18 Reasons To Build a DIY Ebike

December 30, 2015

Editor Note: This essay  was submitted by new electricbike.com writer George Sears from Southern Utah. It s a very thorough thought-process which he makes suggestions on whether or not you should take on a DIY ebike.  We are very proud and pleased to have George aboard the eb.com team.




I’ve followed a lot of “What should I buy?” threads on Electric Bike Review and help out when I can. For people just starting out, one basic decision is whether to buy an ebike or build one. Many people won’t even consider a conversion, it seems. The most comfortable way to buy a bike may be from a dealer, a place with multiple bikes, a service department, and a place that answers to all of your questions.

But…a dealer makes money by adding his profits and his services to the cost of the bike. He pays the shop-rent and also the costs of employees and inventory. If you have a great dealer, it might be worth it, especially for a first ebike. But you may want to find some way to try out an ebike, like maybe renting one, to get a general idea of how interested you are. You may not want to get locked into a dealer if you think you might find another option, like maybe building an ebike?

The ebike industry is changing rapidly. Prices have dropped, partly because of high volume and low-priced crowdfunded ebikes. Dealers cannot make enough profit on ebikes when the price drifts much below $2,000, unless…they can move large volumes of bikes, parts, and service.  That means most dealers are in big cities. Online sources provide most bikes in the $1,000 to $2,000 range, and bikes ship everywhere. There are a lot of bikes on Amazon and Ebay. Price points matter because people have budgets. In general, a conversion can be kept to around $1000, for the battery and motor.

With a bike conversion, you choose the frame, the “bike” to convert. You can convert almost any bike. A bike with a water bottle mount generally means mounting a battery is trivial. Spend enough time with the prospective bike to know if it will work for you, and whether you like riding it. Over the past year, many fully assembled ebikes between $1,000 and $1,500 have shown up, generally online. You may find that spending $1,000 for a motor and a battery gets you a better motor and battery, or…a more suitable frame. $1500 is a competitive price point for a “turn-key” ebike.

No one should be afraid to convert any bicycle, especially if you stay within the traditional power limits and speeds. The new California rules (opening up LEGAL 28-MPH ebikes), should push people toward beefier bikes with very good brakes. With higher power levels, you would look for a bike that can handle more speed. In the past, most people started with an ebike that stays within the performance envelope of a regular bicycle.

The bottom line of any conversion is that you add a battery and a motor. (The electronics may or may not be in the motor.) This isn’t a tutorial on how to build a bike. It’s an overview on why buying these parts, the motor and the battery, can be a better way to go. If you buy a bike and bring it home, you own an ebike. If you have a bike, add a motor, and add a battery, the bike is now an ebike and you own an ebike. So…what’s the difference?


  1. You can understand what you have. You start with a bike. You end up with the same bike with more parts, the parts that you attach, or the bottom bracket you replace. It’s obvious what is what. It’s obvious how the power is getting from the battery to the motor, whether the motor is in a hub or in the bottom bracket. It’s clear that there is wiring for brake levers, a throttle, or a display. You can’t really put a bike together and not have some sense of how the thing works. You can view the pieces as modules. The motor is one module, maybe with a controller inside. The battery is another module. Anything else serves these two pieces, and is attached for information, or safety, or user adjustments. So, if you know what any part does, and how you put it on the bike, then…
  2. You can fix it. This starts with what you can learn, doing step #1, but also covers the general accessibility of most kit bikes. You may want to replace parts, up to a point.  If you attached the motor, you can probably replace the chain. Things like gears wear out. If you want to take a Bafang BBS02 apart, to get to the gears, you can watch videos.  If you don’t want to open the case to replace a gear, you can swap the motor or remove the motor, and ship the motor for repair.  You don’t take the bike back to the dealer, generally. You can limit service to removing the major modules, the motor or the battery or the support parts like throttles.  Given the lack of dealers in many places, a service strategy built around shipping parts is going to have to work, for kit companies and online dealers of assembled bikes (like Amazon). The resources to fix kit motors,
  3. (like the BBS02) are massive, from YouTube to electric-fatbike.com. It’s an evolving industry, and resources are bound to increase over time.
  4. You can buy the exact motor you need. There’s a tendency to sell dealer bikes based on very nice optics. They look great. Test rides generally showcase the pedal assist function, which is very pleasing for many people. But pedal assist can actually mask motor performance. The first rule of a test ride should be: ride up your toughest hill. The bike has to do that. If a bike can’t pass that test, it’s not as likely that there is a motor upgrade from a dealer model. When people come online, to the EBR forum, looking for a bike, the best first question is “What are your hills like?” Mid-drives are much better for hills than hub motors. (Basically, the kit market right now is build around a single mid-drive kit, the BBS02.) The mid-drive vs hub debate is too complicated to discuss here, beyond the very real ability of mid-drives to climb hills. You can’t find high wattage versions of most dealer mid-drives, and most posted wattage numbers are garbage anyway. If you want to carry heavy loads up real hills, wattage is a serious issue, even with a mid-drive. Bottom line? There are more choices on the builders’ side. Many dealer bikes are built to European standards, and the US has much more flexibility. Once you get past hub vs mid-drive,  (read our story), there are other prime considerations that empty out  the bike shop. Like, the frame
  5. The frame is still the bike you ride. The universe of bikes with no motor is vast, and a motor can be added to many of those bikes. The universe of bikes that sell as factory-ebikes is small, and actually very small for a basic dealer in a smaller city. If you look at the major online dealers for bikes without motors (like Bikes Direct), they may have a hundred bike models, huge ranges of component groups. You probably don’t want to convert a carbon road bike or a race bike, but any hybrid, fat tire bike, mountain bike, cruiser, or comfort bike is a likely candidate. These bikes usually have a wide selection of frame sizes. Older riders often buy bikes with step-through frames. Heavier riders may need a full range of options (instead of only the few ebikes on the showroom floor of a local ebike shop).
  6. Choosing the battery. This is a long, long essay that will have to wait for some other time,  because batteries matter way more than people think. This is the one minute overview: For a basic bike that will be ridden 15 or 20 miles, the standard battery “might” work. Capacity comes down to Watt Hours (WH), and amp hours times volts (read our story on ebike math). You almost need to ask someone who is experienced, or do some research. Range and the battery are tied together. Good advice is to buy 50% more battery than you think you need, as long as it is reasonable. For a 20 mile range, the dealer bike is probably not going to get close to this number. A second battery generally works, but you need to consider the cost. The dealer bike will often have a completely integrated battery, or a custom battery. The cost of batteries for a kit bike should reflect the prices of the cells inside the pack, how the pack is built, and some profit. Cell prices have dropped, but many packs remain at lofty prices. Kit batteries now have enormous capacities so a big Amp-hour battery is easy to find. Batteries are often a profit center, especially if the only battery that ‘fits’ is from that same manufacturer. With a kit, you can buy a small reserve battery, or build a system for different rides. Dealers sell one basic battery, generally quite expensive, and you buy as many as you need. Most dealers mystify batteries, and which batteries will work with their systems. They may ‘chip’ their batteries, or make custom connections nearly impossible. But what works, the basic characteristics of batteries? it is simple enough. Dealers rarely mention more advanced issues with batteries, like discharge rates. They basically don’t sell performance batteries, anyway. With kits…you get to determine the voltage, capacity, and discharge rates. Voltage is voltage, but capacity should be the focus, at least until you are buying a motor with serious performance, like a high wattage motor. This is a lot to sort through, but consider what the batteries you can buy for an ebike will cost. And also…the battery you choose is only as good as the charger it comes with…  
  7. You can buy the charger you need. A year or so ago people were told to fully charge their batteries every time, or something like that. Very hard evidence suggests this is not ideal. Electric car companies charge to 90% or less, most of the time. Why? To double the cycle life of the batteries. This gets back to getting a big battery. When you have excess capacity, charging to 90% doesn’t affect the range you actually need. Not many chargers make it easy to charge to 90%. All you can do is ask. You might want to compare the price of a second charger, or a replacement charger, from a factory bike vs  a charger from a conversion parts company. You might want something more than a basic 2 amp charger, which is pretty slow, with newer and higher capacity battery packs. There are ‘Swiss Army knife” chargers that handle different types of batteries. (read our article on charging and advanced ebike chargers)
  8. You can swap the motor. A fair number of people buy dealer bikes and find out it won’t quite climb the hills they have. Then what?  If you bought a kit motor, like a very basic hub motor, you could probably maintain the bike and battery, but use another motor. There is a much better upgrade path available to you on a bike with a kit motor. (It’s still better to get close to what you need from the start.)  Repairing a damaged conversion bike is relatively straightforward. You can replace the frame, the motor, or the battery. A good motor like the BBS02 has resale value, by itself, and is easy to ship. If you want a BBSHD instead of a BBS02, it’s just a question of what the newer motor is worth, to you because can probably swap the two motors. Hub motors are more specific because of wheel sizes and brake configurations, so a swap can involve more labor. With any installation or swap, there are likely to be basic adjustments like spacers or different chain rings.
  9. Your warranty can end up being ‘a pile of parts in the garage’  (And maybe a big brown truck). A real warranty is a nice thing. You take the bike to the dealer and a day or two later, you get it back, completely fixed. This business model probably works for a lot of people. But what if the dealer isn’t really in the same neighborhood? You have to think about…how far is too far? knowing you drop it off and then, later, go back to pick it up.  If you have a conversion bike that you will need every day, you may be able to determine the parts that might fail, and keep spares for them around. People know the weaknesses of the BBS drives, the MAC motors, etc. With a less expensive motor, it might be worthwhile to keep a spare. How much will you pay for a warranty? Probably a few hundred dollars. How many parts can you buy with that? Kit vendors may want to work on variations of ‘depot service’, swapping parts or repairing parts quickly. Third-party repair facilities might emerge for a motor as popular as the BBS series. If you don’t have a dealer fairly close to where you live, factory ebike parts and repairs are more difficult. Conversion bikes tend to be simpler.
  10. Building things generally feels good. Taking a break from harder issues, and then building anything feels pretty good. It’s yours. The more it works out, the better you will feel about it. And it probably will work out.
  11. A rougher bike has some theft deterrence value. It’s hard to know what to do with a bike that is essentially a work of art. How useful is the GPS tracking that tells me where the bad guy is, after the bike is stolen? Do police departments have Ebike Recovery Squads? If a bike is not very attractive, it’s a lot less valuable for a thief. How hard you want to work at this is a personal choice, driven by where you live and ride. Building an electric junker is one way to minimize the theft issue. Building a basic bike with a basic motor, and removing the battery, is another approach.
  12. Start with a bike that you actually like. This was covered before, with frames, but…many people have  a sentimental attachment to a certain bike. The bike is unique, or the bike has a lot of meaning or history. It might be the bike they rode in college. Bikes are converted because riders age, or suffer from various afflictions. A small motor and battery may add years to the useful life of a bike. Kit bikes can be fairly unobtrusive, preserving the character of a bike. It’s possible to build a very understated conversion bike, starting with a traditional bike.  
  13. Wiring and lights.  A finished ebike, factory or kit, should probably have good lights that are integrated with the battery. Chasing down AA cells is no fun. A bike you build will have some exposed wiring, or at least, some accessible wiring. You will have only two wires coming out of the battery, positive and negative. These days, you can buy lights with DC-DC converters. The converter ties into the battery at 36V or 48V, and converts it to 12V or whatever the light needs.  You find a wiring path to the battery, run the wires, and mount the lights. By contrast, a dealer-bought factory ebike may be sealed. You might void the warranty if you go splicing into the basic wiring. A good light is a good light. There are some fantastic lights for bikes because of LED tech. Conversion bikes are ready to use whatever is the latest best bike lights…
  14. Good instruments. Dealer bikes rarely include watt meters and amp hour meters. People don’t generally understand amp hours without a little coaxing. Every battery is rated for amp hours. That’s the capacity. (To know precisely for a specific battery requires a rundown test.)  Amp hour capacity is somewhat theoretical, but if you know the pack will hold 12 amp hours, an amp hour meter tells you what is left, based on what you have used. (read our story on ebike math for more)  If you charge to only 90%, that has to be accounted for, but…you have a precision fuel gauge. The basic lights on many e bikes, or bars on the LED, that measure ‘charge remaining’?…they are very crude, and they don’t account for loss of capacity over time. Would you buy a car if it had three lights showing the fuel level, especially if one of the lights went out when you accelerated hard? An amp hour meter is the only way to know how much of the battery is left. It’s also the only way to know the true capacity of a battery pack over time. Battery packs deteriorate, so going into the second year, this starts to matter. Another useful measure is watts. Watt meters show people how hard the motor is working. It’s the best way to see how hard the motor works as speed increases. Most motors will get hot, shut down, or maybe break, if you push too many watts through them, under certain conditions. A watt meter gives you some insight into how far to push a motor up a hill. Good meters can make it a lot easier to treat you ebike ‘right’. (even if you fry a motor, a watt meter can tell you how far you pushed that particular motor, if you liked it for the job you used it for)
  15. Proprietary parts definitely lock you into a particular dealer and also the original manufacturer. At worst, this means buying one-of-a-kind batteries that may be very nice looking, but…also very high margin. Where do you get any of the parts for your ebike? There are many stories of parts being back-ordered or not being available when you need that one. A bike that you build will normally have a motor that many suppliers will carry. The batteries will simply be interchangeable from any supplier, as long as you match the basic configuration (voltage), and can mount or carry them. There’s a minimum of ‘planned obsolescence’ when it comes to a bike that you build. New motors may come along, but the sheer numbers of something like a BBS02 mean it will be supported for a long time. If the frame that you build-out is no longer what you want, you can generally move the motor and battery to a new frame. Conversion bikes have interchangeable parts. On the other hand, factory ebikes tend to have proprietary parts, and parts based on specific ‘model year’ changes.
  16. Quality motors. The motor of choice for kits these days is the Bafang BBS series, the 02 or the HD. Since the 02 has an upgrade history, with initial issues being fixed over time, and the HD is a beefy version of the 02, you already know about where you stand. The main gripes are with the shifts, and the stresses on the chain. There are options like gear sensors and internally geared hubs. Many owners disengage the motor with the brake lever to shift. The issues may be there, but they’re widely discussed, along with various methods to cope with them. Overheating is another issue, because people push the BBS to the limits. It may seem more trouble-prone than it actually is, more trouble prone than it would be if people were running the motor within the published specs. The hub motors that are sold by serious online sites tend to be the better hubs. Most of these motors are in upgraded ‘versions’, and continue to be improved. I can rebuild all the parts in a geared MAC hub for around $100, such as the gears and clutch.
  17. Open systems. This is the opposite of proprietary systems, but it’s more than parts compatibility or accessibility. Most kit motors are programmable with a simple adapter cable. This cuts both ways, but…there is a lot of frustration these days with governors on dealer bikes, generally limited to a 20-MPH top speed. The motor may be able to go quite a bit faster, but the top-speed is fixed with limited user access. Right now, it’s sort of a ‘wild west’ situation where many small manufacturers leave the settings to the buyer, while bigger companies tend to follow their lawyers. Given that California will let some ebikes go 28-MPH, it’s a very murky situation. Even if you want to follow the laws right now, they could change in the next couple of years. Then what?
  18. Public information. A dealer and his manufacturer may compile tons of information about the bikes that they sell retail. But there is little reason for them to share this information. They may know that half the motors from a certain series are prone to burning out, but they are not likely to tell you, especially when you are standing on the showroom floor. By contrast, if you want to know everything bad about the Bafang, just Google it. Some of the electronics in dealer bikes are complicated, and any of the troubleshooting procedures are not available. Something very small can make an ebike unusable. Kit motors from ‘zero service’ outlets like Ebay or Aliexpress often have reasonable feedback and large volumes of sales, but there is no way to judge the user experience, or even if the motor that they shipped today was the same motor thay were shipping last week. Many motors, whoever is selling them, are simply generic. In 2015, dealer bikes started to include many lower priced mid-drives. It isn’t clear how these motors will hold up over time.
  19. The second build will be even better. A second build will be based on real experience, especially when it comes to routing wires and laying out controls on the handlebars. Be aware, a bike with a motor is faster, with more stresses. It needs better brakes, and different gears to pedal efficiently. You may want to consider the comfort aspects at higher speeds. You’ll know fairly soon how fast you really want to go. People learn about where to place batteries or racks, and whether they want fenders or not. If people monitor watts and amp hours, and they know how to configure a battery on the second try. The “learning and experience” in general means there is more opportunity to do things right a second time. Any familiarity with the basic building blocks of an ebike really opens things up. You might find a nice bike at a yard sale, and think about a basic motor that you could put on it for a second or backup bike. You might just want to goof around with bikes. How often do we get to make something that actually works, something that can be a meaningful part of daily life?

bottle battery



Submitted by George Sears of Southern Utah, January 2016

Eric has been involved in the electric bike industry since 2002 when he started a 6000 square foot brick and mortar Electric Bike store in downtown San Francisco. He is a true believer that small electric vehicles can change the way we operate and the way we think.


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