How to charge a 6v sealed lead acid battery | DIYnot Forums
It might be sensible to start with a lowish voltage e.g. 7v if the battery has been discharged for a long time. Keep an eye on it in case something unpleasant happens. It doesn''t sound to me as if the power supply that you have is suitable. That assumes that you''re going to remove the battery from the device and connect it directly to the charger.