# Charge While Driving



## Junkman (Feb 12, 2012)

I wouldnt think you would need a 20hp motor thats a big motor (think lawn tractor size) If I were going to do it I would get a 3.5hp B&S motor and pair it with a 10SI internally regulated 100 amp alternator then you would have no worries about overcharging and a much more compact fuel efficient package. Just a thought


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## Duncan (Dec 8, 2008)

Hi Roger

The easy way would be to shut down your generator when your battery is 80% full,
I am planning on monitoring my battery by using a Cycle Analyst - this goes across the battery so that as I discharge the calculated battery level goes down and when I charge it goes back up again

http://www.ebikes.ca/drainbrain.shtml

when it shows you are full switch off the generator


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## charliehorse55 (Sep 23, 2011)

Junkman said:


> I wouldnt think you would need a 20hp motor thats a big motor (think lawn tractor size) If I were going to do it I would get a 3.5hp B&S motor and pair it with a 10SI internally regulated 100 amp alternator then you would have no worries about overcharging and a much more compact fuel efficient package. Just a thought


3.5 hp isn't even 1/5th the power you will need to maintain 75 mph! (assuming you are going to be driving on highways for long trips).


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## Junkman (Feb 12, 2012)

No the 3.5 hp motor was only to run the alternator to charge the batteries not to drive the vehicle


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## charliehorse55 (Sep 23, 2011)

Junkman said:


> No the 3.5 hp motor was only to run the alternator to charge the batteries not to drive the vehicle


What would this accomplish? If you are draining the pack at a rate of 15-20kW, how is charging it at 3kW going to increase your range at all?


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## Junkman (Feb 12, 2012)

I got another idea. I just wont offer anymore suggestions hows that?


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## Mark C (Jun 25, 2010)

charliehorse55 said:


> If you are draining the pack at a rate of 15-20kW, how is charging it at 3kW going to increase your range at all?


OK, so now I have to admit an obvious lack of understanding on my part. How do you calculate the 15-20kW you used as an example? Would it be the same way that a person might state that their EV's max power is 50kW?, because I don't understand that either.


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## Ivansgarage (Sep 3, 2011)

I would put the 20hp motor on the bike, then you could get rid of the electric motor, generator, batteries, and trailer..


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## Ziggythewiz (May 16, 2010)

Mark C said:


> OK, so now I have to admit an obvious lack of understanding on my part. How do you calculate the 15-20kW you used as an example? Would it be the same way that a person might state that their EV's max power is 50kW?, because I don't understand that either.


If you have a 144V system, and you're pulling 105 amps, that's 15kW. 20kW would be pulling 139 amps.

A 144V system with a max amps of 350 would be a 50kW system

That would be the max power draw, max power of the system would be max amps * voltage (while sagging at said amps) * system efficiency (on the order of .85)


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## bluefxstc (Dec 29, 2007)

The first thing I would do is finish the bike, and trailer (minus the generator) so you can figure out exactly how much power you need. You probably don’t want to fill all the power need, just most of it. The idea is the pack could provide some of the power and the generator the rest. Maybe use 70-80% of the pack in 5-7 hours. It may have to be longer if you take long rides, but you can also leave the generator on when you take breaks so it will keep charging then. Once you figure out how much power you need to cruise the rest should be fairly easy. It is just math. You know your pack capacity, power to cruise and how long you want to ride without stopping. Do the math and it will tell you the amount of current you need and with that you should be able to figure out the generator and horse power necessary to provide it. The first thing though is to finish the bike so you are not guessing on numbers. As far as monitoring I would just shut the generator off when the voltage reached a predetermined point. Depending on what cells you use maybe cut it off 0.1 or 0.2 V per cell below the full charge voltage. On a CALB cell with a full charge voltage of 3.6 you would cut it off at 3.4-3.5 V per cell. If you size it right this would only be a problem if you were on a real long downhill, stuck in traffic or in another low power draw situation.


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## Junkman (Feb 12, 2012)

Can you fit a 144v battery pack on a Goldwing? I figured at most he would be running 36v


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## RogerK (Dec 20, 2011)

I will plan on about 72V battery pack using LeFePo. Planning on 60AH batteries. They should all fit inside the frome, above the motor and under the tank and seat. I finally got my motor installed and my drive train working. I put 48V to it today with the back wheel off the ground. It really took off. I had a fair amount of noise in the drive shaft system, I think comming out of the U joint. Need to look closer into it. I think allighnment is good. I'm wondering if a spline type U joint requires heavy grease where both shafts slide in?


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## RogerK (Dec 20, 2011)

20KW is 26.8 HP (at peak rpm). So my 20 HP estimate was close. While it seems a large motor it really isn't for a Goldwing to pull. 20HP motors should be plentiful (old lawn tractors, etc). I'd like the generator to double as an emergeny 220V backup for the house, and perhaps my cabin (that has no power). So I do like this combination. 90% of the time no trailer, but onc ein a while a nice long country cruise and it would be handy. I think I will use a BMS afterall, so that is how I would shut down the generator when I need to.
Thanks,
Roger


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## DanGT86 (Jan 1, 2011)

I saw in another thread a digital volt meter that can turn relays on and off at specific voltage. Its costs about $40. Seems to me you could set it to turn the generator off at a voltage that corresponds to say 70% state of charge for your pack and on at 50% soc. I know votage is not the best way to measure State of Charge but if you stayed away from the upper voltage limit of your pack it seems safe. Might be some bugs to work out but it would be way cheaper than a BMS. Just a brainstorm I had. It might be a terrible Idea. I'm new at this. 

here is a link to that volt meter: 
http://www.lightobject.com/Programm...th-dual-control-Good-for-HHO-System-P408.aspx

When I read your thread title I thought it was going to be another perpetual motion argument. Glad it was an interesting build instead.


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## Bowser330 (Jun 15, 2008)

DanGT86 said:


> I saw in another thread a digital volt meter that can turn relays on and off at specific voltage. Its costs about $40. Seems to me you could set it to turn the generator off at a voltage that corresponds to say 70% state of charge for your pack and on at 50% soc. I know votage is not the best way to measure State of Charge but if you stayed away from the upper voltage limit of your pack it seems safe. Might be some bugs to work out but it would be way cheaper than a BMS. Just a brainstorm I had. It might be a terrible Idea. I'm new at this.
> 
> here is a link to that volt meter:
> http://www.lightobject.com/Programm...th-dual-control-Good-for-HHO-System-P408.aspx
> ...


Good find Dan! Thanks.

Another way to protect your pack would be to connect the generator to your charger instead of rectifying it to the pack directly....that way you can allow the charger to control the level of charge to the battery pack. If you are carrying around an on-board charger anyway, why not use it?

I thought about the same thing, but for a car, but I can't seem to find a lightweight & inexpensive enough APU.


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## m38mike (Dec 27, 2008)

I'm in the process of building a trailer to do just what you're planning. One difference is that I want it to be as automatic as it can be, so I'm using a 10kW charger between the generator and the pack. I bought a 13kW gas generator from Central Maine Diesel. It's got a 20hp Honda engine driving the generator head. Dry weight is 225 lbs, and it sells for about $2,200. I'm buying the 10kW charger from Electric Motor Werks for just under $2000. It's been tested up to 14kW without a malfunction. The pack I'll use is 45 100ah Calb LiFePO cells. 

My EV is the Electro-Willys, a 1952 Willys Army Jeep. The trailer I have is a 1952 Army Jeep trailer. Not very efficient in any way. But it's a solid platform for building this combination. My plan is to have the generator give me up to 75% of the power I need to get down the road at highway speeds. Since I don't drive for long distances without taking breaks, I think that during those breaks the generator will continue to push power into the pack and bring it back up to full power. This is where the automatic charger plays a key roll. It will monitor the pack so I don't have to, and it will scale the power down as the pack fills up. 

I'm going to do some short range tests of this system this spring/summer here in the mountains of Colorado. Then I'll really put it to the test this summer by driving the jeep to Alaska and back. 

Getting back to your build, the generator I've got would easily fit into a motorcycle trailer, so the unit you would tow wouldn't be outrageous. I wish you success. I think this is by far the best, most flexible option for EV owners who would like to go where charging stations don't exist.


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