[brucepick]

Paul,

I owe you a small clarification on the battery project.

The 40 AH LiFePO4 was capable of powering the car (minus headlights) for 3 hours, with minor occasional use of fan or wipers. Nominally rated 12.8V. With an allowable 80% drawdown of battery capacity and a derived approx 10A load due to running the basics (computer & fuel pump), the 3 hour life is about right.

The ~100 AH lead acid, nominally 12V of course, was effective for headlights for only about an hour. This was mostly because 12V isn't really enough for headlights, they need about 13.5-14.5V, subject to user preference and opinion. Of course voltage dropped below 12V pretty quickly. At night the illumination from slightly reduced voltage just wasn't ideal.

The other limiting factor for the lead acid pack was that I wanted to drain it down only about 50%, to preserve its longevity. Lithium, on the other hand, can safely be drained to about 20% of it's rated capacity.

Thus my interest now in several booster converters in parallel, to power the headlights and probably also brake lights and fan.

I'm certain I could have powered the stereo off the lead acid for many hours; it doesn't need ~14V to satisfy my entertainment needs. However performance stereo buffs have been known to use multiple 14V batteries in parallel for earth-shaking bass.