Hello so I was just given a 6v 4.5 Ah (4500mAh) sealed lead acid battery. I have never made a battery charger before but would like to make one now for this battery as it is for a robot I'm building. How would I go about charging one of these batteries, as I have never done this before. Please correct me on this if I'm wrong but to me it seems that you can charge a lead acid battery by just connecting it to a voltage supply equivalent to what its voltage would be if it was fully charged and wait till the amperage pulled approaches 0. also as a side question I have another lead acid battery with the same specs but I have not used it and when i checked its voltage it was 2.8v. is this battery dead or can it be recharged and brought back to its previous state?
edit: how would I find the maximum current they battery can take?
edit 2: in the batteries spec sheet it said: "“Float” or “Stand-By” Service: Hold battery across constant voltage source of 6.75 to 6.90 volts continuously. When held at this voltage, the battery will seek its own current level and maintain itself in a fully charged condition". does this need current limitation? If so what would the name of that variable be or how could I find it?
Edit 3: So the quote in edit 2 is taken from the specsheet, so following there instruction can I give the battery 6.90V and it will seek its current and it does NOT have to be limited or is there still a current limitation requirement?