I grew up in a very German household. My dad left the motherland in his mid-20s and my mom after she could ride a bike. Together, they are a dynamite duo that run a tight ship.
Growing up, I couldn’t just go out and run errands. Before I’d go, we’d optimize my route to save on time and fuel. And I can still hear my dad saying, “Downshift! Don’t hit the breaks, you’ll wear out the pads.” It was engrained in me to be aware of our resources and consciously extend the life of whatever I was using.
So when it came to building my sun bike, it was common sense for me to make it as efficient as possible.
Here’s my Top 4 for building an über-efficienct solar charged electric bike.
1. Find an Electric Bike Engineered to Perform
The Specialized Turbo S is my own American Pharoah for two main reasons.
1. BUILT FOR PERFORMANCE
Motor
It has a 250-watt motor, which only kicks in when I pedal. You don’t use a throttle on this stallion; you got to put a little muscle into it.
The motor is small and light, seamlessly fitting into the rear hub. It is quiet and the power comes out smoothly. It's stealth. 250-watts is right for my needs. You could go for 500+ watts, but my goal is to put some effort into the ride too. This motor allows me to toggle down to provide more of my own input or when tired toggle up to 70% or 100% support.
And to top it off, this gearless hub motor allows for regenerative breaking. So as I charged down the mountain through Jerome, AZ, I was actually recharging as I braked.
Battery
It is a 504-watt hour, lithium-ion battery disguised into the down tube of the bike, right under the water bottle cage. Lithium-ion has one of the highest energy densities, packing quite a punch. And 504-watt hours mean it has an average range of 25 miles. However, with my solar panel constantly recharging the battery, there is no range limit…so long as the sun is out.
2. FIT FOR THE BIKE
Specialized was kind enough to give me a Body Geometry fit, which improves power, endurance and riding comfort. Touring 3,000+ miles, I knew this would be important and Aaron from Specialized gave me the 2-hour fit of a lifetime. Body Geometry is quite a scientific approach measuring your seat bones, flexibility, core strength, and overall body structure. The most wild part was when I hopped onto the Retul trainer and Aaron placed on my joints (from my shoulder down to my ankle) sensors. These sensors emitted light, which was captured by a camera, creating a 3D image and allowing for position changes down to the millimeter. As I close in on the first 1,000 miles, I can confidently say that the tailoring and slight adjustments have made a difference. I feel powerful on the bike, and I’m confident there is no wasted effort. It's all rosy!
2. Add a Fairing
A fairing is like a windshield, a plastic structure that increases streamlining and reduces drag. I went to Zzipper in Santa Cruz, CA to pick up the fairing. It was a phenomenal experience and the highlight was meeting Karl. He hand makes these light plastic bubbles, which stand for efficiency.
But don’t just take my word for it - that a fairing cuts through the wind and improves aerodynamics. Specialized actually put the fairing to the test by placing it in their wind tunnel. It turns out the fairing provided a 30% reduction in wind resistance. So when I have a headwind, the fairing cuts right through, maximizing my speed.
3. Maximize Solar Output
SunPower provided the most efficient solar cells, delivering 30% more power than a standard cell. We built a one of a kind panel that produce 240-watts, a near perfect match to the 250-watt electric bike motor.
This means my 70 solar cells are soaking up every photon of sunlight and efficiently converting it into electricity to keep my battery fully charged.
You can see by the photo below that we are cabling the solar electricity direct into one of the two Specialized battery charge ports -- the port connected to the frame of the bike.
And in the early morning or late afternoon hours, I’m able to angle the panel up to 20 degrees to maximize solar exposure.
4. Use the most reliable and efficient solar charge controllers
We actually built two flexible solar panels and mounted them on one carbon honeycomb composite sheet. The reason for two panels was to have the voltage lower than the 36 volt battery. Each panel produces roughly 22 volts.
The secret sauce to this whole rig are the two Genasun Solar Boost Charge Controllers, which boost the voltage to charge the Lithium-ion battery. Without these controllers, the battery would not be able to receive the solar energy. Also critical is the capability of Genasun to customize the maximum voltage of the controllers. The Lithium-ion battery can handle a maximum of 42 volts. Anything higher would overcharge and damage the battery.
With Genasun under the hood, I’m confidently receiving the most solar energy possible.
Takeaway
Could I have done more? Absolutely. Perhaps tapering the solar panel to a point for better aerodynamics. Or further lightening my trailer load. But all in all, I’m pretty pleased.
Let the metrics speak for themselves:
- Typical Turbo S battery range is 25 miles. With the solar energy constantly recharging my battery, I can go 100+ miles. Only limit is the sun and my seat getting sore from being in the saddle too long.
- The Turbo S Travel Charger is 2 Amps and takes 6 to 7 hours to charge. My 240-watt solar panel is over 6 Amps, charging the battery in 2.5 hours (slightly varies depending on solar radiation).
- My legs are getting stronger. I can now ride using 50% support from the motor. This just extends my battery range even further.
Here's to being efficienct - über-efficient.