Battery at 15+ V, engine off, lights off...

[carpet monster]

... That'll be a knacked regulator then?

[carpet monster]

Engine off, unloaded battery ... climbed to 15.4 v
Idle, no lights ... 18 v
5,000 rpm, no lights ... 18v
Idle, lights on ... 16v
5,000 rpm, lights on 16v

[carpet monster]

No wonder I have to keep jump starting the bugger!

[Richy_T]

To be honest, with those readings, I'd suspect your meter.

Batteries generally can't put out more than 12V. It's the chemistry (six 2V cells).

[Geodude]

Have a read through this guide (http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf) mate. It does sound like reg/rec kaputt but as richy t says try another meter to be sure.

[carpet monster]

Hmm, I will try that tomorrow, it's a bit dark now!

[tigersaw]

check the meter on a smoke alarm battery or a car, sounds wrong.

[kellyjo]

Yep, check the meter. I recently changed my reg/rec and my meter showed the battery as still only charging at 12v. Borrowing a superior meter showed it charging at 14.6v!!

[carpet monster]

Nicked the battery from the smoke alarm, measured it at 8.5v

[tigersaw]

Nicked the battery from the smoke alarm, measured it at 8.5v
Pretty much what I'd expect for a good one.