BionX SL 350 Review

Bionx Sl 350 Electric Bike Conversion Kit 1
Bionx Sl 350 Surly Neck Romancer Pug
Bionx Sl 350 Surly Conversion
Xtracycle Edgerunner Bionx 350 48v Battery
Xtracycle Edgerunner Bionx 350 Display Panel
Xtracycle Edgerunner Bionx 350 Disc Brake
Bionx Sl 350 Motor Internals
Bionx Sl 350 Electric Bike Conversion Kit 1
Bionx Sl 350 Surly Neck Romancer Pug
Bionx Sl 350 Surly Conversion
Xtracycle Edgerunner Bionx 350 48v Battery
Xtracycle Edgerunner Bionx 350 Display Panel
Xtracycle Edgerunner Bionx 350 Disc Brake
Bionx Sl 350 Motor Internals


  • Top of the line kit, 350 watt motor is ~2.5 lbs lighter than the older PL 350 model, includes advanced security features
  • Available in two designs to fit most bikes: mount to down tube or integrated into a rear carry rack
  • Increased torque output with 48 volt XL battery, the strongest BionX makes
  • Versatile drive system offers throttle mode, pedal assist or regen mode in addition to regenerative braking

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Video Review

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SL 350


$1,999 USD

Suggested Use:

Neighborhood, Commuting, Urban

Electric Bike Class:

Throttle on Demand (Class 2)
Learn more about Ebike classes


2 Year Covering Manufacturer Defects (1,000 Charge Cycles)


United States, Canada

Model Year:


Bicycle Details

Total Weight:

16.1 lbs (7.3 kg) (Optional Rear Rack Configuration 18.9 lbs)

Motor Weight:

9.5 lbs (4.3 kg)

Wheel Sizes:

20 in (50.8cm)26 in (66.04cm)28 in (71.12cm)


Optional Black or Silver Rim and Spokes, Battery Comes in Mid-Frame or Rear-Rack Configuration, Rear-Rack Battery Has an Integrated LED Light, System Locks Motor if Display is Removed

Electronic Details

Motor Brand:


Motor Type:

Rear-Mounted Gearless Direct Drive Hub
Learn more about Ebike motors

Motor Nominal Output:

350 watts

Battery Voltage:

48 volts

Battery Amp Hours:

8.8 ah

Battery Watt Hours:

422.4 wh

Battery Chemistry:


Charge Time:

4 hours

Estimated Min Range:

45 miles (72 km)

Estimated Max Range:

65 miles (105 km)

Display Type:

Removable Backlit Monochrome LCD


4 Proportional Assist and Generate Modes, Lighting Controls, Battery Voltage, Trip Distance, Odometer, Chronometer, Average Speed, Clock

Display Accessories:

Independent Button Pad

Drive Mode:

Torque Sensing Pedal Assist, Trigger Throttle

Top Speed:

20 mph (32 kph)

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Written Review

The BionX SL “Super Light” 350 takes the proven, solid performance of the long-lived PL 350 and makes the motor 2.5 pounds lighter while upgrading the 37 volt battery to 48 volts for increased power, awesome! This is one of the highest quality, most feature rich electric bike conversion kits you can buy. It comes with throttle mode, four levels of pedal assist, regenerative “negative mode” and regenerative braking. Instead of using pedelec sensors to track rider input, it uses torque sensors built right into the hub motor making it less jerky and easier to install on the bike. Everything about this kit is high quality, and that’s why it costs about as much as a fully built electric bike.

Now that you know the up side, here’s the down side. BionX kits like this have to be installed onto a bike you already own. That’s a negative because it is time consuming, requires tools or further spend to have a bike shop do it for you. Sure, you probably already know this, it is an electric bike “kit” after all. But unlike some other electric bike kits, BionX systems take more finessing because they replace the entire rear wheel of a bike and that means you have to deal with the derailleur and chain rings. The other tricky bit is adjusting the brake lever system which controls regenerative braking in addition to normal “stop” braking.

Most full electric bikes come with Tektro brake levers that have sensors preinstalled. They tell the motor to shut off whenever you pull the brakes, or they tell the regen system to kick in. That’s also what the sensor does on a BionX kit except it isn’t built into the brake lever. You have to mount it yourself on the outside of the brake lever making it more exposed and ultimately vulnerable. It also means you can only mount the sensor to one brake lever, not both like most fully integrated bikes. The other negative about this and the rest of the BionX kits is that the power cables going from the battery pack to the hub motor and the computer and brake sensor to the battery pack aren’t integrated into the bike frame. It’s a bit less aesthetically pleasing, but it’s not the end of the world and wireless kits are just around the corner.

Back to the good stuff! The motor on the SL 350 kit is really the center piece. It’s an upgraded design from what is offered in the PL 350 kit and weighs 2.5lbs less. It’s brushless and gearless so it coasts silently and last longer than other geared hub motors. It also looks great, having seen the cutaway demo at Interbike myself and feeling the light weight of the motor when it was off the bike, it’s an amazing piece of technology. This light weight design combined with the 48v XL battery pack offers the kind of power that heavier riders will appreciate. It would also suit heavier mountain bike conversions well) and perform better in steep, off road environments.

BionX kits are perfect for people who already have bikes they love and just want to add electric assist. Whether your bike is a recumbent, folding or super light full suspension carbon mountain bike, this kit will take it to the high end of the ebike spectrum for $2K. The computer console has been designed to help you protect your very expensive bike and has two built in security features. If the LCD computer is removed from the bike the motor locks by engaging the highest torque regeneration setting. Also, the console comes with a password built in so even if it’s on the bike, a thief won’t be able to turn it on. With all of this said, if the SL is just too expensive and you’re willing to sacrifice a bit in terms of weight and power, you can spend ~$500 less and pick from one of the PL 350 options.

When choosing between the DT or RR version of this kit, take into consideration the mounting options given your frame and the weight distribution you care most about. I am always a fan of the down tube “mid-frame” battery mounting design because it distributes weight more evenly across the frame from front to rear. This makes the bike easier to pick up and carry, mount on car racks and handle when riding by avoiding tail slide-outs but it also takes the spot where you would otherwise put a water bottle cage. The rear rack by comparison, leaves the bike rear-heavy but provides a great space for hanging panniers or putting a saddle bag. The rear rack design weighs more than the down tube but for some bikes it may be the only option. The first picture below shows the DT (down tube) option with the gray triangle pack and the second picture shows the RR (rear rack) option which mounts to a metal rack. If you choose the second option make sure your bike has threaded braze-on eyelets for mounting a rack.

Note that some users have successfully drilled their own mounting holes for the down tube battery kit but that can compromise the structural integrity of the bike or may not be an option at all with carbon frames. Both battery designs are lockable and the rear rack design has a built in tail light for safety.

Depending on your bike setup, this kit is available with three wheel diameter options including 20″, 26″ or 700c which is equivalent to 29″. The rims themselves are available in silver or black spoke options to match your setup which is nice. Whichever version of this kit you decide on you’ll be getting technology that is feature rich and high quality backed by a solid brand.


  • Lightweight, redesigned hub motor is 2.5lbs lighter and more stylish than PL 350
  • Battery pack offers extra power at 48 volts, great for climbing hills or supporting heavier riders
  • Works with almost any bike, including those with smaller diameters like folding bikes and recumbents
  • Both battery configurations lock to the frame for security and can be charged on or off of the bike
  • Hub motor runs smooth and quiet (gearless and hubless) and has built in torque sensing and regenerative braking
  • Rear-wheel hub motor exerts force onto the part of the frame that is designed to handle it vs. front hub designs, great if you mount to a bike with a front shock
  • Works with disc brake setups as well as v-brakes


  • The amp hours of the 48 volt pack are 8.8 vs. 9.6 on the highest end PL kit meaning it won’t go quite as far. Still, 8.8 is much better than the low end 6.4 amp hour PL kit from BionX
  • Installation is a bit complicated, time consuming or expensive if you hire it done
  • With kits like this the wires and cables aren’t integrated into the frame vs. buying a pre-built ebike that might look a little nicer
  • Trade offs in how you mount the battery: rear rack is heavier and unbalanced, mid mount takes water bottle spot
  • This kit alone costs as much as a high end, fully assembled electric bike
  • Throttle and computer may not mount as easily to road bikes with drop handle bars due to shape and size of tubes and grip tape
  • The rear rack battery design includes a built in light but in many cases you still have to get your own front light vs. an integrated solution feeding from one battery source
  • This kit is only compatible with 135 mm axle size so check your mountain bikes carefully or bikes with thru axles


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5 years ago

I installed the BionX 350XL 48V on a Raliegh 5.2- 27 SPD. Mountain Bike . I have over 3000 mi. of riding pleasure on this bike. My best millage is 49 mi. on one charge Utilizing the right mix of bike gearing and electric assist with re-gen whilst pedaling. Thumb throttle when necessary utilizing mostly plus mode to 4 to start and down assist to plus 2 average speed 12.5 MPH. Re-gen minus 1 except when going down a steep or long downhill grades then a higher re-gen -3 or 4 slow the bike down to 20 mph. Love to watch the battery bar accumulate energy on the plus side during re-gen thus increasing range. So I know I could achieve 60 plus miles in range under ideal weather conditions less than 5 mph headwind. My total cost of the bike with bells and whistles less than $2,600.00. ADVANTAGE I ride a bike that fits Me. Instead of riding a bike I have to fit into. Thanks Team BionX

E.Lynn Leaverton
2 years ago

I had a sl 350 ht rr installed on my Rambler tadpole in 2013 and have ridden well over 6000 miles by January 2016.. My best power mileage was 52 miles Westbound on Idaho’s Trail of the Coeur da Alene. The motor has been strong and dependable. The only problem I had was a battery that would not take a charge which was in warranty and replaced quickly by Gary at NWrecumbent Cycles in Post Falls. You meet the nicest people on the bike trails in the Pacific Nortwest.

Court Rye
2 years ago

Awesome! Sounds like you’ve had a great experience. Thanks for sharing the excellent service by NWrecumbent Cycles, they sound like a great shop :)


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murat dogusan
1 year ago

price of this kit?

Steve Birks
3 years ago

Wow I would love one of those be ideal for our twin grand children one day - one day !!!
3 years ago

I agree Steve, very cool use of technology and lots of versatility with the different add-ons. Xtracycle announced a new version of their EdgeRunner at Interbike last month which uses the Bosch mid-drive and is even more powerful and efficient. Very cool stuff... compatible with the same great accessories. Review coming soon!

Anthony Lobino
3 years ago

I've got a Big Dummy and I'm looking into the 350 HT kits but I'm unsure whether or not the spending an extra $500-600 from 36 volt to 48 volt is worth it; what are your thoughts? Would I be able to buy a 48 volt battery later on and use it with my 36 volt kit?
3 years ago

I believe you can upgrade to 48 volt packs and they will work with older 36 volt motors. From what I've gathered, all of the new BionX systems run 48 volt packs which improves efficiency and of course power. If you do get an older kit, check how old it is because batteries slowly lose their full capacity just sitting on the shelf.  $500 to $600 is quite a bit extra and I'm not sure how much you may or may not need the additional power, I've had good luck with the older 36 volt systems and BionX offers good support if you buy through a local dealer. Hope this helps!

Joe G.P.
4 years ago

that's the quietest electric motor i've seen you review.
Also i heard one of cheap electric bikes a few days ago, sounded like he was dragging a 2by4 behind him
4 years ago

Yeah, this thing is so quiet... Really impressed with the setup. Climbs well, has regen, mounts to the downtube. Good stuff all around and the Xtracycle is a neat platform :)

Torian Allen
4 years ago

+Electric Bike Review, are there any other electric velomobiles's out there worth testing? 

Torian Allen
4 years ago

Ok, perfect! Thank you!
4 years ago

Hi Torian (cool name btw) this is one of my favorites but Yuba also has one called the elMundo and you can see a few other recumbent/cargo style ebikes here

4 years ago

Please do a review of the iZip Express Electric Bike w/ the 750watt motor. Thx
4 years ago

Great request... It's on my list but I just haven't seen it in the wild! There was one at Currie's headquarters a few months back but it was being repaired. I'm not sure if they even sell it anymore?

4 years ago

That is an amazingly well thought out bicycle.