Hi Eli,

You've obviously given this some thought already and realize some of the 
technical problem you'd need to solve.  Modern EVs -- modern cars of all 
kinds, actually -- are pretty much integrated computers-on-wheels.  They 
don't take well to things happening that aren't in their programming, such 
as attempts to charge them through their charging inlets while they're still 
being driven. 

I'm not an engineer, but my guess is that you'd need to start with something 
like the old range-extending battery plug-in-Prius conversions.  In most if 
not all of them, the extra battery was rigged to fool the car's computers 
into thinking the car was being fed the extra charge via regeneration.

If you go that route, make sure you know what you're doing.  Not to scare 
you but rather to caution you: we have a list member here who recently 
bought a junk Leaf for parts.  It was a fire wreck.  The former owner was 
trying to extend its range by paralleling extra battery modules onto the 
pack'a.  Water got in through the holes he'd drilled in the battery tray and 
caused some kind of electrical failure.  The car's interior erupted in 

Do you want to drive continuously on fuel, or are you planning to stop every 
now and then to let the genset catch up?  At your efficiency (238Wh/mi) 
you'll need a genset of at least 14.3kW to maintain 60mph.  Your max of 
6.16kW isn't going to cut it.

One thing you may not have thought about is how dirty and inefficient your 
car will become when you use this scheme.  Maybe it doesn't matter to you, 
although the facts that you own an EV and use the handle "conservation 
architect" suggest that it probably does.  

Efficiency first.  The most efficient EV APU (Auxiliary Power Unit) I know 
of was the "Long Ranger" trailer Alan Cocconi built for his Honda Civic 
hatchback conversion EV about 2 decades ago.  Cocconi is a genius engineer.  
He designed the inverter for the original GM Impact, which became the EV1.  
The original Tesla roadster was also heavily influenced by his T-Zero 
roadster (I think Tesla actually licensed his AC Propulsion drivetrain).

Cocconi used a (Kawasaki?) motorcycle engine in his Long Ranger.  I don't 
think I ever read any information about its emissions, but bikes have never 
been as tightly regulated as cars, and I strongly doubt that it was anywhere 
close to auto engines of the time.  (More on that below.)

It did keep up with the EV's energy use on the highway, though.  Now this is 
about as fuel-efficient as you're going to get, and I recall reading that it 
got a real world 32mpg highway.  For direct comparison, a similar Honda 
Civic VX or HF hatchback of about the same vintage got real world highway 
mpg in the 48-56 range.   

As for emissions, it's no contest.  I ran the calculations on this back in 
2007, so it's far from up to date, but I think my conclusions are still 
worth looking at.  (If you want to see the full assumptions and 
calculations, let me know, and I'll post them, but they're kinda dull.)

I based this on a fairly modern commercial grade genset from a reputable 
manufacturer that met EPA 2000s portable equipment emissions regulations 
(not dubious Chinese crap from Harbor Freight or Ebay), driving a highly 
efficient conversion EV of the time at highway speed.  I assumed that the EV 
could sustain 60mph with a 10kW continuous input.  That's quite a bit less 
than your Leaf, and amounts to about 165Wh/mi -- tough, but maybe possible 
for something light and efficient like a gen1 Solectria Force.  

I calculated only for the regulated pollutants NMHC, NOx, and CO, not CO2.

The genset-powered EV would have emissions in grams per mile of:

2.4 g/mi NMHC + NOx 
117 g/mi CO.  

PZEV / light duty SULEV-II EPA limits (applied to the 2004-2009 Toyota 
Prius, I don't know about current models):  

NMHC + NOx = 0.03 g/mi
CO = 1.0 g/mi

Compared to a 2004+ Toyota Prius), the genset-driven EV produces 

7900% more NMHC + NOx (80 times as much)
11600% more CO (117 times as much)

Can you say "gross polluter"?  :-(

In doing these calculations, I ignored the additional aero drag and weight 
of the genset trailer.  Those would make the results even worse.   So would 
your case, since at 238 Wh/mi your Leaf already uses 40% more energy than my 
prototype EV.

There are also some practical considerations.  For example, have you driven 
with a trailer before?  Parked with one?  Backed up with one?  It's not much 

Then there's the racket and vibration from the genset drifting forward every 
time you stop.  They kind of spoil the EV experience, as does (IMO) knowing 
how much pollution you're spewing into the air.

What you're proposing would be an interesting challenge and possibly a lot 
of fun if you're into engineering and serious problem-solving.  

If you're more into just driving something clean, I think you're much better 
off borrowing or renting an ICEV for the times you need to take longer 
trips.  Alternatively, you could trade your Leaf in on a  PIH.

Heck, you'd even do better (at least on emissions) driving a big pickup or 
SUV and towing the Leaf.

Whatever you decide to do, best of luck with it!

David Roden - Akron, Ohio, USA
EVDL Administrator

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