Bike Generator

[gromike]

I've had a few geared-hubmotor bikes and built a mid-drive a couple of months ago. The mid-drive has no suspension, thin tires, and is one fast bike. That led me to believe that putting the mid-drive motor on a full suspension bike would be so much better. Well, my community bike shop closed and bicycles have been raining down on me. Now I have two decent FSMTB's as donors. Which led me to a thought, I could put a DD hubmotor on one of them and have a head to head comparison of hub motor and mid-drive bikes. Why would I choose a DD hub motor? My thinking is if I put the bike on a training stand and pedal I can generate electricity and charge the battery. Would that work?

 

[fooferdoggie]

there are videos of people trying to power a light bulb. its a lot of work. so if you want a super work out and maybe a week to charge it.

 

[gromike]

I live in earthquake country, so I'm always thinking about how to make some juice.
What can a reasonable fit person put out somewhat continuously. 250 watts, maybe? But that's just a number stuck in my brain. Then the losses of efficiency.
What I probably mean is how much energy could you store in a battery from pedaling a direct-drive hubmotor for an hour?
And, what controller would make that happen?












i

 

[fooferdoggie]

if you could put out 250 watts for a hour you would not need a e bike thats in the start of a pro cyclists efforts.

https://www.amazon.com/Foot-Operated-Generation-Hand-cranked-Generators-Rehabilitation/dp/B0BHQJC5SR?th=1

 

[PCeBiker]

A KT controller allows you to choose between 5 levels of energy recovery.

The better the energy recovery, the harder you have to pedal.

 

[PCeBiker]

You might consider an axle lock to help keep the axle from spinning.

 

[mschwett]

I live in earthquake country, so I'm always thinking about how to make some juice.
What can a reasonable fit person put out somewhat continuously. 250 watts, maybe? But that's just a number stuck in my brain. Then the losses of efficiency.
What I probably mean is how much energy could you store in a battery from pedaling a direct-drive hubmotor for an hour?
And, what controller would make that happen?

the beginning of the lowest category of competitive amateur cyclists is around 225 watts for an 80kg person for 1-3 hours. most people, especially smaller ones, cannot do that. I’d guess more like 150. not sure how much you’d lose in the generation of DC, and then in whatever gymnastics would be needed to charge a battery, but maybe 80%? so, a reasonably trained cyclist riding hard for 3 hours straight could charge a typical medium sized 500wh eBike battery.

interesting to note that this effort would consume around 2500 calories of blood sugar, which have to be replaced by eating food. the carbon footprint of said food is likely higher than the energy required to charge the battery from the grid, if the power sources are good, e.g. the US west coast, parts of Europe etc.

 

[gromike]

I just think it would be cool to have an ebike that can charge the battery.
So, you can just pedal it on the road with regen braking on and it will charge the battery? No trainer needed?
It's not that it cost all that much to add that capability, since I'm going to buy the electrics and put them on a donor bike anyway. My idea of a load is a cpap machine, or a 12v cooler.

 

[mschwett]

I just think it would be cool to have an ebike that can charge the battery.
So, you can just pedal it on the road with regen braking on and it will charge the battery? No trainer needed?
It's not that it cost all that much to add that capability, since I'm going to buy the electrics and put them on a donor bike anyway. My idea of a load is a cpap machine, or a 12v cooler.

no, if the work you’re doing is going into overcoming wind resistance etc, it won’t charge up anything. better to do it on a trainer.

but there are bikes which have regen braking and bikes that charge from pedaling. they’re just not normally designed that way for several reasons.

 

[PCeBiker]

but there are bikes which have regen braking and bikes that charge from pedaling.

My old e-bike does that.

If I pull a brake lever just enough to activate the brake switch, it activates regeneration and you can feel it kick in.
I like the way it works. Instead of wasting all my momentum as heat on the brake pads, it goes back into the battery.
I can see my voltmeter climb to over 40 volts during regeneration.

The e-bike is fully locked to 25 kph, and the motor cuts out at 22 kph.
As soon as I hit 25 kph, the regeneration automatically kicks in and it will not go any faster.

That's when it gets REALLY HARD to pedal. Not only am I fighting wind resistance to go 25, but I'm also charging the battery at probably maximum power.

So I know that a regenerating e-bike can definitely recharge a battery.

 

[PCeBiker]

I just think it would be cool to have an ebike that can charge the battery.

My idea of a load is a cpap machine, or a 12v cooler.

My ebike has a 250 Watt motor but I don't know how many Watts it regenerates at? You definitely feel it though.

If you bought a KT controller and used a trainer, you could set your regeneration amount to what your comfortable with.
It looks like that for a 250 Watt motor you can set regeneration at 0, 50, 100, 150, 200, and 250 Watts?

It all boils down to Watts, how many Watts can you generate, and how many Watts does your device draw that your trying to power?

50 Watts doesn't sound like much as far as an electrical device goes, but it sure is a lot when you have to generate it yourself.

It would suck to spend half a day to generate just enough power to make 2 slices of toast using an inverter.

But, I'm sure that you can easily generate enough power to charge and use your phone and still put some power into your ebike battery as well.

 

[PCeBiker]

My idea of a load is a cpap machine, or a 12v cooler.

My ebike uses three 12v 10 Ah SLA batteries in series to get to 36 volts.

12v is a good number to aim for, because many things run off 12 volts that are designed for use in a car or for camping.

If you charge three 12v batteries in series then discharge them individually or in parallel at 12v, you eliminate the need for an inverter or transformer which are both expensive and waste some energy.

If you've got a bunch of 12v devices, they can plug directly into a 12v battery. (think of things for RVing, fridges, lights, many things run off 12v and most trailers and RVs have a 120AC-12v power supply built-in.)

You can buy a 12v-120VAC invertor that is about 98% efficient, but a "Pure Sinewave" invertor is only about 89% efficient and are more expensive.

Most 120 VAC devices work fine using a regular inverter, but sensitive electronics, like computers, TVs, routers etc. need pure sine wave to operate properly.
Regular inverters make "noisy" 120VAC and that noise can keep sensitive electronics from working and even damage them.

 

[gromike]

I like that idea. A bank of 3 or 4 12v batteries would be handy for powering 12v loads.

 

[PCeBiker]

You could use 18V power tool batteries.

I've thought of putting a pair of my Ryobi battery packs on my ebike to power the ebike, but I never got around to it.

Two 18V batteries would give me 36V to run the ebike.
I could also charge the batteries if the ebike is on a training stand.

I did manage to double the capacity of one of my batteries by adding 5 cells to it.
They wanted $120 for a single high capacity battery.