Battery lesson

Reluctant to head back to home base quite yet, we have stopped in Quartzsite AZ for a few days of free camping in the desert.  We’ve been camped at the BLM’s “Roadrunner” area, which is about five miles south of the town.  This is classic boondocking, no services at all, no established campsites, and no fees.  The lack of amenities is balanced against the feeling of freedom that comes with staking out a little patch of gravelly desert and just enjoying the simpler pleasures of life.


However, sometimes reality intrudes on our attempts to “get away from it all.”  Last night I noticed that the Tri-Metric battery monitor was reporting strangely low voltage in our batteries, despite having used just 33 amp-hours of our total power reserve.  That’s about 15% of the theoretical power available.  Not long after, the voltage dropped to 10.8 volts, the lights began to dim, and I realized we had a serious problem with our batteries.

Around 9 p.m., the trailer was effectively dead. No power means no lights, water pump, or heat from the furnace.  Eleanor and I were outside in the dark examining our battery bank by flashlight.  We have a bank of four Optima “blue top” Absorbed Glass Matt (AGM) 12v batteries. We tried disconnecting each battery and checking voltage, hoping to isolate one battery with a problem, but they all reported the same voltage.  At that point we decided to reconnect all the batteries, and limp through the night without any heat.

By reducing the power load to the small amount required to maintain the refrigerator’s circuit board and a few other “parasitic” draws (radio memory, propane leak detector, etc.), the voltage popped back up to 12.2.  We all piled into one bed and stayed pretty warm, even though the trailer dropped to 46 degrees.

In the morning we hitched up and towed directly to Solar Bill’s, one of three solar installers in Quartzsite.  Solar Bill’s is a fixture in Q, having been in the same location for 22 years.  The guys did a load test on the batteries and found that two of them were dead as a doorknob.  The other two were fine, despite having been installed at the same time.

The problem seemed to stem from our wiring.  Our batteries should have been wired in parallel.  As it turned out, they were wired in two banks of two, in such a way that one bank took all the load while the second bank was basically just coasting.  That mistake contributed to the short life of the Optimas.  They lasted 3.5 years when they should have had twice that lifespan.

Although two of the batteries are still good, the recommendation with batteries is to replace them all at the same time.  This meant the two good batteries would also need replacement, an expensive procedure.  Solar Bill didn’t like the choice of four 12-volt Optimas, so he suggested 6v golf cart batteries, but they wouldn’t fit.

After weighing several options, the best choice overall was to remove all four Optimas and replace them with one huge Lifeline GPL-4D.  This eliminated the wiring issue and freed up our forward battery box for other uses (like tool storage).  The “supercell” sits in the forward storage compartment under our bed, in the space formerly occupied by two of the Optimas.

As a bonus, the Lifeline weighs about 40 pounds less than the batteries it replaced, with a theoretical power capacity about the same.  The two used-but-good Optimas will go to the Caravel, thus doubling the power available in that trailer, and we’ll have one Optima (from the Caravel) left over for future use.

But this has made for a very expensive week.  Four tires, and now a replacement battery.  I was happy with our relatively low maintenance expense in 2009, but so far in 2010 we’ve almost blown the budget for the year … and we are still awaiting the repair or replacement of our catalytic heater.  On the positive side, it seems like we’ve dealt with a lot of the big-ticket items, so perhaps the rest of the year will go well.