# Generator Aid for charging system



## dougingraham (Jul 26, 2011)

At best you will only get about 85% of the power from a generator into the batteries so if you get 200wh per mile a 3kw generator will only extend your range by about 12 miles per hour.

I want a 20kw range extender trailer to pull behind my car but I can't make it work out. When you get to the size where it will keep the car going constantly at highway speed you run into all kinds of issues. You need a cooling system for it and an exhaust system and a starting system. And the very presence of it will reduce your efficiency. And I would use something like this only a couple of times a year so it is really hard to justify. Lots cheaper to just rent a regular vehicle for those two times a year.

As for recommending, Ask the RV crowd what they think. You will probably find out what to steer away from at least.


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## cts_casemod (Aug 23, 2012)

dougingraham said:


> At best you will only get about 85% of the power from a generator into the batteries so if you get 200wh per mile a 3kw generator will only extend your range by about 12 miles per hour.
> 
> I want a 20kw range extender trailer to pull behind my car but I can't make it work out. When you get to the size where it will keep the car going constantly at highway speed you run into all kinds of issues. You need a cooling system for it and an exhaust system and a starting system. And the very presence of it will reduce your efficiency. And I would use something like this only a couple of times a year so it is really hard to justify. Lots cheaper to just rent a regular vehicle for those two times a year.
> 
> As for recommending, Ask the RV crowd what they think. You will probably find out what to steer away from at least.


Same here, I have another Diesel for the trips to Europe, but just want something to give a bit more range, insurance and confort (Aircon, etc) without compromising range too much.

I should get about 97% Rated output, sinceI plan the alternator to regenerate into the batteries with another small inverter. This wil start the thing, allow for quiet operation if required, etc. 
The motor is already derated to account for the losses on the alternator (A 3KW Generator has a 4KW capable engine).

Do you have a link for this RV guys?


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## TEV (Nov 25, 2011)

You should search this forum for " generator extended range " or something like that , it was already discussed, the conclusion is that will be very inefficient, the only efficient way is with the ICE connected directly to the drive train or on a pusher trailer.

Converting gas to mechanical , mechanical to electric and electric back to mechanical power is very inefficient.

There are new types of generators which are more efficient but the prices are prohibitive and/or not available for DIY community.


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## cts_casemod (Aug 23, 2012)

TEV said:


> You should search this forum for " generator extended range " or something like that , it was already discussed, the conclusion is that will be very inefficient, the only efficient way is with the ICE connected directly to the drive train or on a pusher trailer.
> 
> Converting gas to mechanical , mechanical to electric and electric back to mechanical power is very inefficient.
> 
> There are new types of generators which are more efficient but the prices are prohibitive and/or not available for DIY community.


 
TEV, have you read my last topic? 
I Plan to drive the generaor in an inverter/variable speed fashion with output directly to the battery, not fixed 230V output and charger.

It will weight about the same as having an aditional 3KW of batteries in the boot, cost half of that and I have peace of mind that if I ever get stuck all I need to do is wait a bit. Thats more than worth it, at least for me.

I am just wondering which kind of motor shall I buy. I have a few options between 7HP Yanmar diesels and petrols.


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## TexasCotton (Sep 18, 2008)

I have seen range extenders aka gasoline/propane generator modified to charge battery packs


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## cts_casemod (Aug 23, 2012)

TexasCotton said:


> I have seen range extenders aka gasoline/propane generator modified to charge battery packs


 
DIY or comertial? Do you know anything about the motors they fit on them?


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## onegreenev (May 18, 2012)

Check out the beginnings of my project. I am using a small diesel engine and going to couple it to my DC Starter/Generator motor for power to charge when needed. I won't be using it to actually run the vehicle because the voltage output will be less than the pack voltage but the amperage will be high. I could disconnect the main controller and just pump in what ever voltage it will output and run the motor that way and just cycle through the gears as needed. Won't be fast but could get me down the road if needed. Mostly going to use it for the DC power source for charging on the side of the road or rest stops where there is no place to plug in if I need a charge. It will be small and light and with a gallon of diesel should be able to charge at least twice. Might boost a total range up to a hundred or so miles per day. We shall see. If you go with the Diesel be sure to get a diesel with a standard keyed shaft. If you buy a diesel like I did with a water pump attached it will not be a standard keyed shaft but a straight shaft with a screw on end. I need to find a pulley to attach to the engine and another to the motor. The motor has a splined shaft and should be easy to get a pulley for it. The Diesel will not be as easy me thinks. But coupled to my Synkromotive controller I can use the DC output to charge my pack with any where I need. Tow along a tiny trailer and a few gallons of diesel and Im good to go. The Diesel had to pass California emission standards for the small diesel to be sold in California so I am good there. Engine is new and runs like a champ. Just get a pulley setup to allow for high rpm of the motor and I can get some serious amperage. Up to 400 amps and 36 volts. So any DC motor with 36 volts and up to 400 amps should scoot along pretty good if I decide to power the motor directly from the generator. No true throttle control. But at low voltages it should not be difficult. Not sure If I will do that. I truly only intend to use it as a stationary charger for on the go and increased range. 

Anyway check out my page:

http://onegreenev.blogspot.com/2013/04/dc-diesel-power.html


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## cts_casemod (Aug 23, 2012)

onegreenev said:


> Check out the beginnings of my project. I am using a small diesel engine and going to couple it to my DC Starter/Generator motor for power to charge when needed. I won't be using it to actually run the vehicle because the voltage output will be less than the pack voltage but the amperage will be high. I could disconnect the main controller and just pump in what ever voltage it will output and run the motor that way and just cycle through the gears as needed. Won't be fast but could get me down the road if needed. Mostly going to use it for the DC power source for charging on the side of the road or rest stops where there is no place to plug in if I need a charge. It will be small and light and with a gallon of diesel should be able to charge at least twice. Might boost a total range up to a hundred or so miles per day. We shall see. If you go with the Diesel be sure to get a diesel with a standard keyed shaft. If you buy a diesel like I did with a water pump attached it will not be a standard keyed shaft but a straight shaft with a screw on end. I need to find a pulley to attach to the engine and another to the motor. The motor has a splined shaft and should be easy to get a pulley for it. The Diesel will not be as easy me thinks. But coupled to my Synkromotive controller I can use the DC output to charge my pack with any where I need. Tow along a tiny trailer and a few gallons of diesel and Im good to go. The Diesel had to pass California emission standards for the small diesel to be sold in California so I am good there. Engine is new and runs like a champ. Just get a pulley setup to allow for high rpm of the motor and I can get some serious amperage. Up to 400 amps and 36 volts. So any DC motor with 36 volts and up to 400 amps should scoot along pretty good if I decide to power the motor directly from the generator. No true throttle control. But at low voltages it should not be difficult. Not sure If I will do that. I truly only intend to use it as a stationary charger for on the go and increased range.
> 
> Anyway check out my page:
> 
> http://onegreenev.blogspot.com/2013/04/dc-diesel-power.html


Sounds good, but why generate a huge amperage at low voltages!? Certainly your losses will be higher? Or are you planing a series hybrid to add this voltage in series with what your pack is already providing?
Aircraft generators are usualy able to provide low voltages at high amperages and act as good motors

I plan on using a 4 pole alternator at 1500RPM to 3600RPM. Reason being my bateries will not be receptive of the full 3KW if I am not moving, so this will allow me to have a variable output and always match the supply to the demand.

As with speed control, I will have a current controled setup. The voltage will be fixed at 3.60VPC.

What kind of DC motor do you plan to use to have a good voltage regulation?


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## onegreenev (May 18, 2012)

I am using the high amperage and low voltage because for one it is what I have but two it is perfect because the Synkromotive controller utilizes an inductor in the system to boost voltage to the proper pack voltage. This way I don't have to match my voltage or run it through a step down transformer tailored to my pack requirements which is harder to do. I will have an external inductor and the controller will do the rest. Bumping the voltage will reduce that amperage to a more reasonable level. It won't be a super fast charger but more like a good level 2 charger. It would be perfect to take the Bug-O-Rama where you need portable power. 

Pete


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## cts_casemod (Aug 23, 2012)

onegreenev said:


> I am using the high amperage and low voltage because for one it is what I have but two it is perfect because the Synkromotive controller utilizes an inductor in the system to boost voltage to the proper pack voltage. This way I don't have to match my voltage or run it through a step down transformer tailored to my pack requirements which is harder to do. I will have an external inductor and the controller will do the rest. Bumping the voltage will reduce that amperage to a more reasonable level. It won't be a super fast charger but more like a good level 2 charger. It would be perfect to take the Bug-O-Rama where you need portable power.
> 
> Pete


I got it now. Thats a lot of hassle, why not get a equiparable voltage motor/generator and control the field excitation to keep the voltage right? That would be 98% Efficient!

The issues I see are the folowing, but feel free to correct me if I'm missing something:

You need a 400Amps diode or IGBT to avoid energy to flow back to the motor, thats 400*0.7V = 280Watt loss!

Next you need another circuit with an inductor and a switch to take care of the boost regulation. I would say another 400-500Watt (transistor + reverse diode) + Inductor losses and at 400Amps thats not going to be a small inductor (added weight, complexity).

Then, there is the issue to match the input of the geny to your load output.
Say you only require 2KW at a certain time and your generator output is 3KW, Sure you can manually do that, just seems complicated to me since you need to change both the generator speed AND the converter output (assuming you are working with CC-CV in the first place).

Take or give that would be a bit worse that using a 230V generator and a high efficiency PFC corrected charger for efficiency purposes. Lots of losses on the conversion process.


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## onegreenev (May 18, 2012)

cts_casemod said:


> I got it now. Thats a lot of hassle, why not get a equiparable voltage motor/generator and control the field excitation to keep the voltage right? That would be 98% Efficient!
> 
> The issues I see are the folowing, but feel free to correct me if I'm missing something:
> 
> ...



Ok, lets get a bit more technical. I do actually plan on using it as a stationary setup but tow it on a small lightweight trailer. I only need to provide a DC source with enough amperage to allow for boosting the voltage to pack voltage and still have a respectable amperage left to charge the pack with in a timely fashion. The inductor will be external which I have and will handle at least 100 amps but I don't expect to be using that high of amperage. Yes, it will have a cooling fan. The setup requires a set of contactors to reroute the power so it goes into the battery pack and not through the motor unless you plan on using the motors field to be the inductor which I may do again. 

The controller takes care of all the regulation including the CC/CV regulation to your set point. I can set the amperage rate as well as the end voltage where it will hold that voltage until the amperage is at the set parameters. You see, that is the reason I love the Synkromotive controller so much. Not only is it a light weight powerhouse it will also double as a charger. ANY DC source works. If you want to set up from your AC that is easy too as long as you have a high voltage pack that is higher than the lowest voltage of your pack. It works great from AC if you have a 192 volt pack. Take your 110 and rectify it then run that through the inductor and controller and you have your regulated charge setup. You know you can make a 110 200 amp dedicated outlet and make a fast AC charge setup too. 

Since I am using a lower voltage I will just use the solar bank of batteries or the DC generator. No need for adding in all the junk. Its already in the controller anyway. It was designed from the beginning to do just that. Not an after thought. 

It is a very simple setup. I just need to couple the diesel to the motor and see what happens. I will keep you all informed of the progress. 

Works great from a bank of solar batteries. The bank in the video is only 48 volts and charging to 120 volts. I had the amperage very high at one point. Need a large inductor at that point. For low amperages you can use small external inductors instead of the motors field windings. 

See video:


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