# [EVDL] Pedal Power - bike-alternator-battery charging question(s)



## EVDL List (Jul 27, 2007)

I have been working on converting a couple of vw based kit cars to electric, 
none actually running yet,
so my actual ev excperienced is a bit 'unenriched' at this point - a friend 
has hooked up an alternator
to a 23:1 gear ratio on his exercise bike, and wants to charge a battery to 
say run a fish tank or something,
putting his exercise work expenditure to some practical use. Below is his 
question - I told him that as long as
his alternator puts out a voltage greater than his battery, it will be 
charging; he says he gets his alternator
to 1400 rpm using his 23:1 gear ratio.

Question 1: I thought alternators produced current greater than betteries 
could typically safely take, but maybe with 'pedal power' it's pretty safe 
(?)

Question 2: 1/2 hour of exercise at 2300 rpm - is he going to over charge 
this battery? I suppose someway to watch its voltage while he is pedaling 
would let him know in case he's going to overcharge it or something (?)

Q3.: anything else to be careful of?
Thanks for any advice, the alternator, battery and question details are 
below:

(Seth Myers)

"It's a MotorCraft 100amp, 14.4V alternator out of a 1989 Ford Taurus. 
(that's about all the specs I could find even looking online) The battery 
I'm using is a lead-acid, deep cycle Duralast marine battery, 115amp hours, 
reserve capacity 180, and 1000 marine cranking amps. I'm using multiple 
sets of bike gears and have a 23:1 gear ratio, so am getting about 1400rpms 
out of the alternator as I pedal. (which is about equal to idle speed in a 
Ford Taurus)

My basic question is, when charging the battery with the alternator at 14.4V 
how quickly is the battery charging? Is the full force of the 14.4V 
charging the battery? or is it only the difference between the batteries 
12.8V and alternators 14.4V, so only 1.6V charging the battery, which would 
just take a lot longer to charge...

And, do I have to reach the full 14.4V with the alternator to begin charging 
the battery or is something like 13.5V enough to start the process?"


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Some comments inserted below



> Seth Myers <[email protected]> wrote:
> > I have been working on converting a couple of vw based kit cars to electric,
> > none actually running yet,
> > so my actual ev excperienced is a bit 'unenriched' at this point - a friend
> ...


----------



## EVDL List (Jul 27, 2007)

I got a chance to use a pedal powered auto alternator once at a science
exhibit. It was hooked directly to some car headlights rather than a
battery, though, and controlled by a switch. I remember how hard the
pedaling became when the switch was thrown and the headlights lit up. (This
would be a nice, educational experience for the "gen on a wheel" types.) I
don't think there would be a problem with overcharging a battery - more
likely the opposite.




> Seth Myers wrote:
> >
> > I have been working on converting a couple of vw based kit cars to
> > electric,
> ...


----------



## EVDL List (Jul 27, 2007)

If he is using a sealed battery then he might be able to damage it from
over charging, if he is using a flooded battery, he'll just have to add
water a bit more frequently.

Batteries are rated in how many Amp Hours they can hold. A deep cycle
battery about the size of a car battery might hold 70 amp hours. You
can't overcharge a battery until you put in way more amp hours than it
stores.

Watts = Volts * Amps.
So 100 watts = 10V * 10 Amps, or 100V * 1Amp, etc.
Watt Hours = Volts * Amp hours
1 Amp for 1 hour equals 1 amp hour.

A typical human can produce 100 to 150 watts (for 1-2 hours) on a
stationary bike. An very athletic person can produce 200-250 watts, Lance
Armstrong maybe 300-350 watts.
Assuming a 12V battery: Typically in order to charge the battery the
volts must be above 13V, as you raise the voltage more and more current
flows. As the battery gets closer to being full you need to raise the
voltage even more to keep charging. The typical finish voltage for a
charger is around 14.4-14.8V for a 12V battery.

Lets assume your friend is on the high end of average, and can produce
around 150 watts.
You're going to loose some power/energy in the chain/belt/gears in the
23:1 reduction ratio. Figure 30% if he is using a belt drive, 10-20% with
chain (depending on if it's well lubricated or not) and perhaps 5% with
gears.
Without know what he's using I'll assume 20%

So 150 watt - 20% = 120 watts

Now a typical car alternator is about 65% efficient.
So 120 watts * .65 = 78 watts.
Assuming about 13.5V charge voltage:
78 watts / 13.5V = 5.78 amps

The efficiency of a typical 12V battery (amps in vs amps out) is about 90%
Assuming he is using a 70 amp hour battery and has taken 1/2 the energy
out of it (35 amp hours) he'll need to put about 40 amp hours back in.
That would take him about 7 hours of pedaling. After that he wills start
overcharging the battery.

Over charging batteries mostly just causes electrolysis of the water in
them. With a sealed battery, if the charge current is high enough this
will cause pressure build up and the battery will vent. Since you
basically can't replace the vented electrolyte, this causes serious,
cumulative, damage to the cell.
With flooded cells you have to add the water periodically anyway so this
just means you have to do it a bit more frequently.

> I have been working on converting a couple of vw based kit cars to
> electric,
> none actually running yet,
> so my actual ev excperienced is a bit 'unenriched' at this point - a
> friend
> has hooked up an alternator
> to a 23:1 gear ratio on his exercise bike, and wants to charge a battery
> to
> say run a fish tank or something,
> putting his exercise work expenditure to some practical use. Below is his
> question - I told him that as long as
> his alternator puts out a voltage greater than his battery, it will be
> charging; he says he gets his alternator
> to 1400 rpm using his 23:1 gear ratio.
>
> Question 1: I thought alternators produced current greater than betteries
> could typically safely take, but maybe with 'pedal power' it's pretty safe
> (?)
>
> Question 2: 1/2 hour of exercise at 2300 rpm - is he going to over charge
> this battery? I suppose someway to watch its voltage while he is pedaling
> would let him know in case he's going to overcharge it or something (?)
>
> Q3.: anything else to be careful of?
> Thanks for any advice, the alternator, battery and question details are
> below:
>
> (Seth Myers)
>
> "It's a MotorCraft 100amp, 14.4V alternator out of a 1989 Ford Taurus.
> (that's about all the specs I could find even looking online) The battery
> I'm using is a lead-acid, deep cycle Duralast marine battery, 115amp
> hours,
> reserve capacity 180, and 1000 marine cranking amps. I'm using multiple
> sets of bike gears and have a 23:1 gear ratio, so am getting about
> 1400rpms
> out of the alternator as I pedal. (which is about equal to idle speed in
> a
> Ford Taurus)
>
> My basic question is, when charging the battery with the alternator at
> 14.4V
> how quickly is the battery charging? Is the full force of the 14.4V
> charging the battery? or is it only the difference between the batteries
> 12.8V and alternators 14.4V, so only 1.6V charging the battery, which
> would
> just take a lot longer to charge...
>
> And, do I have to reach the full 14.4V with the alternator to begin
> charging
> the battery or is something like 13.5V enough to start the process?"
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Seth
??? Alternators can put out quite a bit more energy than you or I have. There also fairly inefficent. The system I use is simply a PM motor (an old Corvette radiator fan motor) hooked through a diode to prevent the battery from running the motor. You simply pedal the excercycle until the motor is generating more voltage than the battery. No regulator or anything. Want more amps: Pedal harder. You will have to keep an eye on the voltage so that you don't exceed the batterys max charging voltage.?
???? Its best to use a bicycle on a training stand that normally has fans or some other type of resistance device. I replaced that device with the motor wired in my diode and wired the output to the batteries. I also have a couple of 12V halogens and a fan connected for extra load if my batteries are full.?Having gears is necessary because you will occasionally want to do training at different loads or cadence speeds and the motor?(or alternator) will increase load requirements?through a narrow band of?motor rpms.?
???? When my batteries are low I can maintain?5 to 8 amps for an hour which is not too much but remember there are other losses such as tire resistance on the friction roller.?
???? The first motor I used burned out its bearing in only 30 hours or so. It was not?designed for?large hanging loads. Use a quality motor with a?ball bearing on the front end. No bushing motors. and keep the shaft as short as possible unless?you can support it on the far end of the friction roller. 

???????????????????????????? Rick Miller?


-----Original Message-----
From: Seth Myers <[email protected]>
To: [email protected]
Sent: Mon, 28 Apr 2008 10:18 am
Subject: [EVDL] Pedal Power - bike-alternator-battery charging question(s)



I have been working on converting a couple of vw based kit cars to electric, 
none actually running yet,
so my actual ev excperienced is a bit 'unenriched' at this point - a friend 
has hooked up an alternator
to a 23:1 gear ratio on his exercise bike, and wants to charge a battery to 
say run a fish tank or something,
putting his exercise work expenditure to some practical use. Below is his 
question - I told him that as long as
his alternator puts out a voltage greater than his battery, it will be 
charging; he says he gets his alternator
to 1400 rpm using his 23:1 gear ratio.

Question 1: I thought alternators produced current greater than betteries 
could typically safely take, but maybe with 'pedal power' it's pretty safe 
(?)

Question 2: 1/2 hour of exercise at 2300 rpm - is he going to over charge 
this battery? I suppose someway to watch its voltage while he is pedaling 
would let him know in case he's going to overcharge it or something (?)

Q3.: anything else to be careful of?
Thanks for any advice, the alternator, battery and question details are 
below:

(Seth Myers)

"It's a MotorCraft 100amp, 14.4V alternator out of a 1989 Ford Taurus. 
(that's about all the specs I could find even looking online) The battery 
I'm using is a lead-acid, deep cycle Duralast marine battery, 115amp hours, 
reserve capacity 180, and 1000 marine cranking amps. I'm using multiple 
sets of bike gears and have a 23:1 gear ratio, so am getting about 1400rpms 
out of the alternator as I pedal. (which is about equal to idle speed in a 
Ford Taurus)

My basic question is, when charging the battery with the alternator at 14.4V 
how quickly is the battery charging? Is the full force of the 14.4V 
charging the battery? or is it only the difference between the batteries 
12.8V and alternators 14.4V, so only 1.6V charging the battery, which would 
just take a lot longer to charge...

And, do I have to reach the full 14.4V with the alternator to begin charging 
the battery or is something like 13.5V enough to start the process?"


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

does anyone have experiance with using this system on
an electric trike. Yes i know it is not going to
recoup/generate very much energy but when sitting at
stop lights and pedaling when going down hill there
might be some small gains...not sure it would be
enough to be worth it, just wondering if anyone has
done it??? 




> --- [email protected] wrote:
> 
> > Seth
> > ??? Alternators can put out quite a bit more energy
> ...


----------



## EVDL List (Jul 27, 2007)

Sure. It's best if you use a very efficient motor/generator.

You won't be able to match a straight chain drive for efficiency while
moving (unless you spend a fortune on super high efficiency
motor/generators). But, if you spend a lot of time at stop lights, you can
end up with more usable energy over all by banking energy while stopped. 
Plus it lets you keep exercising, and stay warmed up, at the stops.

I'm thinking of switching to something like a crystalyte BLDC hub motor
for the generator. It's not quite as efficient as my current generator,
but I could use a single ratio speed increaser instead of the two stage
one. This might end up with higher overall efficiency.

> does anyone have experiance with using this system on
> an electric trike. Yes i know it is not going to
> recoup/generate very much energy but when sitting at
> stop lights and pedaling when going down hill there
> might be some small gains...not sure it would be
> enough to be worth it, just wondering if anyone has
> done it???
>
>


> > --- [email protected] wrote:
> >
> >> Seth
> >> ??? Alternators can put out quite a bit more energy
> ...


----------



## EVDL List (Jul 27, 2007)

I noticed a friend's new touring bike had a hub generator on the front
wheel to power the lights and such. Of course, my first thought was
that he'd gotten a hub motor... but no, just a generator. Similar
looking, but smaller.

Z



> Peter VanDerWal <[email protected]> wrote:
> > Sure. It's best if you use a very efficient motor/generator.
> >
> > You won't be able to match a straight chain drive for efficiency while
> ...


----------



## EVDL List (Jul 27, 2007)

> so my actual ev excperienced is a bit 'unenriched' at this point - a friend 
> has hooked up an alternator
> to a 23:1 gear ratio on his exercise bike, and wants to charge a battery to 
> say run a fish tank or something,
> putting his exercise work expenditure to some practical use. Below is his 
> question - I told him that as long as
> his alternator puts out a voltage greater than his battery, it will be 
> charging; he says he gets his alternator
> to 1400 rpm using his 23:1 gear ratio.


1400 rpm is not sufficient for most automotive alternators, although it sounds like the load is lower than the alternators usually see so you may be ok


> 
> Question 1: I thought alternators produced current greater than betteries 
> could typically safely take, but maybe with 'pedal power' it's pretty safe 
> (?)

most alternators made within the last 20+ yrs are internally regulated and only put out what is being used, unless the alternator malfunctions it will not overcharge the battery, although by the standards of the people here the charge profile from and alternator is crude and wont provide the best possible battery life 


> Question 2: 1/2 hour of exercise at 2300 rpm - is he going to over charge 
> this battery? I suppose someway to watch its voltage while he is pedaling 
> would let him know in case he's going to overcharge it or something (?)

overcharging should not be a problem but a voltmeter would be a good idea and an ammeter could give him an Idea of how much work he's doing during his workouts each day

> 
> Q3.: anything else to be careful of?
> Thanks for any advice, the alternator, battery and question details are 
> below:
> 
> (Seth Myers)
> 
> "It's a MotorCraft 100amp, 14.4V alternator out of a 1989 Ford Taurus. 
> (that's about all the specs I could find even looking online) The battery 
> I'm using is a lead-acid, deep cycle Duralast marine battery, 115amp hours, 
> reserve capacity 180, and 1000 marine cranking amps. I'm using multiple 
> sets of bike gears and have a 23:1 gear ratio, so am getting about 1400rpms 
> out of the alternator as I pedal. (which is about equal to idle speed in a 
> Ford Taurus)

the alternator is usually spun approx. 3x engine speed, most alternators don't perform well under about 2500 rpm


> 
> My basic question is, when charging the battery with the alternator at 14.4V 
> how quickly is the battery charging? Is the full force of the 14.4V 
> charging the battery? or is it only the difference between the batteries 
> 12.8V and alternators 14.4V, so only 1.6V charging the battery, which would 
> just take a lot longer to charge...
> 
> And, do I have to reach the full 14.4V with the alternator to begin charging 
> the battery or is something like 13.5V enough to start the process?"

in the vehicle most automotive batteries will charge at anything over 13.2 system volts but of course the charge rate is slower than at 14.5 


> 
> 
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

_________________________________________________________________
Express yourself wherever you are. Mobilize!
http://www.gowindowslive.com/Mobile/Landing/Messenger/Default.aspx?Locale=en-US?ocid=TAG_APRIL
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Very helpful, I too have been wondering about pedal-powering an 
alternator....
I looked up the hub generators - no help there, they are in the 3-10W 
range, and designed not to add much pedaling drag.
I looked up Lance too: the new post cancer Lance can make 500w for 20 
minutes or 350W for hours. There is something about lactic acid and 
slow-twitch muscles for bike racer types. I have heard from a friend of 
a friend that his heart is actually bigger than normal in a healthy way too.

The closest designs I have seen are home-made wind alternators, though I 
was thinking of getting a small DC motor with about the right rpm and 
wattage rating. i.e. 80 rpm and 200 watts. Is that a workable alternative?

John

http://www.peterwhitecycles.com/schmidt.asp
http://www.sheldonbrown.com/harris/lighting/shimano.html
http://www.tdfblog.com/2005/06/inside_armstron.html

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Here's plans for a 120V home-made pedal power version made from a motor:
http://ronja.twibright.com/exciter/
does this look like it would work?

j.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> The closest designs I have seen are home-made wind alternators, though I
> was thinking of getting a small DC motor with about the right rpm and
> wattage rating. i.e. 80 rpm and 200 watts. Is that a workable alternative?

LOL, if you can /find/ an 80 rpm 200 watt motor, it won't be small.

Mechanical power = torque * RPM

Really low RPM means REALLY HIGH torque. High torque motors tend to be
large for the amount of power they produce. The lower the RPM, the bigger
the motor.
I'd guess a 200 watt 80 rpm motor would be at least 2 feet in diameter.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Interesting...What kind of Bike or generator if you
can find out???



> --- Zeke Yewdall <[email protected]> wrote:
> 
> > I noticed a friend's new touring bike had a hub
> > generator on the front
> ...


----------

