Maintenance on my Z250SL

Not the afternoon in Cumbria I had been hoping for. My ride didn’t work... stalled at first junction. And the second. So... battery on order as first try fix. Pretty sure the current battery had one cell dodgy when I tried to use it today and now it’s failed... charger won’t get to its switch-off voltage. Photo shows taking the side covers off to remove the seat to access the battery and fuses.
This battery was new to me in March '22 so made before Covid and I guess it was in storage for too long. Tried asking for a warranty replacement but it’s outside the one-year warranty..
This sort of thing always seems to happen on the one day of fine weather in the week. Grrr.