On Monday, May 6, 2013 12:31:41 PM UTC-7, Steve Leonard wrote:
I have two 6 volt and one 2 volt PowerSonic cells in series to make a 14 volt pack for one of my sailplanes. I had one of the batteries go bad, so I did a little checking to see which one. All showed appropriate charge voltage when not loaded, however, one battery went from 6.2 volts no load, to showing -3.8 or so volts when loaded by turning on a S-Nav and GPS-Nav. Now, I have seen an individual battery go to very nearly zero volts, but never negative voltage! Turn everything off, and it slowly recovers back to showing about 6.2 volts no load.



Anyone else ever seen a battery do that before? And please, no comments about 14 volt battery packs or old technology batteries. Age of battery unknown, as I do not remember when I built up the pack.



Just curious.

This is called "cell reversal" and does occassionally happen.

My question is why do you think that you need a 14V battery? All modern aviation electronics is designed to operate on a wide range of input voltage. This is accomplished by a circuit called a "dc-dc converter" that boosts the input voltage to a higher, regulated, internal voltage.

Tom