Voltage Troubles

[Chris_A31]

Since thursday after work my car has had troubles with keeping charge in the battery. When I charge it while disconnected from the car it charges fine but not with it connected. I have not done any electrical work on the car recently, I am thinking the alternator has seen better days as the voltage on idle as around ~10.4V (after a jump start). I rev the motor a little and the voltage increases a little but no higher than ~11.8V.

It misses on idle and low revs, I have turned the alarm siren off as it activates at low voltage.

Also I've noticed the power steering cuts in and out at low revs/speed too, wanting to turn itself back to centre, this has only been happening since the voltage issue.

The battery is an Optima yellow top, about a year of use.

I'm going to get an auto elec to test the alternator, and everything else if thats not the issue, any ideas?

Cheers