We Need More POWER! | Space Engineers | Quantum Threat E.29 

I have not played with the shield mod much but maybe change your power output from kilowatt to megawatt I just tested it with the settings you have. I had about another 500hp to the shields. When I changed to megawatts it went to almost 4 million. With a shield enhancer over 38 million. This is a test with 10 batteries. Hope this helps.

I haven't played with shields in awhile but, I think you need to change the power scale.

the thing is that the mod for shields was not made for stock reactors