MacBook not showing life signs

Hello,

I just got another MacBook off of eBay - all it said in the article is, that it's defect.

After receiving it and opening it up, it was pretty much a mess... Screws were missing, connector of the optical drive was underneath the mainboard (and therefore not connected), keyboard backlight connector was not connected, the battery was not connected and the magsafe board was also not connected. After getting everything out, renewing thermal paste and plugging everything back in, I'm still at a non working MacBook though...

Battery doesn't show any any signs of life when clicking the button on the left (no lights turning on).. MagSafe charger also is not showing any light when plugging it in.. Weirdly enough, one time, the caps lock button had his green light on, when I plugged in the MagSafe charger..

It's really weird and I don't really know, where to start.. The battery might very well be dead, however, wouldn't the MacBook show a sign of life then, when I unplug the battery and connect the MagSafe charger?

You think I can do something here or rather just toss it/resell it/use for parts?