Battery problems

I have been having a lot of problems starting the car. I borrowed a battery charger from Smitty, which does work, but the battery is apparently not charged up enough to get the car started. But I'm learning about all the different ways to charge a battery. I've also learned that a car battery is not very high voltage, similar to what goes into a flash light. The reason it's big is so it lasts.


I wrote to Smitty:


I figured I'd wait for the holidays to pass before I told you the slightly bad news. The car still won't start.
    I tried the battery charger that I had bought, with more juice, but it didn't work (just a single slow crank).
    I tried an "in the cigarette lighter" device, but that didn't work; apparently the cigarette lighter isn't really attached, maybe.
    Then I tried your charger. At first there was no response, but then I tried attaching the clamps directly to the pins, not just around the clamps holding the pin. Then I got some results. I tried the 10 amp and 50 amp. The 10 amp, on for about 30 minutes did charge the battery. When I put in the key, the battery had power enough to light the light and the glowplug light. I could crank several times in a row, maybe 5 or 6 times, but the car wouldn't start. I repeated this a few times. After a while the battery waned again. I recharged it several times, but the cranking never started the car. Is it worth it to try a longer charge?
    I had mentioned that the installed pull knob isn't going back in. I wonder if it's disconnected, or has disconnected something else that may involved. I just mention it as a possible factor.

What do you recommend?
thanks
Max