I recently had an email exchange with Brian Wismann, Brammo Director of Product Development, about a question that has been vexing me of late: why doesn’t the Brammo Enertia have regenerative (regen) braking?
Regen braking is, at its most fundamental, slowing and/or stopping by using a mechanism designed to convert that braking force into electricity. Instead of your brake just creating heat and brake dust while you slow your vehicle, you would actually be re-charging your battery. More detailed information on this can be found here and here. It sounds great, right? Just like anything that sounds great at first, (e.g. chocolate-covered bacon), it has some drawbacks. Before Brian explains the decision process that he and the Enertia design team went through, some introduction is necessary.
Here’s what Brammo’s website has to say about Brian:
Brian is one of the select few whose automotive designs are in production and racing most weekends. From sketching to digital design, Brian wields whatever tools are required to deliver stunning product design with functional simplicity. Holding a degree in Industrial Design from North Carolina State University, Brian leads our design team with experience in both product and vehicle design. His prior experience includes design work for clients such as Dell Computers and Ohmeda Medical as well as race car body and aerodynamics design with Crawford Race Cars.
Brian explained that the motors and controllers on the Enertia were capable of regen should Brammo ever find it to be in the interest of its customers to incorporate it. The decision not to include this feature was a well-considered one. In Brian’s words:
1. Not enough energy to be regenerated off the rear wheel of a lightweight motorcycle. Most braking force is applied to the front wheel of a motorcycle (some 70%) – and applying braking force to the rear wheel is a tricky deal without knowing traction conditions. All of this at the maximum benefit of much less than 10% increase in range.
2. Regen turns your motor into a generator – which means it’s working when it might otherwise be resting. This adds heat to the motor and can reduce the service life of the motor by increasing the duty cycle.
3. Control – regen is a variable parameter and probably requires an additional hand control to be done properly. Vectrix did this by twisting the throttle forward, which was elegant but also presented problems. New riders were slowing only with regen and failed to learn how to apply the true mechanical brakes properly when they needed to stop fast!
4. Range – in most cases, you’ll experience greater range by “free wheeling” and coasting with no regen than you would if regen kicked in when you let off the throttle.
Beyond all of this, it just adds complexity to a bike we’d like to think of as “simple and elegant”.