Volt /Ammeter at odds ??

Some people think all the power runs through the ammeter - its not true.
On a car with no modifications, the normal load on the ammeter is zero or close to zero.
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The exceptions are when the alternator dies, when starting, and when recharging.
Problems happen when there are non-stock loads, such as EFI, electric fans, etc wired to the battery.
Another common situation was with trucks equiped with winches and plows running off a connection to the battery.
Less common, but good to be aware of is using the alternator to charge a completely dead battery.
Charging Battery with Alternator - Warning