I don't actually recall if the intevertor fried (I'm using that as a figure of speach, it actually just stopped working. no smoke) when the solar panel was hooked up or not. I do recall that yes it did work when plugged into a car. And I know when my solar panels are hooked up i see around 20 volts, so its possible that 20 volts went straight to the inverter. I will do another test on another invertor without any panels setup.
I do use a charge controller so I'm safe on that side.
If I was to hook up one of these :
https://www.ebay.ca/itm/5pcs-LM338K...ltDomain_0&hash=item3f0a2a738c#ht_2623wt_1156 , is it just a matter of splicing one into a wire on both of those "holes"?