It can be a high load.
But its only high for how long? And its not usually that high. Sometimes on my car I'll see it swing to 20 amps for a few seconds right after starting. Then its down to 10 amps and then 5 amps in a few minutes.
Only when I (the operator) has really screwed up and run the battery dead does the ammeter get abused. But so is the rest of the line.
When the ammeter is showing 20 plus amps (charging) I'm equally concerned about the whole circuit, the alternator and the battery.
TJ and I have discussed this because we've both had to do it - but driving a car with a battery that low is a bad idea.
Rate of charge is one thing an ammeter will show that a voltmeter can not.
Knowing I'm occassionally prone to doing dumb things, its nice to be able to monitor the charge to try to keep from blowing the battery up or melting a connector.
A voltmeter shows whether the alternator or battery is providing power to the dash circuit.
The operator can only assume that if the voltage indicates the alternator is working, then the battery is getting properly charged.
Thats why I say one is not better than the other. They show different things.
So back to most of the load.
Well the typical load running is about 5 amps.
FWIW Using a clamp meter on my wagoneer's alternator output, I made these measurements.
View attachment 1715786040
The Wag has pretty much the same amount of lights and equipment as any '70 up mopar. Didn't measure the wiper load, but point is none of this goes through the ammeter.
The power wiring is a little more complex because it has a GM SI alternator, but its still a old school setup with the ammeter in the battery line.
However that setup is one reason I would prefer a PTO over an electric winch if I was off roading it. Of course that's not an option for a luxery era grand wagoneers..