Wire, fuse and inverter questions, answered

Size it from the inverter's input current. A 2,000 W inverter on 12 V draws about 196 A at full load (2,000 W / 12 V / 85% efficiency), and Blue Sea's minimum fuse is 125% of the current, so a 250 A fuse. The cable must be rated for at least the fuse, and if the inverter maker specifies a fuse, follow the manual.

On 12 V, 3/0 AWG for a run of 8 feet or less, with a 250 A fuse, using ABYC's rating for bundled cable. On 24 V the current halves and 2 AWG does the job. Keep the inverter close to the battery: Redodo's manual says to place them as close as possible to cut voltage loss.

It depends on the round-trip length and how much voltage drop the circuit can take. Blue Sea's method, from ABYC E-11: measure from the battery to the load and back, allow 3% drop for critical circuits such as electronics and main feeders or 10% for general lighting and appliances, then read the gauge off the table. Our wire chart does that for 12 V and 24 V.

You need at least one fuse that can safely break a lithium short circuit, and Victron calls the Class T well suited to that job. Victron makes it a mandatory safety requirement because lithium batteries can deliver very high short-circuit currents. Class T fuses are rated to interrupt 20,000 A or more, against 6,000 A for a Blue Sea ANL and 1,000 to 2,500 A for MEGA fuses.

Use one ground point, close to the battery. Victron's guidance is to make the battery ground the most reliable connection, with ground cable thick enough to carry a fault current at least equal to the DC fuse rating, and to ground the inverter's chassis. Victron also says not to ground the positive or negative of the solar array, because on its controllers the PV negative is not isolated from the battery negative; the panel frames may be grounded.

It mostly comes down to inverter size. Victron's preferred limits are up to 3,000 VA on 12 V and up to 5,000 VA on 24 V, because a higher system voltage means lower current and thinner cable. If some loads or chargers only work on 12 V, Victron suggests DC-DC converters rather than keeping the whole system at 12 V.

Add up the watts of everything that will run at the same time and pick an inverter whose continuous rating is above that. Redodo's manual says the load must stay under the inverter's continuous power and warns that some devices surge at start-up; its 2,000 W model is rated for a 4,000 W peak. Don't oversize: bigger inverters need much thicker cable.