Simmons Handcrafts

42295-AE Hwy 36, Bridgeville, CA 95526

SOLOPOWER camera ready black and white 7 wide 3.5 high

Solar/PVDeep-Cycle Batteries for the staying power you need


The Better Battery

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Trojan Battery Company

12380 Clark Street, Santa Fe Springs, CA 90670

Toll Free: 1-800-423-6569

STATPOWER 7 wide 4.9 high black and white on negative

PV-Powered Communications

Stephen Bosbach

©1995 Stephen Bosbach

Six months ago we purchased a 1984 VW Westfalia camper van as vacation vehicle. My wife Crystal and I are both ham radio operators and lend a hand in the amateur radio Skywarn program of funnel cloud spotters. I thought it would also be nice to have a totally self contained communications van that could be used to operate radio gear indefinitely with enough sunshine! Weekend dry camps would also be a possibility with a little solar power. I also envision the van as a traveling educational tool to teach the simplicity and benefits of solar power. And there is that wonderful tilt up roof on the VW that could be pointed into a winter sun! I had taken a seminar on photovoltaic applications put on by the city of Austin and was eager to try a small PV project. I needed an excuse to get my feet wet in PVs and this was the best reason I could find!

We recently completed three weeks of vacation travel in this camper outfitted with two 45 Watt PV panels and the new Trace C-12 charge controller. During that time we always had enough power for all our needs. Two weeks prior to our trip we used the van for a weekend to operate in the amateur radio Field Day competition, an annual exercise to test the readiness of amateur operators to stay on the air and handle information without access to the grid. I figured this would be an excellent shake-down for the entire system and should indicate any weak spots. Using our high frequency and VHF transmitters at five watts output, we operated for

Above: "Sunflower," a 1984 VW camper, shows off the PV array on its tilt up roof.

18 hours of the 23 hour contest and only pulled the main battery down 30 percent. This included using the water pump intermittently, using a fluorescent light for three hours, and running packet radio with a laptop computer and terminal node controller. During the competition when the sun was high and we only had one transmitter running, we actually had a net gain in charge! I love it!

Choosing the Batteries

In designing this system, I wanted enough power to provide an optimum charge rate to a 100 Ampere-hour battery (C/20 rate is 5 Amperes). This turned out to be just about what two 45 Watt panels in parallel could provide. Eventually, I decided to use two 100 Ampere-hour, gel cell batteries (Western Auto group 27 marine batteries). One for vehicle starting and operation and the other for coach loads and communications gear with the option of paralleling both batteries in a pinch. I chose to replace the vehicle starter battery with another gel cell so both batteries could be trickle charged when the vehicle is not used for extended periods. With two identical batteries in parallel, the problems associated with different battery types with different peak voltages and charge curves are avoided. This was a compromise with the charge rate when both batteries are charged off the solar panels, but this usually only happens when the vehicle is stored and the controller is just trickle charging. I also wanted the extra storage of a second deep cycle battery for the heavy draws of the refrigerator and high power radio transmitting.

This was an expensive decision, as gel cell batteries are not cheap, but they do have many advantages. They are perfect for RV use where the battery must be located in the interior of the coach. Gel cells are sealed and do not spill or outgas and can be positioned lying down and stacked. They are also more resistant to sulfation, do not need equalization, and have a slower rate of self-discharge. The safety factor of zero outgassing in an environment with an open flame from a gas stove was more than enough reason to spend the extra money on gel cells.

Controlling the Juice

Battery selection is controlled by switches that eliminate the need for a battery isolator and the 0.5 VDC drop an isolator consumes. This was a compromise in automation, so I have to remember to throw the switches manually. Using two single pole / single throw switches from the coach loads to the batteries, I can select either battery or draw from both of them in parallel. Normally when driving, the starter battery is switched online so the vehicle alternator can take the burden of recharge. When parked, the auxiliary battery is switched online to run lights, water pump, short runs of the refrigerator, stereo, and transceivers (both high-frequency short-wave and VHF for local communications). I use a second, heavy-duty battery switch to alternate batteries from the communications loads as the HF transmitter will draw close to 20 amps if run at 100 watts output.

When we installed the Trace C-12 charge controller, it was brand new on the market. It had the features I was looking for, and then some. The big advantage of this controller is its three-stage charge which allows a much faster battery recovery, tapering off to a float charge as the battery reaches full. The pulse width modulation charge method is also a winner, as this decreases sulfation and is a perfect match for the gel cells. An added bonus was the built-in 12 Ampere low voltage disconnect. We got to test this feature on our vacation when I accidentally left the refrigerator connected to the starter battery while we went off on a day hike. On return, we had a disconnected load and a battery that would survive to see many more charge cycles! But, there wasn't enough juice left to turn over the starter motor, so both batteries had to be switched in parallel for a while until I had enough juice available to start the VW. Yes, I know this wouldn't have happened with an

Above: Steve Bosbach (left) and friend work the ham radios during a hot Field Day.

Above (left to right): coach load switches, transmitter switch, C-12 charge controller—all wiring is behind the closet wall shown here.

Above: The Juice Box (a sealed lead-acid battery)— 100 Ampere-hours at 12 VDC. The temperature sensor stuck to the battery goes to the charge controller.

isolator in the system, but I wouldn't have had the flexibility I have now. In a pinch I can parallel both batteries and run the refrigerator on DC for up to 10 hours without drawing down the batteries too much. Normally an overnight stop has us using propane for the refrigerator, but short stops of a couple of hours for sight seeing are much more convenient if run off DC.

The C-12 is also fully adjustable for on and off set points and needs to be set a tad hotter for gel cell batteries. I used the battery manufacturer's recommendations and set the float at 13.8 V and the low voltage reconnect at 12.8 V. High voltage disconnect for the bulk rate (first stage of charge) was set at 14.4 V and the low voltage disconnect is set at a conservative 12.0 V. The blinking LED is simple to interpret with a steady green for full charge and steady red for off (low voltage disconnect). In between there is a sequence of blinks, from an evenly spaced blink to a series of five blinks and a pause before going to a solid light. I found this system to be simple to interpret but not nearly as linear in showing state of charge as the front panel diagram would indicate. The C-12 LED goes from green to red when the battery falls to 12.6 V. The instruction flyer included does explain the amount of voltage difference between each step in LED

VW Westfalia Solar Conversion


System Component



DIY Battery Repair

DIY Battery Repair

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