Originally Posted by ScottsBad

Well those aren't exactly schematic diagrams for electrical of electronics, but they convey the idea at a high level.

As I mentioned in my earlier post, I did a marine grade second battery install in my boat. I did it myself, and its non-trivial if you don't know much about these systems. One of the things you need to add is a way to cut power to the second battery manually, You also need fusing. I had a little background in electronics so that helped.

On my boat system, I also included the ability to switch the secondary battery in line to start the boat should the primary battery fail. This requires a fairly complex switch wired with large battery gauge wire. I think I used flexible welding lead wire which is a pain to work with. This may not be a requirement for a vehicle.

By use of an isolator, and a regulator the system charges both batteries, until the secondary is full. Then just the primary. So anytime the secondary drains to a certain threshold, the system automatically sends some power to it to keep it charged as long as the engine is running.

This is why I strongly urged the use of the Jackery. It may be lacking somewhat, but it is far simpler and easier than doing all the wiring that just sits in the vehicle until you take your next trip. BTW you also have to select the right components depending on the type of battery you will use as a secondary. Choosing an advanced chemistry battery requires the proper charging system. You cannot use the same charging system for all batteries.

All of the electronics are built into the Jackery. You just plug the Jackery into a 10A 12V circuit in your vehicle. It does everything else. Its the isolator, the regulator, and the battery. You just plug your refrigerator into the Jackery, it does everything else.

The one downside of the Jackery 1500 for your needs, is the slow 12v charging. There are ways around that because you can plug two charging sources into it at the same time. But I'll let you discover how to use that if you want.

The Jackery 1500 is also optimized for solar, so you might want to look into getting a couple portable folding panels if you go this route and you have sun.

I would think that a 1500 would power your fridge for 3 days without a charge anyway if the temp wasn't extremely hot and left in the sun. BTW try not to open the fridge often (kids do that). And pre-cool the food before loading the first time and you will get much longer battery life.

I would not recommend the Jackery for someone who lives out of their vehicle, or is overlanding without moving frequently. But for most of us who usually go out for one to four days, and don't use electricity for cooking. I think its a great option.

JMHO




This regulator keeps the secondary battery from being over charged.