In this section we will continue our discussion of ordering the correct parts for your bike
A 500w mid drive motor from Bafang looks like the 750w motor and even weighs the same. The only difference is the 500w motor has a controller (internal to the motor) that is rated at 18amps whereas the 750w motor has a controller rated at 25Amps. There are times when we turn down the amps on the 750w motor to 18amps in order to get increased milage per charge for the client. The only advantage a 500w motor has is it can run on a 36v battery and 36v batteries are less expensive.
The default programming in the Bafang mid drive is sort of a universal catch all and nearly all custom builders reset the programing. Every builder has their program which they believe is the optimal program. At Island City Bikes we have refined our program over the last three years and we believe ours is the best. It takes a bit of knowledge and research to reprogram a Bafang controller. You start by purchasing a programming cable and then downloading the program that allows the change. You have to be carful with making changes to the controller as you can damage the motor, blow out the controller, or burn out the stator. There is plenty of information on the internet on how to program a Bafang mid drive motor.
Most will be choosing between a BBS02b 750 watt motor or the beefier BBSHD 1000 watt motor. Which motor is right for you is the question to ask. For 90% of all riders the BBS02b 750w will be plenty of power. However, there are those who cannot resist the temptation to have the largest motor possible on their bike.
When it comes to a battery for the BBSHD 1000 watt motor you have to use one that has a 30A BMS. Smaller batteries often (not always) have a 25A card. Be sure and ask the vendor who is selling you the battery if it has a 30A BMS
There are many types of electric bike batteries to choose from. For example, there are cube batteries, triangle batteries, downtube batteries, rack batteries, side load batteries, and integrated frame batteries. Also, there are the different types of cell groups: Generic cells, Panasonic, Samsung, LG, and Sony. With each cell there are different variations such as Samsung 35E, or Samsung 30Q. Each variation makes a difference in performance and range. Then there is the size of the battery in terms of volts and amps, For example, downtube batteries come in sizes of; 36v 10.5, 35v 13, 36v 14.5, 48v 10.5, 48v 13, 48v 14.5, 48v 175, 52v 14.5, and 52v 17.5. A lot of choices to consider.
In my opinion, I do not think it is a good idea. Especially when it comes to batteries. Unless a battery has a date stamp you do not know how old it is. Also, a used battery may have been damaged in the past and could catch fire while charging.
Used motors are also a risky buy. For one thing they may be an older version no longer in use and have weak mofsets which are apt to fail.
At our shop we often see people people bring in electric bikes for repair that they bought used from someone and we have never seen a decent one yet.
Ordering and gathering all the parts necessary to convert a bike to electric can be a complicated and imposing task. However, with a bit of research I am sure you will be successful. Remember, batteries cannot be returned so be careful of who you buy from and make sure you have the correct battery for the motor you will be installing.
We take the motor and slide it through the cleaned out bottom bracket shell. It should slide through easily. Do not tighten the motor just yet. However, please secure the motor with the M33 nut to keep the motor from inadvertently falling from the bike.
At this point you are going to look for any obstructions. The motor may be coming in contact with the bike frame, the shift cable, hydraulic brake line, or the brake cable.
This is the motor housing on the drive side of the bike. Notice that it is hitting the chainstay. There should be no contact with the motor housing and the chainstay, or any other part of the bike. If there is contact, when the motor is torqued in place it will pull the motor to one side. If the motor is even slightly ajar it will consume chain, chainrings, and cassettes very quickly.
Pull the motor back off the bike and use 1mm or 2mm spacers on the axle housing of the motor until there remains no contact between the motor housing and the bike.
Remember, whenever you use a spacer on the drive side of the motor you are going to change the chainline. Try to use the absolute minimum number of spacers. The best chainline is when the chain is straight from the front chainring to the center of the cassette. If it is straight from the chainring to the first cog on the rear cassette it will will never reach the last two cogs on the cassette without the chain falling off.
Lekkie chainrings are great for solving problems with chainlines because they have a deep set back that helps compensate for any spacers used to move the motor. The stock Bafang chainring is stamped steel and almost flat.
This is a Lekkie chainring. As you can see it has a deep inset that serves to move the chain inboard in order to establish a proper chainline. Many times we have seen bikes that cannot be converted without the use of a Lekkie chainring.
This is a 46T Bafang stock chainring and as you can see it has very little inset. For some bikes this inset is perfect but for others it has to be replaced. Many do not care for the stock chainring and prefer a Lekkie chainring. There really is not anything wrong with the stock chainring, as long as it fits, other than esthetics. It is made of stamped steel, and will last for years. The stock chainring comes with a plastic cover (only with the Bafang BBS02b) that can take aways from the overall attractiveness of the bike.
To compensate for the use of spacers on the axle housing on the motor, you used a 2mm spacer. That 2mm spacer moved the motor over so it is no longer touching the chainstay. After installing a Lekkie chainring to compensate for the 2mm spacer, the chainring now comes into contact with the chainstay. There are two ways to solve this problem. First, put a smaller chain ring on and see if it clears the chainstay. The other option is to use a special spacer for the Bafang motor behind the chainring. However...to use spacers behind the chainring will once again change the chainline.
This 2mm spacer will go behind the chainring. There are also 1mm spacers available. If you do not have a spacer you can take washers and put them on behind the chainring on each bolt.
Look closely and you will see the silver nut on the pivot arm of this full suspension bike coming into contact with the motor housing. Again, this is something you have to look for before you secure the motor. Us a few spacers as possible until the motor housing is no longer in contact.
This is an example of a poor chainline. This chainline will cause the chain to fall off the chainring and prematurely wear out the entire drive train. Sometimes you will have to lock out the largest cog on the cassette. This is done by adjusting the "low" set screw.
Here you can see both the shift cable and the brake cable running straight in the path of the motor. The motor cannot be allowed to crush or impinge these cables. This comes about through the use on internal routing of the cables. Internal routing of cables has become very popular and is found on many newer bikes. What do you do when the motor rests on these cables? There are a couple of options. The first, and best option is to remove the cables from the frame and reroute them on the outside of the frame. Be sure to use cable guides and cable stops when you reroute your cables. If your bike has hydraulic brakes DO NOT move this line outside the frame. Try to move the line over as far as possible towards the non drive side. There is often just enough clearance for the cable to pass through the opening between the motor housing and the bottom bracket shell.
A Second option is to put a small hard rubber spacer between the motor housing and the bottom of the downtube to keep the motor off the cables and then tighten the motor. If you choose this method be sure to periodically inspect the motor to insure it has not come loose.
This is a picture of of the motor sitting on a hydraulic brake line. In this instance there is little choice other than using a hard rubber spacer. The Bafang motor torque is always forward and it likes to rest on a solid foundation, like the downtube. That is why it is important to use hard rubber as a spacer. Otherwise the motor will begin to rock slightly and then come loose. We have used 1/8" aluminum as a spacer and that works also but a hard rubber spacer with a motor properly torqued will do the job.
Hint: We buy auto heater hose to use as spacer material. We take the hose, cut to length, and then split it down the middle. Heater hose is very strong material that is built to withstand the high heat environment of an automobile engine.
Here you can see the placement of the fixing plate being attached with two M6X12mm bolts. Often, you will need washers between the fixing plate and the motor. If the bottom bracket is 68mm then you will spacers will not be required. If your bottom bracket shell is 73mm then you will need spacers (washers) on the M6 bolt. Note that the M6 bolts are for a 68mm motor. If you have to use spacers then you will need longer M6 bolts.
When installing the fixing plate insure the serrated side is facing the bottom bracket. Please see the picture in the next section.
A fixing plate is used to hold the motor in place by forcing the ridges of the plate into the bottom bracket shell. This plate has a smooth side and a side with ridges. The ridges have to be facing the bottom bracket shell. These ridges will be literally crushed into the bottom bracket shell by force applied on the M33 locking nut.
This is the M33 lock nut that will tighten down the fixing plate. This lock nut requires special tools that are specifically made for this nut. Tools found at your local bike shop will not work. There are certain Park tools that will fit this nut but they cannot grip the nut well enough to apply the needed pressure to force the plate into the bottom bracket shell.
The other part, that has the words "8 Fun" is a fixing cap. This cap will thread over the top of the M33. It is more decorative than anything else and does not require a lot of torque. On many bikes this cap will be left off as there are not enough threads on the axle housing left over once the M33 nut is installed.
This is called a Bafang installation spanner. A "spanner" is what the British call a wrench. These spanners are very inexpensive ($10) and can be found at the usual online market places such as Amazon and eBay. One side of the spanner is for the M33 nut and the other side is for the locking cap.
We do not use this tool because we cannot get the mount of force required to adequately lock the motor in place. Some compensate for this fact by using a hammer to pound the spanner to tighten the nut. We do not recommend using a hammer.
This is a socket that fits the M33 nut. With this socket one can safely apply the necessary torque to secure the Bafang motor to the bike. At our shop (Island City Bikes) we have our sockets custom milled to increase the tolerance even further to insure the safety of installation. We use different methods to secure a motor on different types of bikes. However, any method we use, our first and primary concern is safety. Whenever force is being applied to any part of the bike there is a danger of tools slipping, or nut/bolts/screws breaking free, and the hands going into the spokes, chainring or other part of the bike.
If your bike has a steel or titanium frame it might be difficult for you to apply enough force to lock the motor in place, The reason for this is the frame material is harder than the fixing plate and the ridges of the fixing plate cannot press into the bottom bracket shell. What to do? There are a couple of solutions to this problem. For example, you can tighten the M33 nut as tight as you can get it and then on a regular basis check the motor to see if it is coming loose. Another option is to use a motor brace as pictured in the next section.
This device was created by Doug Snyder of California eBike in Benicia California. Doug is an early innovator of electric bikes and a brilliant engineer. This is a product he created for the purpose of holding a Bafang motor in place without the use of the fixing plate. However, in order to use this part you will have to install a Rivnut in the bottom of the downtube. The installation of Rivnuts is a task that can be learned but I strongly advise that you proceed with caution as it requires drilling into the frame.
Jeff, one of our mechanics, is prepping a bike for the installation of a 5mm Rivnut. You can see the silver motor brace mounted on the axle of the Bafang motor. Once the Rivnut is installed the motor will roll forward and the motor brace will be attached to the bottom of the downtube via the Rivnut.
These are Rivnuts and they are very similar to the water bottle inserts that are already on the bike frame. The water bottle inserts are where the water bottle cages are attached.
There are many types and sizes of Rivnuts so make sure you get the right type, size and material composition (steel or aluminum) for your bike frame.
While we do not use this tool (we use a commercial version) this is the best tool for anyone unfamiliar with the process of installing Rivnuts. It is almost foolproof. To use this tool, you thread the Rivnut firmly on the bottom bolt. Then you insert the Rivnut (with the tool attached) into the predrilled hole. Then you slowly tighten the nut on the end of the tool which pulls up the ramp and in turn sets the Rivnut in the frame. When the ramp reaches to top you loosen and remove the tool. Job accomplished.
Now that the motor is installed let's go back and double check everything. Is motor housing hitting chainstay? Is the motor sitting on the shift or brake cable? Has the M33 nut been tightened? Is the locking cap on? Has the two M6 bolts been tightened? Is the motor rolled forward and touching the bottom of the downtube? If the answer is yes to all of these questions we will move on to installing a chainring.
This is the stock chainring for the Bafang BBS02b 750 watt motor. It is made of stamped steel and comes in 44T (T=tooth) and 46T. Bafang also makes a 48T and a 52T but they are a special order. As you can see, the setback on the stock chainring is very small so sometimes it cannot be used as the chainline is so far off it will cause the chain to fall of the chainring. If this is the case then you have to consider using a Lekkie chainring as it has a much deeper setback.
This is a picture of the Bafang stock chainring installed on a BBS02b 750 watt motor with the plastic cover. Installing the plastic cover is not that difficult and we install it after the motor has been installed. Other, prefer to install the chainring and the plastic cover before the motor is installed.
This is a picture of a chain running from the front chainring to the middle of the cassette. Notice, this chain is straight. If it is straight then the chainline is perfect. If the chain is not straight then you have to begin spacing the chainring out with spacers. In some cases you may have to remove the motor and put a spacer on the axle housing.
No matter how much time or expense the chainline has to be correct. If the chainline is faulty the chain will fall off the chainring
As mentioned previously, the stock Bafang chainring has very limited setback (2mm for the BBS02) and therefore can only be used on bikes that fall into a category where the bottom bracket shell, chainstay, and number of rear cogs are all lined up in such a manner that a 2mm offset is sufficient. On the bikes we convert to electric I would say the standard Bafang chainring is sufficient for 80% of all bikes.
This is a Lekkie chainring for the Bafang BBSHD 1000 motor. Look at the depth of the chainring. Because of this offset it will allow you to move your chainline inboard without the use of spacers....maybe. Never rule out the fact spacers may still be required regardless of the offset of the chainring. Remember, the goal is to establish a proper chainline.
How many miles has the Lekkie chainring traveled? This expensive Lekkie chainring lasted 11 miles. If you looked from the top down you would see the teeth ground to sharp points. This is what happens when the chainline is incorrect. It can damage the entire drive train of the bike.
Do not worry about locking out the largest cogs on the cassette. I know this goes against our nature to take away a feature of a bike but sometimes it cannot be avoided and must be sacrificed in order to get a functioning chainline. For example you have 10 cogs on the cassette. If need be, turn the H set screw until the derailleur cannot move from the 9th cog to the 10th cog. On 12 speed cassettes you can lock out the last two cogs. The Bafang motor is powerful and would never use those last two cogs in any riding conditions.
It does not matter how long it takes or how much money you need to spend, or how many weeks you have to wait for parts, the chainline has to be correct. Sometimes you will need to lock out the largest cogs in the back in order to have everything as near perfect as it can be. Many times when working with a bike with 12 cogs in the back and a single up front we have to lock out the last three cogs in order to establish a perfect chainline.
A poor chainline is dangerous as it will cause dropped chains. In addition, a poorly aligned chain will eat through chains, cassettes and chainrings post haste. Take your time and get it right and you will be awarded with an electric bike that will provide years of trouble free riding.
This small device is called a shift or gear sensor. Originally it was a product developed and sold by a company in the Czech Republic. Today, this product is widely sold by other companies on Amazon, eBay, AliBaba and AliExpress. If purchasing for your bike make sure the connecting end is compatible with your motor. The yellow connector, shown above, is a Hilgo connector used on a Bafang BBS02 and the BBSHD. Note; this part is not included in the Bafang electric bike motor kit. Most sellers of the Bafang motor kit believe this device is essential to the smooth operation of the Bafang motor but none of them include it in the motor kit.
Pretty simple mechanism. It has small rollers that sit on the top and the bottom of the cable as it passes through the device. Any movement of the cable is detected and a signal is sent to the controller of the motor that says "off." Once the shift is complete a second signal is sent to the controller that says "on." This whole process takes less than a second.
Good question. Nearly all sellers of the Bafang motor kit promote the use of the shift sensor and are happy to sell you one. It might be noted that the company that manufactures the Bafang mid drive motors do not sell shift sensors and never include them in their motor kits.
Some riders prefer a shift sensor while others do not. Sometimes, a rough road can trigger the shift sensor causing the motor to intermittently cut out. Those who ride aggressively in off road conditions might be better off without a shift sensor.
When riding a bike, one shifts from one gear to the next by while pedaling. That is not altogether true. Yes, you keep the pedals moving but you do not apply pressure. You may have heard people shifting while climbing a hill. The steeper the hill the louder the noise while shifting. NOTE: Noise does not mean damage. When shifting an electric bike, pause between shifts. In other words, every time you shift..stop pedaling, shift, then resume pedaling. When you stop pedaling the motor stops applying force and allows for smooth shifting.
First, you need to snip off the end cap of the shift cable at the rear derailleur. This has to be done in order to pull the cable through the cable housing. Then you release the anchor bolt. Go to the front of the bike and pull the shift cable free from the shifter. Slowly pull the cable until you think it is far enough in order to cut the cable housing without cutting the cable. Cut the cable housing about in the middle of the chainstay. Take a sharp pick and round out the area where your cutting tool compressed the strands. Put an housing cap on both ends of the cable housing where it was cut. Thread the cable through the housing, into the shift sensor, and through the derailleur and reattach at the anchor bolt. Often the cable will be too short and you will have to remove some of the housing. In addition, cables often fray and cannot pass through the shift sensor. When this happens you will need to use a new cable, so have one on hand. If your bike has a twist shifter, or internal shift cable this can be a very difficult and time consuming task. It is highly advised to install the shift sensor prior to installing the motor.
First and foremost it effects the quality of shifting by introducing considerable drag. While downshifting, this drag is not noticeable because you physically move the chain on the derailleur by the strength of your hand. It is when the derailleur moves back down the cassette that one has a problem. What moves the derailleur down is the derailleur spring. Some expensive derailleurs have a very powerful spring and can overcome the drag. Most derailleurs have a spring that is designed to work without any drag on the system. The drag imposed by the shift sensor is just enough to mimic a crimped, fouled cable housing, or incorrect routing of the cable. Everything will still work fine but it will not be a smooth shifting pattern coming down the cassette with a shift sensor installed.
The speed sensor is a small device (pictured above) that is attached either to the front fork or the chainstay of the bicycle frame. Its function is to measure the number of revolutions per minute providing an estimate of the speed of the bike. The Bafang motor will not operate correctly unless this device is set up correctly. Note: The small magnet in the picture above is a magnet that needs a special tool. You will need a Torx security head tool.
First, these can be very difficult to install. Our first choice is always to install on the rear non drive side chainstay. By putting it on the non drive side we are preventing any accidental contact with the chain. On some bikes, the chainstay is so far away from the spokes (where the magnet is to be attached), we have no choice but to install the sensor on the front fork. To install on the front fork will require an extension cable(s).
You will use Zipties to attach the speed sensor to the chainstay. Above, is a picture of a Ziptie puller. You need this tool to get the Ziptie as tight as possible. When attaching the Ziptie use the largest and strongest possible as you do not want the sensor to move once it is in place. Small Zipties may look nicer but you cannot pull them tight enough without them snapping. NOTE: Only use Zipties with a UV rating for outdoor use.
Here is the magnet is attached to a spoke approximately 2mm or 1/8 inch from the sensor. If the magnet is too far away an error code of 21h will show up on your display. If the magnet is too far away it is possible to either telescope out the sensor, or use a shim underneath the sensor. We do not like to telescope out the sensor as it becomes too easy to snap it off when one removes the wheel. Instead we take hard rubber and place it between the sensor and the chainstay as this make a much firmer connection.
Always remember to use the set screw otherwise the sensor will work loose , come into contact with the spoke magnet and snap off.
The speed sensor is an important part of the Bafang motor system so it has to be installed correctly. Sometimes it will be a simple task and other times we spend hours trying to figure out how to attach it to a bike where the spokes are far from any potential attachment points. Sometimes we have the opposite problem: The spokes are too close to the attachment points and no matter how it is set up the spoke magnet hits the sensor. Every day we come up with new and innovative ways of solving these difficult problems and I know you also will do the same.