How to Hook Up Solar Panels to Two 12 Volt Batteries

Add the voltage ratings of all the solar panels together to determine if you need to connect the panels in series or parallel configuration. With series wiring, where the terminals are connected positive to negative, the voltage is added together, while the amperage remains the same. For example, two 12-volt, 3-amp solar panels wired in series would create a 24-volt, 3-amp system. Conversely, with parallel wiring, where the terminals are connected positive to positive and negative to negative, the voltage remains constant, but the amperage is added. For example, two 12-volt, 3-amp panels wired in series would create a 12-volt, 6-amp system.

Connect the leads of the solar panels together, in series or parallel configuration, so the total voltage of the connected panels does not exceed 12 volts. Some solar panels have leads equipped with clips that plug directly into each other, whereas the leads of other panels need to be hardwired. If you are using the latter, crimp metal terminal connectors to the ends of the solar panel leads using electrical pliers. Connect the terminals together with bolts and tighten the nuts with a wrench.

Cut two lengths of 10-gauge wire using electrical pliers; they should be cut long enough to reach between the two 12-volt batteries. Strip 1 inch of insulation from each end of both 10-gauge wires using the strippers on the electrical pliers. Attach a battery clamp to the stripped ends of each wire with a wrench.

Connect the two 12-volt batteries together in parallel configuration. Attach the battery clamps from one of the 10-gauge wires to the positive terminal posts of both batteries. Connect the clamps from the second 10-gauge wire to the negative terminal posts of both batteries. Tighten the clamps with a wrench. Connecting the positive and negative terminals together will maintain the 12-volt rating of the batteries but will add the amperage capacity of the two batteries together, doubling their life. For example, two 12-volt, 650-amp batteries will perform as one 12-volt, 1300-amp battery.

Attach metal terminal connectors to the wires at both ends of the in-line fuse holders with the pliers. Connect one of the in-line fuses to the positive battery clamp and the second fuse to the negative battery clamp. Tighten the connections with a wrench.

Connect the solar panels to the in-line fuses. Attach the positive lead from the solar panels to the free end of the in-line fuse connected to the positive battery post. Connect the negative lead from the solar panels to the in-line fuse attached to the negative battery post. Secure the connections with a wrench. Insert fuses in the fuse holders, equal to the total amperage rating of the connected solar panels.