Battery not holding charge

[Froggy]

Ok so I've just finished fitting new inlet valves, new head gasket kit, new balance chain kit, new cam chain kit, full service and new battery to my vectra c z22se.
Now my battery is dead after just 1 night???
I had it running yesterday for about half hour idling. Then this morning it's totally dead I think multimeter read around 7v. I just had to jump start car to get it running.
I used a multimeter whilst idle it was around 14.22v. With engine then off it read 12.82v but with a few minutes it went down to 12.55v. I'm gonna give it a couple of hours before I check it again.
Any ideas what could be causing this???
cheers froggy

[GSiFan]

Battery dead. Fit a new one. You won't regret it. Bosch ones are available on eBay for about £100 delivered. There is a remote chance that you have a current draw problem that is draining your battery prematurely - either an electrical fault or an alternator rectifier pack gone south. But my money would be on the battery. Halfords (used to) do a free battery health check. ;-) Paul

[Froggy]

Ok so I left the car 2 hours and multimeter reads 12.2v. So it's dropped slightly.
tried to start the car and it doesn't want to know. Just clicks
Put multimeter on battery again and reads 9.8v???

[GSiFan]

It is an ex-battery. It has shuffled off its mortal coil. It is no more.

[Froggy]

Brand new battery already on it.

[stevoxsi]

Duff battery or something is draining it. Its possible something is shorting after all that work, but probably a duff batt. Take it back!

[Das]

Sounds like the battery is duff to me too.

[Ben50n]

take it to a battery dealer and get it load tested, but it does sound like its stuffed.

[Critch]

Just switch multimeter into amps and put it in series with batt this will confirm if theirs any parasitic drain

[Froggy]

Last night I removed battery from car and gave it a little charge. Before I went to bed it read 12.5v in the morning it read 12.4v. At about 1pm it read about 12.38v. So don't think the battery is draining on its own.
I had it back on the car and running, switched it off and it read 12.58v. I put the multimeter + on battery and - on ground and it read the same figure. So I think I can rule out the battery earth lead.

Where do I start in finding the fault?