There should be snap on panels that cover rubber cell caps just like a lead acid battery. Pop them off and you should be able to add some salt, wine or any other concoction that works to desulfate the mat. Why they dont make a serviceable battery is beyond me. Watch youtube on 'pakistan battery rebuild' pop the top off, pour the acid on the dirt floor (!) and get yourself a iron and a fire. desolder the plates and pull them out. Reverse...yadda yadda...seems totally doable. buy plates, add acid, recharge.
