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This thread is for those people who have decided a series hybrid is the best compromise to fit their needs. What is the best way to combine a short range EV with a range extending generator?

Please note: if you disagree with the idea of a series hybrid, this is not the thread to voice that opinion.
 

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Is a BEV with a genset on a range extending trailer a Series Hybrid? I jsut want to get the parameter straight as not to offend anyone.

My opinion, as expressed in the other thread, is to build a good, efficient BEV with the range you need for the large majority of your driving needs. Figure out how much power it takes to cruise it on a long trip, and size the genset to provide at least 90% of that steady state value, but not more than 100%. This will maximize the range, and lifetime of the battery.

You want the genset to operate most efficiently, regardless of fuel, and that means it needs to be running wide open all the time you use it. This means a single speed generator, with a small displacement, high RPM ICE, such as a motorcycle engine. Whether or not it is part of the vehicle permanently or on a trailer is just a question of what you define as a Series Hybrid.

Jeff
 

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Is a BEV with a genset on a range extending trailer a Series Hybrid? I jsut want to get the parameter straight as not to offend anyone.

My opinion, as expressed in the other thread, is to build a good, efficient BEV with the range you need for the large majority of your driving needs. Figure out how much power it takes to cruise it on a long trip, and size the genset to provide at least 90% of that steady state value, but not more than 100%. This will maximize the range, and lifetime of the battery
You want the genset to operate most efficiently, regardless of fuel, and that means it needs to be running wide open all the time you use it. This means a single speed generator, with a small displacement, high RPM ICE, such as a motorcycle engine. Whether or not it is part of the vehicle permanently or on a trailer is just a question of what you define as a Series Hybrid.

Jeff
look at the specific fuel consumption at differant rpms expresed as lbs/ hp hour like .35 at 2500 rpm and .40 at 3500 rpm
 

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look at the specific fuel consumption at differant rpms expresed as lbs/ hp hour like .35 at 2500 rpm and .40 at 3500 rpm
That depends on the design of the particular engine in question, it is not necessarily a function of RPM, but more of camshaft timing, fuel delivery, ignition timing, and compression ratio.

from wikipedia:

A typical cycle average value of BSFC for a gasoline engine is 322 g/(kW·h). This means the average efficiency of a gasoline engine is only 25%. A reciprocating engine achieves maximum efficiency when the intake air is unthrottled and the engine is running at its torque peak[citation needed]. Efficiency is lower at other operating conditions. For a gasoline engine, the most efficient BSFC is approximately 236 g/(kW·h) or an efficiency of 37%. As seen above, lower values of BSFC mean higher engine efficiency. Diesel engines are generally more efficient than gasoline engines and can have a BSFC as low as 155 g/(kW·h) (partly because of the higher calorific value for diesel fuel) and around 55% efficiency.

so it looks like a small diesel is what we would like to have due to the energy available in the fuel and the increased compression ratio.

Jeff
 

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I agree that diesel is the way to go, but I have yet to see a small, light diesel generator. As many people have mentioned, WVO could then be used.

I have also seen propane powered generators, which I would imagine are very clean.
 

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I agree that diesel is the way to go, but I have yet to see a small, light diesel generator. As many people have mentioned, WVO could then be used.

I have also seen propane powered generators, which I would imagine are very clean.
i'd like to find a small diesel gen. myself
 

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Lets keep this topic going....so what is the idea of the setup...smaller battery pack with high charging-rate batteries plus a generator to deliver power to the battery pack....Motor is DC with excellent torque profile and gears to change through to get optimum speed...
 

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Lets keep this topic going....so what is the idea of the setup...smaller battery pack with high charging-rate batteries plus a generator to deliver power to the battery pack....Motor is DC with excellent torque profile and gears to change through to get optimum speed...
My idea is to have a pure BEV with a small genset included to enable range extending for about 500 total hybrid miles. I would not want to reduce the size of the battery pack any less than 20-30 miles pure electric range. That way you cover most of your driving with just battery, which is more efficient and costs less, and have the reserve capability to travel for 500 or so miles on the genset when you need it. Ideally it would be a diesel genset, and could charge the batteries as the car is parked if no charging station is available.

Yes you lose range hauling a genset around with you all the time. My bet is it is not a big enough factor to really matter in the long run.

During hybrid operation, the genset would supply some amount (say 80-90%) of the current needed for steady state cruise at travelling speed (say 60-70mph). It would not supply enough to charge the batteries while driving. This way, the genset is operating at maximum designed power, which is the most efficient range. With such a low current draw out of the batteries, you are much closer to the C/20 hour rate of the battery, which will extend their life and allow you to maximize Peukert's effect to your advantage. For a typical passenger car this means a smaller ICE to carry than the typical parallel hybrid, but it does mean more batteries.

The hot setup would be an AC drive system to eliminate the transmission, and either NimH or Lithium batteries. But the same setup could be done with lead acid and DC systems if you wanted to, it would just weigh more and be less efficient. But it would still beat a Prius in MPG and efficiency.

Jeff
 

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I completely agree with your setup and I want to build one just like it.

I would also prefer an AC systema nd Lithium Ions, however both are currently rediculously priced.

I want to do research on how to get a simiar system as AC Propulsion has made in China. I presume it could be made for atleast 5X as less..so 25,000 retail to 5000 retail...That makes it a lot more reasonable for the EV builder....

I think this guy is on the right track...
http://www.evalbum.com/1651

btw his battery pack units cost 300$ ea. so his batteries alone cost him 12K$...yikes...

back to the BEV, i do see a problem with how many kwh will be needed per hour to what a generator can provide per hour...A 10kw genset will give 10kw in one hour, by the time you have driven 1 hour though at highway speed you have used 20kwh...so that will effectively give you 50% more mileage if its running while you drive your 1 hour...so it will make your 70mile range (with lithium ions) go to 105 miles...pretty good....maybe i have the genset charging thing all wrong...what do you guys think?
 

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What about emissions? Is one of these diesel generators that we're talking about as good on emissions as a modern car ICE? If not, how about a motorcycle engine? How are they on emissions?

This approach makes a lot of sense. However, it gets tempting to skimp on the batteries and settle for (lets say) a 25 mile range when you really want 40, since you have an efficient, low maintenance generator to depend on. Less batteries means smaller up front cost, less weight, and lower cost to replace the batteries. But if you do that, you end up running the generator a lot, and if it's emissions are worse than a car engine then you're going backwards, as far as emissions are concerned.
 

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I want to do research on how to get a simiar system as AC Propulsion has made in China. I presume it could be made for atleast 5X as less..so 25,000 retail to 5000 retail...That makes it a lot more reasonable for the EV builder....
If you find it, by all means let everyone know! As I understand it, the limiting factor in AC drive systems is power electronics...they are quite a bit more complex that a DC controller. The IGBT's in the output are expensive, and they were hard to come by back when I was working in this field. Unless the Chinese have a bunch over there they are hiding, they won't be much cheaper than here in the US, because ours are made there anyway! The motor is simple, and can be made as cheaply or cheaper than a DC series motor.

A 10kw genset will give 10kw in one hour, by the time you have driven 1 hour though at highway speed you have used 20kwh...
746 watts is equal to 1HP, and most passenger cars use about 12 or 15 HP for steady state cruise. this works out to be about 9 or 11 kW, steady state. If you had a 144 V system, your current draw at 11kW is 11kW/144V=76A. If you had a 10kW genset putting out full rated power, it is putting out 69A. So you are drawing about 7 amps out of your battery cruising steady state. How long will your 144V battery pack go on a 7 amp draw?
 

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What about emissions? Is one of these diesel generators that we're talking about as good on emissions as a modern car ICE? If not, how about a motorcycle engine? How are they on emissions?
Emissions depends on the diesel you choose. There are Kubota engines that have a tier 4 emissions rating, and they can be made clean. Or you can go cheap and use a diesel that runs dirty. So the answer depends on what you put in there....

But remember the trick to this theory is to use it as little as possible, and if you need a 40 mile range often, then don't design your car with a 25 mile range just to save money, because you won't! You will end up putting it in the tank and burning it.

jeff
 

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746 watts is equal to 1HP, and most passenger cars use about 12 or 15 HP for steady state cruise. this works out to be about 9 or 11 kW, steady state. If you had a 144 V system, your current draw at 11kW is 11kW/144V=76A. If you had a 10kW genset putting out full rated power, it is putting out 69A. So you are drawing about 7 amps out of your battery cruising steady state. How long will your 144V battery pack go on a 7 amp draw?
Thanks for the math thats exactly what I needed...but a few more questions too..

How do you know a 10kw genset it putting out 69A?

And I am not sure how to answer your final question, does the answer rely on the AHs of my battery pack? So if i have a 144V pack with 70AH does that mean the pack will power the motor in a steady state for 10 hours? with a draw of only 7 amps? (of course i understand WITH the genset on)
 

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I too am hoping to build a series hybrid... eventually. Initially my car will be pure BEV, but being a ute I am hoping to be able to mount a genset in the tray area along with fuel tanks and such. A small trailer would be a good setup for a regular car, but not the most practical for quick trips offroad as I'll be planning to use the car. For longer trips sure, but they don't happen often.


I would like to experiment with a stirling engine turning a generator, but in the short term I'll most likely end up with a small diesel instead.
 
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