How do I fuse and wire a lithium battery?

Continuous amps = watts ÷ 12.8V ÷ 0.9 inverter efficiency; the fuse is the next standard size at or above 1.25 × amps, and the cable must be rated for at least the fuse.

Because a LiFePO4 battery has very low internal resistance, so a short circuit lets it deliver far more current than a lead-acid battery of the same size, fast enough to melt cable before anything else reacts. The fuse is there to protect the cable and everything downstream, not the battery. It belongs on the positive cable as close to the terminal as practical, so the unprotected length is as short as possible.

It depends on how much current the fuse may have to interrupt, which is called its interrupt or AIC rating. MEGA and ANL fuses are inexpensive bolt-down fuses with modest interrupt ratings, fine for distribution circuits and smaller systems. Class T and MRBF fuses have much higher interrupt ratings, which is why installers specify them as the main fuse on larger lithium batteries and paralleled systems, where a short can exceed what a MEGA fuse can safely open.

Start from the largest continuous current the cable will carry, usually the inverter. Multiply by 1.25 so the fuse does not blow on normal load and heat, then round up to the next standard size. Then check the cable: the fuse rating must be at or below the cable's ampacity, because the fuse protects that cable. A 2,000W inverter draws about 174A, so 1.25 × 174 = 217A, a 225A or 250A fuse, on cable rated for at least that.

Size the cable to the fuse, then check voltage drop for the run length. Short battery-to-inverter runs follow the table above: 4 AWG for a 1,000W inverter, 2 AWG for 1,500W, 1/0 or 2/0 for 2,000W and 4/0 for 3,000W at 12V. Use fine-stranded, tinned marine cable with crimped ring lugs and heat-shrink; keep positive and negative the same length and route them together.

As soon as more than two cables want to land on one battery terminal. A positive busbar and a negative busbar give every load and charge source its own stud, keep the battery terminal to a single cable each, and make paralleled batteries share current evenly. Put the main fuse between the battery positive and the positive busbar, and put the shunt, if you use one, between the battery negative and the negative busbar.

Use the same model, bring each battery to a 100% full charge independently before connecting (to ensure their voltages match perfectly), and make every battery's path to the busbars the same length so they share current equally. Fuse each battery's positive individually. For two batteries without busbars, take the positive from one battery and the negative from the other, the diagonal takeoff, so the load sees both batteries through equal cable. Expion360 12V batteries can be paralleled to add capacity; the limit differs by model.

Only models rated for it, and only in the configurations the manual allows. Series connection puts each battery's BMS in a string, so the manufacturer has to approve it; Expion360's series and parallel limits differ by model (specifically, the Group 24, Group 27, and EX1 models allow up to four units in series, whereas the EX2 Edge 12V and GC2 12V models are strictly limited to parallel wiring for 12V systems). If you need 48V, the simpler path is a native 48V battery: the 48V 60Ah EX2 Edge or 48V 36Ah GC2, both 51.2V nominal, charged at 55.2–58.4V.

Tight enough for full contact, no tighter than the manual says. Expion360 batteries use oversized brass terminals; torque the terminal bolts to 8 lb-ft (96 lb-in), with a crimped ring lug sitting flat on the terminal face and no washers stacked between lug and terminal. Re-check torque after the first few trips, when cables have settled.