Unusual problem regarding old water damage, new battery not charging macbook air mid 2011
I'm summarizing your points, for my own reference and in case I misunderstood a point. Please point out any errors in my interpretation.


Water damage, computer only works when unplugged battery
But unplug charger, computer resets date and time, longer load
Thus, always needed 100% charge
Bought a new battery
But with this, the charger no longer works, battery does
Tried two other chargers, no joy
And with the battery, could use computer until battery drained completely


Okay, with that summarized, I would suggest that there were two-or-more connectors (i.e., problems) that developed oxide as a result of the water damage.

One problem was related to the original battery, which you disconnected.

Second problem was revealed when installing a new battery, which revealed there was still an issue that was not specifically the battery. And you've confirmed that this issue isn't caused by the charger.

For your reference, here's a Teardown of Apple's Magsafe connector, in case of use to you.

I can see that you like to work with electronics, so I won't discourage you from doing repairs because you know the risks. However, if you ultimately send the unit in for repairs, then know that the technician will recognize the unit as a problem because "someone" had a go at repairs (i.e., potential problems introduced).

Good luck.