David Beierl wrote: > Lots of modern battery chargers will pulse-charge at more-or-less full > output once the battery leaves the deep-drained condition. > Yep, it appears that the DC > DC deep cycle battery charger is the culprit. After trickle charging the house battery on shore power all night, there were no observable voltage pulses. So what I saw was the DC > DC charger yanking on the engine battery to bring the house battery up after a few nights of self-discharge. The charger can pull as much as 15A, and appears to have a 900ms/100ms on/off duty cycle, which causes a 300mV pulse every second, which in turn causes the dash and headlights to increase in brightness every second. Mystery solved. I spent the night at a motel a couple years ago and had to keep the van's electric refrigerator running all night in the parking lot because it was a warm night and I had stuff in the refrigerator that needed to be kept cool. I left early the next morning and while driving on the freeway in the pre-dawn darkness I noticed that the voltage at the dash was about 12.1 volts. The headlights were none too bright, either. After some fretting that the alternator might have quit, I realized that what I was seeing was the result of skinny wire and the combined loads of the headlights and the DC > DC charger working full-bore to charge the 30% depleted house battery. I'm going to do a little wire beefing up here and there to provide these two heavy loads with their own dedicated 12V lines. I'll take the time to touch up the grounds, too, even though the large voltage drops tells me that the current paths to ground are in good condition. -- Mike "Rocket J Squirrel" Elliott 84 Westfalia: Mellow Yellow ("The Electrical Banana") 74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.) Bend, OR KG6RCR |
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