E-bikes and Solar Energy—Are They Compatible?

E-bikes and Solar Energy—Are They Compatible?

Ross Levay exhibited this solar E-bike set-up at a San Diego Water Conservation event.

In my household we put a lot of our thoughts towards the 3 R’s (Reduce, Reuse and Recycle), renewable energy and sustainability.   This is one of the reasons we love bicycles so much and fostered our decision to get E-bikes for as much of our travel as possible.   With our community, the world and expenses so important, we feel it is ours and everyone’s duty to get involved in minimizing waste and maximizing our resources.

With our purchase of E-bikes, the next thoughts went towards using the power of the sun to energize them.   As it is, we still do all of our recharging from the grid, but I have spent much time researching and thinking about  how solar energy mixes with the world of E-bikes.   Here are my findings and opinions on this subject.   Plus we will mix in some examples from a few locals who have experimented with this idea.

There are some definite drawbacks to using solar energy to give a E-bike battery the power it needs.   Most E-bikes use some type of lithium battery and these batteries have very specific charging needs.   They use a smart charger that is powered by line current (120 or 220 volts AC) (alternating current) from a basic household power circuit.   The smart charger feeds a set amperage and voltage level to the battery and has a circuit that senses the battery charge condition and shuts off at the correct charge level to protect it.

In addition to protecting the health and lifecycle of the battery, it is also protecting it from possible overheating and a fire risk.   So we can see that the use of the correct smart charger is vital for any lithium battery.   This means that using the specified charger and household current is important in so many ways.   If a (your) home already has a solar panel system then charging your E-bike battery from it is easy.   You just plug it in like any other appliance and things work just right.

A solar panel takes the power of the sun and turns it into DC (direct current) power of a certain voltage and amperage, depending on the size and type of panel system.   In order to run a household, that DC power is converted to AC with an inverter.   Plus it is also hooked to the grid for nighttime and winter power.   Similar to a home solar system but opposite, the E-bike charger turns the AC from the house into the DC that charges the E-bike’s lithium battery.   So at first look, the DC from the solar panel should be just right to be the DC that charges the battery.   And it could be soon, but as of yet I have seen no E-bike chargers that work that way.

Although this set-up is a little risky, it can work if properly tended.

I do think the day will come for a E-bike charger with the correct DC smart charge circuitry to be offered, but for now they all run off of household AC.   That smart charge circuitry is pretty important to the whole E-bike system.   A couple years ago I ran into the guys from Levay Elektrocycles at a water conservation event.   They were showing off a couple E-bikes that were charging off of small solar panels.   This is a little risky, but the very small amount of energy the panels made were not enough to overcharge the batteries unless left on for a long time (more than one full day I would think).   Yet, if the batteries were fully charged and the panels were left connected, problems could easily start brewing.

The correct smart circuitry (which would have to run off DC, not the AC that chargers are designed for now) connected between the panels and the battery could make it safe, but then again the amount of time it could take to fully recharge the battery could be days as opposed hours.   With larger panels that offer more capacity, the charging could be much quicker, but then the need for the smart circuitry is even more pronounced.   So we see that this technology is not ready for us E-bikers yet.

The guys at Levay also mentioned that the panels were there to extend the range of the battery during a ride and not just for recharging.   I have seen such set-ups on-line and on Bike Book (most people call it Facebook).   This isn’t a bad idea, yet the cost and the size of the solar panels can be very restrictive (more on that in a minute).

#164  Solar E-bikes 2

Mark’s E-bike has a lot of potential, but the solar panels on the trailer are expensive and bulky.

Next-up is a solar powered bike.   At my first E-bike seminar here in San Diego (the next one is this October 9th, don’t miss it), a new friend Mark, brought his bike he’s been developing.   It uses a pair of solar panels supported by a bike trailer to power the bike’s motor.   This concept isn’t new, as we’ve been seeing this in solar-powered car competitions for a long time.   Still, for an E-bike this idea is pretty fresh.   The two panels make for a large and bulky item to haul, but did the job.

Being a 24 volt bike, the two 12 volt panels created just enough power to keep the bike rolling at a decent pace, yet having the sun shining is necessary to make it happen.   His plan was to make the two day ride from his home to the seminar and stay the one night at a hotel at the half way point.   The first day went great, but day two was overcast and didn’t allow the trip to continue.   His wife came to his rescue with their van to bring him and the bike to the seminar.

I was impressed with Mark’s efforts to combine a love of E-bikes and solar energy.

That actually worked out pretty good, as he said 60 miles on the bike took a lot out of him (and this behind).   Other than the lack of sun for day two, the bike has performed well.   He has thoughts of marketing his invention, but I haven’t been able to contact him lately so I can’t say how things are going with that.

Although I normally don’t like talking money, now we will.   It is said that it takes about 5 to 10 cents for each recharge of an E-bike battery.   So if you figure in that price on 1000 recharges (the lifecycle of a E-bike lithium battery?), you are looking at about $50-$100.   (The expected life of a quality E-bike lithium battery is 500-1500 recharges over a 3-5 year period).    That is small change compared to what solar panels and all the associated gear cost nowadays.   If you were shopping solar just for your E-bike, price wise it just wouldn’t make sense.   Of course you need to figure in the effect the standard ways to make electrical power has on our environment.  Yet making the solar panels has some effect too.   So having a full-house solar system that runs everything, and also charges your E-bike would be good, but doing it exclusively for your bike isn’t necessarily that good.

So as we wait for new technology to get more efficient and less-expensive solar energy, I do have to say right now it doesn’t add-up for E-bikes.   I have read about some new panels that are coming out that will be much better, but I think we are far from the point of using solar to power our E-bikes easily and inexpensively.   Time will tell and I am all for the power of the sun to roll me down the road.

Power-up, Turbo Bob.

“Melancholy is incompatible with bicycling.”—James E. Starrs.


About Turbo Bob's Bicycle Blog

E-bike Enthusiast Vintage Bike Enthusiast
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13 Responses to E-bikes and Solar Energy—Are They Compatible?

  1. politicats says:

    How about a mobile charging station so it’s off grid but not attached to the bike.

    The big problem for ebiles is still weight. By removing the extra weight the bike can become a joy to ride and the electricity isn’t needed.

    • I meant to also mention that some of these people who help electric car owners to recharge might be off the grid with complete solar systems on their house.
      The future is gearing itself toward electric vehicles, so off-the-grid charging should become more available to everyone.

  2. Politicats, any household outlet can charge an E-bike. That includes inverters connected to autos and trucks.
    When it comes to electric cars they have charging stations for many of the ones on the road, but they are designed for the cars that use specific charging cords and plugs. Electric cars that have been converted by owners and shops that need a standard line voltage and outlet don’t work with them. That is why there is a network of people on-line that offer the use of their household and business electric power to allow those owners to recharge when away from their homes or normal charging stations.
    They could do the same for E-bikes, in fact I have recharged my battery before at friend’s houses and local businesses on long rides. Now that I think about it, there is no reason that E-bikers couldn’t use that same network. If those nice people are willing to let strangers recharge their cars with their outlets, you have to think an electric bike would be accepted too.
    Most E-bikes weigh between 50 and 60 lbs. Some as little as 40 and others in the 70 lbs. range. They are heavy, but that extra heft is just a minor fraction of the 185 that I weigh. Plus, I have a cruiser that weighs about 53 lbs., has a single speed drive train, and I ride it quite a bit. Sure it’s no road bike, but great fun.
    The fun and utility of the E-bike is a universal thing that might not appeal to everyone. Kind of like cameras, they have light inexpensive ones and multi-thousand dollar heavy ones that take better photos. There are different ones for different people and different situations.
    We have light bikes, heavy bikes, folding bikes, old bikes and E-bikes. Each one rides and is fun, but we use each one for certain rides and needs we feel on any given day or ride.
    E-bikes will get lighter, but in the mean time I think they work very well for many people. There are people who wouldn’t ride normally, but they can with an E-bike. There are people who wouldn’t do their commute on a bike, but an E-bike makes it possible and fun.
    There are many reasons people ride them, and I for one are glad they are available and built well.
    Thanks for the input and following along with my bike blog.

    • eric webb says:

      Turbo Bob, where do I find this network of people and businesses that will let me charge up an electric car or bike? I would love to know that information and also to pass it on to other electric vehicle users. You can let me know via email. I am also coming to the electric bike event held at the San Diego Energy Center this Oct. Looking forward to meeting you and learning more about electric bikes.

  3. Terry Hope says:

    Hello, Bob good story… Did you see the last video I uploaded about project SolarCross… I demo my e-bike operating on just 10volts of solar power, from a lightweight solar array and fairing..

  4. Bill says:

    Once again, Turbo Bob, you’ve knocked it out of the park. Your wife is a one lucky lady! Keep it up.


  5. ma says:

    Turbo Bob, I want to thank you for the articles and videos you posted about the E-bikes. I want to buy an E-Brompton from NYCeWheels, but I can’t decide about the gears. Should I just settle for 1-speed, since I will get a big help from the electric-assist or get the standard 3-speed + electic assist? Thanks so much!

    • Ma, I do think having the three-speed is a great option. The electric-assist does minimize the need for too many gears, but having the three makes for a good combination.
      I have tested a couple different single-speed E-bikes and found that having a lower gear for climbing and an upper gear for cruising make for a much better ride than a single-speed bike offers.
      I know the folks at NYCeWheels will treat you great.
      Keep us in the loop about your new bike (when you get it) and how you like it, Turbo.

      • ma says:

        Thank you very much for taking time to read my post. Hope I can send you a pic when I get my brommie!

  6. Bryce says:

    Hello, I work with a solar power startup in Boulder, CO. We have created a pre-wired plug and play solar power system in a weatherproof enclosure that is the perfect size for powering small electric vehicles. We have optimized a single 250Watt panel to provide 100 amp hours a day of clean energy. This would allow you to store solar energy during the day, and use it to charge your bike when you come home from work, making your commute completely carbon-free! It can also serve as an emergency back up system if the grid goes down. Installation is so easy any handyman with no electrical knowledge can install it. Check out our system at http://www.ogpower.com.

    • Bryce, I’m not in the habit of approving comments like this (sales pitches), but figured it fits in well with the theme of this particular article. The “off the grid” factor can help many, yet there is one big draw-back I see here.
      Each E-bike recharge costs between 2 and 10 cents, with 5 being the average from my investigation. With the average lifespan of an E-bike battery being about 3-5 years with 1000 recharges—that would be about $50. Compare that to the cost of your system and you will see that for just the E-bike it wouldn’t be wise.
      As my article says, if you have a home solar system already them it is good for the bike. If you are getting one just for your E-bike than it doesn’t make money sense.
      I would like to be off the grid myself, but we use so little power to start that we haven’t made the jump (for the house at least).
      Thanks for reading and kicking in, Turbo.

  7. Peter Clay says:

    Inspired by folks like you all, I am also trying to build lightweight solar/electric bike kits and have so far had almost 2000 people from 80 different countries respond. While still working out the solar piece, I have over 3000 watts of high efficiency, semi-flexible PV and trying to find the best second battery to integrate the solar with for on and off bike recharging. Trying to build a 50-100 mile per day commuting vehicle – http://igg.me/at/SkySolarElectricBikeKit/x/1805900. Would love to collaborate!

  8. mariposaman says:

    All chargers run off DC. However it is rectified from AC first from diode rectifiers, and smoothed with capacitors, this DC is then used by the charging circuit. Theoretically all one would have to do is bypass the rectifying circuit and feed the correct DC voltage from the solar panel DC voltage into the charging circuit. I have not done this myself, but had seen it done in a solar trailer on YouTube.

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