If your battery is 12V, 7Ah I'm guessing that it's a sealed lead acid / gel cell battery. Per the doc above that should be charged at 14.1 - 14.4V, and stop charging at 13.5V. The doc also states the maximum charge rate, but for a consistent charge rate circuit the more practical rule is to charge it at a 10 hour rate, so for a 7Ah battery you would charge it at .7A.
calvingloster:
Firstly i do not understand how the voltage will change when charging. Say for example i have a flat battery and i put it on a constant current charger, will the voltage be highest or lowest and why?
When you pulling a constant current out of a battery you expect to see the voltage of the battery drop gradually and measurably, don't you? When you're charging the battery with a constant current this is just occurring in reverse; the battery will again show a gradual and measurable increase.