lightest electric bike conversion kits

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In this article, I’m going to be looking at 4 of the lightest electric bike conversion kits currently available. Most of the e-bike kits featured below are remarkably lightweight and tip the scales at under 4kg (including battery and ancillary components).

cytronex electric bike conversion kit
The Cytronex C1 is one of the lightest electric bike conversion kits available

Benefits of a lightweight e-bike conversion kit

One of the main benefits of fitting a lightweight e-bike conversion kit over buying a factory electric bike is cost. Most lightweight e-bikes currently on the market start at around £2000. If it’s an electric road bike you’re after, then you’ll be paying over £2300.

The lightest e-road bikes on the market use the X35 ebikemotion – this system has a total weight of 3.5kg, which is roughly the same as the conversion kits featured below. Big brands like Ribble, Orbea, Willier and Cannondale all have electric road bikes that use this motor.

A lightweight Ribble Endurance AL e road e-bike

If you’re just looking for some help on the hills, but otherwise want to ride without assistance, then you’re not going to want an e-bike conversion kit that adds too much weight to your bike. A typical mid-drive e-bike conversion kit weighs 4kg (for the motor) plus roughly 0.5kg for the ancillary components – factor in a small bottle battery at 1.5kg and the total additional weight would be 5.5kg.

A hybrid bike fitted with the lightweight Cytronex e-bike conversion kit

That’s quite a lot of extra weight to be carting around, if you’re only using the assist occasionally plus you would have the increased drag of the motor when the assist is switched off.

Most of the lightweight e-bike conversion kits featured below weigh 4kg or under. If you fitted one of these kits to an 8kg road bike, you’d have an electric bike that you could easily ride with or without assistance. If you fancied going for a ride without the extra weight, these kits are easy to remove. It only takes a matter of minutes to swap out the front wheel (for the original wheel) and hey presto! Your bike is returned to normal.

The top 4 lightest e-bike conversion kits are…

Unfortunately, there are not a lot of choices when it comes to a truly lightweight e-bike conversion kit, so I’ve found the 4 best options. Both the Sywtch and Cytronex C1 have been around for a while and have lots of positive customer reviews to show. The Bikee kit is quite new and is currently only available to pre-order, but it does look promising so I have included it on this list.

I have included a budget alternative recommendation that isn’t quite as lightweight, but still comes in at under 5kg and offers excellent value for money.

1. Cytronex C1

Tipping the scales at around 3.2kg, the Cytronex C1 is one of the lightest e-bike conversion kits available. A friend recently installed one of these kits onto his wife’s road bike – the total weight of the bike (with the kit fitted) is just over 11kg! That puts it up there with the likes of the Ribble Endurance SL e.

Cytronex is a British company that has been designing lightweight e-bike systems since 2008 when they made the first disguised electric bike system, the first water bottle battery and the lightest electric assist system in the world.

The latest Cyctronex C1 front wheel e-bike conversion kit benefits from British design and engineering. The small bottle battery has a total energy capacity of 198Wh and also contains the system electronics. The e-assist is operated by a small handlebar-mounted button and can be further customised using a smartphone app.

The Cytronex C1 is a very neat system and the small front hub motor doesn’t look out of place on a road bike. I like the single button for controlling the assist level – it works in the same way as the X35 ebikemotion iWoc One control button. You press and hold the button once for assistance, then you press again for the next level up – the changing levels are indicated by different colours.

Each of the three assist levels can be customised by the Cytronex C1 partner app, where you can also alter the button brightness. You place the bottle battery upside down in the charging holder to connect to the app via USB.

Another great feature of this app is you can download important firmware updates.  In the unlikely event, you experience any problems, you can upload diagnostic files from the motor controller and send them directly to Cytronex.

The Cytronex battery also contains the ‘brains’ of the system

Cytronex Battery Range and Performance

Firstly, I would say the Cytronex is aimed squarely at the rider who wants to enhance their cycling experience, as opposed to having a powerful motor that’s going to completely take over. You still need to work, it just takes the edge off – especially on the hills.

My friend’s wife recently completed a 35-mile round trip to Dartmoor, which included about 4000ft of elevation gain. At the end of the ride, there was still one-third of the battery remaining.  Considering the diminutive size and low energy capacity of the battery, that’s pretty good going.

As far as performance is concerned my friend’s wife had no problem staying with the other riders on the long, steep climbs. Despite its small size, the Cytronex motor packs a punch!

The Cytronex system uses a unique assist sensor which mounts on the drive-side chainstay and detects movement in the gear cassette. The assistance given by this system is incredibly smooth and quiet thanks to the virtually silent motor. The electronics are designed and built in the UK.

The innovative Cytronex assist sensor


The Cytronex C1 is a very high-quality e-bike conversion kit. It’s quite expensive, but most of the parts are designed and manufactured here in the UK. You can also customise your kit and get the motor built into a wide choice of very high-quality rims. Cytronex also offers an installation service, or you can choose a new bike from their list and they will supply the bike with the kit already fitted.

It’s very smooth, very quiet and the pedal assist system works flawlessly. It’s unlike any other hub-motor PAS system I’ve come across and works incredibly well.

Despite the small battery capacity, the range is very respectable. The motor and electronics are optimised for efficiency meaning that you can expect a similar mileage as the X35 ebikemotion system.

Cytronex are a small British company and I’ve yet to hear a bad word said about them. They have engineered the C1 to be incredibly reliable and offer a good warranty and after-sales service.

I can highly recommend this kit if you’re looking to add e-assist to a lightweight road bike or hybrid but still want to use your bike unassisted for most of the time.

Visit Cytronex for more information

2. Swytch E-Bike Conversion Kit

The Swytch was first designed back in 2017 after the founder, Oliver Montague saw a gap in the market for a lightweight and easy-to-fit e-bike conversion kit. After a successful crowdfunding campaign, Swytch was launched and has gone on to be a global success story.

Converting a bike to electric continues to be an appealing option despite there being a mind-boggling array of new e-bikes on the market. The great thing about converting a bike to electric is you can generally convert anything from a vintage racing bike to a modern-day city bike. If you have an old bike that’s got sentimental value, adding a motor kit is a great way to encourage you to keep using it.

The Swytch motor kit fitted to a Brompton folding bike

Swytch Battery range and performance

The Swytch e-bike conversion kit has two battery options – a 5Ah and 7Ah battery with respective ranges of 20 and 30 miles. The battery, motor electronics and control panel are all fitted inside a very stylish bag which clips into a handlebar mounting bracket. There is an external pedal sensor which features a split magnetic sensor and sensor.  The whole kit weighs in at just over 3kg making it one of the lightest electric bike conversion kits on the market.

Performance-wise, the tiny hub motor goes surprisingly well and produces no more than a slightly audible hum when working. The pedal assist is nice and responsive, and there’s more than enough power to get you up moderately steep hills with minimal effort.


Swytch is a great e-bike conversion kit if you’re after a lightweight, quick and easy-to-fit way to add e-assist to your bike. There are plenty of cheaper options available, but most front hub motors are significantly heavier, and there are usually external controllers, displays and wiring to deal with.

This kit takes the hassle out of converting your bike and it’s also very quick to remove if you ever decide to put it on another bike. Swytch is available in all the popular wheel sizes, so you shouldn’t have any problem finding the right size for your bike. Read the full Swytch review here.

Visit the Swytch website for more info

3. Bikee Bike Lightest Electric Bike Conversion Kit

Bikee Bike is an Italian company that specialises in e-bike technology. The aptly named ‘Lightest e-bike kit’ looks very promising indeed. The company already sell a mid-drive conversion kit on their website, but this kit is an Indiegogo start-up so it’s currently pre-order.

This small mid-drive motor has a claimed weight of only 1.6kg and boasts a lot of interesting features.

The specification is impressive, to say the least, and if they can deliver on their promises, then I’d say the Bikee Lightest e-bike kit should be popular.  The motor kit is listed with different battery options, but the lightest option would be the 225Wh compact bottle battery.

As I know very little about this motor, I’ve taken some of the specifications from their website and elaborated a little.

Motor dimensions: 85x90x128mm

Torque sensor – this doesn’t measure force being applied to the pedals like traditional torque sensors, but instead uses a chain tension sensor. I can’t comment on it’s effectiveness as I have never ridden an e-bike with this type of sensor.

Bikee claim the motor does not produce any drag, thanks to the freewheel inside the motor.

Quick Release  – the motor can be removed in just 5 minutes. There are three bolts locking the motor in place. You could even split the motor between two bikes if you purchase a spare mounting plate.

Independent drive pinion – Gives the opportunity to have different transmission ratios between human power and motor power.

Bikee claims the chainline is not affected, meaning better-shifting quality (than a Bafang or Tongsheng) and better chain retention.

Ground Clearance – Improved capability of overcoming obstacles without damaging the motor.

Heart Sensor Assist  (Superhero version only) With the HRM feature, just set the BPM you’d like to keep and the assistance level will be adjusted to keep that on track. Seems like a great idea, it would be interesting to see how it works in practice.

KERS regen braking (Superhero version only) – The system will be able to use the braking energy to charge the battery. This is only possible with fixed gear on internally geared hubs. I’m not quite sure how effective this will be and if there would be any measurable benefits.


The Bikee lightest e-bike conversion kit looks very promising. There’s still not a lot of independent information out there regarding this system, and the motor kits are currently listed as ‘pre-order’ with shipping in October 2021. I’ll be tempted to buy one to see if it lives up to its expectations.

Visit the website for more info

4. Yose Power front wheel electric bike conversion kit

Even though this kit weighs a bit more than the others, I’ve included it here as it represents excellent value for money. I have installed a lot of these kits over the years and never had any reported failures.

The Yose Power front wheel motor weighs 2.5kg. Other components include a small 36v controller and display unit, plus a wiring loom and pedal sensor. This brings the total weight to roughly 3kg, and with the addition of a compact bottle battery (1.5kg) the final added weight would be 4.5kg – this excludes the weight of the rim and spokes as does the weights of the Swytch and Cytronex.

So, although the Yose Power kit (with battery) is about 30% heavier than both the Swytch and Cytronex kits, it’s still fairly light in the greater scheme of things.

Yose Power does supply kits including batteries, but these are usually the heavier (3kg) 36v 12.5Ah Hailong type. If you’re trying to minimise weight I would go for something like the 36v 5Ah UPP mini bottle battery (image below) these are very good and only weigh 1.5kg.

I have installed the Yose Power e-bike conversion kit on many different bikes, including road and hybrid bikes. Customers are always surprised at how easy the finished bikes are to pedal without assistance. I have used bikes fitted with this kit and have found that they’re just fine to pedal without the motor activated and the extra weight doesn’t impact rideability.

yose power fitted to hybrid bike
An old Giant Hybrid bike fitted with a Yose Power front wheel kit


If your budget doesn’t stretch to the Cytonex C1 or Swytch systems and you don’t mind a bit of extra faffing around with wiring. The Yose Power e-bike conversion kit offers excellent value for money with not too much of a weight penalty (over the others).

Having installed of 50 of these kits over the last few years, they’ve always proven to be popular with customers and I’d have no hesitation recommending this brand. Read the full review here.

Buy direct from Yose Power (use code BH2E24BXQH for a €10 discount)
Buy from eBay (28″ front wheel)
Buy from Amazon (26″ front wheel)

Which lightweight e-bike conversion kit is best?

I can’t comment on the Bikee mid-drive kit, as it’s not currently available and there’s not a lot of info out there. On paper, it looks fantastic and if it works as they say, then it will be very popular.

Both the Swytch and Cytronex are very similar. Both kits use small, 250w front hub motors and small batteries with integrated controllers. There’s not a lot to separate the two in that respect.

I would personally lean towards the Cytronex C1, as I like the style of the compact bottle battery and the way the electric assist works – it’s very smooth. The Swytch is smooth, but it does have a more on/off feel to the assist. The handlebar-mounted power pack of the Swytch does look very neat, but I prefer to have the extra weight lower down. Performance-wise, both the Swytch and Cytronex are about the same in terms of power and noise.

If you’re looking for a cheaper option and don’t mind compromising on the weight slightly, then the Yose Power front hub motor kit combined with the UPP 36v 5Ah mini bottle battery is fantastic value for money.

Thanks for reading, if you have any of the e-bike kits featured in this article, please feel free to leave a comment below.

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  1. Although Swytch describe their kits as universal, they can’t work with through axles. They also say the same is true of other conversion kits.

    1. That’s correct. Most of the e-bike conversion kit manufacturers still neglect the fact that a lot of modern bikes now have through-axles. I’m not aware of any in the UK at the moment, but Grin Technologies in the US have one available.

  2. Hi, I have a Trek 7500 women’s step through with an ETRTO 622×18 rim and a 700×35 tire. Can I use Yose conversion kit?

    1. Hi,

      Yes the 28″ front or rear wheel Yose Power kit will fit your Trek 7500. You will need to get a rack specific battery as there won’t be enough space due to the low-step frame.

  3. Thanks for the really helpful review (and the other more detailed reviews of specific products). May I ask a couple of questions?
    1. How does the Yose Power motor compare in terms of noise with Swytch and Cytronex?
    2. How does it compare in efficiency, with the additional planetary gearing in the Yose Power hub?
    3. Do you know whether the Yose Power motor is a brushless DC motor (I couldn’t find any information on the Yose website)?
    4. Are there any issues with front-mounted hub motors? I am thinking about the additional torque at the fork ends and strength of fork/crown. For reference, I am considering mounting one into Reynolds 531 competition forks.
    Many thanks for your help.

    1. Hi Martin,

      The Yose Power motors is a brushless DC motor. As far as noise is concerned I’d say the Yose motor is more audible, especially when under load and in high power mode (than the other motors). I’ve mitigated this in the past by removing the motor cover and adding a little more grease (Mobilgrease28) to the planetary gears.

      I’ve fitted the Yose Power front hub motor to a couple of bikes with 531st forks (Dawes Galaxy early 90’s) without any issues, so it should be fine with 531c forks. If it’s going on an older sports road bike, the rims are quite wide on the kit and ideally you would need at least a 28mm tyre width.

      I hope this helps, let me know if you have any more questions.


      1. Thanks Tony, really useful. I’ve bought you a coffee.

        Do you know whether the Yose Power system can be run just from the throttle, or must it also have the PAS installed?

        I like the Cytronex system but out of my price range for now. Swytch are about to build their next set of product but price yet TBD. I think the Yose Power system could be a good starting point.

        Thanks again for your help.

        1. Hi Martin,

          There are settings you can change on the display which will enable you to use the throttle without the pedal assist, so you wouldn’t need to install the PAS sensor.

          In my experience, the Yose Power kits are very good value for money and I’ve had very few issues with them in the past. If you have any more questions, please let me know.

          Thanks for the coffee, much appreciated👍


  4. “Cytronex are a small British company and I’ve yet to hear a bad word said about them. They have engineered the C1 to be incredibly reliable and offer a good warranty and after-sales service.”
    Not my experience at all. Would you like to see my email correspondance with them? I have a kit where the battery overheated within 3 miles of first use and then on the 5th use the system failed completely due to no signal from the sensor. Cytronex have provided almost no help at all and even charged me £38.50 for diagnostic advice which was also no help.

    1. That’s a real shame as I know several owners of the Cytronex system who’ve not had any issues despite covering very high mileages. I can only advise you contact them again to get the problem resolved.

      1. I quote Cytronex:
        “We do not provide unlimited free support for installation because the instructions are very comprehensive, and we will not be able to provide any more remote support now other than my detailed reply here, which more than covers the 30 minute diagnostic booked. If you still cannot get your installation working then and you think something is wrong as opposed to the bike or the installation then you will need to return it to us at the address below for inspection”

        “We are unable to discuss this further and will not enter into any further correspondence unless you decide to send your Cytronex kit back for inspection and upon receipt and inspection of it here in Winchester. Our charges for further technical support/labour whether remote or in our workshop are £38.50 for the first half hour and increments of £19.25 minutes thereafter, plus parts, plus UK VAT.”

        “Also we will not supply you with any further Cytronex product in the future.”

        So I have to pay them to mark there own homework. To be fair you would need to read the whole correspondence, they took exception to me pointing out that a 12mm diameter axle with 9mm flats will not sit in the correct disc brake alignment of the original 9mm diameter fitting in a 9mm slot. The axle sits some 4mm lower. In fact the special washer fouled the ‘lawyers lips. Also the flange nut supplied could not be tightened as it fouled the suspension fork and they refused to provide the thread detail so I had to machine the nuts and now they say, “You have modified the kit which runs contrary to our terms and conditions”.

        The battery overheats when set to 60% power on a hill of about 60m elevation over 1.1km which is about 5.5%, this is not especially steep and is short. I note Cytronex used a Crompton to ride up Mont Ventoux (average 8%, 21km) but the clue is why a Brompton. I say because of the small wheels, it could not be done on the kit they supplied me for a 29″ wheel MTB. Buyers beware.

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