Yes, folks, it is possible to enjoysolar-powered transportation in an off-grid and off-roadsystem. After several years of studying all the angles, wefinally came up with a combination that has survivedthorough testing during the summer of 1998.
Our site is in McCarthy, Alaska, a remote bush communitywhere my partner, Meg Hunt, and I make our home. For elevenyears we've enjoyed the full benefits of solar power.
We wanted to extend our solar usage to includetransportation. None of the many vehicle conversions wereexactly what we wanted. Then the Bombardier NeighborhoodElectric Vehicle (NEV) came on the market. We liked what wesaw. But could the NEV, designed for charging from 120volts AC, be converted to work from solar panels? I amhappy to report that the answer is yes.
Performance
This is a neat little car with plenty of power for realwork. It is fun to drive - very quick to turn oraccelerate. We have yet to try a hill it won't climb or atrailer it won't pull. Our community is separated from theroad system by a river. The farthest we can drive is fivemiles (8 km), climbing about 800 feet (244 m) in theprocess. With driver and passenger, this takes less thanhalf the NEV's battery charge. The downhill return ispractically a free ride. We sized the PV array to allowthis ten mile (16 km) round trip every other sunny day. Inpractice, one clear day gets the NEV back up to fullcharge.
The Numbers
The NEV is 100 inches long, 55 inches wide, and 61 incheshigh (254 by 140 by 155 cm). The curb weight is 1275 pounds(578 kg). The drive motor is a 72 volt, 4 KW, shunt-woundDC motor, geared directly to the rear differential. Poweris stored in six GNB Type M83CHP12V27 Champion 12 voltbatteries connected in series. These are sealed lead-acidbatteries with absorbent glass mat separators between theplates. They are rated at 110 AH at a 20 hour rate and aredesigned for EV use.
The on-board charger draws 15 amps maximum at 110 volts.When the batteries are discharged to their design maximum,80% depth of discharge (DOD), it takes eight hours torecharge. A sophisticated sensor and display system reportsstate of charge (SOC) and status of the power system. Aseparate 12 volt, 24 AH battery supplies power for lightsand accessories. The on-board charger recharges thisauxiliary battery and the main battery. It uses a complexcharge program for the propulsion batteries, finishing witha 2 amp equalizing charge, up to 110% of the previousdischarge.
Maximum speed of the NEV is 25 mph (40 kph), limited bythe motor controller for safety. The design range is 30miles (48 km). This assumes level ground on a paved road,nonexistent here in McCarthy. The NEV is fully equippedwith headlights, turn signals, and seat belts. It is streetlegal where allowed by state slow vehicle laws.
Solar Modifications
We wanted to be able to charge from both the PV array andan AC household outlet. Thanks to extensive and helpfuldiscussions with the design engineers, we can do this. Theon-board charger rectifies the AC power and uses amicroprocessor-controlled DC to DC converter to rechargethe battery. I replaced the AC cooling fan in the chargerwith a DC fan, powered through a full-wave bridgerectifier. So we can charge the Bombardier on either AC orDC.
The PV array design was based on a season of solar powerdata. We logged our data with a Fluke 87 meter from theoutput of a single 48 watt Kyocera PV panel. We designed anarray of seven 75 watt BP panels connected in series fornominal 120 volts DC at about 4 amps in full sun. This wasnot enough power to run the charger for its full programmedcharging regime, but enough to make it work. With ourmarginal PV charging capacity, it shuts down after twohours. I installed a fused panel on the NEV dash, withjacks giving direct access to the main and auxiliarybattery terminals. Parallel pin jacks allowed easymonitoring of the battery voltages.
Switching
At Alaskan latitudes, this is obviously a summer vehicle.Very little sun is available in mid-winter, and sub-zerotemperatures degrade battery performance. But no solarenthusiast is going to let all those PV panels sit idle for6 months of the year, just when they could offer a bigboost to our house system. So we've set up a system thatallows us to switch from EV battery charging to chargingour house battery bank.
The change-over requires switches - lots of them. Eachpanel connects to a double-pole, double-throw, center-offswitch. In one position, all seven panels are connected inseries. In the other position, the panels are connected inparallel to a 12 volt bus bar feeding our house system.This arrangement runs the panel outputs through a lot ofwires. In order to minimize losses, the switch box islocated within six feet (1.8 m) of the array.
A separate switch allows us to select the series outputfrom either six or seven panels; six for direct EV batterycharging and seven for the on-board charger. When we switchthe array to six panels in series, we connect it directlyto the main 72 volt battery. This works fine, but it doesrequire manual monitoring and control. A 72 volt chargecontroller will be the next improvement. My presentpractice is to charge direct, close to the battery gassingpoint, then switch over to seven panels and the on-boardcharger to finish the charge.
The big unknown here is how this modified chargingmethod will affect battery longevity. Good management for alead-acid battery means only withdrawing half of itscapacity and then fully recharging it. By retaining the ACcharging option, I do have the occasional chance to do aprogrammed recharge cycle by plugging into a dieselgenerator.
Downside
The designers of the electrical and propulsion systems ofthe NEV have done a first-rate job. But prospective buyersshould be aware of some peculiar deficiencies.
When it comes to servicing, this vehicle is not justuser-unfriendly - it is downright user-hostile. The mainand auxiliary batteries and the on-board charger aremounted on a single tray weighing 480 pounds (218 kg). Toaccess these components the NEV must be put up on a rack,and the tray lowered by a forklift using a special pallet.The main fuses for propulsion, auxiliary batteries, motorcontroller, and on-board charger can be reached only byremoving the battery tray. If you need a forklift to changea fuse, someone was asleep at the design board.
The vehicle is furnished without a spare tire or jack,which is very optimistic for a street vehicle with a 30mile (48 km) range. Fortunately, a standard four lug,twelve inch (30 cm) trailer wheel serves nicely as a spareand fits in the trunk.
On a dry gravel road, driver and passenger are envelopedin clouds of dust even with the canvas hatch and doorcovers completely closed. Liberal use of duct tape andsilicon sealer helps, but dust still boils up through thebattery compartment vents.
Success
We racked up an estimated 100 happy miles (161 km) on theNEV this past summer (there's no odometer). It hasdelivered just what we wanted at this remote site - a wayto get around, haul supplies, and have a little fun. Takingvisitors for demonstration rides is part of the fun.Freedom from hauling gasoline or diesel oil over a long andinconvenient route was a big motive for exploring EVoptions in the first place. But the real reward was thesatisfaction of designing the PV-powered system forpollution-free transportation. Compared with noisy,gas-powered ATVs common in this area, the silent running ofthe NEV continues to astonish onlookers. And if you want touse wheels to sneak up on a moose, go electric!
Written by:Ed LaChapelle
PO Box 92723, Anchorage, AK99509-2723 ·
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