long way to go

Hi,

After just 3 months the 15V battery charger that came with my Crate Limo TX50DB up and died, i tried charging the 12V, 7.2A sealed lead acid battery with a 12V charger i had lying around but the battery only lasts an hour or two compared to 4-6 hours when charged with the 15V charger. The store i bought the amp from eventually agreed to take the charger back for repair which could take a very long time if there slow costumer support is any indication so in the meanwhile i need to buy a replacement charger. I've tried researching but unfortunately this subject is mostly over me head . Could someone please recommend an appropriate 15V charger.

thanks,
-JJ