If you’re looking to upgrade to an e-bike, you’re probably like the thousands of other new riders trying to find what e-bike is best for you and your intended price point. While there is a lot of information out there, we think one of the best ways to start your search is by examining the motors and batteries. Those two components influence an e-bike’s performance, price, and weight, so finding the right drive unit and battery for your riding needs and budget is the best place to start.
We’re here to do the heavy lifting for you. Start by taking our e-bike quiz below to find the type of ride that best suits your pursuits, and keep reading as we break down the key considerations to make for all the vital portions of an e-bike.
By the time you finish this guide, you’ll know exactly what to look for during your next trip to the shop or online purchase.
All e-bike motors start with the same basic function: converting electrical energy into mechanical energy. Inside a brushless DC (BLDC) motor is a rotor, with permanent magnets attached, spinning within a circle of electromagnets known as the stator. Hall effect sensors switch the stator’s electromagnets on and off in a sequence that spins the rotor, generating torque and making your e-bike go.
All e-bike drive units use this design, but there are three primary motor designs that harness the power of the BLDC to achieve different results.
Mid-drive motors position the motor between the cranks, where the bottom bracket would be. These motors use internal gear reduction to generate high torque in a small package. That, combined with the bike’s geared drivetrain, means mid-drives like the Bosch Performance Line CX can climb hill after hill without overheating.
High torque, efficiency and centered weight distribution make mid-drive motors popular on electric mountain bikes, and e-cargo bikes and higher quality hybrid bikes. However, mid-drive e-bikes often cost more than comparable hub-driven models because hub motors are cheaper to manufacture. But if you’re looking for something that efficiently climbs up hills, goes off-road or simply provides the most smooth, natural ride, go for a mid-drive electric bike.
Hub motors are as they sound: within a bicycle’s front or rear hub. They come in two basic variants, direct-drive and geared. Typically 3 to 6 inches in diameter, the hub has spokes attached to its exterior and electromagnets lining its interior. When you apply power, the electromagnets spin the hub, causing the wheel to rotate. A direct drive hub motor has just one moving part and is therefore cheap to make and reliable—as long as it’s not going over many hills.
Hauling you and your e-bike over a steep hill is not what direct-drive motors do best, however. Without gear reduction, the motors need a lot of current to get up to speed, causing them to heat up and burn through your battery faster. They’re ideal for cruising at high speeds, though, because they become more efficient the faster you go. They’re also the only type of motor you can buy on a complete e-bike that does regenerative braking, putting a marginal amount of power back in the battery by reversing the motor’s polarity when you squeeze the brake levers.
Geared hub motors feature internal gear reduction and potentially higher torque vs. direct drive hubs. They’re popular among affordable e-bikes. Some electric road bikes will opt for a compact geared hub motor when mid-drive torque levels are not required.
However, mid-drives still dominate the high-performance market because geared hub motors struggle in the key areas of heat dissipation and toughness. They’re fine for on-road and light off-road riding, but users have reported internal gear failures after trail riding, and that’s likely why you don’t see them on e-mountain bikes.
Your wallet is going to feel the e-bike’s battery more than any component, so you’ll want to know how you’re spending your cash. Most e-bikes use lithium-ion batteries, the type you find in cordless drills and leaf blowers. They’re favored for their high energy density and durability.
Battery capacity is measured in watt-hours (Wh), a unit of energy. Most e-bikes have batteries between 250 and 500 watt-hours, and you’ll end up paying about $1 per Wh.
An e-bike’s range will depend on the hilliness of your route, the bike’s weight, its tires’ rolling resistance, and other variables. But in our testing, a 500 Wh battery will take most people at least 30 miles under moderate assistance, including a few sizable hills. Bosch makes it super easy to explore range possibilities for all their motors with this handy range calculator.
Before you buy, verify that the bike’s battery is lithium-ion (Li-ion). Some e-bikes use lithium polymer (LiPo) battery cells, which are popular in RC cars and drones because they’re even lighter and able to discharge more quickly than Li-ion cells. However, LiPo batteries typically come in laminate packaging rather than cylindrical cells, making them more prone to damage (read: fire hazard).
For extra peace of mind, try to find a certification from Underwriters Laboratories (UL), a North American product testing company that rigorously inspects consumer electronics to ensure they won’t shock you or catch fire.
Weight and Reliability
Beyond the motor and the battery, you’ll also want to consider an e-bike’s weight and reliability, both of which will factor into your ownership experience. You don’t want an e-bike that’s too heavy to put on a car rack or constantly breaking down.
Weight: Electrifying a bike adds weight that will be more than compensated for while riding, which is another reason to consider the central weight distribution of the mid-drive motors. However, there’s no e-assist for hoisting the e-bike onto a tray rack or into the back of a minivan, so you’ll also want to consider how often you’ll have to pick the bike up. Consider if you’ll be bringing it up stairs or into public transport. If traveling with the bike is top of mind, be sure to choose an e-bike that has an easily removable battery to reduce significant weight. Many hitch racks are now being developed to accommodate the heavier e-bike with easier loading solutions.
Reliability: Just like acoustic bikes, electric bikes sometimes break down and require regular maintenance. The electric components (motor, battery) on an e-bike will not be as easy to replace as the mechanical components (cassettes, shifters), so make sure they come from a sustainable company that has a proven record of longevity. Before you buy, consider how you’d be able to service the bike—something not every bike shop will do. Brands like Bosch have an extensive global dealer network for in-person service, while others may send out a technician or ask you to send the bike back. Either way, be sure to know your options if something goes wrong. [VVJ(1]
E-bike displays can do a lot more than control the basic functions of the bike. Make sure your next e-bike’s display tells you what key data is important to you, whether that’s heart rate data, how much battery you have left, or how to navigate your trip. Here are the Bosch e-bike displays that give you all your ride data with a quick glance.