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Astro · 01-27-2015, 06:15 AM

I also like the idea of a range extender for an EV.
It has been mentioned in other threads.

I am hoping to mount an off the shelf generator to a section of box steel tubing that will slip into the box section on my tow bar. The tow bar gives a nice solid mounting point.
Using this method attaching and removing the generator should only take seconds. A tow bar lock can be added to prevent somebody liberating the generator from the EV.

I realise that the generator will not provide enough power to provide continuous driving but it should increase the range.

I would use such a set up maybe once or twice a month, the rest of the time the generator would sit on a shelf in the shed.

I will try and do some math.

For a long trip i would expect a speed in the high sixties (mph).
Would 20kWh per 100 miles be about right (5 miles per kWh)?

Miles are not my native language

So a 20kWh battery pack gets you 80 miles at 80% DOD. Or about 1 hour 20 minutes travel time. At 60 miles per hour you would need a 12kWh supply to keep going indefinitely.

If you had say a 4kWh generator running for the whole trip assuming a 90% charging efficency. You get 4kWh x 1.333hours x 0.9 efficency = ~4.8kWh That's an extra 24 miles or 24 minutes travel time. During that 24 minutes your generator adds another 1.44kWh getting you another 7.2 miles or 7.2 minutes travel time.
7.2 minutes gets another 2.16 miles or minutes.
2.16 minutes gets another 0.6 miles... And so on.

So roughly 35 miles of extra range (guestimate). Just a bit under 44% extra range.

I am sure there is a nice formula that will give the accurate figure but maths isn't my passion.

So there is no way i am going to be able to fit a 13.3kWh (including charging losses) generator on a small hatchback car. But a 4kWh generator is definitely doable.
It is definitely cheaper than increasing my battery pack size by 44%.

Does this sound correct? My math is probably as bad as my assumptions.

This also gives me a generator that can be used for other purposes.

Emergency power for the house (limited number of devices, mainly fridge and tv)
Power supply when camping.
Portable power for power tools etc.
An emergency charging source if the EV gets stranded somewhere away from utility power.

01-27-2015, 06:15 AM	#15 (permalink)
Astro Dreamer Join Date: Nov 2013 Location: Australia Posts: 350 Thanks: 95 Thanked 214 Times in 151 Posts	I also like the idea of a range extender for an EV. It has been mentioned in other threads. I am hoping to mount an off the shelf generator to a section of box steel tubing that will slip into the box section on my tow bar. The tow bar gives a nice solid mounting point. Using this method attaching and removing the generator should only take seconds. A tow bar lock can be added to prevent somebody liberating the generator from the EV. I realise that the generator will not provide enough power to provide continuous driving but it should increase the range. I would use such a set up maybe once or twice a month, the rest of the time the generator would sit on a shelf in the shed. I will try and do some math. For a long trip i would expect a speed in the high sixties (mph). Would 20kWh per 100 miles be about right (5 miles per kWh)? Miles are not my native language So a 20kWh battery pack gets you 80 miles at 80% DOD. Or about 1 hour 20 minutes travel time. At 60 miles per hour you would need a 12kWh supply to keep going indefinitely. If you had say a 4kWh generator running for the whole trip assuming a 90% charging efficency. You get 4kWh x 1.333hours x 0.9 efficency = ~4.8kWh That's an extra 24 miles or 24 minutes travel time. During that 24 minutes your generator adds another 1.44kWh getting you another 7.2 miles or 7.2 minutes travel time. 7.2 minutes gets another 2.16 miles or minutes. 2.16 minutes gets another 0.6 miles... And so on. So roughly 35 miles of extra range (guestimate). Just a bit under 44% extra range. I am sure there is a nice formula that will give the accurate figure but maths isn't my passion. So there is no way i am going to be able to fit a 13.3kWh (including charging losses) generator on a small hatchback car. But a 4kWh generator is definitely doable. It is definitely cheaper than increasing my battery pack size by 44%. Does this sound correct? My math is probably as bad as my assumptions. This also gives me a generator that can be used for other purposes. Emergency power for the house (limited number of devices, mainly fridge and tv) Power supply when camping. Portable power for power tools etc. An emergency charging source if the EV gets stranded somewhere away from utility power. Last edited by Astro; 01-27-2015 at 06:21 AM..