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Grin Tech

Grin Tech Brompton Folding Electric Bicycle Conversion Kit - Battery Sold Separately

$1,495.00

Grin Tech

Grin Tech Brompton Folding Electric Bicycle Conversion Kit - Battery Sold Separately

$1,495.00

Sold out

SEB has been electrifying the world famous Brompton Folding bike for some time now. 

Brompton's are among the most exquisite of compact folding bicycles, but also among the more challenging to convert cleanly into electric assist. The front fork uses tiny 8mm dropout slots and a narrow 75mm hub width, the rear tire folds into the bottom bracket eliminating most mid-drive options, and the triple fold adds challenges to the cable routing and component location. But once properly outfitted, they make excellent electric bikes. Portable, compact, easy to travel with, and a delight to ride.

We’re happy to offer purpose built conversion kit packages tailored for this bike for the discerning enthusiast, with 2 motor sizes and a range of control options. Please note of course that Brompton does not endorse any 3rd party modifications to their bike and will be quick to point out that electrifying your Brompton bike will void your Brompton warranty, as is their right.  Of course it is your right to do what you like with a product that you purchased and own, and we're here to help you have fun with that. 

We have simplified our Brompton kit options. We only stock the kit with the Cycle Analyst display and pedal assist modes in addition to the throttle function. It is a best of both world scenario and offers the best end result.

You will need to discuss your conversion project with us and select a battery. See our battery options here. 

For small fly safe 100wh batteries click here.

Motor Choice

At the moment, we have two hub motor options for the Brompton forks: a small 1.8kg geared SOFP motor, and the larger Crystalyte SAW20 direct drive motor.

SOFP vs SAW Comparison
  SOFP SAW20
Weight 1.8kg 3.2kg
Diameter 144 mm 184 mm
Motor KV 10.0 RPM/V 13.6 RPM/V
Phase Resistance 0.32 Ohm 0.24 Ohm

 

The geared motor is recommended when you want the most discrete package, when weight is a top priority, or when you want a motor that freewheels with zero drag when pedaling without assistance. It offers decent power levels (upwards of 500 watts) and can climb hills pretty well, but being a geared motor it also some audible buzz and it can't do regenerative braking. 

The Crystalyte SAW20 motor is ideal when you want the fastest and most powerful setup and aren't quite as concerned about motor weight. Being a direct drive motor it is totally silent when running and can also do regen braking, which is a great feature on bikes like the Brompton that only have rim brakes available.   

 

Display 

The V3 Cycle Analyst has a much more complete technical readout of your speed, battery voltage, amp-hours used etc. With the V3 Cycle Analyst, you can not only tune your throttle behaviour, you can also configure the bike for automatic pedalec assist modes with a PAS or Torque sensor so that you don’t need to press a throttle for power.

 

Pedalec Modes

With the  V3 Cycle Analyst display you have the option to add pedalec control of the Brompton without needing to use the throttle for power thus reducing thumb fatigue while riding and lead to a pleasant automatic assistance.

The 12 Magnet PAS sensor installs on the left crank and simply senses when you are pedaling. You then configure the Cycle Analyst to put out a baseline power whenever you pedal, and use the throttle for when you want to override that with manual control.

 

Other Accessories

There are a few useful accessories that aren't part of the kit bundle on the store site but which can be worth adding separately to the order.

 

  • Headlight: Both the eZee LED meter and the Cycle Analyst include a DC power plug bringing out your battery voltage to run a front light with no extra wiring. The Cycle Lumenator casts the brightest beam while the potted Electrolights can mount cleanly under the Cycle Analyst with a long bolt through the enclosure.

 

  • Ebrake Cutoffs: We don't recommend to bother installing ebrake cutoffs with small geared motors, but on the direct drive SAW20 motor this is a great With the 20A Grinfineon and Baserunner controllers you can add any of the ebrake cutoff levers to the order if you want to have regenerative braking whenever you squeeze the brakes. We don’t include brake levers in the kit because for most people it’s easiest just to keep the original levers fitted on the bike, but if you want them they are available.

 

What's in the kit.

    • Front Direct Geared Wheel: 1 x MSAW20F16_Bromp or Front Geared wheel
    • Baserunner Controller with Fork Mounting Bracket: 1 x Baserunner_Z9 - Stand Alone
    • V3 Cycle Analyst: 1 x CA3-WP
    • Handlebar Control: 1 x CA3_MFSwitch
    • PAS 1 x PAS_24P
    • Throttle Choice (Thumb Lever recommended): 1 x T-Lever
    • Torque Arms: 1 x TorqArm_8mm
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