Electric Bike (Ebike) Range Calculator (2023 Updated). Bafang ebike battery

Introduction: Electric Bike (Ebike) Range Calculator

One of the most common questions we get is how to calculate the geographic range of an electric bike. Basically,

  • How far will my ebike go before it runs out of battery power?
  • What is the range of my ebike?
  • How far can I go per charge?

There are many factors that affect an electric bike’s range, including the type of bike you’re riding, as well as the battery capacity, terrain, and the level of pedaling effort you as the rider put in.

If you have a Bosch motor system, then you should probably use the Bosch ebike distance calculator. But for all other ebikes, our Range Calculator is the most sophisticated online today.

The truth is that most ebikes come with a Bafang motor system or its equivalent, since they are the largest ebike motor manufacturer in the world, and have an exceptional reputation. Our ebike range calculator has been designed based on the performance of the Bafang electric bike system.

For a more precise estimate of electric bike range, we have developed a detailed ebike range calculator which has 16 Separate Inputs and Over 100 Variants. Try it now, and start keeping track of your actual range to help us refine the system. If you want to learn all the details about how far electric bikes can go, and how to get the most range from your ebike battery, skip the calculator and continue reading the rest of this article.

Average speed for the duration of your ride, including regular pedaling and use of pedal assist and throttle.

Amount of pedal power you supply to reach the average speed. 0 = Throttle Only, 9 = Eco Mode.

  • 0 Throttle Only
  • 2 Turbo Mode
  • 4 Sport Mode
  • 6 Tour Mode
  • 9 Eco Mode

Total weigh including bike, battery, rider, and any cargo you are carrying on the bike or in a trailer.

  • 100 lbs
  • 125 lbs
  • 150 lbs
  • 175 lbs
  • 200 lbs
  • 225 lbs
  • 250 lbs
  • 300 lbs
  • 325 lbs

On average, how many times do you make one full rotation per minute when pedaling?

  • 10 rpm
  • 20 rpm
  • 30 rpm
  • 40 rpm
  • 50 rpm
  • 60 rpm
  • 70 rpm
  • 80 rpm
  • 90 rpm
  • 100 rpm
  • 110 rpm
  • 120 rpm

Where is the motor located on your electric bike?

NOMINAL MOTOR OUTPUT (Watts)

What is the nominal motor output rating of your ebike? For dual drives, enter the combined total wattage.

What is the voltage of your electric bike system?

BATTERY CAPACITY (Amp-Hours)

What is the capacity of your ebike battery, as measured in Amp-Hours (Ah)?

  • 8.0 Ah
  • 10.4 Ah
  • 11.6 Ah
  • 14.0 Ah
  • 16.0 Ah
  • 20.0 Ah
  • 25.0 Ah

What style of electric bike are you riding?

electric, bike, ebike, range

Select the tire tread that most closely resembles that of the tires on your electric bike.

NUMBER OF MECHANICAL GEARS

Select the mechanical gear system on your ebike.

  • SINGLE SPEED
  • 3-SPEED
  • 5-SPEED
  • 7-SPEED
  • 9-SPEED
  • 10-SPEED
  • 14-SPEED
  • 15-SPEED
  • 21-SPEED
  • 27-SPEED

Select the mechanical gear system on your ebike.

Select the terrain that best describes the average terrain for your ride.

electric, bike, ebike, range

Select which best describes the suface conditions you will encounter most on your ride.

  • SMOOTH ASPHALT
  • UNIFORM GRAVEL
  • ROUGH GRAVEL / ROCKY
  • HEAVILY RUTTED
  • SAND OR SNOW

Which best describes the weather conditions you will encounter during your ride?

How often stop completely, and start from a standing position? Level 1 = Rarely, Level 5 = Frequently

  • NO STOPS
  • A FEW STOPS
  • SOME STOPS
  • LOTS OF STOPS
  • CITY TRAFFIC

Ebike Battery Myth Busting

First, a little electric bike battery myth busting is in order. Every ebike manufacturer should provide detailed specifications for the battery and every other component on the models they bring to market. Many will also provide estimated ranges, but rarely indicate how these range estimates were derived. That is why we built this calculator, so that you could get a fairly precise range based on your ebike specifications and riding conditions.

Estimated ranges provided by ebike brands aren’t based on rigorous testing

Next, let’s dismiss another obvious falsehood. All ebikes can be ridden like conventional bikes, simply by pedaling and using the standard gears. If the electric vehicle you’re looking at does not have operable pedals, it’s not an electric bike.

If you ride your ebike with the electronics turned off, there is no loss of battery charge. And if you ride your ebike without turning on electronics, there is no drag or resistance from the turned-off ebike motor.

There is no drag or resistance from the turned-off motor

That being said, ebikes do tend to be heavier than standard bikes, due to the added weight of the motor, battery and controller. But there are also lightweight ebikes that fold up and are highly portable.

The lithium-ion battery is the fuel tank for your ebike, not unlike the batteries that power your cell phone and laptop computer. In the olden days a few years ago, some legacy ebike brands would use sealed lead acid (SLA) batteries on their ebikes.

You can still find these types of batteries in cars and on mobility scooters. But with improvements in battery technology, the denser and more energy efficient lithium-ion battery has been adopted as the standard for all ebikes. These batteries will vary in their chemistry, as well as their operating voltage and capacity. Do not get a bike that does not have a lithium battery pack. Find out more about electric bike batteries at our Ebike Battery FAQ.

Like the lithium batteries powering your personal electronic devices, ebike batteries will not last forever. After about 1,000 charge cycles, you will notice that the battery is not holding a full charge. For the average rider, it takes about 2-4 years to charge and discharge an ebike battery 1,000 times. These timeframes could be greatly reduced if you expose your electric bike battery to extremes in heat or cold. So it’s best not to leave your battery in the trunk of a hot car, or in a garage that might reach freezing temperatures overnight.

When you finally need to get a new battery for your ebike, have no fear. Usually replacement or spare batteries are available from the original manufacturer, but even if they are not, there are reputable 3rd party battery companies that can provide a high-quality replacement. Our go-to favorite company for this is the Ebike Marketplace in Las Vegas.

Non-Electrical Factors that Affect Electric Bike Range

There are many variables that affect ebike range, including the bike design of bike, rider weight and riding style, terrain, weather, surface moisture, tire inflation.

Bike Design Maintenance. Electric bikes, like conventional bikes, come in many flavors. You have fat tire mountain ebikes, small folding ebikes, and laid back cruiser style ebikes. There are several key factors in bike design that affect range.

First, the weight of the bike is a major factor, but also the width of the tires. Fat tires, for example, have more surface area in contact with the ground, and more traction (friction) compared to a road bike with narrower tires. This adds resistance which can deplete energy reserves more quickly.

Second, it’s important to note that a poorly tuned or maintained ebike will have a shorter range than a properly maintained vehicle. Low tire inflation, poorly aligned gears and brakes, and high wind resistance due to a lack of aerodynamic design will all contribute to reducing the range of an ebike.

Payload. The weight of the passenger and any cargo will also have a dramatic effect on ebike range. All things being equal, a 225-pound rider with a fully-loaded trailer will place a much higher demand on the battery than a 125-pound teenager with a fanny pack. The distribution of the payload on the bike will also affect range, especially if a bike is unbalanced due to heavy loads placed on the rear rack.

Weather Terrain. Headwinds and wet roads each will reduce the potential range of an ebike. Likewise, how hilly your ride is, and if you go off-road on gravelly trails will impact how far you can travel on a single charge.

Electrical Factors that Affect Ebike Range

All electric bikes have 3 essential components that set them apart from conventional bikes. These are the motor, the controller and the battery. Each of these electrical components plays a critical role in the performance of an electrical bike, and if any of them are not working properly, it can adversely affect your ebike performance range.

If you struggle with the concept of electrons running through wires to power a motor, you’re not alone. Check out the Water Pipe Analogy graphic below.

electric, bike, ebike, range

We use watt-hours to measure the energy capacity of a battery pack, and this will help you figure out how long you can ride your ebike before fully discharging the battery. But before we get into watt-hours (symbolized Wh), let’s first review what a watt itself is.

A watt (W) is a unit of power, and power is the rate at which energy is produced or consumed. Think of watts as a measure of electrical flow. Does an electrical device need a big flow or a small flow to work? For example, a 100W light bulb uses energy at a higher rate than a 60W bulb; this means that the 100W light bulb needs a bigger “flow” to work. Likewise, the rate at which your solar energy system “flows” power into your home is measured in watts.

A watt-hour (Wh) is a unit of energy equivalent to one watt (1W) of power expended for one hour (1h) of time. A watt-hour is a way to measure the amount of work performed or generated. Household appliances and other electrical devices perform “work” and that requires energy in the form of electricity. Utilities typically charge you for electrical energy by the kilowatt-hour (kWh), which is equal to 1,000 watt-hours.

An ebike battery is measured by its voltage (V) and amp-hour (Ah) rating. To calculate the Wh of an ebike battery pack, we simply multiply its V and Ah to get the Wh.

  • A battery rated at 36 V and 10.4 Ah will have a 417.6 Wh capacity (36 x 10.4 = 374.4), like on the Eunorau UHVO All-Terrain Ebike
  • A battery rated at 48 V and 21 Ah will have a 1,008 Wh capacity (48 x 21 = 1,008), like on the Bakcou Mule.

To learn more about ebike batteries beyond simply their range potential, check out our Ebike Battery FAQ. And if you want another expert’s opinion about ebike range, check out Micah Toll at Electrek.

Everything you need to know about e-bike batteries [from a battery engineer]

Would you be the person taking the stairs or the escalator?

I’ll be honest. barring the one-off day that I’m feeling particularly sprightly, I would just hop on the escalator with those 30 people on the right. And I’m willing to guess that most of you would too.

What we can gauge from this picture is that most people would rather do as little work as possible to get from point A to point B. This is especially true when it comes to commuting on a bike. The picture above is analogous to the difference between a regular bike and an e-bike.

Even if we address all the concerns when it comes to biking in a city (like safe biking infrastructure), we can’t expect to change fundamental human behavior. when given the option between less work or more work to achieve the same outcome, people will more likely choose to do less work.

Since getting my e-bike, I can comfortably bike from my home in Somerville to the Seaport district in Boston. a roughly 5-mile trip. in just about 20-minutes. All of a sudden, biking 5-miles is a piece of cake. I also don’t have to spend time sitting in traffic, waiting for public transit, or worry about showing up to a meeting looking like I swam across the Charles river to get there.

The beauty of an e-bike is that it makes cycling an inclusive mode of transportation because it doesn’t discriminate by age or physical ability.

When it comes to purchasing an e-bike though, there are a plethora of options for both the bike and battery. So how do you decide which one is best for your needs? As a battery engineer who has built hundreds of batteries and logged way too many hours soldering battery packs, here are my thoughts on the most commonly asked questions when it comes to e-bike batteries.

If you’re new to battery terminology, you might want to start here: Battery terms that every e-bike owner should know.

In this post, we’ll cover the following questions:

What is the best e-bike battery?

This is one of the hardest questions to answer. There are so many variables that go into what makes a good battery and what’s best for you, may not be the best for me. Even then, a good battery can perform poorly if it’s not cared for properly.

Battery packs are made up of individual battery “cells”. Cells are classified into cylindrical cells (like your AA and AAA) and prismatic cells (like the one in your phone). Each class of battery is manufactured in a variety of form-factors (in the battery world we use this term to mean size). The most commonly used form-factor of cells in an e-bike battery pack is the 18650.

A battery pack is only as good as it’s weakest cell.

When it comes to batteries, in my experience, there is a strong correlation between price and quality. I don’t follow this rule when it comes to most things like for example, box wine (I’m just saying, there are plenty of really good box wine options these days!). When it comes to batteries though, you really don’t want to be compromising on quality because you’ll eventually end up having to pay the price.

Here are some things to keep in mind when purchasing an e-bike:

Cell Manufacturers: Panasonic, LG, and Samsung have a good reputation in the battery industry for their high quality cells, so paying a premium for these cells is certainly worth it. If the e-bike you’re trying to buy doesn’t have or provide cell manufacturer information, they’re likely not going to be a reliable source anyway.

Cell Chemistry: Lithium-ion (li-ion) batteries are the best option for e-bikes. Although lead-acid batteries are significantly cheaper, they’re three times as heavy as their li-ion equivalents.

Li-ion has several variants of cell chemistry. The most popular ones for e-bikes are Nickel Manganese Cobalt (NMC), Lithium Cobalt Oxide (LCO), and Lithium Iron Phosphate (LFP). The metrics to look for when selecting a cell chemistry are:

  • Specific Energy: has an impact on the range of your battery.
  • Specific Power: how the battery handles high load scenarios like going up
  • a hill.
  • Safety: does the chemistry have a history of high in-field failures.

There are trade-offs when choosing one chemistry over another, but as we’ve shown in the image below, NMC and LFP are both great options that both offer the best value in terms of performance, price, and safety.

Picking the right battery chemistry has to do with figuring out what matters most to you. Do you want a battery that has a longer range (higher specific energy) but doesn’t have as much power? Or do you want a battery that has a more power (higher specific power) but may not last as long?

In my opinion, the best e-bike batteries are likely going to be made from cells manufactured by Panasonic, LG, or Samsung with either LFP or NMC cell chemistry.

What is the range of an e-bike battery?

The range of a battery pack depends on the amount of energy packed inside of it and is measured in Watt-Hours (Wh). Watt?

Watt-hours are calculated by multiplying the battery capacity, in Amp-hours, by the battery Voltage, in Volts.

Let’s assume that, on average, 1-mile requires about 25Wh of energy. So a 14Ah, 36V battery should get you about 25-miles per charge.

Keep in mind that the weight of the rider, outside temperature conditions, and the amount of pedaling will make a significant difference in range.

A word of caution: the range that e-bike manufacturers provide should be taken with a grain of salt. That number is generated from tests that are run in perfectly tailored lab conditions. Do you charge any of your electronics in an incubation chamber set at 28° C with a lab-grade charger that applies the perfect current while charging? Yeah, I don’t either. And so, We should assume that the manufacture-specified range is delivered only if the battery is charged and discharged under ideal conditions i.e. not real world conditions.

For a more realistic estimate, shave off 15% of the manufacturer specified range and assume this padded number to be your real range.

If you’re looking for a longer range, choose a battery that has higher capacity (Ah). If you’re looking for more power, choose a battery that has higher voltage (V). Learn more why voltage and capacity matter.

What is the lifespan of an e-bike battery?

There are several factors that affect the lifetime of a battery such as:

  • environmental conditions: temperature during charging discharging
  • charging rate: how fast or slow your battery is charged
  • charging voltage: what voltage the battery is charged to
  • depth of discharge (DoD): what voltage the battery is discharged to

The list above isn’t exhaustive but, in general, batteries decay as a function of time in the charged state. Period.

Day 1: You get your new e-bike and charge it up to 100% and go on a bike ride. When you come home, you charge the bike back up to 100% and you’re excited to ride it again soon.

Day 2. 364: Life get’s in the way and you still haven’t been out on your bike since that first ride.

Day 365: One year later, it’s the perfect day for a bike ride and you finally have some time on your hands. You head to your basement, unlock your bike, and excitedly turn it on. 80% charge. What? You clearly remember charging your bike to 100% last year before moving it to the basement!

The truth is, we can’t beat thermodynamics. I’ll say it again: batteries decay as a function of time in the charged state.

Now, because you left your battery at 100% for a whole year in a basement with no temperature control, you inadvertently caused your battery to lose a certain amount of irreversible capacity. Your range will be ~20% lower and you’ll likely have to replace your battery sooner than you expected. The table below shows you how much recoverable capacity exists in a battery after storing it at different temperatures and different charge states for 1-year.

This is why a lot of electronics come with batteries that are only partially charged. to help slow down this decay. That being said, it’s hard to track how long e-bikes and their batteries have been sitting in warehouses before being delivered to your door so you could get a battery that has been decaying for a year or two.

Manufacturers also tend to overrate their batteries and will make claims about certain batteries having a lifetime of at least 1,000 cycles. Show.me.the.data.

The lifetime of a lithium-ion battery is described as the number of cycles until the capacity (Ah) drops below 80% of it’s initial capacity. In general, this is roughly 250-400 cycles (depending on battery chemistry and other factors) which amounts to roughly 1.5 to 2 years if you charge discharge daily and care for your battery properly.

How to charge your e-bike battery to make it last longer

  • The thing that will kill your battery faster than anything else is leaving it charged at elevated temperatures. If it’s 80 degrees outside and you have your e-bike fully charged, move it indoors where it’s cooler and try to drain the battery as soon as possible.
  • Charge your battery at room temperature as often as possible.
  • When sourcing an e-bike battery charger, the slower the charge rate the better. For example, if you have a 2-Amp charger, and your battery is a 14 Ah battery pack, you are charging at 14 Ah / 2-Amps = 7-hours. This is a nice, slow charge which will certainly improve the longevity of your battery pack. Avoid charging at rates that are faster than 2-hours for a full charge.

There’s a lot that goes into choosing the best battery for you e-bike, and there certainly isn’t a one-size-fits-all approach. But if I were buying an e-bike battery today, here’s what I’d do: LFP or NMC, slow charge, avoid storing or charging in hotter temperatures, and leave the battery at around 30% charge if you don’t plan on using it for a while.

Have questions? We’d love to help. You can get in touch using the contact form or find us on @somerville_ev

Also, subscribe below for alerts on our next post to learn more about batteries!

How to convert a bike to electric power | Electric bike conversion kits explained

The best electric bike conversion kits will enable you to add a motor to your existing bike simply and relatively cheaply – at least compared to the price of buying a whole new electric bike.

There are an increasing number of ebike conversion kits out there, and they’re getting more sophisticated and easier to install on your bike, making for a practical alternative to a new purpose-built electric bike. An electric bike conversion kit will include the motor to drive you along and the battery to power it. It also needs to include the apparatus to control the power output level. This usually takes the form of a bar-mounted display.

In addition, a kit will include sensors to detect how fast you’re travelling and your level of pedal input to ensure the power supplied matches your needs. We’ve tested a few electric bike conversion kits here at BikeRadar, but there are lots more we’re yet to try. A full test of the best electric bike conversion kits is in the works – stay tuned. If you want a more detailed explanation of the different types of kit available and things to consider when purchasing an electric bike conversion kit, then head to our explainer further down the page.

Best electric bike conversion kits 2022: our picks

Swytch electric bike conversion kit

Swytch says its electric bike conversion kit can convert any bike into an electric bike. Stan Portus / Our Media

  • Pros: Very compact; easy to install; variety of range options
  • Cons: 100mm threaded front axle only; not compatible with thru-axles

London-based Swytch makes a conversion kit that, it says, is the lightest in the world at 3kg total weight. It can convert any bike into an ebike.

The kit includes a 40Nm brushless hub-based motor that comes pre-laced into a replacement front wheel. The lithium-ion battery pack connects to your handlebars and also acts as the system controller and LCD display.

There’s a crank-mounted cadence sensor, and that’s all you need to fit to your bike to get going.

There’s a Brompton-specific kit available too, with an adaptor for the Brompton’s front luggage mount.

Depending on the range you want, there are three sizes of battery pack available, which provide a claimed range of 35km, 50km or 100km.

Swytch has recently unveiled an even more compact kit with a.sized battery that weighs just 700g and, Swytch says, gives 15km of range.

Latest deals

Cytronex electric bike conversion kit

Cytronex makes electric bike conversion kits for Bromptons, as well as standard bikes. Russell Burton / Immediate Media

  • Pros: Clever sensor tech; decent range
  • Cons: Not much onboard info on battery level and range

Weighing between 3.2kg and 3.6kg, the Cytronex ebike conversion kit is another front-wheel conversion to house a hub motor, but in this case, the battery is designed to fit in a standard bottle cage.

We tested the kit on a Cannondale Quick hybrid and reckon that conversion takes around 30 minutes. The charge level is displayed via LEDs on the battery, which also houses the system controller. We got up to an impressive 48 miles on a charge.

electric, bike, ebike, range

We’ve also tested the kit on a Brompton P Line lightweight folder, where the total weight undercut the C Line-based Brompton Electric. Fit it to a C Line and it’s also cheaper than the Brompton Electric.

Electric bike conversion kits: different types explained

Electric bike conversion kits come in styles to suit all types of bike. Russell Burton / Immediate Media

There are a number of ways to electrify your existing bike for assistance up those hills: you can fit a powered wheel, either front or rear; you can attach a drive unit to the bottom bracket; you can fit a motor above the rear wheel and drive it via friction; or, most sneakily, you can conceal a motor in the seatpost.

Whether you ride a hybrid, mountain bike, road bike or even a folder, tourer or gravel bike, it should be possible to convert your bike.

Many can even be fitted by a competent home mechanic if you’re feeling handy and have an afternoon spare.

So, what are your options? Let’s take a look at the different ways to convert your non-assisted bike into an electric bike.

Powered ebike wheels

The Swytch is a good example of a readily available universal electric bike conversion kit that uses a motor at the front hub. Swytch

Fitting a powered ebike wheel is probably the most practical option for many people.

A powered ebike wheel is built around a special hub that contains a motor. This is usually powered by a separate battery.

This sounds simple, but the main downside is that it adds rotating mass to your bike, which feels harder to accelerate than non-rotating mass.

There’s a steady stream of front- and rear-wheel conversion kits on Amazon and eBay, all looking suspiciously similar, priced from around £150 and with names you’ve probably never heard of.

Be wary of systems controlled by a throttle (also called ‘twist-and-go’) though. Legally, they’re classified as electric motorcycles rather than ebikes, and need to be taxed and insured. Take a look at our guide to ebike laws for more information.

Rear-mounted friction drive ebike conversion kit

Readers of a certain age may remember earlier incarnations of these in the 1980s/90s: a box that sits on your rear wheel and powers it via friction with a rubber flywheel driven by a motor.

The idea hasn’t gone away, and lives on in devices such as the Rubbee, which promises bolt-on electric assistance for nearly any bike.

Rubbee’s base model has a claimed weight of just 2.8kg, with a 16km range that can be extended up to 48km with the top-spec, 4kg version.

It works with any wheel diameter between 16in and 29in, has an integrated carrying handle and clips on and off your seatpost. start from €579.

Concealed ebike conversion kit

The Vivax Assist hid a motor in the seat tube of the frame and applied power directly to the axle of the crank. Vivax

Now we come to the low-key way to do it – hiding a motor inside your bike so no one knows it’s there.

The Vivax Assist was the best-known device for doing this, although the company has now ceased trading. It’s the system that was used by Belgian cyclocross pro Femke Van den Driessche in 2016 to power her way to victory in her home championships. She was found out at a subsequent race, got a six-year ban and quit racing.

Vivax Assist may be no more, but we reckon this idea still has legs – at least for the budding cyclocross cheat.

Mid-drive ebike conversion kit

eBay and Amazon are awash with mid-drive motor electric bike conversion kits like this one from TongSheng. TongSheng

Many commercially available ebikes are powered with motors mounted around the bottom bracket, near the pedals.

These have the advantage of placing the weight low down on the bike, making it more stable.

This isn’t just a ready-made option though – you can also buy aftermarket conversion kits with mid-drive units.

Bafang is a brand that is increasingly focusing on complete ebikes, but it also offers a mid-drive conversion kit on Amazon, as well as wheel hub motors.

Priced from £360, Bafang says the conversion is easy to install using only a few tools to remove the bottom bracket and fit the drive on the front of the down tube.

As above, be careful of throttle-controlled kits that won’t pass the UK ebike regulations and will legally be considered a moped.

You’ll find other mid-motor systems on Amazon too, such as that from TongSheng, which is claimed to fit 95 per cent of standard bike frames and be 30 per cent lighter than a Bafang unit.

It uses a torque sensor, so should fall within the ebike regulations, and is priced from around £350 – although that doesn’t include a battery.

German brand Pendix has a mid-drive system priced from €999 to €2,190 that weighs from 5.4kg for a 28km range. It replaces a BSA bottom bracket and can be fitted to folding bikes as well as a wide range of regular machines.

Folding ebike conversion kit

The Brompton electric conversion from Electric Concepts is one of many kits available to electrify an existing Brompton. Electric Concepts

What can you do if you’ve got a folding bike and want to join the electric revolution?

Well there’s good news if you’ve got a Brompton – a number of ebike conversion kits are available. They generally work with a powered hub in the front wheel and a battery carried in a bag mounted on the front.

As discussed above, Swytch and Cytronex can both be used to convert a Brompton. Swytch’s Brompton kit is priced at £999, although discounts of up to 50 per cent are sometimes available on the site.

As with its other systems, there’s a front wheel hub motor, a clip-on power pack and a bottom bracket torque sensor. Quoted range is up to 50km.

Swytch will also build wheels for folders with other wheel sizes and different fork blade widths, such as Dahon’s models.

Are electric bike conversion kits legal?

If your electric bike uses a throttle, it is technically classed as a moped, and must be taxed and insured as such. Simon Bromley / Our Media

Most electric bike conversion kits are legal to fit to a bike, although the precise rules differ depending on where you live.

In most of the world, the motor needs to be limited to a maximum of 250 watts of continuous power output, unless the electric bike is only used on private land.

You also need to be pedalling for the motor to work – a throttle can only operate at low speeds and assistance needs to cut out once the speed exceeds 25kph. There may be a minimum age to ride an electric bike: in the UK it’s 14.

The rules are different in the US, where higher power outputs and higher speeds are usually legal, while Australia has some variants as well, so it’s worth checking that your electric bike conversion kit is legal where you live before purchasing.

Is converting an electric bike worth it?

An electric bike conversion kit is not cheap, so you want to be sure it’s going to work for you.

You need to have a candidate bike in decent condition to justify taking the kit route.

If you’re going to have to buy a bike to fit the kit to, or going to need to make a lot of repairs to your bike to make it roadworthy, the total cost is probably going to mean it’s not a lot cheaper than buying a complete electric bike.

You need to be confident you can fit the kit yourself as well. If you’re going to have to pay a shop to fit the motor or sort things out if the conversion goes wrong, your savings over purchasing a new electric bike may dwindle quickly.

It’s also worth noting that an electric bike conversion kit may affect your bike’s handling, particularly if there’s a heavy motor and battery mounted somewhere where the bike was not designed to carry it.

Drivetrain components may not be adequately beefed up for the extra power they need to transmit and may wear or break. Factors such as torque steer may be a problem, and cabling and sensors can be unsightly.

In contrast, if you buy a complete electric bike from a reputable brand, it will have been engineered around the motor and battery, and you’ll know what the finished product looks like.

Can you convert any bike into an electric bike?

There are designs of electric bike conversion kit that will work with pretty much any type of bike. Kits are available that are engineered specifically for certain bikes, such as the folding bike conversion kits we’ve talked about above.

A design such as the Rubbee should be mountable on most bikes. However, tyre wear may be an issue with a road bike with narrower tyres, and wet-weather grip between the motor’s drive wheel and the tyre may also be a problem.

But some kits, such as those that work with a specific bottom bracket configuration, may not fit on some bikes. An unusual wheel size may also limit available options, so it’s worth checking the compatibility of your planned solution before buying.

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How to Replace a BMS in an e-Bike Battery

How to replace the BMS of an eBike battery — how to test, buy a replacement, and replace it.

Dana Hooshmand

I’m an entrepreneur and adventure traveller. I build software, immerse myself in other cultures and languages @ Discover Discomfort and make fun of the business world @ The Vanity Metric. posts by Dana Hooshmand.

Dana Hooshmand

Recently (as in a few months ago) I had a problem with my e-Bike where my battery wouldn’t hold a charge, and wouldn’t accept a charge from the charger.

Normally, when I plug my eBike’s battery in, the charger’s cooling fan whirls to life and one of the lights changes colour, indicating it’s charging. This stopped happening!

I did a suite of tests, tried a few techniques recommended on forums and by the lead tech at Luna Cycle, and eventually confirmed my BMS was broken and needed to be replaced.

So in this guide I want to outline

  • A bit about my bike (as background)
  • How to test your BMS to confirm it needs replacing (or whether it’s something else)
  • Tests to do on a BMS and battery before you replace it
  • Why a BMS might fail
  • Where to get a BMS to replace it with — what to look for, and what to pay; and
  • How to change the BMS over

About my electric bike

My electric bike is semi-custom. It is built like a custom, but by Luna Cycle in the USA. It has a Bafang (八方电气, “Eight Sides Electrical Appliances”) motor with a 50A controller that Luna Cycle calls their “Ludicrous” controller, though I have it set to operate in 25A mode.

Because this was a crazy year, it ended up being stored fully charged, and allowed to fully deplete, while in storage. This isn’t good for an eBike battery, it turns out, and so a few things needed to be done to get it back on the road.

The BMS — or Battery Management System — of a battery pack is the part that regulates both input (charging) and output (discharge) voltage and current from the cells.

Even though this might appear to be a guide for one kind of electric bike battery, it’s generally applicable to all e-Bike batteries, and even batteries on other devices like scooters and mobility devices.

Why? Because many of these batteries are built with the same underlying technology — a pack of lithium 18650 cells.

How to test an electric bike’s BMS/charging system

When the charging system of an electric bike fails, it means one of a few things:

  • Supply failure: The charger might be broken (not delivering voltage or current necessary to charge)
  • Mechanical failure: A connector wiring inside the battery might be broken,
  • Cell failure: Some of the cells inside the battery may have failed, or
  • BMS failure: The battery management system may not be operating

To get to the core of the problem, you have to test everything one by one.

The first (and easiest) thing to test is the charger. You measure the output voltage. For a 52V battery like mine, it should be supplying about 58V. For a 48V battery it should supply around 54V.

After you measure the output voltage, you do what’s called the “light bulb test” — where you use an incandescent bulb hooked up to the outlet. This is easier in America (or Japan I guess) where the voltage supply is 110V, but it still works with 220V bulbs.

You could also test it with an automotive bulb if you have one. But it might blow!

Second, test for mechanical failures. Probe around with a multimeter and make sure you read operating voltage in the places where you should.

Also, open up your e-bike battery and check all the wires are intact, and that none of the solder joints have broken. Bikes get beaten up and it’s possible — likely — that a joint will fail at some point, especially if your battery has gone flying across the road because you forget to lock it (guilty! Actually I lost the key for a while. )

Finally, you have to test the internals of the battery.

I did a suite of tests that Luna Cycle said I should do

  • Opened it up and tested all the wires and connections
  • Did a BMS battery reset
  • Tested voltages across the pins — making sure every individual cell was operating correctly

One trick for testing voltage across the pins of the BMS is that they’re often coated with silicon. You should scrape it away gently before checking the voltage.

How does the BMS of an e-Bike battery fail?

A BMS is a delicate issue. There are actually people who believe in charging batteries without a BMS, like this guy on YouTube:

If “jumping” your BMS is unsucessful, you can do more extensive testing on your battery pack and on your BMS.

Watch the video below. The core of it is to check individual cell voltage (confirming they’re in the 3.6-3.8V range), making sure no cell is dead. If it’s dead, you can replace it, probably for about 15-20 of parts (and. a spot welder and some nickel strips).

Look at the number of pins and the style of connector at the top of the BMS.

It seems a lot of BMS manufacturers have an informal agreement as to what the connector should look like. This is good news!

The second rating to look for is the current rating. My bike is rated for 50A peak, so I found a controller that promised to get to that spec.

I would treat current ratings on eBay with a grain of salt. It’s possible they might be truthful, but it’s possible they’re wildly exaggerating. Given they’re so cheap, get the biggest spec one you can reasonably afford, assuming it’ll be a weak point.

Installing the new BMS

There are three steps to installing the new BMS.

Firstly, remove the connector at the top. Mine is a 14-pin connector; you might have 10 or 12 pins or some other number. This should be a plug-and-play replacement for your current BMS.

Secondly, use a low-power soldering iron to de-solder the three connectors at the bottom.

Finally, use the soldering iron to connect the wires to your new BMS.

You should now be ready to power up and give your repaired battery a go. If you’re lucky, like I was, then your charger will whirr to life and your battery will take a full charge.

Optional — I realised, as I was writing this, that there was a chance I could have destroyed the BMS again! The battery was discharged, and a surge might have fried it.

Luckily, this didn’t happen. But you should consider perhaps directly recharging each cell of the battery pack if you have a 3.6V battery charger available.

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