Bought a pair of the Tender Jr. in 2012. I'm sure they have paid for themselves by maximizing the life of my expensive lead-acid batteries. There are plenty of reviews here proving that this is a quality product that has been around a long time. I wish to add that the company that makes Battery Tender products, Deltran, stands by their products. One of my "Juniors" recently stopped working after four years of continuous service. I emailed the company and received a prompt reply. I returned the unit and received a brand new replacement covered under their 5-year warranty. You can't go wrong with this product or company.
Edit: For those considering this product... It is not a battery charger. It is for maintaining fully charged batteries. There are some negative reviews from folks that did not realize what they were buying.