Notebook doesn`t boot up without a charger plugged in
First of all, my notebook is the Lenovo 510s-13IKB, but I could not find that one in the selection.
I have a weird problem, where I can`t start my notebook anymore without the charger being plugged into it. I already tried to hard-reset it, took out the battery, held the start-button ec. Now normally if I start it up with the charger, boot into windows but then remove it, the notebook shuts down. But weirdly enough I noticed, that when I go into the boot-menu, bios or start up Ubuntu and then remove the charger, it does not shut down. Then again, if it goes to sleep or shuts down again I won`t be able to start it up again without the charger.
I`m out of ideas at this point, hoping for help.