Re: Does battery indicator pre-empt flat???
Cranking power is a very very good way of judging a battery's reserve capacity. A volt meter cannot tell nuts other than voltage. Put a little motorcycle battery on the car and you will still read 12.6V but crank the car and the voltage goes to zero. If you like to be precise, record the voltage of the battery when you are cranking and it should read 10V or so. Anything lower and it is time to visit battery shop.
As a good rule of thumb, normal cars with no electrical mods, battery should last 2.5-3yrs, I.C.Eed cars batteries should last about 1-2yrs depending on the build of the battery (deep cycle or gel cells better), Reserve capacity ( >64 A/hr better), average Current drain due to amps pumping bass and finally driving habits (long drives better compared to short trips).
Cheers