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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.

· Administrator
1,802 Posts
I kinda want to back up to the start with a couple key questions....

- Why do you want an electric vehicle?

- What is your budget/what are you thinking you'll spend?

You have basically described the worst case scenario for an EV. High weight. No extra weight. Poor aero. Long range. Mountainous terrain. Occasional use.

You gas milage: -- Something in the range of 10-15mpg.

Most days the van just doesn't move at all.
EVs make the most sense when you want to save money on gas, with frequent daily use, short range.

You need the frequent use to justify the investment in batteries (if not the conversion itself). This is a huge sunk cost up front whether you use the vehicle daily or never. If you were spending $12,000/year in gas, that's financially wasteful and it's easy to say you should invest in electrical. If you spend $300/year in gas, it'll never be worth it.

You need the short range so that you don't need an outrageously-sized, expense, and heavy battery pack.

You have huge power requirements because you have an unaerodynamic shape pushing lots of air out of the way at high speed. You need to be able to accelerate all that weight at a decent speed. You need to be able to push that weight up a hill, at a fast speed. For a long period of time.


I love supporting projects just for the sake of "I want to" or "It interests me", so if that's the case, do as you please.

But even though we're here because we're passionate about EVs, if you came here with your finished EV, a big heavy van with 2-4 huge electric motors, and a hitch with a huge genny and a trailer...

... I would actually suggest "Why not remove the motors and batteries and put that engine under the hood of the van instead?".

I think your current situation is actually the best solution to your circumstances. If you need a cargo trailer, just go buy a simple, cheap cargo trailer, done.

Another thought, yeah you've got a big family now but when the kids become teenagers they'll drive their own cars (and you can force them to chauffeur their younger sibblings, a time-honored family practice :p ), and you won't be making as many family trips. So that means the time before you have to pay off this expensive conversion is narrower that you might imagine.

Just peeing on the parade a little, as a sober-second-thought.

· Administrator
1,802 Posts
1. I've wanted one almost since I heard of the idea.
2. I believe that, battery pack notwithstanding, they can be more reliable than an ICE.
3. I want better fuel economy in town. I love to just get in and drive for awhile, and with my current living situation (foster kids) it's difficult because I'm either leaving my wife to take care of kids, or I'm in a big van that gets ~10mpg in town on a good day.
4. I want to take steps toward a cleaner environment.
1 - I had a feeling that this was a "because I want to" project. I'm all aboard.

2 - Ehn. You're driving a 2010. It'll last you another 20 years with very minimal work. You'll be 73 by then. You will put more work into your EV than it will ever redeem in bonus reliability.

3 - That you'll get.

4 - 50% of the carbon/energy/whatever footprint of a vehicle is in manufacturing it. All the gas you burn in the vehicle's 20-30-year life only makes up the other half. You're driving a newer vehicle. So be rebuilding it, you're wasting huge amounts of the energy of its life. Roughly speaking, energy use scales with cost. Things have cost proportional to the resources they took to make them, if they didn't take that amount of resources, they would be cheaper. Cost effective is generally environmentally effective, and you're probably net negative on the environment.

I guess part of what I'm hoping for is for the van to be more frequently used.
That makes sense too. If you'd do a lot more driving if it wasn't so expensive, that adds a bunch of value to you beyond what your past experience would indicate.

Sorry for the shameless foster care plug.
Naw it's good. It's good to hear about people's passions and what drives them. I'm glad you've found a life that's rewarding for you.


I'm going to piggyback on Brian's suggestion from earlier and it's where I was kind of leaning with my questions. I think you need two vans.

At least, temporarily.

It sounds like you need a van. Most EV conversions that people do, especially because they just want to, take way longer than they would have predicted. I'm 15 months elapsed into what could realistically have been a weekend project, but, life gets in the way.

You don't want to be in a rush. You'll run into headaches you didn't anticipate. It might take you a year to get it done.

Since your van is currently in good condition, I would keep it as such. Buy a second, older van, find one with a blown engine if you can, but good bones, and convert that one. Then when it's done, sell the good one. Or, don't, just add a trailer to it and use it for long trips.

In terms of effort, 2 vans is easier. In terms of conversions, not having to worry about a generator and second fuel tanks and all that is way faster and cheaper. Motor and batteries and you're good. Maybe cheap enough to buy the second van carcass. You should be able to get a 15-year-old one for, what, $2k? If you're looking to spend $30k, that's pretty small in comparison. That's what a used genny is going to cost you, minimum.

For long trips you just eat the cost of gas 100% of the time, whether trailer is parked or not. But around town, your 90% use case is electrical.


Another option you might like even less...

Don't buy a second van. Don't build a generator trailer. Build an EV push trailer.

You'd need a junkyard diff, probably a single big motor, and minimal batteries. And a trailer skeleton. Done. Mount it however you want, super easy.

The tradeoff being that now when you're tootling around town every day, you've got the trailer with you.

As a bonus, you could charge it by regening while driving. And it's much safer than a gasoline push trailer regening the van up front.

Bonus.. you could hook it up to anything with a hitch.

It would also be an easy way to get your feet wet with EVs, without taking use away from the van. If you want to cannibalize it later for a full EV conversion down the road, maybe on a second van or whatever, you still can in about 15 minutes.

You could probably get it all done for $5k.

It's probably not what you envisioned, but, food for thought.

· Administrator
1,802 Posts
I will absolutely not make a push trailer. we discussed it earlier in the thread.
Well, that was a gasoline push trailer that you'd use to recharge batteries by regen braking on the lead vehicle.

This is just an electric push trailer. No braking, no charging. Unless you want to charge the batteries from the engine, in which case it's just like pulling a slightly heavier trailer.

But, I get it. You want an EV. Not a trailer :p

· Administrator
1,802 Posts
Brian said:
Why would the batteries be "minimal"? It would need the same capacity as any EV for vehicle of this mass... no, more because it is so heavy and has so much drag.
Lemme clarify...

Because he would only need it for going around town and could even undersize it.

So if he says 95% of his trips are under 30 miles, but 5% of the time he needs (really needs, or it would mess up his day) to go 60 miles. As a pure EV he's gotta have capacity to do 60 miles. With the normal van as-is, big deal, 5% of the time he burns a little gas, it's never an issue and he could cheap out on the median use, rather than have to prepare for the common extreme.

through-the-road battery charging (which is not regenerative braking). Pushing the van with a trailer hard enough to accelerate the van is downright scary.
Well, semantics. Through-the-road charging is functionally regenerative braking. I mean technically if speed isn't being reduced you're not "braking", so, okay, but otherwise they're the same. You're charging the vehicle by attempting to slow it down (converting kinetic energy into battery juice), you're just balancing that by adding power to maintain the same speed.

EV racers do it all the time (through the road regen), fastest way to charge up between runs. Get towed around in circles and hold the regen brakes. The car doesn't know any different, so, it's just a difference in semantics, not technology.

And, it's a common-ish DIY bicycle thing to have a push trailer, since it makes it transferable among virgin bikes (and cyclists often have a variety of bikes for different uses). - "The guy with the EV porsche pushed by the VW Rabbit trailer claimed no oversteer problems even with (if I remember correctly) full push and the tightest turn radius. No snow in CA, though."

Ken said:
Using a push trailer to regenerate from the van... Let's see how well that works. By rule of thumb one can expect regen to recoup about 10% of the energy. So we have all the losses associated to get power to the wheels, and then you push the van forward. And from there you lose 90% of whatever's actually "on the road" by using regen.
Err, no, that's not what I meant. You're right, if that's all it was.

Using regen you can expect to add about 10% to your range. I think you're mistakenly thinking that you only get 10% recovery of the energy that goes into the regen system as taken away from momentum (normally heat in the brakes). Which isn't true, you get decently high efficiency at turning momentum into battery juice. The reason that regen is not as big as deal is because there just isn't that much energy lost in a typical drive where you actually convert momentum into heat in the brakes.

What I mean is driving with the van (gas engine), and engaging some regen braking on the EV trailer. This will make the gas engine work harder, as it appears like you're towing a heavier or less aerodynamic trailer, but meanwhile it charges up the batteries.

Jackknifing/etc, yeah, if you go ham on the accelerator in a sharp corner and it was your only traction. But that's the beauty of it. You still have a gas engine there, so it's kind of still 6-wheel (4?) drive.

But okay, enough stupid ideas. Just throwing shit out there that as options that would let you get away with a much cheaper and more compartmentalized conversion for your different-er needs.

Genny mounted in a trailer. EV Van up front. Carry on.
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