Ouch on the voltage! I'm assuming your gains aren't set right and your clipping the shit out of it... just my guess. Do as above upgrade to a second batt or just replace the stock one it will help alot.
My friend had the older mojo like the ones Frito posted he had 2 12s and lets just say my lvl4 demolished his and I only had 1k on my 18 and he had a kicker 2500 so yes DC ftmfw!!!