strange battery/ac adaptor i haven't seen mentioned elsewhere

Hey everyone!

got an inspiron 1564 here, running windows 7 pro, core i3.

Had Dells for years and never really had a problem, picked up an unknown one off ebay fairly cheap as times as hard.

when i tried to turn it on it would power up for a second and the battery light would illuminate before going out and the whole laptop turning off, powers on ok without the battery but if i insert it when the laptop is on it will cause it to instantly power off.

i tried another good lead but the same thing happens so i ordered a new battery confident it would resolve the issue.

with the new battery in and the AC lead in, the laptop doesn't mention it is plugged in and charging or even that it is plugged in and not charging it just has the battery logo with a %.

been through all of the steps i have seen mainly on here, i want to update the bios but can't as i need a battery and AC lead plugged in but like i say when the battery is in it thinks it is just on battery although never actually drains down.

i've had the power socket out which looks fine, i've even ran over the solder on each contact which didn't help.

in the BIOS the adaptor type is listed as none.

all i can think is either there is a fault with the power socket, something on the motherboard maybe if it isn't software related.

i had to put a fresh install of windows on it before i got the battery and i recall years ago have issues with a Dell laptop as i had installed windows without the battery fitted,

the leads i have are 65w, i've ordered a 90w one as it was cheap.. i have seen 65w & 90w leads for sale for this model laptop though.

any advice at all or suggestions for me to try would be massively appreciated no matter how remote, if i end up having to use it as a constantly plugged in machine it's not a huge issue but i really would love to be able to use it properly!

thanks so much and sorry for going on!