Batteries and multimeters

Bollocks.

There was the additional requirement of an "understanding of electrics not extending beyond GCSE Electronics", which you appear to have failed. (If you're claiming a multimeter can't find high impedance faults).

Beyond the voltmeter, the ohmmeter and the ammeter, the continuity tester and the diode tester, a multi-function DVM isn't much use, then? Are you on drugs?

So, earlier you said "you need expensive test gear to do any car electricv stuff". Now you're saying "I have the test kit but I only ever use the really cheap simple stuff". Cheaper, even, than a DVM.

Really? Do you know what you mean by that?

Yes it will. If you're not getting 13.8-14.8v at the battery, you've got a charging problem. If it's under, then the alternator is putting out enough amps, and if it's over then it's putting out too many amps. For general charging system testing, you don't need to know what amps the alternator is putting out, as if it's not putting out enough then you won't see the required voltage at the battery. Some of the basic laws of physics cover this, but the bottom line is, you don't need to know the current flow to know if the alternator is charging or not.

The only time you may want to test alternator output amps, is if you suspect the alternator isn't putting out it's rated capacity (ie. if you're suffering from slight under charging, and you suspect a failed diode).

That's why you always test for voltage with the circuit under load. Basic bit of electrical diagnosis that.

All you need for car electrics is something with Volts, Amps (10/20A is more than enough), and Ohms. Diode tests can be done by using the ohm function, but are far better done by testing under load with a test lamp in circuit. Testing diodes under load will provide a far better answer as to whether they're working or not.