Fuel for Thought

Diesel/Solar Electric Hybrid Sprinter

The foundation of my auxiliary power system is two Lifeline GPL-6CT, 6 volt AGM batteries (non-gassing, maintenance free). I set them up in series, so they act as one 12 volt battery with 300 amp-hrs of storage capacity. I try to keep all my voltage requirements DC, so I don’t lose power while converting to AC through an inverter (I’m in the process of installing an inverter, but that’s a different story). My major power consumers are an Espar heater, Engel refrigerator, power ventilation, overhead lights and laptop computer. I never take the batteries below 50% of the 300 amp-hr capacity to extend the life of the batteries and avoid extra battery maintenance. To help ensure I stay above the 50% of capacity, I have a Xantrex C35 set up as a load controller between my appliances and the battery. I set the controller to cut power to the appliances when battery voltage falls to a certain level, so the batteries never see 50% or lower.

The power for charging the batteries come from two Mitsubishi PV-EE125MF5F panels on the roof of the van. Each panel is rated at 125 watts, 17.3 volts and 7.2 amp output. I cut those numbers roughly in half to give me an idea of what I get in a real world application. The electricity going into the batteries from the panels is controlled by a second Xantrex C35 set up as a charge controller. My C35 is a three stage charger with a battery temperature monitor, so the charge going to the battery is precisely regulated according to the current condition of the batteries. Winter is the hardest time to keep the batteries fed, but with close management, I keep things running. In the winter, I also assist the solar panels by running a line off the starter battery through a battery isolator and to the auxiliary batteries. When the vehicle is running the battery isolator allows power from the alternator to help charge the auxiliary batteries. In an ideal world I would add a couple extra batteries, but at 96 lbs a piece batteries get heavy, fast. In the summer I disconnect the line to the alternator to keep from overcharging the auxiliary battery bank. I mounted the panels about five inches off of the roof to keep heat from building up under the panels, because excessive heat reduces the efficiency and lifespan of solar panels. I lose about one mpg to the turbulence of the raised panels, but I’ll live with that. I could install a wind deflector, but at this point in time, it probably won’t happen until I’m installing a new system on a new vehicle. The next vehicle may even get an extra panel, since 26 lbs for one panel is a manageable number.

I won’t talk about how much I spent on the system, since panel prices are almost half of what they were, and my panels may even be considered obsolete today. I’ve bought components from several places, but these days I almost always start my research for information and parts at North Arizona Wind and Sun.

It’s been three years, and the auxiliary batteries and solar panels are still running strong. The system has even saved a load for me. One night with a load on board the alternator died. When the sun came up, I jumped the auxiliary batteries and solar panels to the starter battery, and I ran an additional 250 miles to a place I could transfer the load to another driver and have my van fixed. Now I claim that my Sprinter has the solar hybrid option.

eb