Low performance without battery, normal? [Solved]

[Nodarkthings]

Hi!
When I had a real Powerbook, twelve years ago, I was amazed when I noticed it went to a crawl after its battery died and I only used it on power adaptor.
Today, I've noticed my DELL E6320 has also lost performance — compared with Geekbench (-30%) and Cinebench (OpenGL: -10 % ; CPU: -30%) — and this is consistant between my two OSes (10.11 and 10.9).
I've tried a few things that had changed in the recent months and the only other thing I can think of is that I updated Clover to Tonymac's "Clover Legacy Boot Mode v2.4k r4961"...
So, I'm wondering if the battery could be guilty?
What ya think?

 

[Nodarkthings]

After a bit of inquiries and more tests, looks like it's typical behaviour for PC laptops with too weak an adaptor, and indeed, putting back the 90W one restored the performance.