Installing Mavericks on a brand new machine that shipped with Yosemite pre-installed? Due to battery backups not working properly in Yosemite, I need to downgrade a machine to Mavericks. Unfortunately, this is a brand new Mac Mini and it shipped with OS X 10.10.0 installed. 

I read various questions here, as well as some articles from other websites, and created a Mavericks 10.9.5 installer on a USB stick. I can boot from this USB stick on an iMac we have here, but the Mac Mini will not allow me to. 

Is it even possible to run Mavericks on this machine--Macmini7,1?
It's a great big "Maybe".

The installer will likely decline, but it will really depend on the hardware and drivers the hardware needs.

Here's what you do:

Get an external drive. USB > 8Gb will work. Plug this drive into a Mavericks-compatible machine and install Mavericks on the external.

Now plug it into the new Mini. Reboot holding the Option key, wait for the boot picker to appear. Choose the external with Mavericks.

If you get a kernel panic, the new Mini will not run Mavericks.

If it boots to the desktop, you're good. Get some cloning software like Carbon Copy Cloner, erase the Mini's internal drive and clone Mavericks from the external drive to the Mini.