Battery Problem?

Just a quick question as to if you think that it may be a battery problem I have or something else.

I stopped riding my bike for winter in about october, but because of moving house, I couldn't find the optimizer for the battery for about 3-4 weeks, before putting it on charge, I decided to run the bike for a few minutes because of putting some fuel stabilizer in, it didn't start, so I charged the battery for a few hours and it then started no problem.

I kept the optimizer on it over christmas and at the beginning of January I moved the bike to a different storage location, it's only about 10 minute ride, but the bike cut out a couple of times when approaching traffic lights ( I thought I was stalling it because I was wearing overly thick gloves and was obiviously a bit rusty from not having ridden for such a long time.) But it stayed in storage for about 3 weeks (without an optimizer) and then this weekend I came to start it and once again, it didn't, so I put it on charge overnight and on Sunday it started fine, I got about a mile down the road and when slowing down for traffic lights, it cut out again (definitely not to do with my poor clutch abilities this time) however, this time it did not start back up, so I had to push it back into storage and now i'm not sure if to get a new battery if not or if it could be more serious?

Opinions please, thanks.

I don't know if this would put a spanner in the works, but when I bought it from the dealer back in July, they had to fit a new regulator rectifier (i think that's what it's called and I beleive these are to do with the charge in the battery).. Are these prone to going if they've already gone once? Or does it still sound like a battery issue?