Recharging batteries while in a project
So I'm thinking of a few projects using rechargeable batteries and I wanted to try something. I want to have a power cord attached to the project that can plug in to a standard AC socket to recharge the batteries. I have no experience with rechargeable batteries beyond putting them into the box and sticking it in the wall. I want to be able to hook up 6 AA rechargeables and have no idea what DC voltage I should be using.
I have an old charger for a two way radio that runs at 9V and was designed to charge the 4 AAA batteries inside. Would this work? It would be nice because it's small and even has an LED to indicate the charging status. Is this possible and is there anything other than DC voltage I need to worry about? Also, is it safe to hook that up as long as there's a switch to disconnect the batteries from the project? Any help is appreciated!