- Versatile electric bike conversion set with four levels of assist, four levels of regen and throttle mode
- Available with five battery pack configurations including two rear mount and three downtube mounted
- Deep Sleep mode protects cells when system goes unused for extended periods (2 months or 2 weeks if < 10% charge)
- LCD display is backlit, removable and symmetrical for use on right or left handle, also includes external button pad
The BionX S 350 electric bike conversion kit includes a light weight, gearless hub motor designed for rear-wheel use, an LCD display panel and button pad as well as a battery pack of your choosing. It’s one of the most polished, flexible and sophisticated ebike kits around and offers everything from pedal assist to throttle, regeneration mode and regenerative braking. This kit resembles the older SL 350 which was produced through 2014. BionX has been shortening their naming conventions to make the space less confusing and that’s where the S comes from. This kit in particular is really their bread and butter and thanks to the five battery options it will offer you weight savings, increased range or power. You also get to choose from a rear-rack design or a downtube mounted setup.
The motor included with this kit offers 350 watts of power in a high torque configuration. It delivers up to 29.5 lb.-ft (40.0 Nm) of torque with nominal output of 6.6 lb.-ft (9.0 Nm). That’s pretty good considering its relatively small visual footprint and weight (the SL and S series from BionX weigh roughly 2.5 pounds less than the earlier PL 350 series). I like the new wavy design on the hub casing and have long been a fan of the near-silent operation of these gearless kits. This motor activates very smoothly, relying on a torque sensor built right into the hub. In order to make it go you just turn on the unit, choose an assist level and begin pedaling. Alternatively, you an use the variable-speed trigger throttle but the bike must be going at least two miles per hour for this to work (the minimum speed requirement is a safety feature).
Being gearless, the S 350 motor relies on powerful magnets inside to drive the bike forward. These tend to last longer than plastic gears used on geared hubs. The magnets also enable regeneration riding modes that will help to slow you down when descending hills or provide an added challenge when pedaling on flats in a sort of “workout mode”. There is also a standard regenerative braking trigger that activates when you pull the right brake lever. The downsides of gearless direct drive systems like this are increased weight and some cogging when the system is not actively assisting. Cogging happens when the magnets inside the motor pass the stater (a metal rod that becomes magnetized as electricity flows through) and repel it as shown in the video review. While cogging can’t really be helped, BionX has done a great job of reducing its affect on the ride quality of their kits. One area they could improve however is by offering two regenerative brake sensors or an option for complete ebike specific brake levers. Tektro makes some great levers that are included with other kits but the downside of this is that they only work with mechanical brakes (not hydraulic) and may be of a lower quality than the levers your bike already has… and having an extra set of levers also creates waste.
The battery pack options for the BionX S350 are plentiful and possibly confusing. Let’s break it down in a second but first off, it’s worth mentioning that all packs use Lithium Manganese Cobalt cells by Panasonic. These are light weight, durable and warrantied for two years. All packs also include the Deep Sleep system which automatically cuts all power draw after two months (or two weeks if the battery is lower than 10%) of inactivity, helping to prevent damage. Now, which pack to get? There are three size designations including L (Large) XL (Extra Large) and VL (Very Large). There are also two types of mounting options including D (Downtube) and R (Rear). So when you mix the letters together you get the following rear rack options: S 350 RL (rear mounted large 48v 6.6ah) and S 350 RX (rear mounted extra large 48v 8.8ah).
And you get the following downtube options: S 350 DL (downtube mounted large 48v 6.6ah), S 350 DX (downtube mounted extra large 48v 8.8ah) and S 350 DV (down tube mounted very large 48v 11.5ah). Simple right? Please note that the images above aren’t perfect, while they do show BionX rear-mounted battery packs they don’t show the latest decals which are black and show little bars (like a bar chart) from left to right. The Large pack has one bar, the Extra Large pack has two and the Very Large pack has three (the goal is to make it easier to understand the whole size thing, more bars = more juice inside). Okay, back to the review… My preference is for the downtube mounted packs because they keep weight low and center to the bike but they also take up the spot where a water bottle cage might otherwise go. Since the hub motor is already mounted at the rear of the bike, having a heavy rack there as well is not ideal. One thing I do like about the rear packs however is the inclusion of a built in LED light for safety.
The second generation (G2) display panel used on this and other BionX kits is quite good. It’s large and easy to read, backlit for use at night and symmetrical for easier use by left and right handed riders. There are two buttons on each side of the display which activate the unit and allow you to choose from one of four regen modes, zero mode or four levels of assist. You can operate the system just fine from this main panel but BionX also includes a stand alone button pad that can be mounted extremely close to grips and brake levers for even easier access when riding. This pad includes a + and – button (for navigating assist levels) as well as a red variable-speed trigger throttle which can activate the motor without pedaling. It’s a beautiful design and so thoughtfully constructed that it works with all kinds of bicycle cockpit setups, not just standard flat bars. Even with the recumbent trike shown in the image below, which has vertical handle bars, the button pad works great and the LCD display panel is still visible mounted front and center. In addition to being easy to use, the display panel is also removable so you can keep it safe from weather, tampering and vandalism. Awesome.
BionX was started in 2000 as EPS (Electric Propulsion Systems) and was acquired by Magna (a Canadian automotive company) around 2008. Since then it has grown into one of the largest, most trusted high-end manufacturers of drive systems for electric bicycles in the world. The S 350 is their workhorse kit that is sold directly to shops (for install on end user bicycles) and OEM manufacturers like OHM, Yuba, Xtracycle and Smart. It’s a great setup and one of the best options for people who have a beloved or unique bicycle that they want to convert to electric. The kit is available in a wide range of wheel sizes including 20″, 26″ and 700C and can also be configured to power third party lighting systems.
- Lightweight, redesigned hub motor is 2.5 lbs lighter and more stylish than older PL 350 models
- 48 volt battery system is more efficient and thus, longer lasting than older 36 volt BionX systems
- Works with almost any bike, including those with smaller wheel diameters like folding bikes and recumbents
- Both battery configurations (rear rack or downtube) lock to the frame for security and can be charged on or off of the bike
- Gearless hub motor runs smooth and quiet, 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 used on bicycles that have front suspension forks
- Works with disc brake setups as well as v-brakes and isn’t too wide to accommodate a cassette
- Installation is a bit complicated, BionX sells directly through shops who will handle it for you or as a built in option on OEM electric bikes
- If purchased as an add-on kit the wires and cables won’t be integrated into the frame which might not look as nice as a purpose-built ebike
- Trade offs in how you mount the battery: rear rack is heavier and unbalanced, mid mount takes water bottle spot
- this is one of the most expensive electric bike conversion kits around but also one of the best with many options and a solid warranty
- 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
- This kit is only compatible with 135 mm axle size so check your mountain bikes carefully or bikes with thru axles