Dont know where you are getting your quoted voltage from - the old type moving coil meters they used to install in cars arent at all accurate.. And even with a decent digi meter it depends on where you measure the voltage.
With that proviso, the alternattor regulator is normally set to change at something around 14.5 / 15 volts. If you use a trickle charger to maintain a full battery it would be set at about 13.7. Your 13.2 is only 0.3 v above the voltage of a charged battery standing on its own ie not being charged.
Yes batteries do discharge on their own - they have internal leakage and they slowly self discharge right down to zero if you leave them long enough. But many cars have small discharges anyway for things like clocks and radio memories not to mention alarms and immobilisers. My Ferrari will discharge low enough to have starting problems after 2 weeks or so of standing.
The thing that kills your ability to start a car assuming a reasonable battery is resistance in the circuit. Most starter motors are around 1kw in power so for the very short time they are in action they can take almost 100A with the battery voltage dropping to something like 9v. Put in circuit a bad earth connection or a battery with poor capacity and you simply wont get the welly to turn things over. Dont forget that a battery can still show 12.7 volts without holding much leccy at all .
Last edited by howard; 28/06/22 04:27 PM.
