Agree 100%the charger is way to big for that little battery and will kill it, especially as its a Sealed Lead Acid
get an optimate, a solar charger or similair that kicks out less than 1 amp
I use a Cetek, which constantly monitors the battery and changes it rate accordingly
I used a car 12v charger on the 12v battery for my Suzuki vstrom 1000. It killed the battery. It cost £70 for a battery and £30 for a bike specific charger.
I now have an SAE battery lead on the bike. It is access able with the seat on the bike, meaning 8 can leave the battery charger connecter to maintain the battery and simply unplug when I use the bike.