Usually not easy to find a battery-alternator arrangement that is wired in series but they are wired in parallel.
The battery is connected to the buss thru a battery relay and an ammeter. The alternator is connected directly to the buss thru a circuit breaker.
The ammeter measures charge or discharge of the battery and when it is being charged, current is flowing from the alternator to the battery and the buss.
Hope this helps but I think on G1000 something could be different.
BAT and ALT are both connected to the Main Distribution Bus. In flight, the alternator is supplying all the electrical power to that bus and is charging the battery (by virtue of having a higher voltage output).
The Cessna-style (+)(-) and (0) ammeter works because it is literally wired in series with the (+) battery lead wire, which is routed behind the panel between the Battery Contactor (operated by the Master Switch) and the Primary Bus Bar. When current is flowing from the bus bar into the battery, the ammeter shows a (+) deflection. If the alternator fails or is switched off with the ALT half of the Master Switch, current flows through the ammeter in the opposite direction - from the (+) terminal of the battery into the Primary Bus Bar - thus the needle is deflected the opposite direction towards (-) (also the ACU detects a low voltage condition and illuminates the "Low Voltage" warning light). If the battery charge is topped off and the electrical system is in happy equilibrium then the needle is vertical at (0), because no current is flowing either into or out of the battery.
