# EV Range extension using a GenSet



## Anaerin (Feb 4, 2009)

Looking around eBay, I found a few interesting things:

http://www.ebay.ca/itm/Belt-Driven-...67776171?pt=BI_Generators&hash=item5ae3bb8dab
http://www.ebay.ca/itm/10-200-watt-...53186185?pt=BI_Generators&hash=item35ae0a6f89
http://www.ebay.ca/itm/PTO-Driven-M...56021545?pt=BI_Generators&hash=item5ae3083129 (albeit having removed that step-down gearbox)
http://www.ebay.ca/itm/Tapered-Cone...19874157?pt=BI_Generators&hash=item588cd4bc6d
These all have a generation speed (apart from the PTO one) of 3600RPM, which is nicely in the power band for most small ICEs.

So, if you took one of these, and a small engine (Say, the 3-cylinder diesel motor from a Smart car, or a 30hp+ motorcycle engine, so probably 500cc or higher), mounted the pair on a small trailer, and hooked it up to a reasonably sized charger (probably on-board the vehicle), you'd have a cheap, fuel-sipping (usable with SVO or biodiesel if you go for the Smart engine), and adequately-sized range extender. 

If you're doing a pickup conversion, and used Direct Drive with the motor in place of the gearbox (or even shortened the drive shaft and moved the gearbox back), this would easily fit in place of the large V6 or V8 lump they put in there with room to spare for a few batteries and the controller/electronics.

It seems that most people, if they're talking of range extenders, advocate pusher trailers. I'm unconvinced, especially in conditions like we get here in Canada with ice and snow leading to poor grip, and the potential for jackknifing. It also means that in case of power outage you have a long-lasting power backup unit available (As, probably most of the time, it'd be at home, only brought out for long journeys, when you wouldn't be home anyway).

It certainly seems cheaper (and smaller) than buying an aircraft APU (not that I can find many/any on eBay) and a lot cheaper than buying a pre-built generator for the kinds of capacities an EV needs to stay on the road (10kw+ for a medium-sized vehicle maintaining 110KPH/70MPH on a level road).

And if you wanted a cheap, headless version to use as an (AC?) drive motor, one of these (http://www.ebay.ca/itm/6500-watt-re...94459003?pt=BI_Generators&hash=item483efdb27b http://www.ebay.ca/itm/3000-watt-re...62150393?pt=BI_Generators&hash=item48371ad3f9) would probably do the job.


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## piotrsko (Dec 9, 2007)

actually you could save tons of equipment by just selecting the battery pack voltage properly and regulating the genset output appropriately. This however might lead to requiring a 'Zilla or Soliton or some other Hi-voltage controller. Most of the "purists" here will degrade you for the thought, but from one standpoint, it does work. I have the capacity in the ranger and room to provide a small generator for boonies recharge, but it won't be elegant (another sticking point on the forum). BTW 3600 is the magic 60 hz typical line frequency of an American home. You really don't need 3600 rpm, anything from 3000 to 4000 would work for a transformer isolated power supply. Switching power supplies could generally care less about frequency. If you have a DC output genset, anything above, say, 1500 rpm would be fine.


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## ChristianThomas (Nov 29, 2011)

What you're talking about is getting closer to a series hybrid (as opposed to a parallel hybrid, like the Pruis).
I'm not advocating either the pure EV path or the series hybrid path. But if a series hybrid is what you're looking for, tossing the big battery pack and using that space/weight for a better gen-set, and then using high duty cycle capacitor banks to handle surge demand, will get you farther/faster/cheaper than trying to build both an EV and a hybrid in the same vehicle.

Just food for thought.

As to their functional worth, all of the old diesel submarines worked this way. If the system was reliable enough to put in a submarine, it might just work for your car too.


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## Anaerin (Feb 4, 2009)

ChristianThomas said:


> But if a series hybrid is what you're looking for, tossing the big battery pack and using that space/weight for a better gen-set, and then using high duty cycle capacitor banks to handle surge demand, will get you farther/faster/cheaper than trying to build both an EV and a hybrid in the same vehicle.


Oh, I know that. For the most part, I'm suggesting building a trailer for most EVs. Then if you don't need the genset, you don't have to take it with you, or it could be used by "recovery services" to get stuck EVs back on the road quickly, or even something like u-haul or avis (Rent-a-genset). I believe most EVs (commercial and otherwise) explicitly disallow using the charger and driving at the same time, so a commercial venture making towable gensets for range extending would be a real problem. But if there could be a way of making a towable, on-the-road usable genset with a J1172 connector, and an on-board charger that supports J1172, and provides enough power to run the EV at medium loads (Cruising at highway speeds, for example) with a little bit extra, we'd have something really worth going for.


ChristianThomas said:


> As to their functional worth, all of the old diesel submarines worked this way. If the system was reliable enough to put in a submarine, it might just work for your car too.


Oh, I know. And most diesel-electric trains still work the same way too.


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## HYPRDRV (Aug 20, 2009)

I have a similar set up on an Electric Catamaran. 15kw genset that charges the batteries at the same time I'm running the props (2). The motors are eating 50A and the rest (20A to 30A) goes to the batteries. Since it's a sail boat I don't have to do it much but it has come in handy. Some guys are using the small Honda Gensets to do the same thing.

Steve


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## charliehorse55 (Sep 23, 2011)

Mahle makes an amazing EV genset - it produces 30kW of power and only weighs 70kg (including generator). It's very small and therefore quite easy to fit into an existing EV build. 

http://www.mahle-powertrain.com/C1257126002DFC22/vwContentByUNID/A708E950D66EA44BC12578860027969B/$FILE/Range_Extender_Engine_EN.pdf


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## bjfreeman (Dec 7, 2011)

The design I implemented is similar in principle.
I have a power processing board the takes all forms of external power and applies it as DC to the Raw DC bus. the Charger takes the Raw dC to charge the Batteries that all Controllers run off.,

This is Canbus controlled, and monitored.

One of the first EV in the 90's had a pull behind power source.

Now if you think of a Genset, with some tinkering, as a alternator, then all you have to do is regulate the output for max voltage and current.
Also the engine can be variable speed for fuel economy.

the one factor not talked about is the extra weight that would effect the need for more power to pull the trailer, especially up a 15% grade (mountain passes)


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## enp13 (Mar 26, 2009)

charliehorse55 said:


> Mahle makes an amazing EV genset - it produces 30kW of power and only weighs 70kg (including generator). It's very small and therefore quite easy to fit into an existing EV build.
> 
> http://www.mahle-powertrain.com/C12...860027969B/$FILE/Range_Extender_Engine_EN.pdf


I am very excited about this. I've just begun building my own with very similar specs using a Rotron 294 engine but buying one of these would same heaps of time. Do you know any more about them? Can you actually buy them yet? I've sent them an email so will report back if they reply.


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## enp13 (Mar 26, 2009)

Anaerin said:


> Looking around eBay, I found a few interesting things:
> 
> http://www.ebay.ca/itm/Belt-Driven-...67776171?pt=BI_Generators&hash=item5ae3bb8dab
> http://www.ebay.ca/itm/10-200-watt-...53186185?pt=BI_Generators&hash=item35ae0a6f89
> ...


Presumably these generators are all permanent magnet types so the voltage and frequency they output are proportional to the speed of the shaft? So it would be quite important to choose an engine that couldn't overspeed or there would be a risk of over-voltaging whatever charger the generator was connected to? There would also be a practical limit to how slow the engine could turn while still producing enough output voltage (and a high enough frequency) to run the charger.

I am also presuming that these are single phase so for large powers (say 30kW like the Mahle unit produces), 3 would be used to output to a 3 phase charger (or output to a 3 phase rectifier to charge the battery bus directly if an overcharging detection system is present)?


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## charliehorse55 (Sep 23, 2011)

enp13 said:


> I am very excited about this. I've just begun building my own with very similar specs using a Rotron 294 engine but buying one of these would same heaps of time. Do you know any more about them? Can you actually buy them yet? I've sent them an email so will report back if they reply.


Alas, I sent them an email and discovered that they are currently at the prototype stage and a single one of these would cost $120,000 (as they would have to make it special order)


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## Bowser330 (Jun 15, 2008)

15kw Genset, 363lbs. 2,300$

What the hell makes it so damn heavy?!

Is it possible to directly connect multiple smaller gensets to the battery pack, instead of one huge, heavy genset?


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## enp13 (Mar 26, 2009)

charliehorse55 said:


> Alas, I sent them an email and discovered that they are currently at the prototype stage and a single one of these would cost $120,000 (as they would have to make it special order)


They have just told me 150k pounds which is even more! It has a regulated DC output selectable between 100-360V and spins at 4000RPM for 30kW, 2000RPM for 15kW. Seems like a fairly good design if they can make it for a sensible price.


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## gor (Nov 25, 2009)

Bowser330 said:


> 15kw Genset, 363lbs. 2,300$
> 
> *What the hell makes it so damn heavy*?!
> 
> Is it possible to directly connect multiple smaller gensets to the battery pack, instead of one huge, heavy genset?


simple, just ratings. cont/peak.
Engine Displacement (cc) : 992.0 
when cont. rating 1L -15kw; peak ratings (1L ICE on the bike) could be ~ 60-100 kw +...

same with e.motors(gen) - warP 15kw cont,- peak (few sec)-???? not riched yet : ))


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## coulombKid (Jan 10, 2009)

charliehorse55 said:


> Mahle makes an amazing EV genset - it produces 30kW of power and only weighs 70kg (including generator). It's very small and therefore quite easy to fit into an existing EV build.
> 
> http://www.mahle-powertrain.com/C1257126002DFC22/vwContentByUNID/A708E950D66EA44BC12578860027969B/$FILE/Range_Extender_Engine_EN.pdf


At 70 Kg (less fuel tank) one could plug it into a receiver hitch for that occasional weekend trip to the mountains.


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## nat_ster (Oct 19, 2012)

HYPRDRV said:


> I have a similar set up on an Electric Catamaran. 15kw genset that charges the batteries at the same time I'm running the props (2). The motors are eating 50A and the rest (20A to 30A) goes to the batteries. Since it's a sail boat I don't have to do it much but it has come in handy. Some guys are using the small Honda Gensets to do the same thing.
> 
> Steve



I would love to see this topic continue. So much more to be explored.

Thanks for all the good informative reading. I just joined the forum so I could see the pics in the build threads to better understand what is going on.

Thanks Nat


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## Baldbruce (Aug 1, 2011)

Check out the diesel powered gensets from Panda. They claim to be the lightest solution because they use a DC generator directly charging your battery. I have a book somewhere around here that described an EV conversion with the "standard" seriec DC motor in the front of the car and one of these in the trunk....
http://fischerpanda.com/marinegen/dc-generators/agtpm6


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## charliehorse55 (Sep 23, 2011)

Baldbruce said:


> Check out the diesel powered gensets from Panda. They claim to be the lightest solution because they use a DC generator directly charging your battery. I have a book somewhere around here that described an EV conversion with the "standard" seriec DC motor in the front of the car and one of these in the trunk....
> http://fischerpanda.com/marinegen/dc-generators/agtpm6


This is way too small to be viable for an EV. You need 20-30kW continuously to sustain high speed driving.


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## Baldbruce (Aug 1, 2011)

You can lead a horse to water, but you can't make him drink.....
Panda makes many other size generators and custom DC output voltages. I simply pointed you towards the stock liquid cooled 5kW as a starting point. Up to you to decide which one fits in your design.


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## Tesseract (Sep 27, 2008)

charliehorse55 said:


> This is way too small to be viable for an EV. You need 20-30kW continuously to sustain high speed driving.


First off, you are making a sweeping generalization without even a speed or a vehicle aerodynamic profile (ie - CdA) as caveats. Secondly, any amount of power supplied by the generator would offset power supplied by the battery pack, extending range as a result. E.g. - if it takes an average of 10kW to maintain 60mph on level ground in a given EV then a 5kW continuous output genset would essentially double its range. A 10kW genset would extend the range indefinitely (well, as long as it was supplied with fuel), etc...


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## charliehorse55 (Sep 23, 2011)

Tesseract said:


> First off, you are making a sweeping generalization without even a speed or a vehicle aerodynamic profile (ie - CdA) as caveats. Secondly, any amount of power supplied by the generator would offset power supplied by the battery pack, extending range as a result. E.g. - if it takes an average of 10kW to maintain 60mph on level ground in a given EV then a 5kW continuous output genset would essentially double its range. A 10kW genset would extend the range indefinitely (well, as long as it was supplied with fuel), etc...


To maintain 60mph in a small, aerodynamic sedan (cd 0.28, A = 2.0 m^2) takes 18kW. A 6kW generator extends your range by 1/3, at the cost of removing about 12kWh of pack capacity. 

Unless your pack is larger than 36kWh, you would actually lose range by installing this. 

Anything smaller than that sedan wouldn't have room for the generator anyways.


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## Tesseract (Sep 27, 2008)

charliehorse55 said:


> To maintain 60mph in a small, aerodynamic sedan (cd 0.28, A = 2.0 m^2) takes 18kW.


Please show how you got that number, because I come up with ~6.7kW. Of course, some additional power will be required to overcome rolling resistance, but it will be more like 3-6kW, not another 12kW. EDIT: here is an online calculator that does all the tedious bits for you: http://www.apexgarage.com/tech/horsepower_calc.shtml

That said, I have no problem with your argument now that you've provided a specific example (albeit an incorrectly calculated one).



charliehorse55 said:


> A 6kW generator extends your range by 1/3, at the cost of removing about 12kWh of pack capacity.


Not if the generator is on a removable trailer. Ie - something that can be added to the car for long trips when necessary, and left off most of the time. This makes a lot of sense to me, given that there are not nearly enough charging stations as there are gas stations.


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## charliehorse55 (Sep 23, 2011)

Tesseract said:


> Please show how you got that number, because I come up with ~6.7kW. Of course, some additional power will be required to overcome rolling resistance, but it will be more like 3-6kW, not another 12kW. EDIT: here is an online calculator that does all the tedious bits for you: http://www.apexgarage.com/tech/horsepower_calc.shtml
> 
> That said, I have no problem with your argument now that you've provided a specific example (albeit an incorrectly calculated one).


I calculated using figures for the winter, because the car needs to be usable year round. 

Cd = 0.28
A = 2.0 m^2
Rolling resistance = 0.012
Air temperature = -10C
Speed = 60 mph = 26.8224 m/s
Weight = 1600kg
Pack to wheel efficiency = 75%

Total drag force:

Aero: 0.5 * 0.28 * 2.0 * 26.8224**2 * 1.3413 = 270.2 N
Rolling: 1600 * 9.81*0.012 = 188.4 N

Total = 458.6 N

Power at wheel
458.6 * 26.8224 = 12.3kW

Power at pack
12.3kW / 0.75 = 16.4 kW

I did the calculation more precisely this time, I originally got 18kW from looking at a spreadsheet I've made. 18kW is the value for 100 kph (62 mph).


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## coulombKid (Jan 10, 2009)

charliehorse55 said:


> I calculated using figures for the winter, because the car needs to be usable year round.
> 
> Cd = 0.28
> A = 2.0 m^2
> ...


Goin' round the other side of the barn, many EVers pride them selves on knowing how many watt hours their car uses at (say) 60 mph. On sustained long trips even when I drive the speed limit the average speed, including all pit stops, meals, etc is closer to 55 mph. Given that, even if the generator could only produce 90 % of cruising watt hours per mile over the course of a day it would most likely keep up. At stop lights its charging. During meals its charging. During pit stops its charging. Even if your motel had no charging provision an auto shutoff on full charge would be simple to do.


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## Baldbruce (Aug 1, 2011)

Youtube of the book/car I was refering to:
http://www.youtube.com/watch?v=Rba3_S3AobY
Link to the publisher of "The Zero-Carbon Car":
http://aztext.com/zero_carbon_car.cfm

A Mazda Miata with a 9" motor driving the stock transmission. 120V of lead accid mounted on top of the electric motor. A 10kW Panda diesel DC generator mounted in the trunk that runs on bio-diesel. Controlled by a PLC and the software ladder logic is available for free download. Built in 2007, I would love to know how it has stood the test of time....
(I wouldn't want to try this kind of idea in CARB land!)


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## BobD (Dec 26, 2012)

I just noticed this posting and, after reading most of it, thought I'd chime in. Back in the early 90's I built an EV conversion of an Oldsmobile Firenza that used a 120-volt DC system, Curtis controller, and Edison Nickel-iron cells. I added a 6 kW, Briggs & Stratton IC, gasoline-powered, on-board generator to extend the range. The output of the generator was wired directly into bridge diodes on big heat sinks, down in the lower airstream at the front of the car. Since the peak voltage output was around 145 volts and the battery resting voltage was 120, I was basically pulse-charging the cells most of the time and bulk charging when they were under load. When I switched the keyswitch to ON it was purely electric, but when I turned it to START the generator started up. My calculations at the time showed that I'd have enough output to maintain 45 mph on flat, smooth roads with no wind. In practice, the output was about right but the damn generator was so noisy I could hardly stand it.

In our current conversion I've thought about adding a tiny, "quiet" Yamaha or Honda inverter-type generator running with a propane conversion kit. The whole set-up, even with a 20-pound LP tank, could easily fit below the rear hatch without adding more than 100 pounds. But I now run a 144-volt system and gel cells, so the whole thing would have to be voltage-boosted and more regulated, which means running through a charger and BMS. I'm not sure that all of the added nonsense is worth the effort, especially when it burns fossil fuel.

Another range-boosting possibility, even with our series DC motor, is adding regenerative braking. The front shaft of our 9" Warp9 motor currently just powers a tachometer sensor. I could put an electric clutch on it with a pulley running to an alternator. This wild 3-phase could exceed the battery voltage during downhill stretches, but I'd need more voltage read-outs to match load to output and I'd have to choose the right gear to reach sufficient RPMs and voltage. Again, is it worth the effort?

At this point I think the easiest route is to use the car as-is until its lead-acid gels are worn down, then replace them with hopefully lower-priced lithiums that have double my current capacity for the same weight. At this point the cost is prohibitive and I have more than enough juice to commute to town and back, so no big motivation for added financial pain.


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## enp13 (Mar 26, 2009)

If you do go with the idea of an engine directly connected to the motor via a clutch and pulleys, please let us know. I'm now seriously considering this exact idea with my Rotron engine, having struggled to find a suitable electric generator to attach to it to use to recharge my batteries (it is difficult to find something light enough and high enough in voltage for a high power conversion). It should also be a bit more efficient too and provide a convenient belt to drive the existing aircon compressor and power steering pump.

The big challenge I anticipate will be finding a suitable clutch for the engine. Does anyone have any suggestions? 

Interesting to see the calculation for 18kW @ 100kph. Personally I am budgeting 23kW @ 105kph to cover all bases (dark, undulating road, head wind, raining, cold, full car etc).


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## qryptiq (Dec 29, 2012)

found this: http://zjtiger.en.made-in-china.com/product/QqMnZdivpOhF/China-168F-1-Gasoline-Engine.html

and this: http://kidsonroll.com/Generators/NewStarEngineJF-168Generator.php

Not sure if it's applicable. what do you think?


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## enp13 (Mar 26, 2009)

Way too little output power and way too heavy.

Probably cheap though!


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## Yagi-san (Jan 2, 2013)

Please delete this post !


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