yamaha townmate?

I have a T80 townmate H reg 1991

When I start it the lights run, front and rear, they get brighter as i rev engine. The indicators are really poor though as is the horn and oher electrically bits and bobs. I took battery out and charged it as I thought this would help. The charger said it was fully charged.. I started bike without battery and all electrical bits are the same. I am a little mixed up... is the battery at fault? And will a new one mean the rest of the electrics will work again.