I cut the grass on Saturday, whilst I was out there, I thought I would see if my motorbike would start. Predictably it didn't. It only turned over 3 or 4 times before the battery gave out. That's not one of it's usual symptoms, so I figured I hadn't connected the charger properly. So I put it away, made sure the charger was connected, and left it.
Sunday I tried again, it turned over a few times and gave up again. I stripped the battery out, not knowing why, it's not like I can do anything with it. Once it was out however, I noticed it had maybe 80% of the acid missing.
I've topped it up with deionised water and replaced it last night, I was going to try it this morning, but it's peeing it down, so maybe tonight I'll go and see if the battery is totally knackered, or if I have a working bike again (till the next time it breaks, which looking at it's history, won't be long).