I have had two radios installed in my car for a long time. While I have never run my car battery down to the point that the car will not start, it is always in the back of my mind. The HF radio when running at 100 Watts draws nearly 22 amps when transmitting. Our car batteries are not meant to power accessories for a long while. They are designed to provide a large amount of cranking amps for a short time. Most if not all car batteries will not perform very well if you drain them below 50% charge and it could effect their life.
So while I was thinking about making a change to my mobile installation I came across an advertisement in QST for an ISOpwr+ from West Mountain Radio. I had seen this advertisement many times in the past but I wasn’t giving it much consideration. But this time I decided to go to their website and learn more about it. The ISOpwr+ by itself will isolate your radios from the car battery when the car is not running. While that is nice, I want to be able to use my radios when my car is not running and fortunately the ISOpwr+ will allow you to connect a auxiliary battery to power the radios when you car is not running. I thought that is perfect for what I need. So I purchased the ISOpwr+ from HRO for about $120 and a 35 AH deep cycle battery from Batteries+ for about $80 and installed them into my car. The system works flawlessly (the auxiliary battery is charged by you car when running) and I never have to worry about running my car battery down or shortening its life.
Depending on the equipment you want to power you may need a larger or smaller battery to provide enough energy for however long you want to run your radios when you car is not running. I would advise you to download the instruction manual from West Mountain Radio to fully learn about its capabilities before doing anything. So far this has been a great solution for me. I have no affiliations with West Mountain Radio, HRO, or Batteries+.