A simple solar panel wiring circuit
The simplest possible solar battery charging circuit is just to connect the positive wire from a solar panel to the positive battery terminal, and the negative solar panel wire to the negative battery terminal.
This was the main practice back in the day, and will quite happily charge a battery! However, there are two potential problems:
1) At night, electricity can leak back into the panel, which will slowly discharge the battery. In fact, the amount of leakage is usually small, and not worth worrying about - but if you do want to prevent it you can easily fit a diode (a sort of one-way valve for electricity) in the line, as in this diagram (pictured right - drawn for your viewing pleasure circa 2008, how times have changed!).
2) This problem is more serious - the solar panel, if left on it's own, can overcharge the battery. To avoid this you are better to use a charge controller, which has circuitry to stop power flowing from the solar panel to the battery when the battery is full.
12V Off-Grid Solar Wiring Diagram
Off-grid solar kits have moved on so much in the past decade, that it has led to spiralling options so that the possibilities are endless. To try and simplify this, the vast majority of solar off-grid kits for narrowboats, motorhomes, caravans or sheds fall into the 12V category. The number or size of the solar panels may vary, from a single 100W panel to a dozen or more 400W panels. But the other vital components will stay the same for any 12V off-grid kit (as pictured below).
If you would like a complete off-grid kit like this one, take a look at our 700W Complete 12V Off-Grid All-in-One Solar Kit here.