Eric- Thank you very much. I am still a novice in electronics, so I don't quite understand how you got some of your numbers. Like how did you get the .65V voltage drop across the resistor?
The base to emitter voltage to turn ON a transistor is about 0.65V
'turn ON', means that current starts to flow from the collector to the emitter.
I'll keep it that simple at this stage.
I also don't get how transistors work in general, so your explanation, while I am sure is correct, makes no sense to me. I have read, and read, and read, and transistors are still mysterious to me. I need to do some more reading about them I guess. Any advice on where to go to read up on them or any books to buy?
There are loads of good tutorial ebooks on the web
Also, you mentioned adding a voltage sensing circuit, for the LED. What would that consist of? Would a transistor and resistor(or potentiometer) suffice for voltage sensing to turn on the LED when the battery reaches float voltage? I don't know,
A transistor could be configured to give a rough indication of the 13.8V terminal battery voltage.
I am kind of shooting in the dark, because like I said before I don't fully understand transistors, but I think I have seen them used in that type of application before.
And yes, I just want this to be a float charger, so 13.8Vsounds good.