Generator Motor

[fitek]

Hi all,

I'm looking to do some pedal power generation but am having trouble finding suitable motors. I'd like to charge the batteries of an electric bike with a generator/alternator.

One problem is matching the motor voltage to battery voltage. It's easy to find 12v DC motors, but these won't charge a 36 or 48v battery pack.

The other problem is the motor speed. I checked my pedaling speed and can range from about 30rpm to 170 rpm, although about 40-50 seems nice and comfortable. Standard bike parts can do up to about 4:1 to 5:1. I don't want to resort to expensive planetary gear reducers, etc.

Any thoughts?

 

[safe]

The other problem is the motor speed. I checked my pedaling speed and can range from about 30rpm to 170 rpm, although about 40-50 seems nice and comfortable. Standard bike parts can do up to about 4:1 to 5:1. I don't want to resort to expensive planetary gear reducers, etc.

How about starting with a hub motor?

They have very low rpm requirements.

As for charging is there any reason that you can't divide your pack into 12 volt units and then charge them individually?

The other option for gearing is to use a large (114 tooth) go cart sprocket and using a #35 go cart chain run it through a small sprocket like 11 teeth. (they even have 9 tooth)

http://tncscooters.com/product.php?sku=106122

250W GEARED Motor - 36 Volts (Model: MY1018Z)

MY1018Z
36 Volt
250 Watt
2750 RPM
8.9 Amp
permanent-magnet motor.

9 tooth sprocket for #35 chain.
12 gauge power leads.
Gear Ratio: 79:11 (7.182)

Which means this runs at 382 rpm for the rated speed... so you could even use a regular bike chain, something like a 52/13 setup. Now that's REALLY easy.

Only $48.

 

[billvon]

Hi all,

I'm looking to do some pedal power generation but am having trouble finding suitable motors. I'd like to charge the batteries of an electric bike with a generator/alternator.

Any thoughts?

If you have a hub motor you could just pedal the bike. Get the motor above base speed and the diodes in the controller will turn the motor into a generator. If you want to pedal slower, put the regen circuit on (basically a three phase bridge with a chopper.) DO NOT use an automotive alternator. They are indeed cheap, but there's a reason they're cheap.

 

[safe]

What's the cheapest hub motor out there that might work?

A lot of the hub motors cost an arm and a leg. Something simple like a little brushed motor would be ideal. It has to be under $100... unless price is no object.

 

[vanilla ice]

Ebikes.ca has a <i>26 inch DC Rear Wheel with 7-speed freewheel & Disk Brakes</i> for $150.

I was also thinking that 36v geared unite would be good. If you spin it fast enough you could probably get it to charge a 48v pack.

 

[safe]

I was also thinking that 36v geared unite would be good.

Yeah, I posted that above... only $48.

 

[vanilla ice]

I know, thats why I said <b>also</b>... its the first one that came to mind for me too. I guess that means we think alike?

$1 per volt, what a bargain!

 

[fechter]

I was thinking about the same thing.

That Unite geared motor looks like it would be in the ballpark. A 48v version might be better, but the rated voltage does not really matter as long as you can spin it fast enough to generate.

It should be possible to do the math on it.

One of those is much cheaper than any hub motor that would work.

The cool thing about that setup is you could contribute human power regardless of bike speed. It is not efficient, but if you have something like Lowell's bike, you couldn't spin the cranks fast enough to help the bike at 'typical' speeds with direct gearing.

 

[vanilla ice]

I run the 24v version at 36, so the 36v should take enough rpm to get to 54v without breaking. Which is about what you would need to charge a 48v pack I think.

Still the "DC" hub motor seems very reasonably priced at 150$ for the complete wheel assembly. Whats the catch, does it suck that much compared with the 4 series?

 

[fitek]

Hey guys,

actually I should have mentioned the idea was to charge the bike while its in motion. True, it's not terribly efficient, but I found that the dumpster of a local bike store is chock full of parts every week, and I was thinking of making a tandem trike. Working out the chain and so on seems like a nightmare-- it might be easier just to use a hub motor and two small generators. Then each person charges the batteries and I don't even have to bother with a chain or gears at all. I ran the numbers and the transmission efficiency should fall to 50-80% versus mid to high 90s for a chain. Well, that's not great, but if you can get in the 70%+ range it isn't too terrible either.

 

[fitek]

Forgot to mention that my bikes seem to fall into disrepair all the time, so while the efficiency of a chain is supposedly 98%, I think a rusty chain with a rusty idler wheel probably is quite a bit lower.

 

[safe]

...actually I should have mentioned the idea was to charge the bike while its in motion.

There's a saying:

"Keep It Simple Stupid"

...if you want to charge do it while you have a treadmill setup to watch tv or something. The losses of generating and storing electricity are too extreme to even bother with this idea on the bike. It's like "regen braking"... it sounds like a great idea, but when you realize that 90% of all the energy you put into a bike ends up pushing the wind (and is not recoverable) it falls flat on it's face.

 

[Rassy]

fitek wrote:

...actually I should have mentioned the idea was to charge the bike while its in motion.

I agree with safe on this. When I throw the brake switch "on" and try to pedal my trike, I can just get up to a few MPH because of the drag. The motors are just trying to light up some 12V headlight bulbs, and they don't produce 12V until I reach 10 MPH (20" wheels). The same motors in 26" wheels produced 12V at about 12 MPH, and when I did some tests with an ammeter, the increase in voltage seemed to be linear, which means 30 to 40 MPH to reach 36+ Volts.

 

[fechter]

I think you should be in the 70% efficiency range with one of those Unite motors used as a generator. Unless you have legs like Lance Armstrong, you won't be even close to the motor's power rating.

If you are pedaling while the motor is running, the losses in charging / discharging the battery won't be in the loop. Your power will go straight to the motor.

If your legs can supply 100w, then that's 100w the batteries don't need to supply. It can only help your range. If your batteries go completely flat, you could park it on the kick stand and pedal until you get some juice back.

It might get some strange looks if you're waiting at a red light, but pedaling.

If you use a full bridge rectifier, you could pedal backwards and still get power :wink:

 

[fitek]

I think you should be in the 70% efficiency range with one of those Unite motors used as a generator. Unless you have legs like Lance Armstrong, you won't be even close to the motor's power rating.

If you are pedaling while the motor is running, the losses in charging / discharging the battery won't be in the loop. Your power will go straight to the motor.

If your legs can supply 100w, then that's 100w the batteries don't need to supply. It can only help your range. If your batteries go completely flat, you could park it on the kick stand and pedal until you get some juice back.

It might get some strange looks if you're waiting at a red light, but pedaling.

If you use a full bridge rectifier, you could pedal backwards and still get power :wink:

For $48 I think this is worth a try Is this a reputable site to buy from?

That scooter site has some other cool parts. I wonder if the 8mm D-shaft sprocket fits my BMC motor?

I also thought about what looks one might get, when pedaling cadence isn't related to speed. But I think if you are riding a tandem trike that will probably be strange enough to solicit some gawking.

Bicycle Science 3rd ed gives some power output numbers for people of various fitness levels over time. A person can output a lot of power, but only briefly. I think 100w is a pretty good number for some 'casual' pedaling. Interestingly, pedaling backwards increases burst output.

 

[vanilla ice]

This thread is worth checking out. Page 3 has a guy with a working generator set up on a hub motor trailer. I'm not sure if they are a member here.

http://www.motoredbikes.com/showthread.php?t=6444

 

[fitek]

This thread is worth checking out. Page 3 has a guy with a working generator set up on a hub motor trailer. I'm not sure if they are a member here.

http://www.motoredbikes.com/showthread.php?t=6444

Thanks Vanilla Ice. Hmm, never thought I'd say that.

I bought the 36v 250W geared DC motor. I will report back when I get it.

I think I'm also going to try one of the cheap kollmorgens.

 

[bobmcree]

This thread is worth checking out. Page 3 has a guy with a working generator set up on a hub motor trailer. I'm not sure if they are a member here.

http://www.motoredbikes.com/showthread.php?t=6444

Thanks Vanilla Ice. Hmm, never thought I'd say that.

I bought the 36v 250W geared DC motor. I will report back when I get it.

I think I'm also going to try one of the cheap kollmorgens.

some of the gear reduced motors will have a freewheel that could prevent using them as a gen. i'm not sure if the one you suggest does or not.

i have several of the Hi-Koll motors with bad controllers that could be used for a generator with a 3 phase bridge. if you want one i'll let you have one for $10 and $9 shipping in the US by priority mail. if you want to use one of these as a gen you will need to disable the internal controller anyway, so having a motor without the controller is fine. i have some metal plate covers for the back that replace the modular controller and make the unit shorter by 1/2" or so, and can include one of them or a back cover with a blown controller.

these motors work great with an external controller, so the ones with blown controllers can still be used, otherwise i would send you one for free

 

[fitek]

some of the gear reduced motors will have a freewheel that could prevent using them as a gen. i'm not sure if the one you suggest does or not.

i have several of the Hi-Koll motors with bad controllers that could be used for a generator with a 3 phase bridge. if you want one i'll let you have one for $10 and $9 shipping in the US by priority mail. if you want to use one of these as a gen you will need to disable the internal controller anyway, so having a motor without the controller is fine. i have some metal plate covers for the back that replace the modular controller and make the unit shorter by 1/2" or so, and can include one of them or a back cover with a blown controller.

these motors work great with an external controller, so the ones with blown controllers can still be used, otherwise i would send you one for free

Thanks for the heads up on the geared motors. If that is indeed the case I will take the motor apart and see what I can do. It'll be interesting to compare how well a series DC motor compares to a brushless DC with a bridge.

I'll email you about the Kollmorgen

 

[fechter]

If it has a freewheel, you can just turn it backward or put a screw through the freewheel mechanism to lock it up.

 

[vanilla ice]

I don't think any of the unites include a freewheel.

I still think it'd be worthwhile to consider a way to direct drive a wheel with the ICE. I mean as long as you're going to haul that extra weight around, may as well make it as versatile a system as possible.

Bob, if you've got any more of those Koll extras you want gone, let me know!

 

[bobmcree]

I don't think any of the unites include a freewheel.

I still think it'd be worthwhile to consider a way to direct drive a wheel with the ICE. I mean as long as you're going to haul that extra weight around, may as well make it as versatile a system as possible.

Bob, if you've got any more of those Koll extras you want gone, let me know!

remember when i took so much flak for saying the revopower looks like a scam? well, they have put off the product release until 08 now, and i bet that turns into 09 in a few months. if you really want a 7500 rpm 2 stroke weedeater a couple of feet away for $599 you might consider one of those

i do still have a few hi-koll motors, i can send you one with a dead controller for $19 shipped, and also have new working ones ccw for $40, cw for $50 and now i have modified some so they can be reversed with an external line that is grounded or left open, for $75. 2 motors will fit in a $9 flat rate priority box. contact me off list if interested.

 

[fechter]

Reversable motor? Cool 8)

I assume you located the reverse pin on the controller chip burried in the epoxy somehow. Would that be easier to attack than swapping all the wires around if you wanted to change direction?

 

[bobmcree]

Reversable motor? Cool 8)

I assume you located the reverse pin on the controller chip burried in the epoxy somehow. Would that be easier to attack than swapping all the wires around if you wanted to change direction?

its kind of a tossup which is easier. when you swap the wires around if you do not replace them properly they can overlap and cause pressure on the pcb which causes it to rub and overheat. that happened to a couple of the first ones i reversed and sent to knoxie, but we got past it and with some practice rewiring them is pretty simple.

when you hack through the potting there are some components tacked on top of the MC33035 controller chip you can damage, and the chip itself is easy to blow with esd. i blew one just by cutting off the pin with a dremel. you really need a set of angled flush cutters to cut pin 3 loose from the pcb after digging through the potting.

when i first found these motors the fellow who told me how to reverse them asked me not to release the info and i have honored that. since i discovered this myself i am not so bound, and we are here to share information, so here's the technique, and a photo.

draw a line from the far cap to the brown hall wire and measure 1.3" from the cap. that will be the location of pin 3. if you cut it loose the internal pullup will make the motor run CW, and if you ground the pin it will run CCW. DO NOT REVERSE THE MOTOR WHILE TURNING, IT WILL BLOW!!!

 

[fechter]

Excellent!

Thanks for sharing.