E-Bike Batteries: Volts, Amps, Watt Hours Explained
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What Are These Volts, Amps, and Watt-Hours? How Battery Specifications and Capacity Equate to Capability and Cost
Understanding e-bike batteries can be challenging, even for those of us in the know; the nitty-gritty details are figured out by electrical engineers with years of education and experience under their collective belts – and for good reason, it’s all chemistry and math over there!
You’ll encounter a host of terms when reading about e-bikes or looking at electric bike battery specifications: things like battery size, capacity, voltage, amp hours and watt hours. Some of these words are more-or-less interchangeable, others are related but distinct. All of them can be confusing, but they are also hugely important in understanding electric bikes and their capabilities – most notably when trying to interpret how far they can take you before needing to be recharged.
In this guide to e-bike batteries, the helpful writers at Electric Bike Report will help you to understand the meaning of common battery terms and their relation to the performance of the electric bikes they power.
E-Bike Batteries Explained
Batteries are one of the core elements of electric bikes. They are needed to supply power to the motor, which in turn provides assistance to the rider, and reduces the amount of human effort needed to move the bike.
E-bike batteries come in various sizes, and can be mounted to the frame in different ways. Some are fully internal, and are sealed inside the bike’s frame. As such, they are not removable, except by using special methods and tools available to professional technicians. Others are removable for easier charging and replacement, whether mounted completely externally (outside the frame), partially recessed (sunken into the frame to some degree), or completely recessed (sunken entirely and nearly invisible on the bike).
Regardless of their type, all e-bike batteries are actually battery packs, and are made up of groups of cells, similar to the standard AA or AAA batteries used in everyday applications. The number of cells and the method used to cluster them together determines how quickly they can provide power and how long they can continue to supply it.
In contrast to standard AA or AAA batteries, however, those used in e-bikes are most commonly rechargeable lithium-ion batteries similar to those used inside smartphones and in conjunction with cordless power tools. Lithium-ion batteries are efficient and can be recharged hundreds or even thousands of times if cared for properly. The Light Electric Vehicle Association, or LEVA, has a great article that they allowed us to re-publish regarding proper battery care and safety to ensure maximum life span.
Fully integrated batteries such as the one on the Velotric Nomad 1 can match the bike’s color and disappear into the frame.
Electric Bike Battery Terms and Definitions
Before we dive deeper into the details, let’s consider a couple of examples of e-bike battery specifications in relation to how they usually appear:
V = Volts and Ah = Amp-hours
V = Volts and Wh = Watt-hours
Both examples convey two basic measurements, albeit a little differently. In both examples, we see volts first; this measurement relates to the availability of the electrical energy the battery can deliver. Next, either amp-hours or watt-hours are shown; these represent a battery’s capacity, or the amount of power it can store.
Let’s define these words (and a few helpful additional terms) a bit more clearly:
Current: the flow of electricity, or transfer of electrons, through a circuit.
Circuit: a closed system of wires and electrical components through which current can travel.
Volts (V): the amount of electrical force or pressure the battery can produce; the speed of the battery’s output of current. This is also sometimes referred to as the electromotive force, and is more specifically the speed at which electrons move through the system.
Note that this is a nominal rating that is used for classification purposes. In reality, a battery’s voltage varies based on the amount of power being drawn from it at a given moment, as well as the battery’s present level of charge. As current is drawn from the battery, its voltage decreases. This can be seen in an e-bike battery voltage chart.
Voltage is determined by the number of battery cells arranged “in series”.
Amps or amperes (A): a measurement of the strength of the battery’s output, or current. specifically, the volume of electrons passing through the system. This is limited by the size of the wires making up the system. Larger wires allow more current, smaller wires allow less. Generally, systems with higher voltage should use smaller wires (that limit amperage) to prevent overheating.
Amps can also be thought of as the amount of energy being drawn from the battery by what it is powering, and can fluctuate from moment to moment. In the case of e-bike batteries and their motors, a greater number of amps are drawn as the motor works harder (i.e. going uphill or using only the throttle).
Amp-hours (Ah): a measurement of charge; the amount of energy that can be delivered through an electrical system over the course of an hour.
In the case of a 10 Ah battery, it can deliver 10 amps of power in one hour, or 1 amp of power for 10 hours, etc, depending on the needs of the component that is delivering power to.
Amp-hours are determined by the number of clusters of battery cells arranged “in parallel”.
Watts (W): a unit of power, determined by volts and amps; the amount of work that can be done by one amp of current delivered at 1 volt. The amount of work is determined by the rate at which the energy is used.
This measurement is generally applied only to an e-bike’s motor, but its battery must support the motor’s needs.
Watt-hours (Wh): another measurement of capacity. In this case, the amount of work that can be done, or the amount of power that is spent, over the course of an hour. This is a direct result of a battery’s voltage multiplied by its amp-hours.
As such, a 24V, 20 Ah battery and a 48V, 10 Ah battery might look different on paper, but they have about the same amount of energy. This makes watt-hours a more reliable indicator of capacity when comparing different batteries.
Controller: A device that limits the flow of electricity through a circuit, and prevents a battery from discharging its energy all at once. In terms of an electric bike, this is the “brain” that adjusts the pedal assist system, the amount of input the motor contributes, and the e-bike’s speed.
First of all, the most common and popular voltage for high-end e-bikes and ebike kits is 48V or 52V. This is different then most lower-cost ebikes and ebike kits which run off 36V. This can also differ by sales region since in the United States 48V 52V is the standard while in Europe 36V is the standard. Lower voltage batteries are cheaper but the main difference between lower and higher voltage batteries are that the higher the voltage the better the power and performance!
Note: Our Mid Drive motors are compatible with with both 48V or 52V batteries however our Front hub motors only work with 48V batteries.
Why would you choose a 52V battery over a 48V battery?
range. 52V batteries when compared against 48V batteries with the same rated Ah will have more range as they have a larger battery capacity (Watt-hours rating).
Power. 52V batteries can provide more power to a motor when the motor needs it. 52V batteries also provide a better voltage range for the motor to operate in when compared with 48V battery.
Efficient. 52V Batteries can allow your motor to run at a lower current (amp) draw when operating at the same conditions when compared to a 48V battery. This can help reduce the amount of heat being built up in the motor and reduce overheating and premature failure
Versatile. 52V batteries will provide better performance than a 48V battery when used in cold weather
Why you may not need 52V battery and a 48V battery maybe enough?
You are not needing any additional power for offroading or climbing steep hills and you are just looking to do city riding and commuting.
The 52V is more effective, meaning better performance.
The reason is that a 52V e-bike battery provides greater efficiency using fewer amps generating the same or better power for your bike.
A 52V e-bike battery provides a faster speed to the motor than a 48V.
One of the most important differences is related to the range, a 52V e-bike battery offers a range wider than a 48V.
A 52V battery fresh off the charger will produce almost 59 V while a 48V battery will produce around 54.5V.
Putting Together Battery Voltage and Motor Operation
Keep in mind that BBS02 and BBSHD Mid Drive motor controllers can take a range of voltages from 40V to 59V, so clearly these units perform better at the higher end of the range however if the voltage drops so will the power.
As a battery drains and the voltage drops a rider will experience that they are no longer be getting the same power from the motor which will also be noticeable with the throttle lag. This difference in power will be more noticeable with a 48V battery than with a 52V battery.
Which is the best battery to get?Unfortunately, it is not that easy as ebike battery packs are in no way a one size fits all item which is why we offer so many different battery options! In order to see the estimated range based on the motor and battery pack that you are looking at we recommend clicking the button below to learn more about our range estimates!
Li-Ion Ebike Battery Charge Charts
Whats an 80% charge on a 48v battery? on a 36v? 52v? These charts give answers to questions like these on all common ebike battery voltages.
Remember, ALL numeric charts show ballpark values that may be numerically correct, but no generic chart can match your individual cell characteristics, your pack’s age or its chemistry. Bottom line: imperfect charts like this are still good baseline references. Use these and teach yourself how to read the voltage gauge on your display screen.
Quite some time ago, I produced a series of charge status charts for a variety of common lithium-ion battery voltages. They’ve become a fairly common link to help folks out on various groups who use these battery voltages in their ebikes.
I built them using Google Sheets, so they are not web pages, which I suppose has kept them from being widely linked in search engine results when people are looking at such things.
Here for the first time are direct links to the charts on a normal web page.
Volt (10S) Battery Charge Chart
The first link is to the lowest voltage: 36v. Generally this is the lowest voltage you will find on a modern, commercial ebike. Note that its called ’36 volt’ but really that is the ‘nominal’ value. A 36v battery is actually fully charged when it is at 42.0 volts.
Volt (13S) Battery Charge Chart
The next common size is 48v. These batteries are fully charged at 54.6 volts.
Volt (14S) Battery Charge Chart
The next battery voltage is 52v and very common. 52v batteries will work on systems designed for 48v, and why is easier to understand when you become aware that a ’48v’ battery really tops out at over 54 volts. A ’52v’ battery tops out at 58.8v, so it essentially lets you use a 48v system for a longer time at higher voltage levels that it is already designed to utilize.
Volt (16S) Battery Charge Chart
With a 100% charge voltage of 67.2 volts, when you have one of these you are getting into high voltage territory
The best electric bike conversion kits 2023 and how to fit them
The best electric bike conversion kits can give you an extra boost of power without the expense of purchasing a new electric bike. We’ve fitted some of the best e-bike conversion kits ourselves, so will walk you through the process, how easy it is and how the different systems perform.
E-bikes are soaring in popularity – and for good reason. The best electric bikes replace a car for running errands around town and greatly increase the distances it’s possible to ride on one of the best commuter bikes. An e-bike can also be a great tool for boosting your fitness, whether that’s enabling you to ride with a greater range of people or offering the motivation of a greater range of roads to explore.
But is an e-bike worth it,? As the best ebike conversion kits promise to add power to an ‘analogue’ bike for a lot less than a full ebike, it’s an easy, cheaper way to get an electric boost.
In this guide we’ll take you through the surprisingly broad range of benefits an e-bike conversion kit has to offer and – most importantly – how to perform an e-bike conversion, based on our hands-on experience. For a walk-through on how to do it, you can check out the video above or read on for a step-by-step guide – it genuinely is so much simpler than you would think.
When buying an ebike conversion kit there are a number of factors you’ll need to consider. Most importantly you’ll need a kit that will fit your bike. To help with this it pays to take a few frame measurements, notably the width of your forks and the width of the rear stays, as well as noting the wheel size and the type of brakes. You can then match these details to the kit specifications.
Naturally you’ll also need to consider the cost and how much you chose to spend on an ebike conversion kit will be dictated by not only your budget but also your needs. If you’re unsure of just how much you’ll use the converted bike then it’s prudent to opt for a cheaper kit. you can always upgrade down the road.
You’ll also want to consider where the motor will be located, and match this to your bike and your mechanical prowess. Front hub motors are typically the easiest to fit, while mid-drive motors require more effort. A rear hub motor lies somewhere in between the two, and like a front hub option is applicable to a wide range of bikes.
Other considerations include the type of battery and the wattage rating. 36 or 48 volt battery is standard, with wattage usually running from 300 to 600 watts.
The Swytch kit is super-simple: just swap out your front wheel, wire up the controller and battery and you’re off. The battery is also very compact, allowing you to remove it from the bike easily to carry with you.
The TongSheng kit positions the motor at the centre of the bike, so it will fit to a wide range of designs. It’s lightweight for its high torque and power output, although you’ll need to buy the battery separately.
The Voilamart kit is an inexpensive rear wheel conversion option, although you’ll have to source a battery separately. It’s slightly fiddly to fit as well and requires additional waterproofing if you plan to ride in wet weather.
The best electric bike conversion kits
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Our team of experts put in hard miles testing cycling tech and will always share honest, unbiased advice to help you choose. Find out more about how we test.
Wheel sizes: Each wheel is custom built – specify your required size at checkout (Bromptons also catered for)
Reasons to avoid
The newly updated Swytch system is one of the simplest conversion kits to fit out there. The latest version, launched in August 2022, has a smaller, neater battery pack that improves the bike’s dynamics and lowers its weight. There’s the choice of the Air battery (700g, range 15km) or the Max battery (1,100g, range 30km). Both use the same mount, which places the battery to the front of the handlebar.
The motor sits in the front hub and we found it to be pretty discreet. Incidentally, the new batteries will work with the original motor and pedal sensor, so if you already own the original kit you can upgrade it with just a new battery without having to buy the whole kit again.
The Swytch kit is incredibly easy to fit. It took us around 30 minutes working at a steady pace.
We tested it on both a reasonably light two-speed steel bike and a heavier Pinnacle utility bike. It transformed the ride of the two-speed bike, making it fast, nimble and responsive. We also found the stated range to be conservative: after 20 miles on setting number two (medium assist) it had only used two bars out of five on the battery.
With the heavier Pinnacle on maximum assist (and on draggy routes) we were getting slightly under the 30km for the Max battery. As with all e-bike batteries, range depends on the terrain, weight of bike and level of assist.
Great customer support makes this one of the best kits for people who are new to working on their bike and who aren’t familiar with electrics. And even if you do have a strong background in both those areas, a simple system is always appreciated.
Reasons to avoid
Like the Bafang mid-drive system below, the TongSheng offers the same benefits of compatibility with a wide range of bike designs and a high torque for steep hills and off-road terrain. However, the TongSheng mid-drive does manage to be a little lighter than the Bafang for approximately the same power.
This model doesn’t come with a battery included, so you’ll have to source your own 36v item. As a rule of thumb, around 10Ah will give a range of 29km / 18mi, whereas going up to 18Ah will typically give around 53km / 33mi, so be sure to factor that in when you’re making your choice.
There’s a huge range of batteries sold on Amazon, but Green Cell is a particular brand we’d recommend.
We found fitting to be reasonably easy. As with most mid-drive systems, you replace your crank and chainring with the one provided in the kit. There’s an LCD display for attaching to your handlebars and you’ll need a battery to be hooked up to the motor.
Read more: TongSheng TSDZ2 conversion kit review
Reasons to avoid
A mid-motor drive system offers a number of benefits over hub-driven conversion kits. With the power delivered at the cranks it can produce more torque, making it more effective on particularly steep and bumpy terrain.
Another perk is that the compatibility is much greater – no concern about wheel diameters, hub widths, axle standards and brake type. No matter whether you’re running rim brakes or disc, quick release or thru-axle, the crank driven system is compatible with all.
The only proviso is that the frame material must be alloy and the bottom bracket width is 68–73mm – but that covers most bikes you’re likely to be fitting this system to.
There are a few aspects to be aware of, the first being that this system doesn’t include a battery and that typically makes up about half the cost of a conversion kit. Finding an e-bike battery is quite straightforward with many being sold on Amazon, with Green Cell being among those we’d recommend.
Just make sure to get a 36V one for this motor as a higher voltage can damage it. Also you should be aware that capacity of 10Ah will give you a range of about 29km / 18mi, while a capacity of 18Ah typically gives about 53km / 33mi – so be sure to factor in the distances you’re planning on riding.
Reasons to avoid
This radically different approach from Rubbee makes for an e-bike conversion with much fewer parts. The battery and motor are housed in a single unit which powers the bike directly turning the rear wheel with its integrated roller.
Not only is the initial installation notably fast and easy, the quick release system means that you can take off the unit for rides that you don’t wish to be assisted on. At 2.8kg, it doesn’t add much weight to that of the bike, making the bike easier to handle.
The range of this model is quite low, limited to Eco mode it only offers a range of 16km / 10mi – although taking the device off to charge at the other end is easy to do and it only takes an hour to top up. There is the option to increase your range by buying additional battery modules that fit into the base unit.
Up to three can be accommodated, which in turn increases the maximum range to 48km / 30mi, or around 23km / 14mi with moderately heavy use. However, unlike many other e-bike systems, the Rubbee X supports regenerative braking, allowing you to scrub back some power on the descents.
Reasons to avoid
Bafang is a well established maker of electric bike motors and offers a front hub based motor, if you’re not a fan of the bulky profile a mid motor conversion system creates. You can buy this kit without a battery – although why would you? – but if you sensibly also opt for a power-pack there’s a choice of amp hours, and you can select either a downtube or a rear-rack mounted version.
The setup follows the same principles as most front-wheel e-bike conversions. First you need to set up the wheel with a disc rotor, tyre and inner tube and install that into the bike. Then attach the cadence sensor – so it can tell when you’re pedalling and need assistance – then attach the battery and the LCD display and you’re essentially good to go!
It’s worth bearing in mind that although this conversion kit comes in many different wheel sizes, it is only compatible with bikes that have a front disc brake and a Quick-Release axle. If your disc brake bike is a newer, more expensive model, it might not be compatible, so worth checking first.
Remember, that in the UK electric bike laws mean that e-bikes are not permitted to have a power output of more than 250w and shouldn’t propel the bike when it’s travelling more than 15.5mph – you’ll have to make sure you select the right model with the relevant limitations.
Reasons to avoid
We’ve also tested the Voilamart kit, which comes with six main parts: the replacement rear wheel, the replacement brake levers, the control screen, pedal sensor, throttle and the control box. It doesn’t come with a battery however.
On review we found the kit pretty straightforward to fit, although you’ll need to remove the bike’s crank to fit the pedal sensor and this element of the conversion was a bit fiddly. Another potential drawback is that the connectors, which link to control unit, aren’t waterproof, with only a bag supplied to house the delicate electronics. While it does a good job of keeping everything tidy, we decided to buy a plastic enclosure, cut the wires to length, solder the connections and then heat shrink for added protection.
As for the ride, the rear wheel kit delivers plenty of power. However, since the pedal sensor only detects when you’re pedalling rather than how hard you’re pedalling it delivers the power as soon as your start to turn the crank arms. Fortunately, you can quickly adjust the level assistance, with five power options available.
All in all the Voliamart rear wheel kit is an affordable way to ‘go electric’, although it requires you to be mechanical competent to fit it and you’ll need to factor in the additional cost of a battery.
How to convert your bike to an e-bike in four steps
Here’s our step-by-step guide to how to add an electric bike conversion kit to your pedal-powered bike.
Swap the tyre and tube
Firstly, remove the tyre and tube from your current front wheel and then install them on the new wheel from the kit. Make sure to check if the tyre is directional, if it is, ensure that the tyre is mounted so that the cable sticking out of the hub is on the left-hand side (non-driveside) when the wheel is installed in the bike – otherwise it’ll be powered in the opposite direction to your direction of travel!
To swap the tyre and tube over, you will need some tyre levers and a pump. If you want to go over how to do these, we have a guide that can be accessed here.
Final points are to do up the nuts on the wheel’s axle to keep it firmly in place in the forks and to check that the brakes are correctly adjusted for the new wheel. If you’re unsure how to do that, we have another guide here.
Attach the bracket to the handlebars
There is a strap that needs to be attached to the bars to keep the bracket in place and stop it rotating around. There are also some adaptors included in the kit which can be used if your handlebars are a little skinnier.
But essentially all that’s needed to be done here is a couple of screws to clamp the bracket tightly to the bars.
Attach magnet disc and sensor
The magnet disc has a split design so it can just clip around the inside of the left (non-driveside crank) and is then held in place by its retention ring. Next, stick the sensor on the frame directly in line with the magnets – this will ensure that the sensor can tell when the cranks are moving.
Plug in the cables
The thickest one is the main power cable and that just needs to be plugged into the cable extending from the hub. The other orange cable attaches to the cadence sensor and this just needs plugging in as well.
It’s then a good idea to use some cable ties to tidy up the lengths of the cables a little bit, so they aren’t flapping about and risk getting caught on the spokes or on the cranks.
The blue cables, you don’t need to worry about, these are for an optional brake sensor upgrade kit.
Why convert your bike to an e-bike?
What types of conversion kit are available?
You can get conversion kits that power your front or rear wheel or power the bikes via the cranks.
Wheel-based systems usually have a hub motor and require replacement of your existing wheel with a compatible motorised one.
The alternative is a system like the Rubbee that drives your wheel by pushing on the tyre. Tyre wear can be an issue here though.
Finally, there are systems that power the e-bike via the bottom bracket.
Usually the e-bike’s battery will bolt onto your frame or be attached to your handlebars, although sometimes you can fit a battery pack to a rear rack.
We’ve more on compatibility. which can be an issue. below.
How much does it cost to convert a bike to an e-bike?
vary depending on the type of conversion kit and the size of the battery. To give a rough Band, you can expect to pay a total of between £500 and £800 from a reputable brand, but there will be outliers at either end.
Is it worth converting a bike to an e-bike?
There are many reasons to upgrade your bike to offer a little e-assistance. On the one hand, it can greatly increase the usefulness of your bike, enabling you to replace short car journeys – such as around town, to the shops, or to work – with going by bike instead.
It’s a lot more environmentally friendly getting about on two wheels than in a two-ton metal box. It can also save you time – bikes are able to take more direct routes and are less affected by traffic, as well as eliminating the need to search for a parking space at the other end.
But beyond just their practical benefits, e-bikes can also be a potent tool for boosting your fitness. Consistency is key when it comes to exercise, so making commitments with friends is a great way to ensure you’re heading out the door. Previously, differing fitness levels could make it difficult to find a riding partner but with an e-bike levelling the playing field, getting in a productive workout (for both of you) with a friend is much easier to do.
Added to that, an e-bike can be much more motivating in that it opens up a far greater range of roads than you’d be able to access just under the power of your own two legs. Exploring new roads is part of the fun of riding a bike and an e-bike can help preserve that.
Can you convert any regular bike to an e-bike?
Most bikes can be converted to an e-bike – it just requires getting the matching the right conversion kit to match the specification.
For conversion kits where the motor is located at the wheel’s hub, you’ll need to consider the wheel’s diameter, the width and axle standard of the hub and whether it uses rim or disc brakes. For instance, a 700c (AKA, 28”) disc brake wheel with a 100mm wide quick-release hub is a relatively common spec. Once you’ve determined what type of wheel you need, the conversion is quite a straightforward process
Crank driven systems are generally easier in terms of determining compatibility; the requirements are typically just an alloy frame and a bottom bracket width of between 68 and 73mm – which is the standard for all road and mountain bikes, it’s only specialist bikes that have a different spacing there. In replacing the crankset, these systems are a bit more involved to fit than a hub system, but still well within the remit of a home mechanic.
Other kits, such as those that directly drive the rear tyre, have almost universal compatibility – provided your tyres aren’t too heavily treaded.
Are electric bike conversion kits any good?
You won’t be getting the very best motors and the largest, seamlessly integrated batteries with an e-bike conversion kit. But with that said, e-bike conversion kits are much cheaper than purchasing a whole new e-bike and they do deliver many of the same benefits.
Converted e-bikes are great for commuting and utility cycling, giving that extra boost to help flatten hills, motor along the flat and lug about heavy loads. E-bike conversions are also good for leisure cycling, helping to moderate your effort level as needed and greatly extending the range you can explore.
For more specialist utility needs, buying a new cargo e-bike would help boost your carrying capacity and range. Equally, for the aesthetically conscious, the latest breed of e-road bikes are almost indistinguishable from a non-powered bike at first glance. Then again, both those options are much more expensive than a conversion.
How we test
Where we’ve been able to link to a review, it means that we’ve put the ebike conversion kit through its paces. We’ve assessed how easy it is to fit and maintain as well other factors such as quality of the components and battery life and charge time. Riding the bike once fitted with the kit, we’ve taken into account the ride quality, the ease of use and the battery range.
Where we haven’t yet had the chance to review an item, we’re still confident in recommending it as one of the best, because we either know the brand really well, and have probably tested another product or the previous version and can still happily recommend it as one of the best.