Battery draining?

Hello to you all.
Been dipping my toe in the forum for a while and bought my first Disco, a '97 300TDi manual which I think is fantastic! Today though she let me know she wasn't too chuffed with the constant trips from Gloucestershire to Portsmouth, and put on her battery light while I was a couple of hours from home. The rev counter and the rear wiper stopped working at the same time, but the rear wash still works. I can't find anything else that doesn't work, but now she has stopped, the battery doesn't have the oomph to start her. She tries to turn over, but just "chatters" for a few seconds before sounding the alarm until I switch her off. Could anyone please point me in the right direction 'cos we have to go back to Portsmouth on Tuesday and I am b******d if I can work out whats wrong. I have checked some fuses, but can't find one that covers whats wrong. I am by no means a mechanic or auto electrician, but I can probably get hold of the right end of a screwdriver or spanner if the missus shouts loudly enough. Needless to say she is gloating, she wanted to buy a jellymould but gave in after the floods round here looked like they might return. Any advice on what may be wrong and how to fix it would be greatly appreciated.
If there have been freds on this before I cant find them, (I've got a mac and it doesn't seem to allow me to use the search function).
Thank you for your help.
JK

The battery light coming on indicates that the altenator is not charging the battery.
First check the auxiliary belt at the front of the engine - is it loose?
Re-charge the battery or get a jump start and see if it is turning the altenator and not slipping.
If that looks OK, get a multimeter across the battery terminals (on the 20V range). With the engine running, it should read 13.5 to 14.5V. If it's less than this then suspect a problem with your altenator.
Check that all of the connections to the altenator are secure and clean, also those to the battery and the big earth strap from the engine to the chassis.
If the voltage is still low then suspect a faulty altenator or (less likely) a duff battery.

Thanks very much for the advice. Got to take her ladyship out today but should be back in plenty of time to have a go at this.
Will update with the results.

Right, checked the auxiliary belt and I can push it in a bit, but not too much. Jump started her and the alternator turns (at least the bit that the belt goes round does!) Makes an awful noise though and the voltage across the battery with the engine running was down at 12.17V. The rest of the cables look alright.
Guess me alternator is bollixed then. Is it difficult to change? Do I need any special thingumyjigs to make the new one fit?
JK

Aint too hard.
Git yerself a haynes manwell or download the RAVE from the FAQ section on here.

Cheers Treworgey. Sounds like a plan. I will dust off me spanners.
Thanks for your help!
JK

Right then. Got a new alternator from Craddocks, (the missus even fetched it for me!), stuck it on and she's good as new again (the Disco, not the missus).
Just got back from Portsmouth and never missed a beat!
Thanks Treworgey for your advice!
Jobs a goodun' and maybe I'll have a go next time something packs up!
JK.

happy to help.

Treworgey 90 said:

happy to help.

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Thats a first then.

wotchit
I got a dozen Fenn Traps and 15Kg of Warfarin in me shed.

Treworgey 90 said:

wotchit
I got a dozen Fenn Traps and 15Kg of Warfarin in me shed.

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best place fur tha, Trewy is Colliford Reservoir.