MacBook Air frequent shutdown with shutdown with shutdown cause -128

I took it to the lab, there they unplugged the battery and plugged it back. That solved the problem.

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.