# Charging at home using a 1kw generator - efficiency



## frk2 (Jan 2, 2009)

Also - some of these generators are so tiny now that they can be built INTO the car itself - letting you simply turn the generator on whenever you leave the car parked to charge it up.


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## Tesseract (Sep 27, 2008)

frk2 said:


> ... According to my calculations - a simple 1kw petrol generator running at aout 3500rpm utlizes roughly 0.57 Litres per hour. My EV takes 6 hours to charge completely - so roughly 3.42 litres. On this charge I am able to travel about 60km giving it a theoretical efficiency of around 17-18 km /litre or 42 MPG - which is still not bad for emergency charging.
> 
> Do those figures sound right?


Depends... how much power does your mains-operated charger actually consume to recharge your car in that 6 hours (ideally, by measuring it with a kwh meter)? I suspect it will be closer to 2kW...

I'm saying this mainly because going 60km (~37mi) on only 6 kwh of energy implies driving at slow speeds and/or a very light and aerodynamic vehicle. Not impossible, of course, but somewhere around 10 kwh is more typical.

Also keep in mind that getting 1kW in electrical output from a petrol generator will consume fuel as if ~1.2kW were being demanded (because the generator head is likely 85% efficient). 

Finally, if you want to run a small petrol (and diesel) engines continuously you should only demand 80% of its rated power - that's usually were the best fuel consumption rate is at, too.

Keep in mind I'm not a small engine specialist or anything like that, so, Your Mileage (literally) May Vary


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## major (Apr 4, 2008)

frk2 said:


> ........ My EV takes 6 hours to charge completely - so roughly 3.42 litres. On this charge I am able to travel about 60km giving it a theoretical efficiency of around 17-18 km /litre or 42 MPG -.......Do those figures sound right?


Hi frk,

Without going thru all the conversions and using 100% efficiency for everything, I get this:

6 hours at 1 kW gives you 6 kWhrs. 37.5 miles then is 160 whr/mile.

I don't know what your EV looks like, but 160 whr/mile is likely a lot lower than what one would expect. And when you throw in efficiency for the charge/discharge of the battery, I think you're probably off by a factor of 2 or 3.

Just my opinion.

major


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## frk2 (Jan 2, 2009)

I guess I need to do some more researching - but basically are you guys saying its NOT going to be as efficient? anybody has any experience with this? Will I be burning more fuel than a gasser?

Just wondering - since this would almost be a requirement where I live


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## major (Apr 4, 2008)

frk2 said:


> I guess I need to do some more researching - but basically are you guys saying its NOT going to be as efficient? .... Will I be burning more fuel than a gasser?


I have no hands on experience. But from seeing this discussed numerous times over the past few years (mostly about using an on-board generator), the consensus seems to be that fuel economy is likely to be less than with an original equipment internal combustion engine (ICE). And also the emissions would be a lot worse.



> Just wondering - since this would almost be a requirement where I live


Hey, you gotta do what you gotta do. Just like these guys that race EVs. Often times they have to use portable gas driven generators to charge at the race track. I've done it. But it is the price you have to pay to have fun and show off the EV.

And another thing. Especially if the generator is used occasionally. What is the average overall effect? Like if you can charge off grid most times. Then even with burning some gas, you still could be ahead of the economy/emissions equation in the long run. 

Also, driving the EV can promote alternate transportation in your part of the world. 

Good luck to you.

major


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## frk2 (Jan 2, 2009)

Got it. I also intend to put somewhat oversize LiFePo4 batteries to offset this problem. I'll be using it for daily commute from tomorrow onwards so lets see!! my workplace is close by - around 9km one way so i'll have ample room to test the batteries.

Btw- its great to see that EVs are gaining traction atleast in the DIY space. This must really, really concern big auto companies. I wonder if the future of the EV is small 'cottage' industries manufacturing localized EVs.


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## frk2 (Jan 2, 2009)

I guess depends which car you are talking about- Im doing this on a ultra compact car. Again, I dont have real results - havent tested it fully yet. However this particular car which I have driven goes roughly 192 Watt / mile (tested):

http://www.revaaustralia.com.au/revaspecs.htm

This is a indian car - the car im using is similar, only a bit heavier.


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## CliffordK (Oct 8, 2011)

You might talk to your electricity supplier and ask if there is an optimum time to recharge. Around here, I believe that the hydro power suppliers prefer late night power usage as other energy consumption drops.



frk2 said:


> my workplace is close by - around 9km one way so i'll have ample room to test the batteries.


It may be that if your car has a range of about 100km, then you may be able to drive several days without a full recharge. 

It may also be a comfortable bicycle commute as your backup on days you aren't comfortable driving your EV.

As far as charging with your generator, look at your EV charger power consumption. So, say you have 110V at 12A. That works out to be about 1320W (amps x volts). 220V at 30A ==> 6,600W. My 110V charger takes forever to fully charge my EV.


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## remy_martian (Feb 4, 2019)

Why are you talking to the ghosts of 13 years ago?


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## CliffordK (Oct 8, 2011)

remy_martian said:


> Why are you talking to the ghosts of 13 years ago?


Oops, sorry, it popped up.

DIY Electric seems to like to suggest interesting topics, and I wasn't paying attention to dates.


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