16v battery not charging fully and car turning over slowly

[Philpy]

On my 16v Ive got a problem which is a major head ache.
Basically if I charge the battery over night and connect it up, the car fires into life instantly. But slowly over the next week to 10 days it struggles to start and turns over really really slowly until it wont turn over hardly at all and fails to start. When its nearly flat, but just starts I can drive 10 miles and turn if it off (Expecting the battery to be charged) I come back an hour later it stuggles to start again.
Its got a 2 year old battery which works fine on another golf..... And the alternator was brand new just before Ive bought the car and has done around 2000 miles.
Ive had a search on here and alot of people suggested the earth strap. So I bought a new one and connected to the - and to another gearbox bolt so now I have 2 earth straps. But this made no difference.
Basically it seems to charge a little bit but hardly at all.
Please help as its driving me mad. 

[Chris-White]

Before anything, get a multimeter out and check the battery when switched off, and then on.

Should be just below 12v when off, and just over 13 when switched on. 

Check what your getting at the starter.

Try out a known good starter if you can, stater could be starting to go sticky.

[Mew]

On my 16v Ive got a problem which is a major head ache.
Basically if I charge the battery over night and connect it up, the car fires into life instantly. But slowly over the next week to 10 days it struggles to start and turns over really really slowly until it wont turn over hardly at all and fails to start. When its nearly flat, but just starts I can drive 10 miles and turn if it off (Expecting the battery to be charged) I come back an hour later it stuggles to start again.
Its got a 2 year old battery which works fine on another golf..... And the alternator was brand new just before Ive bought the car and has done around 2000 miles.
Ive had a search on here and alot of people suggested the earth strap. So I bought a new one and connected to the - and to another gearbox bolt so now I have 2 earth straps. But this made no difference.
Basically it seems to charge a little bit but hardly at all.
Please help as its driving me mad. 

Could be something like the boot light constantly on?

[Conker]

This web page has some interesting battery tests:

http://www3.telus.net/chemelec/Projects/Alternator/Alternator.htm

[MeTsU]

Like chris_wht said, check using a voltmeter.

Check your alternator too, could be that it's not charging properly.  I know you said it's apparently fine, but there's no harm in taking it off and taking your your auto-elec. to put it on a test bench...

[Philpy]

Basically Ive had this problem since I bought it and thinking back the bloke before bought the new alternator to try and solve this problem, so it was doing it with the old alternator.

[Lap]

If you are sure the battery and alternator are good then maybe there is something that is draining the battery when the engine is off? A faulty stereo or alarm for example? Get yourself a multimeter and measure the current drawn when everything is off. I'd expect it to be under 0.5 amp.

[monzablue16v]

Earth for the starter motor. Take it off, clean it up put it back on I had that when the battery was fully charged it would start fine but after that 1 start it was hard to start, slow starter.

[Philpy]

It cant be anything draining the battery as it wont charge after a run.....Thanks so far guys! 

[monzablue16v]

Earth for the starter motor. Take it off, clean it up put it back on I had that when the battery was fully charged it would start fine but after that 1 start it was hard to start, slow starter.

Pretty sure that's your problem