Electric cars are fantastic, clean, transportation, and some people would consider a SOLAR-POWERED electric car to be the Holy Grail of electric vehicles. However, there are a number of challenges, including the cost of solar panels, PV efficiency compared to the surface of a vehicle, increased wind-resistance, and more.
But I didn't let that stop me from building a Solar-Electric Car for about $12.
Full Disclosure time — it's a children's ride — on POWER WHEELS toy. Okay, Okay..... so it's not a full-size, freeway-capable vehicle, but my two-year-old LOVES it!
This all got started a couple of years ago when some of my friends were competitively souping up kids toy cars, converting them into unusual adult go-carts, and racing them against each other. If you've been to any of the MAKER Fairs, you may have seen some of them in action. I had picked up a Power Wheels for free on Craiglist. I simply posted an ad "WANTED: Power Wheels, working or not." Sure enough, I got a reply saying that somebody had one but it didn't work, as it had no battery or charger. Perfect!
I never got around to hot-rodding the Power Wheels for competition. (I helped out on my friends projects, and acted as a replacement driver and pit crew during the races.) My life had gotten busy with a new baby at home, change in employment, and the usual challenges. So, I still had the stock Power Wheels Jeep just kicking around two years later.
My little girl is now big enough to drive a Power Wheels. Of course, it still didn't have a battery or charger. I had a few old batteries from various projects, including my electric motorcycle and electric car. I still didn't have a dedicated small charger. Typically, these cars use a proprietary battery, with a special plug and special charger. The car doesn't work unless you use their brand of components. I looked at the big box store and saw that the car required TWO 6V batteries, each of which was nearly $50 ($100 total,) and a charger, for another $35.
It also dawned on me that the reason the batteries on the cars fail is that the parents don't get in the good habit of removing the battery, taking it to the garage, and putting it on charge. Instead, the car just gets left out in the yard, where the battery is run down, and ends up with a severely shortened life.
What if leaving the car out in the yard was a good thing? I already had a few solar panels (PV) around that I had bought a while back for experimenting and learning about solar energy. Wouldn't a solar-powered Power Wheels just recharge itself if left in the sun? I checked the specs on the solar panels, and they basically output one amp at 12V charging voltage. Two in parallel would put out 2 amps — just about the right charge rate for a 20AH battery. Even better, two of the solar panels together was almost the exact right size for a roof on the Jeep!
I quickly got to work digging through my garage for scrap materials that might work. I found some pieces of 1/2" inch electrical conduit. That material is a thin, hollow steel tube. It's cheap, easy to cut, bend, and weld. I took some measurements to see where the steel frame of the the Power Wheels was under it's plastic body. I also measured the solar panels, and then made a basic layout that would fit the solar panels to the car, sort of like a pickup-truck ladder rack. I designed it to be high enough for my little girl to get in and out of the car without hitting her head. A little cutting, a little welding, and a can of black spray paint, and I had my rack!
I drilled four holes through the plastic body and set the rack down to the frame of the car, and attached it with a number of self-tapping metal screws. To connect the solar panels to the top of the rack was a little more complicated. The PV didn't have any dedicated bolt holes — but the frame itself was a C-channel aluminum extrusion. I got some machine screws with heads that were big enough to catch the lip from the inside of the extrusion, but they were too big to get in there in the first place! To solve that, I ground down one edge of the head, inserted it, and then rotated it to lock it down. The panels went down onto the rack, where they were permanently connected with washers and nylock nuts.
The Jeep now had a solar powered roof, but no place for the energy to go! I found that I had a 20AH sealed lead-acid battery that fit nice in the front compartment, but it didn't match the special connector on the wire harness. I took an old dead Power Wheels brand battery that I got from a friend, and lopped off the special battery connector. I added a 30 amp in-line fuse and crimped on ring terminals that went right to the battery. I could now plug in the battery to the car, without otherwise changing its wiring.
I routed the wires from the solar panels to the solar charge controller that came with as part of the Harbor Freight kit. From there, I wired the output to a splice on the wires going to the battery. The solar panels could now charge the battery, and the battery could power the electric motors that ran the back wheels of the toy car!
Since the new components were larger than the original ones, I couldn't put the plastic hood back on. Instead, I made a new one with some scrap plexiglass. I simply cut the plexiglass to size, and added two holes for bolts to hold it down to the car. The plexiglass serves multiple roles as it holds down the battery, protects the charge controller from the rain, and shows off the modifications.
So how's it working? Great! My little girl has been driving the car every day about about the past three weeks. When done, it just gets left out in the yard, where the sun recharges it. I haven't had to plug it in to the wall even once yet!
The Solar-Powered Jeep was easy to build from materials that I already had. I did spend about $12 as my out-of-pocket total. I did have to buy some additional conduit ($1.99 for 10 feet) a new can of spray paint, and I splurged for some stainless steel nuts and bolts, as this is an outdoor vehicle.
The car is also a great exhibit to show the basics of how EVs (electric vehicles) work and the principles of recharging with renewable energy resources. Not bad for a tinkerer Dad on a Saturday afternoon, and a little girl who loves her new electric car!
Take a look below at the videos for more information on how I built the car, mounted the solar panels, and even watch the car going out for a spin around the backyard!
Ben Nelson is a self-professed non-expert, who doesn't let that stop him from learning about, building, and teaching electric vehicles, renewable energy, water conservation, and anything else he can figure out. He blogs about DIY clean transportation at 300MPG.org and about eco-friendly home and yard projects at EcoProjecteer.net. You can also finding him speaking about all his projects at the Mother Earth News Fairs.