please remove
does all power in car go thru it?
No.
A myth widely perpetuated by the internet. :(
Perhaps because people mistakenly beleive that the battery powers the car's electical equipment. Automotive battery's primary purpose was for starting the engine. Once running, the alternator takes over.
Ammeters, which were very common on cars and trucks for many years, shows current flow.
The ammeter is located in the battery feed.
You can observe for yourself how much current is flowing through the ammeter under various conditions.
When the ammeter needle points toward D, that means the battery is Discharging.
When the ammeter needle points toward C, that means the battery us Charging.
Most Chrysler ammeters were calibrated to show 40 amps discharging to 40 amps charging. Center is zero.
You can estimate from that.