Using a car alternator with a bike to power my home? How much energy can I produce?!

Sooo I have to admit that from time to time
I do mistakes which can lead to videos in which pretty much everything goes wrong. Case in point, the video in which I tried
turning an induction motor into a generator so that I can rotate it with my bicycle to
generate power. Now even though the “induction motor generator”
didn't work well back then, I am still to this date interested in hooking up a generator
to my bike and creating my own electrical energy. And thankfully the comment section had the
idea to simply use a car alternator to do that which you can get more or less inexpensively
from Ebay.

And in case you do not know, such generators
are obviously used in cars and are turned by the motor of it in order to create electrical
energy and thus charge up the cars battery to power all of the electronics. So I ordered one those generators and as you
can see it seems to be able to output a maximum of 120A at 12V which equals a power of 1440W
which should be more than enough to power most of my home appliances. So in this video let's hook this alternator
up to my bike in order to finally create my long desired bicycle generator setup and find
out how much power I can truly produce on my own and whether I could power my home with
it! Let's get started! This video is sponsored by JLCPCB! Feel free to visit their website JLCPCB.com
to not only find out what awesome PCB and Assembly services they offer but also to easily
upload your Gerber files and thus order affordable and high quality PCBs quickly. First off let's have a closer look at the
car alternator.

As you can see the front side comes with a
gear that features 6 rips, which is pretty typical for such alternators. The backside was a bit more complicated though
with two big terminals which are both the plus output poles of the system, while the
enclosure is the minus pole. And there were also two smaller pins a bit
more hidden whose function was not obvious yet.

But anyway, to confirm that this alternator
works, I simply hooked up my multimeter to its main output poles and gave the rotor a
good spin and as you can see we get absolutely nothing on the multimeter, brilliant. At this point I thought that because the generator
construction probably comes with 3 main coils whose AC output voltage needs to get rectified
with something like a Sechspuls-BrĂĽcken-Schaltung, the voltage drop of those diodes would be
too high to get a useable output voltage at a low RPM.

I mean the voltage drop seems to be around
1V and my low RPM might be able to create just that. And considering that a car uses at least 1000
to 2000 RPM to get 12V on the alternators output, it was time to rotate faster. So brought in an old bike I had lying around
that came with a decent shifting system, at least for one side of it. I actually had to do some tinkering at the
back wheel in order to get it into the highest gear. But after doing that, I was able to measure
an RPM of around 300 to 400 while powering the bike with my hand. But as you probably already guessed, that
was still not good enough which means we need another additional gear system. And once again it was the comment section
that presented me with the most simple, but promising solution. By simply removing the back wheel, deflating
it and removing its tube as well as its tire, we are left with a rim which we can use as
one complete gear wheel of the system while the car alternator comes with the other wheel.

And since the alternators gear wheel features
a diameter of around 7cm, while the rim features a diameter of around 57cm, we will get a gear
ratio of around 8.14 that will hopefully be enough to turn the alternator fast enough. So next I measured the approximate length
for the mandatory drive belt as well as the width for it and finally decided on this 4
ripe belt with a length of 2.49m, which seemed huge after receiving it but on the plus side,
it fit both sides perfectly and the system looked pretty promising so far. And after reinstalling the back wheel to the
bike it was time to do what I am best at,…..woodworking! I know, my jokes are the best but honestly
I had to create a wood construction that not only holds the front wheel in place, but also
something that elevates the back wheel and holds it in position as well for which I also
had to do some metal working. And after using some zip ties for the back
wheel, everything seems pretty tight and secure. So last but not least I added a big plank
to the back of this wood construction onto which I then aligned the car alternator, before
I secured it in place with metal brackets and a couple of screws.

And just like that the basics bicycle powered
generator setup was complete. So I once again hooked up my multimeter to
the output of the alternator and turned the wheel as fast as possible but as you can see
we still got no output voltage from the alternator even though I reached an RPM of around 1500. Now the reason is actually quite simple to
understand and can be experienced when we turn the rotor which does not oppose any kind
of resistance.

But when we for example turn a BLDC motor
on our own then we can feel some kind of resistance which is due to the utilized permanent magnets
which are actually mandatory to create an output voltage with a generator. Now the car alternator does not feature such
permanent magnets but its rotor comes with an exciter coil that we can power with a DC
voltage and thus current in order to turn it into a magnet.

But after doing a lot of research online about
my particular car alternator, I found pretty much no information on what pin to use for
that, so I had to do some experiments and as it turns out the upper pin here seems to
be somehow connected to the exciter coil. So I simply applied 12V to it while I connected
the minus pole to the chassis and as you can see we get the resistance we were looking
for and we can also create a DC output voltage, awesome. That means that after applying this knowledge
to the bike setup, we can finally create some power.

As a test subject I went with this 12V 21W
light bulb which after connecting it to the alternator and a power meter, can apparently
get powered by this system without a problem but using my hands to pedal was not really
the best solution any more. So it was time to get serious; and after I
figured out how to properly sit on this bicycle construction, I was able to create a maximum
power of around 20W for a brief moment. But notice how the exciter coil current changes
constantly and thereby ruining my effort to pedal at a constant rate. The reasons is the regulator circuit of the
alternator.

When used with a car, it is utilized to basically
create a constant 12V output voltage no matter if drive at a lower RPM of 2000 or a higher
RPM of 5000 by simply adjusting the exciter current. But since I am using a bicycle, this control
circuit is just a hindrance which is why I want to avoid it and directly power the exciter
coil. And after mistreating the alternator quite
a bit, I found the 2 wires which were directly connected to the coil and thus I continued
the bicycle test by using them. As you can see with an exciter current of
1A I got an average power of 8W, with 2A around 12W and 3A did once again only deliver 8W
because the resistance was apparently too big which caused the belt to slip. But with a current of 2A I was able to create
a constant max power of around 20W at which point it was actually a good workout. That means since I personally require around
2500kWh of energy per year for my home, I would have to ride my bike generator setup
for around 14.27 years to produce that amount of energy.

But only of we ignore that we also need 12W
of power for the exciter coil which makes this generator setup almost useless; except
maybe if you want to charge up your phone. But all in all I finally got my bike generator
system thanks to the comment section and I hope that you learned a thing or two as well
through this video. If so don't forget to like, share, subscribe
and hit the notification bell. Stay creative and I will see you next time..

As found on YouTube

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