Replaced just about everything, battery won't charge.

A few months ago, I started getting the dreaded "Charger not recognized" error on startup on my 1545. Sometimes a simple restart and the error would go away and the batter would charge normally. Finally, that walk-around stopped working. Laptop would function normally, battery would not charge. I replaced the charger to no avail. Bought a new battery, that still didn't fix the issue. Bought and replaced the charging board, still nothing. Finally I replaced the motherboard from a known working 1545 that had a bad screen, and the error went away. Or at least on startup it did. Battery still will not charge. When I enter setup on startup, and navigate to the appropriate menu, it still says "Charger type unknown" -- Even with trying 3 different Dell chargers, which all 3 work on other laptops I have in the house.

What else could be causing this? What might I be missing?