Dell Inspiron 6400 indicates the wrong power adapter is plugged in and will not charge the battery

"Having just paid over £100 to have the the power board inside my daughter's Inspiron replaced and had the explanation confirmed by the Dell engineer, here is what happens:

The power connector consists of 3 pins, 2 are power and earth, the 3rd is a signal line to identify the PSU as a compatible (Dell) unit. If the Laptop does not get the signal, it does not allow the PSU to charge the battery, it will, however, allow it to power the laptop. The fault is a common one and happens because the plug sits so proud from the side of the laptop that it constantly gets knocked and causes the connector on the power board to fail, most commonly open circuiting the signal line.

To clarify, the power board on some Inspiron models is a separate unit to the motherboard and has the power socket mounted directly on it."

"To answer your question about the power supply size, look on the power brick label for ""output"". It should say something like this:

DC 19.5V(19,5V) 4.62A(4,62A)

That means it provides 19.5 Volts with a maximum allowed Amperage draw of 4.62 Amps. Going back to basic electrical theory, we know that you multiply Amps by Volts to get Wattage.

So doing the Math, we get the following:

19.5Volts x 4.62Amps = 90.09Watts

So plug in your own adapter's numbers to figure out your maximum wattage. You can generally use an adapter with a higher wattage than you need, but rarely can you use one that is lower.

To reiterate the other answers, you'll need to contact Dell support for assistance with this. without equipment to swap, you'll have to get Dell to fix it for you."