Is a battery isolator compatible with a 2010 HHR?
 

I have installed a dual battery system into our HHR however I want to add a isolator so my wife wont run down the main battery. the instructions that came with the isolator claim that some gm alternators are not compatible with Isolators. Has anyone put one into a HHR? I will be looking into this today I was hoping someone could save me some time if they have already done this.
Thanks in advance.

Don't recall anyone advising they had installed an isolator. But maybe one of the audiophiles will speak up.

No need for an isolator, see:
https://www.chevyhhr.net/forums/general-hhr-4/second-duel-battery-21309/

All that is needed is a continuous duty solenoid powered by the fuel pump solenoid. You will need some way to activate it from the isolated battery when the main battery is dead.