MacBook Pro 17" shuts down when not on AC
I'm experiencing frequent "Blackouts" with my 2011 17" Macbook pro (El Capitan, latest): when running on battery (only then) the computer (sporadically) suddenly goes dark, shutting everything down. Reboot is unproblematic. The problem does not occur when connected with the MagSafe Adapter (which, by the way, is always nicely green).
Now I discovered that the same thing occurs when I press "ctrl alt shift power" with the system running (also when connected to AC): it just shuts down.
As "ctrl alt shift power" is for SMC reset, does that mean that the SMC is damaged and I have to replace the logic board? Or are there any other ideas?
About everything in the macbook has been replaced before: Board on warranty (it used to have those Graphic card problems), RAM (16GB Corsair), SSD, and the battery as well.
Ah, and the (original) Superdrive currently refuses to accept any CD or DVD...
Here are the screenshots from coconut battery:
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