Issues with charging notebooks. Is it the AC adapter, the battery or the system itself bios flash?

inspiron 1520 says no charger connected, have 5 running dell's 1721, 1721, 1520, 1521 all inspiron, so I know charger is ok, and so is battery.

runs for hours with 100% battery, so it is getting power just doesn't it.

tec says its a bios problem, bios program says it can,t update without battery and charger connected.