reganative bicycle with car alternator???

[mrfeelgooddrag26]

i have a some what weird idea to recharge batterys.
having 2 bikes one would be your e bike the other bike would be a modifed bicycle with a car alternator.
the way im thinking is you take a gear from a motorizied bicycle that smashes toghter on the spokes then mount the alternator in the frame. then take a gear that matches up to the 415 sprocket and mount on the alternator then run a chain and a chain tensioner just like they use on gas bicycle conversion kits. also to contain the power would be some sort of 12 volt car battery on the rear rack???. then when you ride the bicycle around your charging up your 12 volt car battery witch when full you hook into a 12 volt inverter and run your lithium charger or your lead acid battery charger.
on the flip side would it not be easier to have a solar panel and 2 12 volt car batterys and have the solar panel on the roof of your house to charge the batterys? then use the inverter to charge from the energy created by solar?

 

[Drunkskunk]

You could build a stationary bike with a car alternator that could generate power. Unfortunatly, the efficancy of a car alternator is very low. And Lead acid batteries aren't very efficent at being charged. But most importantly, your body can only produce around 150 watts of power sustained, if you're in shape. And of that 150 watts per hour you can make, you're only going to have maybe 75 watts usable going into the 12 volt battery. and from there, you'll lose another 10%-15% getting the power into the Bicycle's battery. So you will spend many hours pedaling hard to save $0.05 of electricity.

Its a nice theory though. It would technically work. The Solar pannel is a better idea, though.

 

[Gregory]

The 36V 22Ah battery you mentioned previously holds 800Wh, so figure at least 8 hours of pedalling at 100W to recharge it! Would be easier just riding the pushie.

 

[mrfeelgooddrag26]

im starting to think solar is the better way to go you can get 100 watt solar panels cheap at harbour freight i might get 2 of thoose and build a lead acid 48 volt battery bank thats tied toghter in series they did it on the tv the colony in the first season all be it they had twice the number of batterys in there battery bank it would still be more than enough power to charge up an e bike assuming i use lithium batterys or lipo and with a dc to ac converter with 48 volts of power should be plenty to charge from the inverter

 

[dogman dan]

Yep, go for the solar setup. At least 80w of panel will be needed to gather 500 or so watthours in a reasonable time, one day if nice and sunny. A 12v system will run an AC charger, with a fairly small inverter. RC chargers often just run on 12v. So that could be an option too.

Pedaling up power is cool, but more useful for smaller wattage needs, like run a stereo, charge a bunch of phones, run some 12v lights for one evening. It's just too much pedaling for a big ebike battery.

 

[999zip999]

You mean I can't put pedals in the back seat of my Tesla and have my kids peddle charge my batteries as we go ?

 

[pdf]

Some good comments here. I would point out, though, that unless you don't have access to the grid, an ebike uses so little energy that there is very little point (except if you just want to do it) to not using the grid. As a data point, I have a round trip of between 13 and 14 miles and use 2.5 cents worth of electricity. I use more energy than that getting my car out of the garage.

However, if you want to do something just for the heck of it, go for it.

 

[lbz5mc12]

I've thought about this before too. Now unlike the little dc generator motors that have a ton of resistance aren't the alternators almost resistance free? Couldn't the alternator actually be spun by the wheel itself and not the cranks? Basically you have your drive side chain, gears and cranks and say the left side of the rear wheel has a gear and chain running to the alternator. So when your ebike is powered by the hub motor it's also spinning the alternator. Instead of using a heavy 12V SLA, you could use one of those lithium drop in replacement 12V batteries. You know the ones that look like SLA batteries but aren't? Of course you'd probably need a recumbent trike/bike or a long cargo bike to be able to fit everything in and balance the weight.

 

[Chalo]

Now unlike the little dc generator motors that have a ton of resistance aren't the alternators almost resistance free?

Not only do they cause a lot of drag when making power, but they require power to energize the field coils-- they aren't permanent magnet generators. They spin freely when not hooked up to anything, but they are less than desirably efficient in normal use.

 

[dogman dan]

Any generator will have resistance proportional to it's output. That's why pedaling a dd motor slow is easy enough to not bother strong pedalers. But speed it up, and the resistance gets more and more.

If you run gas generators, you hear them dig deep under loads, like when you turn on a 1500w heater. brrrrrrrr-BUHHHHHH.

To make power, stationary pedaling would be best, no energy lost to wind and other drag. With the right kickstand, you could do this with a rear hubmotor. But better eat a lot of carbs first. Lotta work to fill a 500wh battery at 50w (after losses) output.

 

[mrfeelgooddrag26]

on most bikes if you take off the rear tire and tube you can use the rim as a pully you get a really big belt and you can hook straight to the rim to an alternator even under load it dosent take much to spin an alternator its alot of work yes but its not hard to do just time consuming

 

[999zip999]

It can be done, but who wants to peddle for 6hr. to charge a battery for 1hr. ride ?
You would be better off to ride with a kite in a thunder strom like old Ben and wait for lighting. With rubber and not steel wheels.