Hello everyone, I've recently taken up building circuits as a hobby and this is my first post on this forum so apologies if I've placed this question in the wrong category. Anyway here goes: I'm trying to build a relatively simple solar battery charger. My questions are these: 1) I realize that in order to charge a battery you must meet certain voltage requirements. It is my understanding that if I want to charge say a 9V battery I need a little more than 9 V to do it, 12 or so say. I figure this is because if the potential was higher on the battery than it was from the charger, charge would actually be pushed out of the battery rather than into, the potential being highest there. Is this the correct way to think of it? 2) if it is true that a slightly higher voltage is needed to charge a lower voltage battery, is there a limit on the voltage of the charger that will work? For instance, say instead of charging my 9V with a 12V supply I used a 40 or 50 or even 3000V supply, what is the practical limit of voltage from a supply to charge a lower voltage battery? 3) Assuming you do have the correct voltage to charge the battery, is there any requirement on the amperage? E.g. If you used the proper voltage with only a minuscule current, would the battery charge at all (even if very very slowly) or is there some minimal threshold current needed to charge a given battery as well? Thank you all for any and every response!