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DIY Electric Bike

We wanted kits that would provide good performance and range, but not weigh too much. We required hill climbing ability and needed to go 20-30 miles on a charge, plus pull a bike trailer sometimes. This called for a strong motor and good amount of energy storage at a fairly high voltage. The kits would not be cheap, but here you get what you pay for. Check the conversion kits page for more kit information.

We selected rear wheel geared motors for their slow speed climbing ability. The rear geared motors are reported to provide continuous torque under low speed, uphill grinds. Ours kits came with 22 amp controllers and 36V batteries which could produce 792 watts of working power.

The kits had pretty much everything needed for the conversion except enough shims. You may need to add your own, we did.
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DIY eBike 2.0
DIY Electric Bike -Kit Motor and Electronics
Slotted shims
3 slotted shims installed on axle
2 slotted shims installed on axle to keep gears away from frame
Thumb throttle switch - right Power on switch - left
Diamondback - DIY Electric Bike kit Total Cost - about $900 - It goes great in all kinds of terrain.
Ebike Conversion Kits
Completed DIY Ebike in the mountains
See the 2.0 version climbing on YouTube.
The motor on the bike above failed, while the other one keeps on going. The one above has been replaced by a BMC motor and 48V 20 AH battery pack. See it on the next page.
Donor Bikes

We decided to convert each of our 20 year old bikes to a DIY electric bike.
One was and is a Schwinn Cruiser, the other a Giant MTB. Both were garage sale specials. We had been riding the bikes as daily commuters for 5 years. They were in need of paint, cables, bearing and cone cleaning and reset, tires, and general tune up anyway.

The first job was to strip all the old parts off of the bikes. This was pretty straightforward, and took about a day. After removing the parts came the sanding. The frames were not sanded to bare metal. The bikes were well scratched and pitted, so a medium grade of sandpaper was used first. A fine grade of sandpaper was then was used to feather out the pits and scratches.

Since the bikes are pretty old but not vintage, they tend to scratch quickly no matter what, and due to budget constraints, it was decided to paint with spray can paint. No primer was used. To make the job blend well, colors close to the original were selected, and not all of the original paint was removed: they were not sanded to bare metal.

Two common brands of paint were used for comparison. The Giant got Krylon brand burgundy, and the Schwinn a can of Rust Oleum green. The Krylon can featured a rotating nozzle which changed the plane of spray. This worked well to align the spray with the length of the tubes and made the process somewhat more efficient. The Rust Oleum however went on thicker to begin with and so less paint was used.

The finished frames are not likely to win any shows, but they look acceptable, and will work well as a platform for a DIY electric bike. The paint scratches more easily than the original factory enamel, but there is paint left over for touch up, and since not all of the original paint was removed, a few scratches can be touched up.

Before painting, it was clear that the brakes on the Schwinn were probably too wimpy to stop the extra weight and power of an DIY electric bike. The plan was to install new forks with V Brakes, but no forks long enough could be found. The conversion was switched to our other commuter bike, a Diamondback Sorrento. The Diamondback had great brakes and a speedo.

Installing the Motors

The instructions that came with the motors were for front wheel installations. One good hint on the instructions was to be careful to lock the axles in the forks to prevent the axles from spinning under torque load. Good quality, heavy duty lock washers are included.

The Giant was first up.  It seemed simple to just replace the old 7-speed rear freewheel with the new 6-speed freewheel and motor combination. Making the replacement turned out to be another matter.

The motor - wheel combination is wider by an inch or so than the original freewheel setup. The frame was just bent, pulled out to widen it enough to accommodate the motor for this DIY electric bike.

Note that the motor and wheel comes with one aluminum shim about ½ inch wide which goes on axle on the side opposite the gears. The shim effectively pushes the motor casing away from the side of the bike frame so it doesn’t rub during operation. The shim does provide the needed spacing on that side of the wheel. However, the geared side of the motor has no shim which means that the lowest gear jams into the frame once the motor is installed.

This is where you will need to make or buy some kind of shim for the geared side of the wheel. There is only problem: the wire connections on the end of the wire coming out of the geared side axle will not allow a shim anywhere close to the diameter of the axle to pass over it. What to do?

After a few trials with (too soft) aluminum tubing, we decided to cut slots in steel washers, bend the washers, slip the bent washers over the wires, bend back to flat, and slip them in place. Note also that if you wan the washers to fit snugly on the axle, you will need to use a Moto-Tool or some kind of round file to grind out the holes in the washers big enough to just fit over the axles.

After some trial and error, it was determined that 2 standard washers were needed to push the gears far away (about ¼ inch) from the side of the bike frame to prevent the gears from digging into the bottom bracket and seat stays of the frame.

Once the gear side washers were installed however, the wheel was pushed off center towards the side of the frame opposite freewheel. 3 extra washers installed on the opposite were enough to push the wheel to the center of the frame.

Installing the Switches

Thinking ahead, we would have put the switches on the Giant DIY electric bike before putting the brake levers and gear changers back on. Oh well. Anyway, you will need to remove your brakes and gear changers if you want the e bike switches in a useable location.

We were supplied with Wuxing brand thumb operated throttles. While they work very well, they get kinda crowded along with brake levers and gear changers. The Wuxing brand brake levers supplied are nicely finished and include kill wires.

When you pull the lever a signal is sent to the controller to stop the motor. We found these redundant, but if you are concerned about your ability to cut the power, use them: they are well finished.

Probably the hardest part of the whole DIY electric bike switch installation is removing the rubber handlebar grips. Pry the grip out with a screwdriver and pour some detergent water in there and wiggle the driver around. They will loosen after a few minutes.

Take a few zip ties and carefully attach the switch wires to the handlebars. Lead the wires back or forward to wherever you plan to place your battery pack. That's about it for the switch installation.

Battery and Controller Box

One of the requirements for Li-Ion battery packs is to protect them from shock. Unlike good old lead acid batteries, Li-Ion packs do not do well if poked, prodded or banged! Since these packs cost over $500 each, You will want to insulate and protect them. Check the ebike battery page for more batteries.

One thing NOT supplied with the DIY electric bike kits were battery boxes. You will need to buy or build a box to protect your battery and controller. The box can double as a theft deterrent at the same time if made of metal and locked.

Our first boxes were the plastic food type, and worked well to hold the batteries, but were not very secure. You can put controllers in there as well. 

Controller and Pack Installation

You do not have to mount the controller, but it is recommended. There are plenty of slots along the base of the unit for that purpose. Take a few minutes and decide where you want to place the controller in your battery box, drill a couple of holes, and install it.

We cut slots in the side of the boxes to let in the switch and motor wires. They all fit together pretty well.

We had 22 amp controllers with a lot of connections. Not to worry, they were all keyed differently. It was pretty hard to screw up the connections. 

Next, place your battery pack in the box. We placed the batteries in the nylon zip bags provided with the kits after lining the bags with some old foam. The bags were then simply placed in the boxes. The battery and controllers fit snugly in the plastic boxes to minimize any bouncing about.

At the time of writing we are looking into steel security boxes to replace the plastic ones.

Cost of Conversions

The kits and battery packs cost $1,750 delivered. The boxes, paint, shims misc. Parts came to about $50. The total cost was around $1,800 for the two books. The total time to do the 2 conversions not including painting was about 30 hours.

How much did we save? Comparable built bikes range from about $1,600 to $2,600 and these bikes come with 10AH battery packs. You can compare bikes and prices here.

Performance

The DIY electric bike performance is in a word - fantastic. We are located at the base of the Sierra Nevada mountains and wanted the e bikes for hill climbing as well as general commuting.

The first time out we tackled a 6% grade that is used for training purposes by locals in training. We biked right up the grade with ease at 10 mph. We could have gone faster. The next time out, the 65 pound dog was towed behind up the same hill in the bike trailer - no problema.

Regarding range, it depends on: weight, grade of hill how fast you go, and temperature. The weight limit for good performance is about 250 lbs or less. If you weigh more, get a more powerful motor and or 48 volt system with 20 AH battery pack.

The one thing that will dog your motor, heat it up, and drain your pack is grades over around 10 degrees. You can pull 6 degree grades OK, and over 10 degrees is pushing it. 20 degrees and you will probably want to walk alongside the bike. The motor will pull the bike.

Speed is another drain. This system performs the most efficiently at around 1/2 throttle. You can run wide open, but it will impact your range a lot.

Cold temperatures will reduce the range considerably. For instance, we put our ebikes in the house at night when the mercury dips below about 30 degrees and we want to get some good range the next day.

The great thing about these bikes is that with the thumb throttle, you just apply as much power as you need to help you along. You can use only the power, or pedal along, which extends your speed and range.

If you convert your existing bikes, you will be very comfortable on the e bike version. They actually pedal easily on the flats and roll very fast downhill! So, if you run out of battery power, you can still make it home no problem.

If you are thinking of a DIY Electric Bike, we highly recommend it.

New Battery Boxes

After using the bikes a few times the plastic battery box lids warped and needed  more strap power to hold on. The lids still did not fit all the way around. Additionally is the idea of security.

If you want to go into a store, your expensive battery and controller are sitting there in a plastic box. We had planned to just unplug them and take with us, but with all the wires, it quickly became too much trouble.

After looking around a lot at Home Depot, Lowes and the like no suitable boxes were found. Finally on Amazon a couple of File Security boxes popped up that were just the right size.

The security boxes are steel for strength with locking tops for security. The locks aren't great, but way better than plastic.

Mounting the 2 boxes took one whole day to line up, drill and bolt. We just lined the boxes with some old foam for protection. The batteries and controller fit in the boxes snugly, and look pretty good. The lids open easily for charging too.

After some use however, the lids failed to close and stay closed on the Buddy Boxes. It happened that the cam locks used some kind of soft metal washer that deformed under pressure of the closed lid and padding. The fix was to silver solder the washer on the lock. This worked great, and the lids now close and stay closed. Alternately, one could just replace the locks for a small cost.

Riding Update

Here we are two years later. Our DIY eBikes are fantastic. They take us shopping and into the back country. We have had a few minor problems. First, the racks used to support the battery boxes have worked loose a couple of times and broken once. This was fixed by adding a few braces and supports. Also, we like to place a bit of Goop on the threads where the racks bolt to dropouts, this prevents them working loose.

You will loose power in the very cold and hot. We bring our bikes inside in the winter at night if riding the next day. The summer you need to find the coolest place possible.

The geared motors we are using here are not serviceable by most of us. They are pretty well sealed. Mine started making a slight clicking sound last year, but still works as well as ever.

Flat changing is a hassle, no doubt about it. You will need to set aside a little time to fix a flat. You need to undo the wiring to get the wheel out, then re-zip tie the wires on re-installing the wheel. We use thorn proof tubes with slime to minimize flat fixing.

Motor Failure

After 2.5 years and about 2,500 miles, the geared motor on one of the eBikes on this page failed. It started making a huge racket. The casing is aluminum and could simply not be opened up by us or dealers. We scrapped the motor and kit for a new BMC motor, controller and battery pack. It is on the next page.
DIY eBikes - One of ours shown herehas three years and is still going strong. The other has failed after 2.5 years and 2,500 miles.
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The DIY electric bike can be an interesting, fun, useful, and money saving project. Do a little homework, a little mechanical work, and you can build an e bike that will really get you places. This page will show you how to put together a electric bike using a donor bike and e bike kit.

All you need is a bike, motor, battery and box, controller, switches, rack, wiring and some patience to make your own eBike. You can get most of the stuff needed in an eBike kit if you want to simplify the process.