Ebike Charges In The Sun

Ebikes are slowly taking the place of many cars, especially for short trips. Most ebikes can take riders at least 16 kilometers (10 miles) without too much effort, at a cost that’s often a single-digit percentage of what the same trip would have been with an internal combustion engine. If you’re interested in dropping the costs of your ebike trips even further, or eliminating it entirely, take a look at this small ebike with integrated solar panels.

While any battery can be charged with a sufficiently large array of solar panels and the correct electronics to match the two systems together, this bike has a key that sets it apart from most others: it can charge while it is being used to power the bike. Most ebikes don’t have charging enabled during rides, so if you want to use the sun while riding to extend the range of the bike you’ll need to find one like this. This bike uses two 50 W panels on the two cargo areas of the bike, attached to a 400 W MPPT charge controller. The Lectric XP 2.0 ebike has a motor with a peak rating of 850 W, but in a low pedal-assist mode the solar panels likely output a significant fraction of the energy used by the electric drivetrain.

Even if the panels don’t provide the full amount of energy needed for riding around, the project’s creator [Micah] lives in Florida, so just setting the bike outside in the sun for six to eight hours is enough to replenish most of the battery’s charge. It’s probably not going to win any solar-powered bike races anytime soon, but for an efficient, quick bike to ride around town it’s not too shabby.

38 thoughts on “Ebike Charges In The Sun

    1. Indeed no doubt the solar will do a good amount of work, quite likely enough even on the cloudy day to recharge entirely for most users.

      Though practically I doubt it really works out – along with the weight and wind as you mention I half expect those panels to end up cracked in short order, as the corners are rather exposed – while it would be a less optimal sun catcher (at least on average through a day) I think the two panels likely should have been a somewhat open book put down on the table type shape behind the rider – sticks out so much less, probably helps smooth the airflow off the riders back too and by bringing both panels together in a smaller footprint on the frame you can add a little bit of bumper to hopefully prevent real damage to the panels for very little additional weight. And if you have the weight budget to spare you could even hinge them at the top so when the bike is on its stand/leaning against a wall or even while riding a long way in a consistent enough direction you can tillt both panels to the best angle for right now.

      Still a neat project that with some care should be good for a long time to come. Really shows how simple it can be.

        1. Nobody, however the linked website does show them that way, and if you were going for a static installation to charge your ebike why isn’t it a bigger panel on your garage roof, with a spare battery or two to run the garage lights!

    2. I think it can be done in a proper way:
      Using the panels as a base for some kind of crate for carrying stuff. Cargo bikes are (at least in parts of Europe) quite common nowadays.

      When not in use for carrying stuff, just remove the “frame” to expose the panels. Those panels can withstand quite the impacts and forces…

    3. Why not have them fold down to be online with the bikes frame? That should resolve most of the drag, though, I doubt their current setup causes a huge amount of drag at low speeds.

  1. Ebikes are only replacing pedal bikes, for fat and lazy people, they are absolutely not a substitute for a car, or even a full motorcycle. Same with e-scooters, there is nothing more tragic than some overweight person gliding along on one of those things without moving. And for the record, I personally don’t drive a car at all. As for the solar panels on the bike, I think a couple of flexible curves front to back then one of those long flexible panels on the top would be a lot safer and less likely to do harm to a pedestrian. Basically you want a flexible but stiff structure to suspend a lightweight panel from, perhaps the type with eye holes so it is all held under tension like a canopy above the rider.

    1. I’m fat and lazy, that is true. It is also true that I ride my e-bike to work, rain or shine (or most probably snow). I wouldn’t do that with a regular bike, at least not in the winter when biking through droves or wet snow is just not possible (not always possible even with an ebike though, but it helps a lot).
      E-bikes allow me to not having to cold start a car twice a day. While it does not negate the need of a car where I live, it at least cuts down on the amount of shorter trips.
      So, while I’m fat and lazy, I don’t think I’d be less fat and lazy by driving everywhere, which is absolutely what the alternative would be.
      I don’t *love* riding my bike (or driving my car for that matter), but I need to go places some times. And I like not showing late and sweaty. I’m sorry I can’t live up to your standards.

    2. A rather stupid take, Ebikes especially in Europe where they must be pedal assist are a way to allow those too old/unfit to cycle up that monster hill or actually make it all the way to work to ride. Its hardly tragic for these folks to be able to get around without requiring their SUV, and eventually as even the just the act of balancing a bike is more involved than sitting in a car with power steering etc…

  2. Most panels do not produce any power if partially shadowed. In many driving conditions, the driver (or trees) will shadow a panel. In addition, the panels are not aligned well with the sun. The aerodynamic drag by those panels probably outweighs the minuscule charging current if you drive faster than walking pace. The only case where this would make sense at all is long distance biking far away from any civilization, but even then you’d be happier with some of those thin and light folding solar cells in a pannier bag.

        1. for every watt you get out of the turbine you have to putt more than a watt into driving… no different than trying to charge the battery from a generator attached to the wheels.. except even worse efficiency.

    1. Have you heard of a perpetual motion machine?

      If you have a solar panel power an LED, and the LED shine on the solar panel, what happens?

      If you’re thinking of a wind turbine that would be used only when the bike is sitting idle, then, the solar panels are probably more efficient in most areas.

      If you are thinking of a wind powered vehicle that travels faster than the wind, it requires a very specialized turbine.

      1. It’s not perpetual motion machine. Think about it – the wind is going to hit your body anyway whilst moving, so why not put a turbine in front of your body? If it was very small it would create no extra drag. Work out how large it can be before it starts to create drag and change blade angle to parallel to wind when you dont want to use it for any reason.

        1. A wind turbine does not stop the air – it will hit your body also. Your body doesn’t stop the air either, it just changes the path as it flows around you. The turbine would increase turbulence, which increases drag. I agree that if the turbine would direct the air on an optimal path to give laminar flow around your body, it would not increase drag – but typical turbines do not do that.

          The net energy from a wind turbine mounted on a moving bike is probably about equal to a turbine on a stationary base. Such small turbines are pretty inefficient in practice.

          1. Yes it does. Turbines or propellers extract a large portion of the energy of the air flowing through the area of the disk they create. Air mostly flows around your body and a significant amount of drag is from the turbulence behind you. If you are shaped like a fish the drag is lower – like the bike helmets on racers. Turbines slow the air down significantly. How else could they get energy?

          2. “The turbine would increase turbulence, which increases drag” …. sounds reasonable …. but by how much? If the turbine was relatively small, would the net turbulence be larger than the cyclist’s body alone?

        2. The turbine creates drag as it extracts power from the wind. The smaller the turbine, the less drag it creates but also the less power it extracts.

          Next, convert that power into electricity. There will be losses because power conversion is never 100% efficient.

          Next, use the electricity to power a motor and add that into the drive train. Again, not 100% efficient.

          What you’ll have is a system that increases drag by more than the power it adds back.

          1. “What you’ll have is a system that increases drag by more than the power it adds back” ….. yep, this is the question, but can it / has it been proved either way to be true or false?

          2. RC:
            You can’t say with absolute certainty…if the turbine was smaller cross section and in the cross section of the rider and bike. If bigger, then no, it’s going to be a net loss for sure.

            It would take serious work to make it breakeven, making it net positive is very doubtful. Targetdrone listed the losses. Also weight, to be at all efficient it would have to be variable pitch. I wouldn’t even try, KISS. Spinning blades are hazard to pedestrians. Blade tips are generally pretty sharp.

            Also anything not nailed down…

            Paul downthread nails the conventional argument against putting solar on vehicles. Just put solar on roof and let it generate, best use of resource. Goes double for wind.

          3. @Reluctant Cannibal Lets put it this way any energy you extract from the air/ground speed differential came from you/your motor and was extracted will losses (unless it is also windy) – so you would always be better off just improving the aerodynamics.

  3. Well the cross section exposed to the wind is like an inch, and compared to the cross section of your torso… it’s seriously a non-issue.

    As far as weight goes? It’s like what, a couple pounds, 5 lbs tops? That’s like pigging out on some beer and pizza. So, again, your concern is extremely minor.

    The point here is being able to charge while riding, *and* charge while off the beaten path away from charging stations or your home base, *and* charge up for free for decades and tens of thousands of miles of zero cost transportation.

    Put another way: efficiencies are getting really good now such that for a meager investment you get a fast ROI that can reduce your commuting costs to zero, and pocket that money. This wasn’t really possible with off-the-shelf gear even 10 years ago.

  4. The comment about energy used versus internal combustion reminded me of the Honda 50 motorcycles of the 1960’s. They were advertised as 225 miles per gallon. This was actually possible on flat good quality surfaces and low speed. 100 to 170 around town was realistic and 50 to 70 for a kid giving rides to all their friends.

    Assume 170 mpg (72kpl) and fuel at $6/gal, California blend, at eBike speeds. This is 3.5 cents a mile (2 cents in Oklahoma). So is that a single digit percentage of eBike costs without the solar?

    How much power does the ebike use? In parts of the US that 3.5 cents will get you 1kwh of electric power into the charger (2.4 cents per kwh in Bridgeport Washington). Other areas of the US can be as high as 20 cents. Places in the EU can be over 50 cents.

    Anybody know eBike power who will pencil this out a little?

    1. Euro legal ebikes are limited to 250w pedal assist only. As you’d expect when ‘those people’ are in charge. Many Tour de France cheater bikes are illegal to ride in France under any circumstances (Motors and batteries hidden in frame).

      But in the good old USA 5kw is common enough (V8/Glory days F1/Top Fuel Drag speakers optional). Most are lower, look on Amazon for kit selection. Complete bikes are mostly Walmart grade, Craigslist bike shop bike plus kit is better choice.

      CA limits 750w or motorcycle license is required. But can have ‘off road’ mode that you’re not supposed to use on street. Wink, wink, nudge, nudge…she’s a goer.

    2. Ultimately the effective MPG for the ebike should be better, as its always going to be lighter and more efficient than the moped combustion engine – the moped might take you further, as its fuel is rather more energy dense – way more than enough to make up the efficiency losses of ICE, and in the areas of the world with speedlimits and pedal assist requirements a moped is almost certainly faster (though that then likely means way way more drag for even worse mpg as few mopeds are streamliners).

      But there are too many variables to really state the exact ratio for every location in the world, it is however in my opinion going to be pretty much always vastly vastly cheaper to run the e-bike to the point the articles description I would call fair enough. As where petrol is cheaper electric tends to be too – you don’t get super expensive electric and cheap fuel at the same time usually.

      1. The question is about cost. Or how much power does it take to get a battery charged enough to run the ebike per mile. I’m sure it is cheaper, but the author claimed it costs less than 10% as much. (I think Honda 50 and 90 at about 125 lbs were much lighter than a moped.)

        1. > always vastly vastly cheaper to run the e-bike to the point the articles description I would call fair enough.

          Or more explicitly the answer is less than 10% is probably true enough to just call true – as in nearly all combinations of grid electric to fuel cost with the usually vastly more efficient and lighter ebike that will need so much less energy it will be lower than that.

          BUT you can’t state exactly as I’m sure you can find places where petrol is basically free and electric more expensive, and there are some very impressive lightweight streamliner ‘mopeds’ that are light and pretty efficient.

          1. “at a cost that’s often a single-digit percentage of what the same trip would have been with an internal combustion engine” I read that as 9% or less.

    3. I can’t answer the price question, but what we’ve found as a bunch of bike racers who have converted a couple of bikes, is that 250W (of human or electric) will get you 40km/h on flat ground. 300W will only get you about 45km: you’re into the range where air resistance is by far the largest power sink.

  5. How about mounting the solar panels in an optimal location, NOT mounted on the ebike, and just charge a second battery that you swap out each day? The panels won’t ever be shaded, do not cause drag on the bike, don’t have sharp corners that hurt people, aren’t prohibiting the bike to be locked to most bike racks, etc.

    And you’ll get more km per day of charge too.

    Better still: save the cost of the solar panels, and just plug a second battery in a convenient wall outlet…

  6. The Sun Trip 2019 (the solar powered bike race mentioned near the end of the article) ended up collecting some interesting data. It turns out that on a moving platform like an ebike (or on a trailer behind it) that solar tracking isn’t as important as imagined. All of the contestants averaged near 4Wh per watt installed solar per day, regardless of if they were flat or tracking.
    There were multiple mentions however of most of them angling towards the sun while camping to collect the morning sun before they awoke, but that doesn’t require active tracking.

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