E-bikes and Solar Energy—Are They Compatible?
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.
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).
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.
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.