Haven't had the opportunity to test yet, bought as a backup replacement. Price seems slightly higher than average or maybe I'm used to swapmeet deals. However, this accessory will allow me to power 12 volt devices connected directly to Battery. In my case, I always pack a fully-charged spare battery in van when I go off primitive camping, or attend outdoor events with no electric hook-up. I'm able to power larger drain accessories without using main vehicle battery -or- my portable jump pak w/12V DC source. To go even further, could also run a power inverter or solar charger to re-charge the battery itself ! . . .Always good to be covered !!