Dual battery setup using solar regulator
Installing a battery isolator / dual battery system.
This system described above does not protect your secondary / deep cycle battery from being flattened. You may prefer to use a battery regulator as used in the solar power system diagram below. You will typically need a 10 watt regulator. Ideally you should select a regulator which has six separate cable feeds. A positive and negative each for the power source, the battery and the load. Solar power regulators tend to serve this purpose well. Below is a photograph of the solar power regulator I use.
If you only use the car alternator to power the battery and load you can connect leads up to the car battery as shown below.
It occurred to me just today that in many ways it makes better sense to use a solar power regulator in a dual battery system than an auto switching solenoid. Pretty much you can create a system much like this:
In this case the solar power regulator acts as the cut off between the two batteries and also regulates power to the load. This has some very distinct advantages. Firstly, no matter what sort of power comes out of your car or van's alternator, this system ensures that your secondary battery is not overcharged, as the solar power regulator prevents that. That is it's prime purpose. The second main advantage is that your two batteries will not be overly discharged. The regulator, if properly designed and chosen, will cut off power to the load if it gets below a certain point. Many regulators will cut off power when your battery reaches about 11 volts, though some go as low as 10 volts, which pretty much is a flat battery. I don't recommend leaving your battery at lower than 10.8 volts. That's mainly based on literature which I have read that indicates that below that voltage damage will occur to your battery.
Now I have not tried this, so I am not sure if all solar power regulators are designed to handle the voltage and current coming out of a car regulator. I would suggest a 20 amp regulator would handle it. An 8 amp regulator, nope, probably not. Of course, the higher the power rating on your regulator, the better it will be able to handle the job.
This sort of regulator that runs at 12 volt and up to 20 amp should be able to handle this job.
This smaller one on the other hand might not be able to do the job.
