Voltage reducer makes radio turn to static
 

So I have a 08 precedent I just bought recently and the wiring is a mess from the previous owner so after finishing the 8 6volt battery install I started to clean up some of the other wiring I wanted to fix. I rewired the voltage reducer and wired it to a relay so it only comes on with the key. It appears to work fine but what I noticed is that when it comes on the radio in my garage goes to static. Very strange I pulled it back apart and just hooked it directly to the batteries and it does the same thing. It's a 4 wire reducer looks like a cheapy but it works. I think.