I bought and installed this product along with my oil pan heater and block heater. I live in Alaska and i have three high output gel batteries for my all RF 2000 watt stereo system and i don't want my batteries freezing and going bad. I have over $5000 on my car audio so the price of this little unit was great insurance to keep a good charge during those cold months. I would recommend to others who want to protect there cars from cold weather or long periods with out starting to charge. Easy to install, great info and directions. Looks good as well.  Thanks Amazon!