I have been building solar electric vehicles for years. I built a 72 volt EZ-GO golf cart and a 1973 Harbilt English postal van. These vehicles were real workhorses. Just park them in the sun! But something was missing. I realized I needed to take it to the highway. I chose a Volkswagen Bus for this reason and also the surface area of its roof. I imagined a large PV (photovoltaic) array that could tilt for maximum solar exposure. It also occurred to me that the large space underneath the panels could offer some more elbow room in the vehicle.
The roof consists of 4, 305 watt LG panels. The 1,220 Watt array pivots in the front of the van. I can access the space above from below through the van’s moon roof. Actuators (one on each side) tilt the array up to a maximum of about 40°, adjustable for maximizing output. I'll have the camper top open as the sun sets, getting kids ready for bed. With an 180° spin of the vehicle, I'll be able to position the array to catch the morning sun. At full tilt I have 40 degrees of angle allowing me to be directly facing the sun for far more than the six hours stationary panels can attain. Being able to move the van ensures that I can always get the most exposure. I needed to use 4 Drok Dc Dc boost converters to boost each panel voltage from 40 Voc to 55 Voc. These converters are then wired in series for around 220 Voc. The array can theoretically put out 8 amps total at 150 volts into the battery.
The panels sit on two rails of 3 inch aluminum angle running the length of the array. The panels are sealed together with silicone sealant providing a solid leak proof roof that can also flex a little and still seal.
The panels lift with two 300lb linear power screw actuators. The motors can each pull 6 amps and push 300lbs. I have them together fused at 7.5 amps. The motors are only working about half as hard as they need to.
Twelve Trojan T-1275 lead-acid batteries provide 150 Ah at a 20-hour rate. Series connections bring it up to a 144 volt nominal voltage. Since I load the batteries at a minimum of 50 amps or C/3 and up to sometimes 2C I have seen about 80 amp hours out of each battery for an approximate 80% DOD. Peukerts law describes this relationship between load and amp hours. So the lighter I go on the batteries the farther they take me. Finally a good reason to slow down! I have a 12 meter display on the dash...one for each battery. I feel more comfortable seeing the performance of each battery. The batteries sit under the kids' seat so monitoring the state of each battery is an important safety feature. Reading the total series pack voltage will not show one battery dropping dangerously below the others. Also stopping the discharge is related to the DOD of that lowest battery. These batteries were selected for affordability. For three times the price, I could have installed some lithium iron phosphate batteries, but I'm trying to make a point about the affordability of such a vehicle. I’ve spent a lot of time working with lead-acid batteries, and know how to maximize their life and performance. Check out the solid copper wires. I smashed some round stock in a 50 ton press to give me a perfect non-soldered non-crimped connection.
I’m using an AC motor and 500 A, 144 V controller from Hi Performance Electric Vehicle Systems. At first I ordered the AC76, a larger motor with a lot of torque, but it had a misplaced winding and burned a black streak down one of the phase wires, making my maiden voyage disappointing. I swapped it for a smaller AC51 motor, which lightened the load by about 100 pounds. I have more power than I ever need. I'm glad I went with a smaller motor. The Motor Controller combo is a great package. The Curtis controller is awesome. It has a great regenerative function. I put back massive amounts of power while simultaneously saving brake pads.
Although a liquid cooling package is recommended for the Curtis controller, I opted for the air-cooled heat sink. I mounted the controller upside down so the wires would directly meet the motor without crossing. I also like the heat sink on the top since heat rises. two 5 inch fans keep the controller plently cool even in 100 degree weather.
A MeanWell 660 W, 144 V to 12 V DC-to-DC converter keeps my 12-volt accessories operating. I have another 100 A converter ready as a spare.
I have a thunderstruck motors converter on deck.
This converter has since went out for at this point unknown reasons. It has been replaced with a Thunderstruck motors 144 volt 50 amp isolated DC DC buck converter.
The inverter is an EV Enterprises Blue Flash 2 kW unit, which inverts 144 DC to 120 AC quite efficiently without any magnetic component. I can cook, cool, and run basically any AC appliance. Oh yes...and my Husquavarna electric chain saw. effortlessly..
Charging from the Grid
I have two ThunderStruck Motors 2,500 W chargers. At 20 amps each I can charge full in two hours 20 minutes. Programming the chargers is a snap and I can create charging profiles for 110 VAC as well as 220. A 110 charge, roughly 10 amps in a t 150 volts takes about 10 hours. I notice slow charging gives me my best range figures.
Vacuum assisted braking
I use a small vacuum pump for the brake system which runs when 12 V key ignition is on. The brakes work as they did with ic engine vacuum. The regenerative brake adds stopping control for the heavy vehicle as well. Up to 150 A hits the battery bank just by letting off of the accelerator pedal. It’s nice to not have to use the friction brakes and get much of that energy back into the batteries.
After finding some brake issues ( brake pistons stuck out and engaged!), I went from a 35 mile range to 50 miles. Driving slowly, (35mph) on appropriate roads is the way to get even more than that. If I really nurse it I can get one mile per amp hour...I can get up to 80 amp hours. That's a potential of 80 miles. If I go 40 -50 mph I'll get 30-40 miles. Much depends on the elevation changes....and the speed to amps draw figures likely reflect wind resistance more than anything else.
This a camping mobile and I’m interested in the scenery.
The panels put out an actual 6-7 amps with the inefficiency of the controllers I'm using. Parked by my house in Ashland, Oregon I get about 25 amp hours in a day...15-20 miles of city driving. If I work it, tracking all day and such I will get approximately 50 amp hours out of my required 80. Of course the driving conditions determine how far that gets me....see range.
The vehicle was designed for a one day full charge. Join me in the technical details section to see how we will move into the 8 amp range.
Also visit the Apparent Energy section to see how we can get even more of that energy into the batteries.
Installing the Solar Array
Vacuum Pump for Brakes
and 12 Volt Accessory Battery
Solid Copper Connector
JLD404 - AH Meter
The bus when we first got it
The battery pack
Building the frame for the panels
-all on a swivel chair
Volt Meter For Each Battery