems which are far more complex and less reliable than the catalytic converter on a gasoline engine. The problems of making a diesel to meet current emissions regulations are so extreme that Caterpillar dropped out of the business of manufacturing these engines for heavy trucks in response to the regulation changes - they just couldn't make it work economically and reliably. And of course most people have heard of Volkswagen's "dieselgate" nightmare. If you use an old engine you avoid all of that, but it's strange to promote EV conversion (which is often chosen for environmental reasons) then run a filthy engine. If you do, a pre-2007 common-rail electronic injection engine from a light commercial application (not something intended only for cars) is probably the most efficient and reliable choice... although I would want to avoid the parts prices of Mercedes engines.

With respect to efficiency I'm going to have to ask for proof. My dad's truck frequently pulled a 40 foot trailer with 20+ tons on it, and it still got 15 to 17 mpg. He drove it until it had 300k miles on it with minimal maintenance.


If your claims about gas engines being more efficient were true, or even if the efficiency were close to true, the commercial haulers (big trucks and trains) would be switching over.
A good diesel run as intended is more fuel-efficient than a gasoline engine under similar conditions. I was just pointing out that the engines which are available in light vehicles which are optimized for hybrid operation (nearly constant power at an engine speed unrelated to road speed) are those gasoline engines.

If you show me real-world proof that your gas engine is more efficient and more reliable than a diesel generator then I'll pay attention.
Modern gas engines in cars light trucks are more reliable than diesel engines in the same vehicles, due to the problems with current diesel emission controls. Of course heavy diesels are reliable (other than the emission controls), and there is no gasoline comparison (although they would be just as reliable) because diesels are cheaper to fuel - due to both fuel consumption and fuel pricing - so no one builds large commercial gasoline engines.
 

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Right now I'm focused on a generator on a trailer, with storage and power cables.
If the van has suitable battery capacity for local use as a pure battery EV (running on battery power only), that capacity will be lots for series hybrid operation with the trailer. A plug-in hybrid car typically has about 16 kWh of capacity; the much bigger van with trailer would be a reasonable plug-in hybrid with about three times that capacity, and you'll want that for routine operation without the trailer anyway. Unless you want long battery-only range with the trailer, I don't see any need to make things complicated (and expensive) by putting more battery in the trailer.

The trailer could be treated as a mobile charging station for the van, but the van will need to accept a charge while driving, which is not normal for EVs. You do need the connection, but there are off-the-shelf connectors for high-rate DC charging of EVs at up to 400 volts and a couple hundred amps.
 

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Discussion Starter #18 (Edited)
If the fuel tank is at the centre of gravity, then the engine can't be behind the fuel tank (the trailer would have negative tongue weight without cargo), so it must be ahead of the fuel tank. That's pretty front-heavy. A more practical configuration would put the fuel at the axle, and the engine and generator immediately in front of that.

Of course the fuel could be on top or under the genset, but that's not reasonable for a large tank. It could also go in saddle tanks on each side, I suppose.

Even then, the cargo is all going in front and rear trunks on the trailer. That can work, but doesn't sound like a convenient thing to use, and requires attention to distribution between front and rear. On the other hand, if this is a simple build, the front and rear cargo compartments can just be off-the-shelf cargo boxes.

The axle has two wheels. Side-to-side balance is not incredibly critical on a trailer but important enough you don't want it too far off. Mount the engine such that with no cargo and no fuel the trailer is correctly balanced. Tanks are either to either side of the engine or higher, is usually how mobile generators work. Mount them so that empty or full, the trailer is balanced properly. Hitch weight should be 10% of total loaded trailer weight. Actually usually the tank goes above the engine, but that would put the gas tank in the rear window of the van; commercial mobile generators for commercial construction tend to be pretty high.


Luggage goes where it fits. The van currently has a 25 gallon tank. I can't imagine needing more than 50 gallons, but probably a pair of tanks with a combined capacity of 40 would be most practical. Once the generator (and I'm thinking of buying a commercial built-to-spec motor/generator already on a trailer for this, whether new or used) is mounted and the tanks are mounted, you can look at your trailer to determine the best place for luggage.


No matter what the trailer, balancing and securing the load is critical. This goes for 18-wheelers as well as the one you put behind your lawn mower. So loading the trailer will ALWAYS require more attention than loading your car, and loading your car when it's going to pull a loaded trailer will ALWAYS require more attention than if you just had the car. It's not complicated, it's just important to pay attention. Good tire pressure, good grease in the bearings, good brakes, proper hitch weight for the trailer weight. Proper load balance front-to-back on the tow vehicle. Good lights. There's a check list just like on an airplane.



The problem is that a mechanical injection pump is more complex than a complete gasoline injection system plus a complete ignition system. Modern diesels use electronic injection systems which are similar to gasoline injection systems but at much higher pressure; modern ignition systems have no moving parts and routinely go for the life of the vehicle without failure or repair... and a couple hundred thousand kilometres without even changing the plugs.

On top of that, modern diesels have both diesel particulate filter (DPF) and selective catalytic reduction (SCR) emissions control systems which are far more complex and less reliable than the catalytic converter on a gasoline engine. The problems of making a diesel to meet current emissions regulations are so extreme that Caterpillar dropped out of the business of manufacturing these engines for heavy trucks in response to the regulation changes - they just couldn't make it work economically and reliably. And of course most people have heard of Volkswagen's "dieselgate" nightmare. If you use an old engine you avoid all of that, but it's strange to promote EV conversion (which is often chosen for environmental reasons) then run a filthy engine. If you do, a pre-2007 common-rail electronic injection engine from a light commercial application (not something intended only for cars) is probably the most efficient and reliable choice... although I would want to avoid the parts prices of Mercedes engines.


A good diesel run as intended is more fuel-efficient than a gasoline engine under similar conditions. I was just pointing out that the engines which are available in light vehicles which are optimized for hybrid operation (nearly constant power at an engine speed unrelated to road speed) are those gasoline engines.


Modern gas engines in cars light trucks are more reliable than diesel engines in the same vehicles, due to the problems with current diesel emission controls. Of course heavy diesels are reliable (other than the emission controls), and there is no gasoline comparison (although they would be just as reliable) because diesels are cheaper to fuel - due to both fuel consumption and fuel pricing - so no one builds large commercial gasoline engines.

OK what you're saying is at least plausible. I'll look into that, the emissions specs did ping on my brain a few years back, and I remember the dieselgate thing. As I said I had planned to use a diesel generator set, not mate a generator I found to a motor I found somewhere else. Don't particularly want a stinky engine around though either, so it may be that a gasoline or e85 engine may be a more viable alternative. The hovercraft I built awhile back had a VW inline 4 in it, and I kept the computer and the catalytic on it.



If the van has suitable battery capacity for local use as a pure battery EV (running on battery power only), that capacity will be lots for series hybrid operation with the trailer. A plug-in hybrid car typically has about 16 kWh of capacity; the much bigger van with trailer would be a reasonable plug-in hybrid with about three times that capacity, and you'll want that for routine operation without the trailer anyway. Unless you want long battery-only range with the trailer, I don't see any need to make things complicated (and expensive) by putting more battery in the trailer.

The trailer could be treated as a mobile charging station for the van, but the van will need to accept a charge while driving, which is not normal for EVs. You do need the connection, but there are off-the-shelf connectors for high-rate DC charging of EVs at up to 400 volts and a couple hundred amps.

The space under the floor is at least 8 or 9 inches top to bottom and there's a ton of room between the frame members, especially if you can remove the drive shaft. If rear-mounting the motor(s) pans out, then there is easily enough room between the frame rails to put 5x the battery pack of a plugin hybrid in there. Not saying I'll need it, just saying there's room. There would also be all that room under the hood and in the doghouse.


I was thinking of putting raw 3-phase AC through the trailer connector. Thinking now on it that probably won't work so well, a generator set will probably be either 240 or 480, or maybe 400. There's probably no reason to route around that circuitry, and the EV charging circuitry will be set up for one of those too most likely.


What sort of voltage does a highway-capable (65mph) EV run these days? It would be good to avoid unnecessary voltage conversions through all this, which is why I was thinking of 3-phase through the trailer connector.


I was also thinking of gadget power in the vehicle, we have a ton of phone chargers and tablets and whatever crap we need for baby food. How many people run an AC wall outlet in the car? It's either that or a whole crapload of 12v or USB plugs. Or maybe all of the above.


Back in the day, EV builders had a high voltage battery pack and then a 12v battery for the automotive systems. Is this still the practice or do you run an inverter-pwm regulator for that sort of thing?
 

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As I said I had planned to use a diesel generator set, not mate a generator I found to a motor I found somewhere else.
That gives you a matched set of engine and generator, but a genset with high enough output is going to be a massive thing, intended for stationary industrial operation.
 

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Discussion Starter #20
Go look at a construction site where they're putting up an apartment building, a hotel or some commercial building especially in a remote location. They have generators on wheels that have 4 cylinder automotive-sized engines or even bigger. Most of the ones I've seen are diesels, but the key here is that they are designed to run as a generator: constant speed, reasonably constant load, day in and day out. They'll be there until the power is hooked up to the site.



The trailers they are on are set up to be hauled onto a site when the dirt work is not done yet. So the COG is very high, ground clearance is high too.


If the site has a crane they tend to hook onto the generator and pick it up for the night to prevent theft, so you'll see a louvered box on a trailer 40 feet in the air after hours.
 
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