Its difficult to measure the current but the B&C link earlier shows what voltage you should find at different places and is the best way to diagnose the system. At least 10V at the battery while turning the starter and at least 9V at the starter terminal.
The best aircraft battery chargers are the Optimate type as they charge the battery and then drop the voltage to a maintain level so can be left in place all the time you are not flying. They also can cope with sealed batteries which some aircraft (and motorcycles have).
ZA