Vauxhall Astra H Starting Trouble

[Spathodus77]

Hi, please can someone help me fix a problem with my wife’s Astra.

On Friday my wife went to start the car and the starter motor made a clicking sound but the car would not start. Battery voltage showed as 12v.
On Saturday we jump started the car successfully and I took it for a long drive, I stopped at various points to check the battery voltage (with engine running) and each time it was 13.1v to 13.5v. The only weird thing was that switching on lights, rear screen heater, fan etc did n’t lead to an increase in engine speed or voltage.
I noticed that the boot had been left slightly open so figured the boot light had caused the original problem (boot light now unplugged to prevent this happening again).
We have not driven the car anymore over the weekend,but my wife just went to start the car (Sunday evening) and it won’t start - did n’t even have enough juice to power the central locking.
My wife reports that the trip computer has not been showing any values just “F” for the past few days, not sure if this is relevant.
What should I check next to get to the cause?
Ralph

[DaveGib]

Start with a proper battery test 12V means nothing if you don’t have any Amps in the battery.
Do you have breakdown cover?

[GreenV8S]

The symptoms point to a flat battery. The voltage you saw while running is on the low side and might also point to a charging problem as the cause of the flat battery. Since the battery has been deep discharged at least twice now it is likely to have been damaged and may already be knackered so I suggest you plan to replace that anyway, but do get the charging system checked afterwards.

[Spathodus77]

Thanks. I removed the battery, trickle charged it for today, and then had it professionally tested. It was dead. New battery now fitted - as you suggest I’m still not convinced on the charging side. Are there any checks I can perform with a multimeter to determine if it is charging properly?