minibike alternator/generator?

[CarPlayLB]

Hello OldMiniBikes'ers!
I am working on a double top secret project right now and I am trying to figure a solution for running an alternator/generator as a way to charge a battery. I am thinking a small 12v lead acid battery powering LED's...but want no maintenance as far as external power to recharge the battery. And NO! I am not a Tecumseh guy! This will be run from a hopped up Briggs 5HP engine with a billet flywheel. I have no problem fabbing brackets to run this either off the PTO or the jackshaft (less appealing option!). I could run a jackshaft clutch and run it off the jackshaft as an option.
A 12v lead acid battery needs between 13 and 14.4 volts to properly charge. I have seen some small windpower systems that produce the correct DC voltage, I just don't know if 200 watts is enough! Regulators for these are also available so I don't boil the battery!
I have also seen some alternators from larger garden tractors that could work, but I would need to convert it to DC and it may take too much power to run.
I got to thinking about this after seeing "thejoker"'s listing for the Tec alternator that runs off the recoil. I believe those run directly to the lights and not a battery.
Thoughts? Help? Is this idea crazy enough to border on genius?

 

[Harleys Papa]

While I haven't done any research into this, I would say you will have a hard time finding something that will give you the voltage you need at the inconsistent rpm's you will be turning :shrug:

 

[OND]

Hey Eric ...I'm building a 5hp Briggs engine to, and the bike that I'm going to put it on could and should be lighted. I was thinking of the lighting coil under the flywheel....but that's a different lighting coil, block, flywheel and blower housing.... I hope you can figure this out, and let me know if I can help.

This could work...maybe !

Harley Davidson Shovelhead EVO 32 Amp Charging System 1970 1999 | eBay

 

[Tink]

Interesting idea you have.
When I was goofing around with wind generating there were references to DC treadmill motors to charge batteries.
I did not encounter a treadmill motor within the budget(free) .
Here's one gas engine running one...

My Improvised DC Generator Build

 

[CarPlayLB]

HarleysPapa,
car engines run at inconsistent rpm's and they get along just fine! I know I will need to find a "range" to operate, but that will be later in the project!

E
that Harley one is way too many amps! I am thinking like 14 volts at 4 amps should be enough to charge the batteries after using LED lights...I am not putting a boom box on this one! The I/C motor I am building has the lugs for the charging coils, but I will be using a billet flywheel...as my junk has way more power than your junk!:laugh:

Tink,
you are on the right track here. The treadmill motors are talked about a bunch on the internet. I think it still may be too big for what I am wanting.

 

[OND]

I like Tinks Idea E ...but its just to bulky for a mini....:no: You know when we were kids we had the little generator that kick over into the tire...only problem was when you stopped the headlight stopped. Theres got to be something smaller out there.

Powr Port Bicycle Bike Generator Charger Head Tail Light Dynamo | eBay

Motorized Bike Friction Generator Head Taillight Kit 12V 6W Ideal for Most Bikes | eBay

 

[CarPlayLB]

I like Tinks Idea E ...but its just to bulky for a mini....:no: You know when we were kids we had the little generator that kick over into the tire...only problem was when you stopped the headlight stopped. Theres got to be something smaller out there.

Powr Port Bicycle Bike Generator Charger Head Tail Light Dynamo | eBay

Motorized Bike Friction Generator Head Taillight Kit 12V 6W Ideal for Most Bikes | eBay

I am think along those lines. The battery powers the lights and the generator recharges the battery! Generator could run off the jackshaft and charge only when moving.
I am thinking more like this
12 V DC 48Watt Motor Generator Wind Turbine | eBay

 

[OND]

Yea E that's a nice size right there....It would be nice if you could mount it to the front of the engine and run it off the flywheel.

 

[massacre]

I am think along those lines. The battery powers the lights and the generator recharges the battery! Generator could run off the jackshaft and charge only when moving.
I am thinking more like this
12 V DC 48Watt Motor Generator Wind Turbine | eBay

Wow that is really cool
And your crack about the billet flywheel had me dying lmfao

 

[control4userguy]

Some things to consider here are:

-Current charges batteries so is 40W (3.3A) sufficient?
-Where will the battery live? Lead acid?? Ah is proportional to form-factor.
-How will you use the PTO (what, 5/8" or so) to drive a very small pulley? Over-driving a small dynamo won't work for very long
-You want to charge only when the engine is operational? Or, place the battery on a trickle when parked? If latter, might as well skip generator and invest in larger capacity, newer technology, battery and wall charger.

I've looked at this idea coming and going and, for my use, it boiled down to the touring bicycle lighting selections. Self-contained, huge lumen ratings and multi-purpose usage aspect. What eventually killed that idea was the overall usefulness of lighting on a mini bike. Not good economics.

But, I understand, it's fun trying...

 

[CarPlayLB]

Some things to consider here are:

-Current charges batteries so is 40W (3.3A) sufficient?
-Where will the battery live? Lead acid?? Ah is proportional to form-factor.
-How will you use the PTO (what, 5/8" or so) to drive a very small pulley? Over-driving a small dynamo won't work for very long
-You want to charge only when the engine is operational? Or, place the battery on a trickle when parked? If latter, might as well skip generator and invest in larger capacity, newer technology, battery and wall charger.

I've looked at this idea coming and going and, for my use, it boiled down to the touring bicycle lighting selections. Self-contained, huge lumen ratings and multi-purpose usage aspect. What eventually killed that idea was the overall usefulness of lighting on a mini bike. Not good economics.

But, I understand, it's fun trying...

Thanks for your input!
economics aside, I think that 3.3 amps at 14v would be a sufficient charging source. I like the idea of a single large lithium ion battery, but I do not want to have this dependent upon 110V wall charging. Lithium batteries have become so inexpensive that it makes perfect sense...small package, large power delivery, light weight, and possibly more durable than a lead acid battery. My main concern is the volatility of the battery itself. Having sold cell phones for over 25 years, I remember when the LiIon batteries first arrived in the market. There where issues with overcharging/overheating of the batteries that cause them to either bloat, or catch on fire! I have not investigated commercially available solutions for that, but that could be the missing link here!
I also realize that I would need to calculate the right speed to turn the generator and they will not like being overdriven. I am thinking about the possibility of have a machinist friend make pulleys and use a vacuum cleaner belt to drive it. If a gear reduction is needed, we can fab that up as well.
Keep the ideas and comment s coming!

 

[control4userguy]

LiION? No, I was thinking more like a 3S LiPo which would yield close to 12VDC. I have a Blueshape Li-ion that does 90Wh but that thing is large & expensive. The idea is slightly retro as most doing mobile field-charging are using panels.

 

[control4userguy]

The other thought is charge @ 24vdc.

 

[control4userguy]

So, I didn't see you mention a goal here other than to charge a battery. What is it that are trying to achieve involving a minibike (crazy assumption)? Lighting? If so, what type- to see or to be seen? Significant difference in power demand there...

 

[control4userguy]

Here's more thoughts (because I have time now). How about a Sunup unit? Not much power but great form-factor. Also, look into eddy current units. Very little street activity with these right now but there are a few units out there. I still prefer the bottle generator idea myself...

 

[CarPlayLB]

Here's more thoughts (because I have time now). How about a Sunup unit? Not much power but great form-factor. Also, look into eddy current units. Very little street activity with these right now but there are a few units out there. I still prefer the bottle generator idea myself...

Now you're talking crazy talk!:laugh: You are way over my head now!

My plan is to have a minibike with working headlight and brake light. I am not wanting flood light type effects with the headlight! I will use LED's for all lights. I am thinking the lower consumption of power will be beneficial! I did not want to rely solely on generator power for lights as that will not give you anything when stopped. I just figured it would be a better system with a battery that requires little maintenance, daily or long term!

 

[control4userguy]

I got it. LED for a "be seen" condition. That is the easier of the two paths. However, given the fact you do not want to rely on mains-charging, that is what makes this project a little more complicated. So, with that said, if you have a contact who can machine miniature pulleys, an ebay dynamo might work for you. Just for reference, a SunUp spoke unit will run about $125.

 

[control4userguy]

Yet another idea- Find a used PowerBox and remove the pedals, mod the bore for 5/8 or whatever you have and run the output to a small transformer under the seat which then goes to your battery for charging. Since this is a human powered device, serious re-gearing will be in order.

 

[mrpat]

Stepper motors from an old inkjet printer? Those are DC motors. Don't know if they put out enough juice though but heck, you can get them for free. Then some kind of voltage regulator. Voltage regulator is the key with variable rpm's.

 

[mrpat]

USB Bike Generator