HI

I went to start my xj600 this morning after being away for a month. Absolutely no juice from the battery. I put it on charge and very quickly the charger read full. I replaced it back in the bike but it was still dead. I then decided t jump start it from the car and it started fine, I eventually disconnected the jump leads. I left the bike running for another 30 mins then switched it off. Went to start it again and the battery was dead again. I know this is probably a stupid question but have I got a dead battery? or could it be something else?

Could have dropped a cell. Next time its running put a voltmeter across the terminals. With the bike running you should expect around 14v pretty constant if the bike is good..

For me, if 30mins on the car jump leads didn't put anything into it nothing will. BTW not recommended jumping a bike from a car, car has far more amps than the bike wiring can handle. You can easily kill bike charging and electronic systems that way.

Yes, it could be something else, but the first port of call is the battery. You need a known good one to start the process.