As noted earlier it's only a ¾ amp maintainer so we are in agreement that the maintainer isn't capable of charging a sulfated battery.I don't know what you're using as the picture bombed out thanks to "the cloud" hosting the forum (and image upload being mostly broken), but it's probably the battery maintainer that's at fault ...
I you go the CTEK route don't cheap out and get anything less than the MUS 4.3 and go straight to the RECOND mode keeping in mind that mode shouldn't be used more that once a year. If you keep the CTEK hooked up when not riding you won't need to do another RECOND. If you battery is an AGM (no sloshing acid inside) use the snowflake (*) mode once it is reconditioned. I used the bike mode initially, years ago, which didn't do the job mostly because mine is an AGM. If you have a 'sloshing' electrolyte then I think I'd use the car mode. Our undersized batteries have to work pretty hard. Available at Amazon for $68.95I'll have to look into that tender. I'd like to not have to buy a new battery at this point since the one that is in there has been working flawlessly since I've owned the bike. I wouldnt think one kill like this would send it to its grave...
Even if you end up buying a new battery the CTEK will pay for itself by not having to replace that battery in 3 years :wink: