Compaq presario cq62 cracked screen and no power

hi i know youll probably tell me to just get a new laptop but i will NEVEEERRRRR give up haha
so here lie the problem:
i cant get it to power on at all
when plugged in and power button pushed the light by the little lightning looking sign starts flashing. if i push the power button again the flashing quickens for3 flashes.
i dont get any lights from the power button of sound of the heat sink fan.
the light by the plug is on constantly and have checked if it is a faulty plug , but its all good.
i have tried hard reset and just running with plug and on battery but as soon as the battery is out i dont even get the flashing light anymore. just deadness.
i have cheaked ram seated correctly and clean,
i have checked harddrive seated properly, i have cleaned fan and re seated cpu and replaced compound.
im pretty sure the battery is buggered but surly i should be able to run without , i know my screen is cracked but was planning on running it through an external.....
any ideas???