Living off the Grid, Part II: Northern Exposure

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2. Any home-electrical system, whether grid or independently supplied, has to have a ground wire to protect against shock. The ground connection in Kips system is a clearly marked lug right on the Powercenter. He attached an #6 bare copper ground wire into the lug, attached the wire to an 8-foot copper-clad steel ground rod and drove the ground rod into the earth.

3. The next step was to connect the Powercenter to the inverter with 2/0 welding cable. All the connections there are clearly marked box lugs.

4. The gasoline generator produces 120volts AC. It's main function is to recharge the batteries when the solar panels are not producing enough electricity, but since the battery bank is wired to 24-volts DC, the generator's power must also be changed to 24volts DC. What all this means is that it has to run through the inverter/battery charger. Kip installed an input circuit breaker between the generator and the inverter/battery charger. Kip installed an input circuit breaker between the generator and the inverter and connected them with a single #10/2 "with ground" SO cord. He used the same type of cord for the one wire connection between the circuit breaker and the inverter, as well as the one wire connection between the inverter and the AC load center.

5. The next and final major step was wiring the battery bank and hooking it up to the powercenter. Here's where the powercenter does some very valuable work. It regulates the amount of energy flowing into the batteries, protecting equipment against overcharge and power surges (such as a lightning strike near the solar panels). It also regulates

the 24-volt DC power flowing out of the batteries and into the inverter via a current-limiting fuse. The inverter will then change that power into 120-volt AC that can be used in the house.

Kip wired his battery bank in a hybrid of series and parallel ( see diagram ), similar in design to the connections of the solar array. Each battery outputs 6-volts DC at 220 amp-hours, so in order to establish his 24-volt system, he wired them in four groups of four to bring the battery bank up to 24-volts DC at 880 amp-hours (wiring in series increases the voltage, wiring in parallel increases the amperage). Kip screwed box lugs to the positive and negative "RV" terminals on the batteries and made all the connections with 2/0 welding cable.

Even though Kip was dealing with relatively low voltages in the battery bank, its amperage was still very high and potentially dangerous, so he was mindful that connections between battery terminals had to be made with caution. He carefully wired the batteries, and as an insurance measure, he attached a Class "T" catastrophic, 300amp fuse to the last positive terminal, then ran 2/0 welding cable from that fuse to the powercenter. The last negative battery terminal was connected directly to the powercenter with 2/0 cable without a fuse.

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