im trying to charge a 6v 4,5Ah battery with a 12v 10W solar panel, its giving an output of 18v 480ma, and after the regulator the output is 8.4v and 450ma ,but the problem is when i connect it to the battery and put my multimeter to measure the current the battery is drawing i measure only 220ma,why is this? and how can i fix this ,so that the battery can get full current.
If the regulator is a typical constant voltage regulator then there is no way for it to 'force' a constant current into the battery. The current that flows will follow will be the result of the difference between the regulator's 8.4vdc output voltage and the gradual raising terminal voltage of the battery as it charges up. In that kind of charging mode (constant voltage) the charge current will be highest when the battery is at it's lowest terminal voltage and will taper off as it charges. There must also be some kind of voltage monitor to stop charging when the battery reaches full charge voltage to prevent overcharging.
There are other charging methods and chargers controllers avalible. Battery chargers and charging can be quite complex and really requires searching out and reading up on the subject. Simple answers tend to be incomplete at best and often inaccurate.