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How most chargers and alternators work

Let's say you have a battery charger or an alternator that says it's a 35 Ampere/Hour machine.  Well, that's its "maximum" output, not its "normal" output.

Here's how it works.  You have run the battery down to pretty much nothing.  So you plug your charger in or start your engine and away we go.  If the battery is absolutely dead, you will get 35 amps from the start.  If you have an ammeter (which chargers usually do; but alternators usually don't), you can stand there and watch it very quickly drop.  It will be down to about 1/2-speed (17 amps) in about half and hour.  Then it will slowly drop to about 5 amps and stay there forever.  Even if you'er working with a 90-amp car battery, it will take at least 12 hours to be fully charged.  The reason fo this is called "regulation".  They are assuming that you are stupid and that you will go away and forget about it.  Well, you can.  You can come back in 24 hours and it will be down to 0 - and you haven't hurt anything.  You're not really fully charged either; but you certainly have enough charge to start your car and then you have the alternator working so you don't care..

That's not what we're up to in an RV.  We want to listen to that damned generator as little as possible.

I just have to leave you with this story.  When I first started, back in 1974, I was pulling a 27-foot trailer with my 68 Cadillac.  We had two of those so-called Heavy Duty Marine batteries.  They are slightly bigger than a Sears Diehard; but not much.  Each morning, they would be deader than a doornail.  The car had a 55-amp alternator.  Well, no problem - just drive for 4 hours and you be all set.  But, we'd drive for 10 hours and we still didn't have much battery power.  I bought an ammeter and put in the wire coming out of the alternator.  I left it sticking out the back of the hood so I could watch it.  When I first started the vehicle, it went right over to 50 amps.  About 10 minutes later, it was down to 20 amps.  After 30 minutes, it was down to 12 amps - and it stayed there aaalll daaay looong.

Now part of the reason was that the trailer batteries were 20 feet away and the car battery was 2 feet away.  The regulator was reading the car battery.  However, I've seen the phenomenon work the same on a boat where the batteries were each only a couple of feet apart..

Bottom line - - the "stupid" method doesn't work!  You have to use the "intelligent" method.  "You" have to be in charge.

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