300tdi alternator too much juise?

ive had trouble starting my disco due to the fact whoever had it before me decided that a small battery would be fine! My alternator is throwing 17volts to the battery at tick over its cooking the small battery but is this reading right? Ive been told it should be around 14- 14.5. Ive got a heavy duty battery ordered but ive also been offered a new alternator by a mate for 40 notes does it need replacing? My dad's got a 300tdi disco his reading is the same and he's got a new alternator. So its all a bit confusing!

That voltage sounds a bit high to me,

you might cook a heavy duty battery anorl stickin that much up it,

Your alternator voltage should be 14.4V, mine is.
It sounds to me that your alternator voltage regulator is faulty.
17V to a battery will ruin it, whatever size it is.
Your test meter does read correctly?

your regulator in the alt is knackered as it should give 14.5v max.

cheers for reply's look's like ill be having a alternator off my m8 2moro! May as well replace the belt as well while im there!lol