On 02/05/2020 23:49, The Natural Philosopher wrote:

Total crap. There is no pint in having a 150A capable alternator to
do THAT

You are forgetting the internal resistance of the battery.

I am the one with the degree in that subject,

What, your a Bachelor of Batteries?

I am not forgetting it.
You simply have no idea of its value.

I fit ammeters in all my vehicles, ever the tractor. Even after a bump
start because of a flat battery the charge settles to below 30A within
seconds.

As a matter of fact, I initially fitted 60A meters in the motorhome but
soon changed them for 30A ones. (Later I re-did the control panel and
fitted digital ones.)

I've just done a search for vehicle and marine ammeters. The vast
majority are 30-0-30. A few are 60-0-60. According to you they should
all be 150-0-150.

Like I said the battery has sufficiently low internal resistance to be
able to deliver 700A to a starter motor, it can sure handle 50A with
only a half a volt or so increase in charge voltage.

Yes but the alternator keeps the charge to a sensible level, to prolong
battery life. Extremely rapid charging is bad for lead-acid cells.
That's why milk floats are on charge all all the time they are in the
depot. It's why disability scooters are charged at 8A or 4A depending on
the battery, which can be inconvenient in summer if the user wants to go
shopping in the day and out for a meal in the evening.

There's no doubt you can push 100A into a big lead-acid battery if the
supply is of high enough voltage, but do it routinely and the battery
won't last as long as it should.

The other factor concerns the alternator voltage. Once a flat battery
has received a bit of charge, its terminal voltage rises to the point
where to maintain a 100A (say) charge the alternator voltage would have
to be so high as to over-run filament bulbs and other equipment.

So if you spent three years getting that Bachelor of Batteries degree it
looks like you wasted your time, because you know nowt.

Bill