Battery Depot says he has everything else needed outside the kit. He wires the espar to the vehicle battery. He said when I put a power inverter in he would rewire it no charge.
Don't let them wire the Espar to the vehicle's starting battery. It needs to be wired to a separate battery. A 1 amp draw can kill a starting battery overnight, especially if the battery is a year or more old, and
especially especially if it's cold outside, because the colder it is the fewer amps you have available in the first place. A 1 amp draw from a 0 degree F battery is Peukert Corrected to 1.71 amps because of the temperature. And because it's cold, the Espar may spend considerably more time at Medium or High power, drawing 1.5 to 2.0 amps per hour. That translates to an effective Peukert Corrected draw of 2.1 to 2.8 amps per hour.
Let's call it 2 amps per hour. You've been sitting 12 hours, so that's 24 amps gone from the cranking battery. That translates to 40% of your Cold Cranking Amps, on a 1000 CCA battery. When it comes time to crank the engine, not only are there fewer amps to begin with because of the temperature, but you've removed more than 400 of the CCA to the Espar. So instead of 1000 CCA, you've got 600 or less. So the battery will have to work even that much harder to start the engine. Even if it starts the engine, it's classic textbook on how to dramatically shorten the lifespan of a cattery.
Cranking batteries are designed to start the engine, to give large amounts of amps in a short burst. They aren't designed for anything else, nor should they be used for anything else. Marine deep cycle (and truck batteries, they're the same) are designed specifically for long term, low amp draws, the exact kind the Espar draws. In the same way a cell phone battery is designed for a cell phone, an auxiliary deep cycle battery is designed specifically for what you need it for. You wouldn't connect your car battery up to your cell phone, so why connect a long term, low amp draw appliance to your cranking battery?