Series Hybrid Weed Eater Powered WE BD48

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Wow Spock. This is really "illogical." Did you make a "guestimate" on this! Great work. Hope it works like you planned!

Well, does it work? How much do all the parts cost?

I hope stealth wasn't one of your goals :wink:

Good job though.

Keep us posted on actual performance.

Cool. Good pictures.

I'll be interested to see how much power it makes. It's a bit smaller looking than my Honda GX-31 engine.

TAP-N-GO, BABY!!!

I assume you have plans for ducting the fan(?).
Also, how do ya voltage regulate?

Anyhoo,
It B da Schitz.... I hope you get plenty range.

Glad someone else started on this sort of setup, i hope to do similar myself down the track since i have oodles of space...

looking forward to results/specs best of luck... nice pics to

Kim

TD no 40's ? there's duct tape man DUCT TAPE!!1111

AussieJester said:

TD no 40's ? there's duct tape man DUCT TAPE!!1111

Click to expand...

The metal and plastic work offset the ghetto factor. :?

Nice work.

Ahem...

I daresay we are seeing the work in progress. 40's are for duct-tape (and the like) in finished projects. 8)

:: takes notes of 40's requirements :: i shall not make the same mistake again TD ;-P

As long as he matched the (engine speed/ generator KV) to the max voltage of the pack he is all good. Adjusting the throttle of the motor will adjust the output voltage. Awesome idea and implementation! I wonder how far he could ride on one gallon.

The build thread is here:

http://www.motoredbikes.com/showthread.php?t=14198

Its raining and I haven't had a chance to ride the thing yet, except for a quick spin around the block.

I need to test it a bit and see if anything breaks, then I will move on to controlling the throttle based on output voltage. Right now I am using the idle screw to run it at a fast idle, which at no load condition seems to hold voltage around 55V to 60V. My target voltage is 57V, the fast charge voltage for a nominal 48V lead acid battery system.

The duct tape is only temporary! I have to clean up my wiring too. But it actually runs now, so I am announcing the birth of the weedeater range extender!

The dc permanent magnet motor was about $30 delivered from ebay.

A couple of bucks worth of fasteners.

Weed Eater was thrown out by my neighbor, I picked it off the curb on trash day.

I bought a fuel filter and fuel line, by the time I got the right size and length, probably a total of $10.

Angle aluminum and plate aluminum was scrap out of the garage.

Flexible coupling was $20 delivered from Reid Supply (along with a couple of drill bits), next time I will get someone with a drill press to drill it out to the right diameter for a few more bucks. The flexible coupling is the key to this whole project. Once I figured out how to couple the two parts, the rest came together pretty easy.
http://www.reidsupply.com/aDetail.aspx?N=1004576&A=GU-2102&An=1004576&On=1004576&ST=

Some scrap wire, a few connectors and powerpoles.

The 20A toggle switch was a little pricey, I think it was close to $10 from DigiKey. Not sure on that though.

Maybe $80 total.

With a brushed motor, all you really need to do is connect the motor to the batteries. It will act like a starter motor. Once the engine is running, the rpm will be limited by the generator load. I don't think you need to worry about regulating it much. You could keep an eye on the battery voltage, but I doubt you will ever get into overcharge as long as you are still riding. I thought one could design a voltage regulator that simply cuts off the engine whenever the voltage gets up to the maximum allowable for the pack and cuts back in as soon as it drops below a slightly lower setpoint.

With the batteries connected, the engine will rev up to the point where the generator is making power, then it will be very difficult to make it go any faster. I think you will need near full throttle. The trick is to match the voltage constant of the generator to the system so the engine runs near its most efficient rpm while generating.

And frugal setup to boot fantastic!! I'm also a member of that forum some very talented people over there and ALOT less 'bashing of others ideas' than here i have found...pitty they aren't as many members there with electrics :-( Shall venture there and have a read through the worklog, as i mentioned in earlier post I had planned doing something very similar wih my trike but using one of the 49cc two stroke motors... cheers for links and info

Test Results

Saturday, Sept 20
64F, dry
start T: 9:30:20AM start time
initial V: 53.4, from overnight charge, likely float charge still on batts, 52V more likely true charge
mode: battery power only, wide open throttle
end T: 9:44:00AM
end V: 47.9V, after 5 minutes had rebounded to 49.1V
4.4 mile course measured on Google Earth
4.4 miles / 0.2276 hours = 19.3 mph average speed.
Notes:
No gas motor use.
Saw operating voltages between 25V and 46V.
Really slow at end, slow up Police Dept hill.
Appears to be roughly 6V drop between no load V and top speed V, example, 51V no throttle to 45V full speed WOT.
The batteries are old and not in top condition.

Saturday, Sept 20
73F, dry
start T: 1:40:00PM start time
initial V: 53.1, from 3:40 hours charge, likely float charge still on batts, 52V more likely true charge
mode: generator plus battery, generator at fast idle speed, hubmotor at wide open throttle
end T: 1:52:00PM
end V: 49.4V, after 5 minutes had rebounded to 50.1V
4.4 mile course measured on Google Earth
4.4 miles / 0.20 hours = 22.0 mph average speed.
Notes:
Saw operating voltages between 45V and 51V.
Made it up Police Dept hill no problem, lowest voltage seen was 45V.
Generally saw 48 to 50V at full speed, WOT, level ground

Generator Only

I started up the generator then unplugged the battery pack. The gas motor was running at fast idle speed. It was able to move the bike slowly, under 10mph, better than walking speed but not much more. I saw voltages of 60V to 70V under no load, with the motor slowing way down and voltages of 20V to 30V under load.

I wanted to try the gas throttle but was unable to reach it while riding. I will try to set up a hand throttle. I believe that with the throttle, the gas motor will be able to provide at least a "get home" speed of 15mph, maybe more. In other words, if the battery is dead, the gas motor can limp home as long as there is gas in the tank.

Analysis

Due to lead acid battery chemistry, range is determined by how far you can go before you reach a 50% discharge rate. 50% discharge is a rule of thumb that you can discharge a battery pack to without damaging the cells and can then recharge it again and again for many cycles. For a 48V system the 50% discharge point is 48V.

My old and no longer in prime battery pack charges up to approximately 52V (after the float charge is removed). The range of this system is how many miles I can run before reaching a 48V level on the battery pack (no load).

My experiment under battery power alone showed that I could run approximately 4.4 miles before reaching the 48V level. Starting voltage 52V minus end voltage 48V is 4V. 4.4 miles / 4V = 1.1 miles per volt drop.

Under generator and battery, the voltage dropped 2.6V over 4.4 miles. 4.4 miles / 2.6V = 1.7 miles per volt drop.

The range provided by the generator system is approximately 150% of the battery only range:

1.7 miles per volt drop / 1.1 miles per volt drop = 1.54

So with the gas motor running at fast idle, range is 50% better than battery alone. With motor control of the gas throttle, this may be able to be improved.

Can you measure the current going from the generator to the batteries?

I could probably set up the multimeter to do that. Right now it has a powerpole on it, would take a little rewiring.

Under battery plus generator, it runs between 2 and 3 amps, hanging around 2.8a generally at speed and WOT.

Under generator only, full load from hubmotor, between 4 and 5a.

Since the dc motor is rated at 5a, there may not be any more to be gained, even at higher throttle.

I made a simple throttle control. When running with no batteries, the generator puts out about 5a at a fast idle and while trying to accelerate. The motor rpm slows down when load is added. It barely moves the bike along at a walk speed or maybe a little faster. When the throttle is turned, the motor does not speed up, it dies out. There appears to be a lot of load on the gas motor, caused by the dc motor.

E=IR said:

I believe that with the throttle, the gas motor will be able to provide at least a "get home" speed of 15mph, maybe more. In other words, if the battery is dead, the gas motor can limp home as long as there is gas in the tank.

Click to expand...

This is of particular interest to me having some form of 'backup' option as i dont have the ability to wheell/push the bike home, You say the motor 'dies' when load is added, would simply using a larger motor say the 49cc china motors rectify this enough to be a useable 'back up ' option do you think? probably a hard one to accurately answer i guess ...Keep up the excellent work good to have a 'guinea pig' to sort out some issues before attempting the same thing hehehe...best of luck mate look forward to future updates

The system I built was put together cheaply to learn about how a hybrid system works. For real life use, make sure that the dc permanent magnet motor/generator has an amp rating that will power your hubmotor at a reasonable speed. Also, make sure that the dc motor provides an adequate voltage level at the gas motor rpm which you wish to run at. Make sure the gas motor has a good muffler!

I have not weighed the system yet, but expect it to be about 20lb, in other words, heavy. I tried to get by on the light side using a small dc motor. My system is a range extender but not a real hybrid system where you can get home on gas power alone. A useful system will be heavier than my lightweight system.

Is a hybrid system worth it? When putting together a motored bicycle, it is already far more efficient than most other machines. Does it really need a hybrid system? Probably not, when a gas only system will give you 100mpg easily and 200mpg or more with some hypermiling techniques. The noise of a gas motor ruins one of the biggest benefits of an electric system. Instead of a hybrid system, how about a spare battery pack?

It is definitely interesting to experience how the motored generator and the hubmotor affect each other under various load conditions. The gas motor is far too loud to ride under normal conditions (this is something that could be solved with a better muffler). It was an interesting experiment but I don't see it as being very practical. However, hybrid systems seem to be the future of automobiles, so it was interesting to see some of the design challenges.

I went for a ride again tonight. The generator system works fine, as originally expected it is a range extender. 150% range extension is pretty good. However after building it I realize what I really want is a true hybrid that is not limited to range. It has a number of weaknesses that could be upgraded: the weedeater motor is a high rpm, low torque motor, not really the right kind of motor. The generator seems to do the job but has a limited output that I seem to be maxing out. It seems to give its rated power or a little less. Well what did I expect?

I have been trying to work out some things to experiment on. First of all, I have a rectifier on the way and will try to run a motor off of rectified 120VAC, maybe with a big electric motor starter capacitor to shave the peaks a bit. I will start with extension cord power but the goal of this experiment is to see if a 2000W 120VAC generator could be used as the basis for a hybrid. This is based on the availability and low cost of these powerplants. I don't think I would use my hubmotor for this, I would want to upgrade to a motor rated for higher voltage. I need to experiment to check it out but I think it will be about 110VDC (pulsed) after rectification. I may pull the Bosch dc motor off of my generator system and try it out, see how it handles pulse dc. It is rated at 110VDC I believe.

Probably the best type of generator would be a 3 phase generator which is easier to rectify to dc. This would be like a car alternator. I don't know if they are available in the 1500W to 2000W range. I would suspect that is what is used in hybrid powerplants. I wonder if I could rewind or modify a car alternator to get 60VDC. I could make that work with my hubmotor.

There is a new law in MI that apparently grants a $7,500 tax exemption for a plug in electric hybrid. I wonder if they will accept a homemade version of a plug in electric hybrid.

The next build will be set up for hypermiling. The gas motor will go on only when there is a load on the electric system. While waiting at a light, it will be silent. When I press the throttle, the motor will start up and run hard to produce a lot of power. As I reach cruising speed and let up on the throttle, there will be a threshold where the gas motor turns off and electric power does the job. Then when I am coasting, no power will be used. This will allow me to do pulse and glide engine off coasting to save on gas.

I really wonder how Prius and Honda hybrids are designed. I think I am learning a bit about it but it is not so easy as to slap a generator on a gas motor. It takes a lot of engineering and experimentation to get the kind of efficiency they are getting.