Dim charge light no battery icon

I have upgraded the ram in my 2009 MacBook Pro. Since I did I can only get a dim flashing glow from the charger, and the computer is totally dead.cleared the SMC no luck, after leaving it plugged in for about two hours it started, but when booted showed no battery icon, in power management it showed battery charge 0%, when I an icon it had a cross through it, clicking on it showed message no battery connected. Run it for a few minutes then shut down, now dead again. Looking on the web, the three possible answers seem to be, battery problem, charging circuit problem or logic board. What are the chances it isn't the battery, have tried the charger on another MacBook, it works fine.

Have you opened up the computer and checked all the connections are good

Revert to the previous memory, (checking that the new memory is seated correctly)

That does rather suggest that a connection has come loose, but if it is the original battery then it is a bit long in the tooth.

Yes have disconnected the battery and reconnected again, still no go, the worry is it remains the same with the battery disconnected. I left it connected to the mains all night, still nothing, only managed to get it to boot the once.

Have you reseated the memory or swapped back to the memory you were using previously.

Another thought - I think there is a small coin shaped battery in the machine check to see if it is giving a full charge.

Ok i have sprayed the external part of the charging socket, and the end of the charger plug with switch cleaner, and got the computer to boot (am typing this on it). In energy preferences it says the battery has 0% charge and i have a battery with a cross in it at the top of the screen, though the computer is obviously running on the battery at the moment, as the power lead is disconnected, if i connect it it just lights dimly so am wondering what will happen when the battery runs out.

I doubt it will take more charge. What does About This Mac say?

Under power in about this mac it says battery as current power source, even when plugged into the mains.

What's the cycle count?

There is no Battery information at a all, the general stuff is there but nothing of any use telling you the battery condition, i tried coconut, but that reports very little, except the battery is discharging, so the macbook is getting no information about the battery, which is probably why i have a battery with a cross in it in the menu bar. So looks like the problem is somewhere within the charging circuit.