Now that summer is here, I spend less time on the pedal generator and more time on my mountain bike and going for casual rides with family. Ive found that the more aggressive forward leaning position of the mountain bike isnt the most comfortable for just tooling down the canal path or open road when Im out with the family, so decided to make a beach cruiser of sorts out of an old mountain bike. The goal was a more comfortable, upright riding position, along with some accessories to allow for a more pleasant and safe family outing.

To do the conversion from MTB to beach cruzer, I sourced a few items to accomplish this:

This has been a fun little project, and I feel much more relaxed on family rides, just cruising along with one finger on the handlebars, not a care in the world.

Take a hot shower then grab:

1. A shaving brush https://amzn.to/3fFnZBq
2. A decent disposable razor https://amzn.to/3c8xpEP
3. Glycerine soap https://amzn.to/34bsezc

This pandemic has given all of us an opportunity to try something new or explore an idea that we would have otherwise not had time to do. Thanks to being stuck at home, here’s what I decided to do with my new found time. For many years I’ve been had an interest in human powered electricity, and my first adventures pursuing those interests resulted in my pedal generator designs (exercise bike, bike trainer and spin bike versions). I thought it might be a fun challenge to build a rowing machine generator.

Building a rowing machine generator has some unique challenges, mostly due to the2 cyclenature of the rowing machine. Cycle one where the chain is pulled and power is created, and cycle two is the return stroke where no power is generated. In this design I do a couple of things to solve the challenge of smoothing out this cyclic power:

To make the story short: these two things did the trick and I’m able to generate 100-120 watts steadily and get in a great full body workout.

Let’s get into how I built it. A great big shout out goes to Jim Flood for coming up with and sharing his rowing machine plans that can be built with common lumber and wood tools and a few other parts. Check out his website athttps://openergo.webs.com/

I took Jim’s plans for the Mark 1 design, followed them almost entirely as he describes, but instead of using a bicycle wheel and some fins for resistance, I put in an e-bike motor along with some a circuit to charge or power electronics. The circuit is basically this:

E-bike motor-3 phase bridge rectifier-meter-ultracapacitors-charge controller

The charge controller is a 24v-12v step down controller that connects to a couple automotive sockets which can be used to charge phones, laptops or power a TV or other devices with a DC to AC inverter.

Let’s talk about the build.

The first minor hurdle: Jim’s plans are all in metric. I did some quick conversions to come up with similar dimensions in inches. If I’d had ametric tape measure, I probably would have just used his dimensions and been done with it.

I picked up some fixed casters to use as part of the sliding seat, and decided I wanted to put a couple grooves for the wheels for a track. I used my router table to add a groove with a round nose bit the top of a couple 24’s, which would be the basis of the rower. A couple small boards in the back for one support, some 30 degreecuts here,60 degree cuts there for other boards along with some leftover deck screws and the frame was together in a couple hours. One tip, I first put on the back base and cross support, then shimmed up the front until it was level, then clamped and screwed the front braces on. The key distance you need to keep in mind is the width of the top posts needs to be around 135mm, the width of a standard bicycle rear end. I used a 24 and a 3/4” pine board to get the right thickness. I ended up adding a cross brace later on (see top photo or photos further down) in the front just under the e-bike motor as I noticed some twisting due to torque while rowing. The cross brace addressed this.

The sliding seat was pretty straight forward. I used some more of the 3/4 pine board I had to make the base, adding a couple 2x4s for bracing. I then measured the distance from one groove to the other (bottom center to bottom center) and used that distance to center the caster wheels on the seat. Once built and placed on the track, a fancy chair cushion makes for a comfortable rowing session!

To create a mount for the e-bike motor (generator) I notched out a couple pieces of steel so the e-bike shaft fits in the notch, then mounted those two brackets onto the frame.

The e-bike motor shaft has flat sides on it, 10mm wide. So I made 2 mounts out of slotted flat bar using my reciprocating Dremel MultiMax.

For the flywheel, I had a local water jet cutting company create a couple 1/2 thick steel donuts. I gave them the inside diameter just inside of where the machine screws mount the side plate of the e-bike motor, and a little under 18 for outside diameter. These each weigh about 28 pounds, total of 56 pounds. With the flywheels in hand, I then took off the side plate of the e-bike motor and overlaid it on each flywheel marking where the machine screws needed to go. Using my drill press, I drilled out the mounting holes (slowly, applying oil as I went for cooling and ease of drilling). Due to the 18 diameter of the flywheels, I needed to take the head unit off my drill press, overlay the flywheel, then re-mount the head unit in order to get the drill bit in the right location.

Rather than use the multiple gears the motor came with, I swapped it out for a BMX style single speed freewheel. The first one I tried was super loud, the second one was a little more expensive (Shimano) that is much quieter.

You could use the multi-gear cassette if you like, I just wanted more control over the chain line going to the jockey pulley to limit the chance of chain derailment.

Flywheels mounted on motor, motor mounted onto rower with the customized slotted flat steel plates using a couple nuts and bolts.

For a handle, a 1.25 oak dowel felt good in the hand. It came in 36 lengths. A 20 cut, with a hole in the center for an eye bolt seems just right. A couple wood screws with duct tape on them serve as the stop or rest for the handle when not in use.

For the chain, I used 2 full length bicycle chains, connecting them together, and on the ends with Nite-ize25# clips. I used a jockey pulley as a guide just below the e-bike motor. AtfirstI mounted the jockey further back, but found the stroke was too short and the Nite-izeclip would hit the pulley and derail the chain.

I used an exercise band to provide tension to pull the chain on the return stroke. I bought a set with different tensions or “weights”, thinking I might need to adjust to a stronger or weaker band. I started with the 10# band, which worked perfect.

I ran the band to a wall mount pulley mounted to the rear brace and used a metal hook through the loop on the band to the front of the rower frame, just under the e-bike motor

I decided to get a little creative with the other 16 of dowel. Using a 1.25 Forsner drill bit, I drilled through the rower frame and inserted the 16 dowel. I then drilled a couple 8 sections of 24 with the same bit, right at the edge. I mounted those on the 16 dowel, then screwed on a couple 3/4 by 12 pine boards to the base 2x4s on the dowel. Adding large washers and wood screws to the ends keeps the foot rests from going off the end. Finishing touches included adding a heel rest (make this 1/2 or more tall to keep your heal from lifting out on the return stroke) and some velcro straps (screws with washers to limit tear out).

Lets dive into the circuit used on this rower generator. Looks like a mess, I should have used a bigger project box for a little more room, but it all tucks in there nicely.

Its actually not too complicated. The 3 thicker wires out of the e-bike motor are the 3 phases of AC (alternating current) that we want to convert to DC (direct current) so we can charge/power stuff. To convert AC to DC, we use a 3 phase bridge rectifier. I chose to make my own using Schottky diodes, but you can use a pre-built one if youre not up to making one. I like the Schottky diodes one better because it doesnt generate as much heat, and is therefore more efficient. I soldered some 4mm banana connectors onto the 3 AC wires and onto the bridge rectifier. I find using helping hands makes soldering tasks much more manageable. I covered the exposed wires and connectors with heat shrink tubing. I used 12 guage wire and Wago connectors where I could to limit how much soldering I had to do, and to make it easier to change stuff around if I chose to. The charge controller takes the 18-36 volts of DC coming from the bridge rectifier and turns it into a useable 12 volts suitable for automotive chargers, like USB chargers, laptop chargers and inverters. I connected a couple automotive sockets to the charge controller, you could add more if desired.

Ive been able to consistently generate 120 watts with this rower generator.  Thats a comfortable workout for me, but if I want to step it up, Ill need to invest in some bigger capacitors, then I believe I should be able to go well over 200 watts.  The little ultracapacitors I used are the limiting factor.  I could add more of them in series, but the connection point on these for the wire only allows a really small gauge of wire to be used and I suspect will limit the watts that can be pushed through.   Once I get some extra spending money, Ill pick up 3 of those monster ultra capacitors and report back how it goes!

I welcome any questions on building this, and please let me know if you do build it!  Your support motivates me to keep doing these projects and following the Amazon links helps me pay for hosting this site along with funding my crazy experiments!

If youre looking for a way to build an inexpensive but powerful and efficient pedal charger, youve come to the right place. When comparing bike generator plans, here are some things you may be wondering:

Before I came up with my pedal generator designs, I looked at many of the plans you will find on the internet. Some plans are better than others, but I would argue the plans youll find here at Genes Green Machine are superior for the following reasons:

You can find other bike generator plans (or even products for 100s of dollars) on the internet, but look closely at all the details and I think youll find the faults with those designs and why the plans youll find here are well thought out and among the best options. Ready to get started? Go to the Bike Generator Plans!

Following the theme of my bicycle trainer pedal generator, I wanted to build something with a more substantial flywheel in order to take advantage of momentum the added weight will provide. An exercise spin bike is a perfect candidate for making a pedal generator with just a few parts and fairly simple electronics. Like my other design, we will use an RC motor and a 3 phase bridge rectifier for the core of the design. This design should be adaptable to most other spin bikes with little or no modification.

Here’s what you’ll need for this project:

Aspin bike. I’m using one from Sports Authority, but most are of a similar design. If you don’t have one,Amazonhas some for a reasonable price, also look on Craiglist, garage sales, etc if you dont want to buy a new one
140KvRC motor, this thing is capable of 1200 Watts and 34 Amps so this wont limit our max potential!
35 Amp 3 phase bridge rectifier
DC Meteror thisbigger one, both are powered by the input voltage
Wire, I use 12 GA, you can use smaller (14 or 16 GA) if you dont plan to generate 100s of watts
Female disconnects, also known as spade connectors to connect to the bridge rectifier and the car sockets
3 to4mm bullet connectorsandheat shrink tubingOR
MT603 wire bullet connector (my motor came with a Female MT60 connector so that’s the path I took)
Zinc Steel flat punched bar
All threador bolts, go with .25 inch or whatever size the holes are in the punched bar for a snug fit. I went with smaller bolts so the drilled holes in my spin bike is smaller and not very noticeable if were to ever want to sell the spin bike in the future. If you are going all in, go full size, because the mount will be more solid!
Nuts
Lock washers
Thread locker
a bunch offender washersthat match your all thread rod or bolt diameter
BaneBots T81 8mm Hub(get the right size for your RC motor shaft if you choose a different motor)
BaneBots Wheel 2 7/8”
bungee cord(s)
Radio Shack Project box

U bolt to attach project box to handle bar measure your spin bike handle bar to get the right size
12v car sockets, 2, 3 or more depending on the size of your project box and how many things you want to charge at once. You can also consider getting asplitter/extenderas well.

5 Conductor Wago Connectorsto wire connect the meter to multiple car sockets
heat sink or cooling plate for the bridge rectifier if you dont go with theRadio Shack project box

Additional/optional componnets:

12v battery jump starter
12v DC to 110v AC inverter
USB car charging adapters(this6 USB chargeris a also a good choice)
USB fan(must have for me to keep you cool!)

Tools:
soldering iron
some goodsolder
flux
helping hands
hack sawto cut the all thread
drill
drill bits
ruler
measuring calipers
wire stripper/crimper tool
metal file
snap ring pliers
Allen wrenches
adjustable wrenches

Lets figure out how to choose the right RC motor for this project. Our goal is to have a motor spin at a rate that will generate between about 12 and 15 volts when we are spinning on the exercise bike. RC motors are rated by how many volts they produce per RPM. A 1000Kv motor would need to spin at 1000 RPM to produce 1 volt. To get to our 12-15 volt range in this case, wed need to spin the motor at 12,000 to 15,000 RPM. Lets get some basic measurements from the spin bike.

The circumference of the flywheel on my spin bike is 57 inches

Pedaling the spin bike at a comfortable pace rotates the flywheel between 250-350 RPM, which I confirmed using adigital tachometer

The BaneBot wheel we chose is 2 7/8 inches diameter = 2.875. Youll recall that circumference is Pi times diameter. The circumference of this wheel is about 9.

If we take the low end and use 250 RPM and multiply that by the 57 inch circumference of the flywheel, we get 14,250 inches per minute. Dividing the 9 BaneBot wheel circumference, we get 1583 RPM. We want our motor to produce 11-12 volts at this RPM, so divide by 11 and 12 and get 131.9 and 143.9. So our target motor should be around 140Kv. We found thisBalancing Scooter RC motorthat fits the bill.

If you have a significantly different circumference flywheel, or choose to use a different drive wheel than what I have, you can use the above steps to determine an appropriate motor to use. Otherwise, just use the140Kv motoras I have.

There are many ways you could mount the motor, but in this project we choose to use 2flat punched steelbraces along with some nuts and bolts/all thread and washers. First you’ll need 2 equal lengths of flat punched steel.

7 or 8 inches each is fine use your hack saw to cut, then file the rough ends so no one gets cut on the burrs.

Now the trickiest part measuring and drilling the holes to screw onto the motor.
measure the distance across the face of the motor from one threaded hole to the other hole on the opposite side of the motor shaft. Do this withcaliperspreferably. Check and double check your measurement. Mine was 38mm center to center. Now, measure and mark where you should drill two holes on each side of a punch hole in the flat steel in about the middle of the bar.

The motor shaft will go through the punch hole. The bolts for my motor were 2mm, so I drilled holes slightly bigger so the bolts would fit in. Drill the holes and mount the motor with theAllenhead bolts that came with the motor.

Mount the T81 hub on the motor shaft using the right sizeAllenwrench.

Mount the wheel and install the locking snap ring that comes with the hub. This task is much easier if you havesnap ring pliers, but can be done with other pliers, a screwdriver and determination.

Next step for the motor mount is to use all thread or a 5 to 6 inch bolt to connect to the second bar/brace. Tighten the bolt, nut and lock washers on the non-motor sideflat punched steel bar. Put on 2nutsandlock washerson the other side with the motor mounted bar sandwiched in the middle, but leave them loose. Place the non-motor bar against the right inside brace of the spin bike just above the flywheel. Adjust the bolts left or right to get the BaneBot wheel in the center of the flywheel, then tighten the bolts.

On the spin bike, carefully measure and drill 2 holes, just above the flywheel, you want to be just high enough to not touch the flywheel with the all thread or bolt. Use a stack offender washers, along withlock washersandnutsto mount the motor assembly to the spin bike. Use enough washers to center the BaneBot wheel with the spin bike wheel. Once all lined up, tighten all the nuts. Somethread lockercan also be helpful as vibrations from spinning may loosen the nuts.

Final step in the mounting is to add abungee cord(I used 3 little ones) to add some tension from the motor wheel onto the spin bike fly wheel. The ends of the bungee’s hooked onto the transport wheel brackets of my spin bike, hopefully yours is similar. Only hook up the bungee when using the generator, otherwise you may get a flat spot on the rubber wheel.

We have the motor mounted, now we need to make some electrical connections. We need to take the 3 phase alternating current of theRC motorand convert it to DC using the3 phase bridge rectifier. The motor I have comes with afemale MT603 wire bullet connector so I just made a 3 wire whip with one end having amale MT60bullet connector and 3female spade connectorson the other ends of the wires.

These 3 female spade connectors plug into the alternating current spade contacts (marked with a squiggly that looks like an S) on the3 phase bridge rectifier.

Order of connecting these wires doesnt matter. Next we need to come off of the DC plus and minus posts and go into the DC meter (optional, but highly recommended). TheDrok meterI used has some wires with alligator clips that seemed to connect securely enough to the rectifier. Maybe I’ll add some spade connectors later. On the output side of the meter, we’ll connect to a12v socketor two. One socket is easy (use the alligator clips), two or more will need a splitter of some sort. I used some5 wire connectorsI had, but you can splice wires together, use adistribution block, somewire nutsor whatever.

Once you have it all hooked up, give the bike a spin and see how many volts the meter reads. The goal is to have 11-15 volts, which is ideal for usingcar socket chargersandinverters. If the voltage is too low, pedal a little faster. If that isn’t working, you may need to use a smaller wheel on the motor to get the RPMs up. If the voltage is too high, pedal slower or use a larger wheel on the motor. With the combination I have, the140Kv motorwith a2 7/8” BaneBots wheelputs me right in the sweet spot for voltage.

Lets tidy things up a bit by putting the electronics in a project box. I like the ones fromRadio Shackthat have an aluminum bottom plate on them because we can use it as a heat sink for the bridge rectifier, which is especially important if you are pushing 50 or more watts for any period of time. The size of the project box really depends on how many12 volt socketsyou want to use, along with the size of theDC meter. In the project box shown, I put in two12 voltsockets, aDrok DC meterand the3 phase bridge rectifier. I could have easily put 2 more sockets in this box. Cutting the hole for the meter was the most challenging, but heres the approach I took. Measure the dimensions of the multi-meter. Placemasking tapeover the area you plan to cut out for the meter. Measure and mark on the tape where to cut, then use a sharputility knifecut out the hole. Start gently to be sure to stay on the lines. Keep tracing the lines with the blade, pressing firmer and firmer until you cut through the plastic. Im sure there is a better way to do this, but with patience this approach works. For socket holes, a1 3/16 hole sawdoes the job very nicely. Drill a hole in the metal backing for the bridge rectifier, and use a nut and bolt to secure. I also used aU boltto mount the box to the handlebar (measure your handlebar and get the right size U-bolt). A couple more holes in the metal plate will be needed to mount the U bolt. You can either drill another hole in the metal plate for the wires to go through, or you can cut/drill in the side of the plastic box. You can get fancy with awire clampif desired. I didnt this time, I just notched the plastic with somewire cuttersfor the wires to go through.

Charge!

Okay, the moment weve been waiting for lets start charging and powering things with our human powered generator! Drop in some 12vcar phone chargers, plug in some devices and see how easy it is to put power into them. You may want asplitterto allow connecting more devices. Abasic 12v to USBsocket charger will only put about 5 watts to your mobile devices, which is why I suggest using somebetter quality chargersthat can put 10 or more watts into your phones,tablets,e-readers,portable battery banksand other devices. Youll also find having afana welcome addition once you start pedaling.

The more devices you plug in, the more resistance youll feel as you pedal. For me, anything under 50 watts doesnt feel like much resistance at all. 75-100 watts begins to feel like a good workout. Around 150 watts is about my limit for a 30-60 minute workout.

Heres some typical devices and the watts to power them:

iPhone 7/8/X 10 watts with adecent charger
QuickCharge 3.0 phone 15 watts
USB Fan 3 watts
Makita 18v automotivebattery charger 70 watts (I use this in combo with theirUSB adapterto charge slow charging devices like iPads, Kindles and other portable battery packs)
32HD LED TVthrough aDC to AC inverter 30-60 watts
55HD LED TVthrough aDC to AC inverter 50-120 watts (varies widely by model/features)

For generating and powering mobile devices like cell phones and USB battery banks you wont really need to add in a 12v battery as buffer. If, however, you are going to power a TV or other devices through aDC to AC inverter, youll want to consider adding a battery. One of the nice things about this design is adding a battery to the circuit is quite simple and requires no additional electronics because the3 phase bridge rectifieracts as a blocking diode (its actually a circuit made with a handful of diodes), preventing the battery from putting power into and spinning your RC motor! The easiest way to add a 12v battery is with acar power bank or jump starteralong with asocket to socket adapter. Plugging in the battery will power the DC meter and provide a voltage reading on the battery. Anytime you are producing more volts that that reading, youre putting amps into the battery and powering your devices. Be careful, however, to not spin so fast that the voltage goes over 15 volts as this could damage the battery.

Adding the battery will act as a buffer for powering devices that are spiky, in other words, that need a bunch of power to start or during various phases of operation, then settle into a more manageable power draw. I found trying to power a 55 LED TV was difficult without having the battery as a buffer. It wasnt that I couldnt generate enough power, it seemed that my pedaling wasnt smooth enough current. Adding the as battery as a buffer solved this problem.

Why would anyone want to build a pedal generator?  There are many reasons.

Whatever the reason, youve come to the right place for an easy to build, efficient bike trainer generator.  In this post I will provide step by step instructions and all the information youll need to source the parts for this project.  Ive always had an interest and fascination with alternate energy and human powered energy in particular.  As a fair weather mountain biker, I find pedaling on a trainer or spin bike in the off season uninspiring, and often think what if I could harness some of this energy, or I wonder if I could power the TV Im watching while I pedal.  I wonder no more.

I’ve checked out many pedal generator products on the market as well as in the DIY world and found the commercial products for sale were too expensive, and the DIY projects were often really complicated and/or required you to take your bike apart to hook it to the generator.  My first attempt at a pedal generator was expensive to build, although not extremely complicated.  So I set out to design a low cost and easy to build bike generator that you just drop in your bike when you want to use it, allowing you to easily take your bike for a ride when not generating electricity.  

I built this bike generator so I could charge my iPhone and other mobile devices while I get a workout.  If I want an easy workout, I’ll just charge my phone and a battery pack or two.  If I want a more challenging workout, I add more stuff to charge, or power TV!

Some things I’ve charged or powered with my bike generator, and the typical watts they require:

The more watts you plug in to power, the harder it is to pedal. Most people should be comfortable with anywhere from 40 to 150 watts.  Trained athletes can generate upwards of 600+ watts, but not for extended periods of time.

Some people have a need or desire to charge a 12 volt batteries, and this bike generator will do that if desired, but I would suggest that direct charging/powering is more efficient due to losses in charging lead acid batteries (15%), so putting 100 watt-hours in gives you only 85 watt-hours out.  Read more about this in my blog post: http://genesgreenmachine.com/direct-charge-grid-tie-battery-bank/

Parts list:   

Optional parts:

Tools:

For less than a couple hundred bucks you could have a working bike generator (assuming you have most of the tools) far cheaper than most products on the market, and much easier to build than other DIY designs.  Let’s get started!

Detailed build video:

Step one:

Unscrew the 3 screws holding the outer shroud on, remove shroud.  Take magnet resistance parts and resistance cable out of bike trainer, along with the metal ring of magnets inside the outer shroud.  The metal ring was glued in a few spots on mine so took a little work to get out.  

Step two:

Add the shaft coupler.

The motor I am using has an 8mm shaft, and the trainer has a 10mm shaft. This shaft coupler connects the two shafts together quite nicely. I tried a grub screw style shaft coupler, but it made a really bad vibration, this one worked great! If you use a different trainer or RC motor, be sure to measure what you have before ordering the shaft coupler they make many different sizes and you should find one that will work.

Put on the coupler, tap with a mallet if needed to get it seated all the way in being careful to not tap the shaft out (brace the flywheel side when tapping). Tighten the Allen screw on the trainer shaft side.

Step three:

A bit about the RC motor selection process math alert!

In selecting an RC motor, we need to determine which motor will give us between 9-15 volts at normal pedaling speeds:

Attach RC motor to bike trainer housing. Drill the center hole of the shroud a little bigger so the RC motor shaft wont rub. Screw on the + bracket to the RC motor.  Place over the shroud hole as close to center as possible.  Align holes in bracket with solid part of shroud, mark holes, drill and bolt the + bracket to the shroud.

You can also connect through the inside of the shroud as shown below.

Both ways work the real purpose is to keep the motor base from spinning, so there isnt much pressure on these connection points.

Step 4:

Replace shaft housing, connecting to the shaft coupler.

Attach 8mm RC motor shaft to shaft coupler and attach trainer housing back on trainer.  I found drilling a hole in the bottom of the housing made it easier to tighten the Allen screws to the RC motor shaft.  Replace the 3 screws that hold the housing on, check for clearance by spinning the shaft, if all good tighten the Allen screws onto the RC motor shaft.  If something is rubbing, you may need to move the shaft coupler further onto the 10mm trainer drive shaft and try again.

Next well cover the electrical here a diagram of the wiring:

Step 5: 

Connect motor to bridge rectifier.

The 3 phase bridge rectifier sounds fancy but serves a simple purpose, it will convert Alternating Current (AC) coming from the 3 wires of the RC motor into Direct Current(DC) which is useful for charging.  A small amount of voltage is lost in this conversion process (about 0.7 volts), and some heat is generated, but this unit has substantial cooling fins so heat should not be a problem at the amperages we will be working with.  Okay, let’s make three (3) wire connectors between RC motor and 3 phase bridge rectifier well need bullet connectors on one end and female spade connectors on the other.  Solder 3 x 4mm bullet connectors to 3 equal lengths of wire, then cover with heat shrink tubing to insulate from shorting with the other bullet connectors. I’m using 12 AWG wire, you could go as low as 18 AWG wire. Crimp and/or solder 3 female ⅜” spade connectors to the other ends of the wires.  Finish with heat shrink tubing if desired.  Connect the bullet connectors to the RC motor wires, connect the 3 other ends to the 3 Alternating Current (AC) male spade connections on the bridge rectifier.  The order of the connections to between the bridge rectifier and the motor make no difference.

Step 6:

Connect to the DC side of the bridge rectifier.

Add ⅜” spade connectors to a black(-) and red(+) XT60 wire assembly and connect to the 2 Direct Current (DC) male spade connections on the bridge rectifier, ensuring to put the red(+) on the + connector and black (-) on the connector.

Step 7:

Add a meter.

Adding a meter is optional, but strongly recommended to help you not go over on voltage, and to help measure how many watts you are actually producing!  For our build we used an RC power analyzer connected using XT60 connectors.  This meter will show Watts, Volts, Amps and scroll through Watt Hours (Wh), Amp Hours (Ah) and other measures.  The XT60 connectors make solid circuit contact and prevent plugging things in the wrong way.  Wire so the “source” is the bike generator, soldering each connection and sealing with heat shrink tubing.

Step 8:

Add a car socket adapter in the parts list we link to a 3 port socket connector that should be suitable for 80% of users.  The 18 AWG wires limit the total wattage to about 150 watts, which is fine for most people and has been plenty for me, but strong riders may want to build something with 12 AWG wire using separate sockets and a project box.  To hook up the 3 port socket adapter, just solder on the XT60 connector to the matching wire colors, add some heat shrink tubing (put the tubing on before soldering, far up the wire so it doesn’t get hot) and plug in!

Step 9:

Get charging!  If you just plug in car charger adapters, most will start charging at around 9v input, and the good quality ones (like the Anker models referenced in optional parts) will handle up to 24v input without a problem.  If you only charge with these type chargers, you can pretty much pedal to your hearts content and not worry about limiting voltage if you followed the parts design outlined above.  Need an easy ride, just plug in a cell phone or two.  To add more resistance, add more car adapters and devices.  I’ve tested this generating up to about 225 watts.  It can go higher, but that’s nearing the limit of the 50 year old pushing the pedals (me!).

If you want to power something that plugs into a wall outlet, or have a desire to charge a 12v battery, then you’ll need to be mindful of the voltage you are generating, and keep it to under 14.7 volts or so.

Here you will find everything you need to for an easy to build, powerful, quiet stationary spin bike pedal generator. Ill cover tools and parts needed, along with diagrams for wiring and things Ive learned along the way that can make your build a success. Let me start by saying that I am not an electrical engineer, nor a mechanical engineer, this was just something I was interested in and wanted to go about building. If you have suggestions or a better way to build it, Id love to get your feedback!

Lets get right to it! First youll need a spin bike, also known as a stationary bike or exercise bike. If you dont have one already, check eBay, Craigslist or garage sales. Otherwise, there are several  models from Sunny Fitness that should work. Be sure to get one with a chain drive (not belt).

The next key component is a e-bike hub motor. Hub motors come in many different models, front, rear, 24 volt, 36 volt, 48 volt, 350 watt, 500 watt, 1000 watt and so on. For this to work, youll need a front hub e-bike motor, as front hub motors will fit between the typical spin bike front braces. Youll also need to have  a disc brake mount on the hub motor. More on this in a minute. For my build, I went with a 24 volt setup, using a 24 volt 500 watt motor. You can use a 36 or 48 volt brushless gearless front hub motor with disc brake mount if you cant find the 24 volt variety, just make sure you get an appropriate step down converter to match.

Now you may be wondering how we plan to drive the e-bike hub motor with the chain drive of the spin bike. This took me a little while to figure out, but it just so happens that some people use the disc brake mount on a bicycle to mount a fixed gear. There are a few companies that sell sprocket kits just for this purpose. The one I recommend is the 16 tooth sprocket from Origin8. Just take off the free hub adapter parts (the red things) and bolt the sprocket on the disc brake mount on the motor. Some Loctite might be advised.

Once the sprocket is on the motor, pull the original flywheel off of the spin bike and replace it with the hub motor, ensuring you route the chain over the newly installed sprocket.

When you turn the e-bike hub motor the permanent magnets pass over the the copper coils of the stator in the motor, generating alternating current electricity. To convert to more usable direct current, we need simple component called a 3 phase bridge rectifier it sounds really complicated, but it is really just a basic circuit which takes the 3 wires of alternating current from the hub motor and converts it to direct current. The fat wire coming out of the hub motor consist of the 3 wires just mentioned, and some thin hall effect sensor wires used by a typical e-bike controller to determine RPM of the motor. These sensor wires can be clipped and/or tucked out of the way. For the remaining thicker 3 wires, well put female spade connectors on the ends and connect them onto the 3 posts of the bridge rectifier marked with the s squigglies. The other two posts on the bridge rectifier deliver positive (+) and negative (-) direct current. The side of the bridge rectifier has a map of the posts.

Next challenge the voltage coming out of the bridge rectifier is anywhere from 20 to 40+ volts. This is assuming a 24 volt hub motor spinning anywhere from a leisurely pace to frantic sprint . Wed like this power to be a steady 12 volts so we can charge cell phones, iPads, and run things like fans and coffee makers. With 12 volts output, we could also use a DC to AC converter to charge our laptops, cordless drills or power a TV. Enter the step down converter! If you go with a 36 volt motor, you may want to get a 36 volt step down converter. This critical component is often used in electric golf carts to step down the 48/36/24 volt battery power in the golf cart to 12 volts to run fans, radios, lights and other things that plug into a 12 volt car socket. Heres a diagram of the wiring, including an optional multi-meter it really is very simple.

Thats it! Those are your basic components to make it all work.

This really is a fun project. With most of the challenges of how to make it all work spelled out above, whats stopping you from building your own pedal generator?

Some optional components, basic tools and supplies you may need to complete this project:

Please support this site by purchasing any needed components through the links above. It will help pay for hosting this site, and will fund future adventures in alternative energy projects Id like to pursue.

Check out the latest updates Ive done to this design!

What is the best use of your pedaling time on a pedal generator? There are 3 typical avenues you could direct your watts:

There are advantages and disadvantages to each of these.

I advocate for direct charging, and Ill explain why.  Going out on a limb here, but Ill assume everyone uses a mobile device or two, and maybe a tablet. Assuming you charge these things regularly, lets look at the scenario of charging these using the methods above.

Direct charging:

Pedal generator - Charge controller (90%+ efficient) - 12v car charger  - device(s)

Grid Tie:

Pedal generator - Grid tie inverter (80% efficient) - 110VAC wall charger - device(s)

Battery Bank:

Pedal generator - Charge controller (90% efficient) - Battery bank (85% efficient) - DC to AC inverter (90% efficient) - 110VAC wall charger - Devices(s)

As I discovered in the previous blog post, wall chargers have losses up to 30%+, whereas 2 out of the 3 car chargers tested had losses of just over 1%. Using either grid tie or a battery bank may result in 50% or more of your efforts wasted on conversion losses.  I do want to point out that the charge controller used in my pedal charger design is 90%+ efficient, so you will lose up to 10% in that conversion, resulting in a max of about 12% loss if you include the car charger losses but far better than the other two alternatives!

Have you ever wondered which kind of charger is more efficient?  Are wall chargers we use to charge our devices just as efficient as 12v car chargers?  In this blog post, youll find out!

I grabbed 3 quality wall chargers and 3 quality car chargers with the intent to see how many watts each consumed, and how many they actually put into an Apple iPad Mini.  To find these measurements, I used a wall AC meter, a DC power meter, a USB dongle meter and an Anker 1 ft Powerline cable.  Here are the results.

Wow!  I didnt expect to see such a difference in efficiency between the wall chargers and the car chargers.  After a little digging, it makes sense the wall chargers need to convert AC (alternating current) into DC (direct current), whereas the car chargers are just changing 12 volt direct current into 5 volt direct current that is the standard for USB.  Even the worst car charger was 10% more efficient than the best wall charger crazy, right?

I suspected AC wall chargers were less efficient from my experience using my pedal generator.  I could see the wattage used by the wall chargers put more of a load than the DC car chargers, but it was great to quantify the real difference.  I had no idea how much more inefficient wall chargers were!  I will definitely be using car chargers whenever possible for the most efficient charging of my devices.  On the other hand, if I need more of a challenge on my pedal generator, I can always substitute in the AC chargers!

If youre living off grid, you may find this information very helpful in deciding how you should charge your mobile devices.  Directly charging with solar or a pedal generator would be the most efficient way to go, rather than dumping all power to a battery bank, then converting to AC and charging with a wall wart (thoughts of all the efficiency losses in this cycle is making my head spin!).

I use a stationary bike pedal generator to charge my cell phone and other devices.  Getting the most watts into my devices helps me make the most of my pedaling time. A typical 1 amp charger puts about 5 watts into most phones, but will take several hours to charge even the smallest device battery. In this post, Ill compare the output of several chargers and how many watts they can put into my iPhone 7 Plus.

Chargers included in this test:
1. Original Apple 5 watt wall charger
2. Original Apple 12 watt wall charger
3. RAVPower 24W 4.8A (2.4A x 2) Dual USB Wall Charger
4. PowerGen 4.2Amps / 20W Dual USB Car charger
5. Anker 24 wattdual USB PowerDrive 2 Car charger
6. Anker Quick Charge 3.0 42W Dual USB Car Charger

While testing each device, the phone was plugged into each charger with a low state of charge (~15-25%) and left on the charger for a couple minutes to ensure the circuitry of the charger had time to identify the device and provide the maximum charge it was capable of delivering. We use a low battery as the rate of charging slows once you approach 80-90% charge on the battery. You may have noticed getting the last 10% charge into your phone seems to take an eternity. This slower rate of charge is to protect the battery from damage and is by design.  Lets see how each of the devices fared in this test.

As expected, the 5w Apple charger delivered just under 5 watts.  The 12w Apple iPad charger kicked out over 10 watts initially but settled into just under 10 watts after half a minute or so.  The PowerGen 12v car charger non-Apple port was the worst of the bunch, pushing only 2.36 watts, however its Apple specific port cranked out a respectable 9.13 watts.  The 24 watt Anker managed about 9.82 watts out of each USB port.  The final USB car charger in the test, the Anker Quick Charge 3.0 and IQ charger managed less than 5 watts out of the QC3.0 USB port, but cranked out 10.18 watts out of the IQ only port.

Overall winner: Anker 42 watt!

I suspected based on my experience using these chargers with my stationary bike generator that this would be the outcome I would get, but its was good to have metrics on the actual watts going into my phone.  Pushing only 10 watts on the pedal generator requires almost zero effort, so I typically change my iPhone along with battery banks (Ill review what works best among those later) and any other devices around the house that need a charge.  Adding more devices to the mix creates more resistance when pedaling.  Devices I typically include are iPads, other family members cell phones (if I can pry them away long enough), an iPad mini, an iPod Touch, my Microsoft Surface Pro 3 , Chromebook, bluetooth headset, FitBit, and cordless drills to name a few.  I try to get 60 watts or more in order to get enough resistance to make it feel like Im doing something.  Ive been able to generate over 180 watts with the pedal generator, but I cant sustain that for too long.  Ive found the best range of wattage resistance for me for any length of time has been between 60 and 130 watts.  In future posts, Ill test the limits of the pedal generator (and myself!) to see what the upper end of wattage is that can be produced.