The quick version
- Size cable for the inverter’s continuous amp draw, not the wattage rating alone, and always check the manufacturer’s cable chart.
- A DC fuse or breaker goes within 7 inches of the battery or busbar, sized to protect the cable, not just the inverter.
- Loose or corroded lug connections cause more inverter shutdowns than weak batteries ever do.
- Chassis ground and AC neutral bonding are two separate jobs, and mixing them up creates ground loops or nuisance GFCI trips.
- Lithium’s flat discharge curve means your inverter sees stable voltage right up until the battery is nearly empty, so undersized wiring shows up as sag long before the battery does.
The first inverter I wired into a lithium system was a 2000 watt Xantrex in a Sprinter van, and I underestimated the cable run by about eighteen inches. That extra length dropped voltage at the inverter terminals just enough that it faulted out under a coffee maker load, even though the battery itself was sitting at a healthy 13.2 volts. It taught me that inverter wiring is really a math problem wearing a tool belt.
Lithium batteries change this equation compared to lead-acid. Because LiFePO4 holds a nearly flat voltage across most of its discharge curve, your inverter sees consistent power right up until the battery is nearly empty, unlike AGM which sags gradually. That means wiring mistakes show up immediately as voltage drop under load rather than being masked by a battery that was already sagging anyway.
Sizing the DC cable correctly
Inverter cable sizing starts with amps, not watts. Divide your inverter’s rated wattage by your system voltage to get continuous amp draw, then add headroom for surge loads like a compressor starting up.
For a 2000 watt inverter on a 12V system, that is roughly 167 amps continuous. Manufacturers including Victron and Xantrex publish a cable chart in the inverter manual that accounts for voltage drop over distance, and I follow that chart over generic wire gauge tables because it is written for their specific unit.
| Inverter size (12V) | Continuous amps | Cable size (under 3 ft) | Cable size (3 to 6 ft) |
|---|---|---|---|
| 1000W | ~83A | 2 AWG | 1/0 AWG |
| 2000W | ~167A | 2/0 AWG | 4/0 AWG |
| 3000W | ~250A | 4/0 AWG | 2x 2/0 AWG |
Keep the run as short as physically possible. Every extra foot of cable adds resistance, and resistance under a 200 amp load turns into real heat and real voltage loss, not a rounding error.
Tip: If you are between two cable sizes on the chart, go up a size. The cost difference between 2/0 and 4/0 for a typical 4 foot run is usually under $15, and it buys you headroom for future loads.
Fusing the inverter circuit
Every inverter needs DC-side overcurrent protection sized to the cable, placed close to the battery. ABYC standards call for the fuse or breaker to sit within 7 inches of the power source connection, and that guidance exists because the unprotected stretch of cable before the fuse has no protection at all.
Use a Class T fuse for anything over 100 amps. Class T fuses have a very fast trip time and a high interrupt rating, which matters because a dead short on a lithium bank can deliver an enormous fault current in milliseconds. A slower ANL fuse will work on smaller inverters but I default to Class T on anything 2000 watts and up.
If you are unsure how to size the fuse against your cable and inverter draw, our guide to fusing a lithium battery correctly walks through the amperage math step by step.
Choosing between busbar and direct-to-battery wiring
On single-battery systems I sometimes land the inverter cable straight on the battery terminal, but on anything with more than one device pulling DC power, a busbar is the cleaner and safer approach.
A busbar centralizes your connections, keeps the battery terminals from turning into an overcrowded stack of lugs, and lets you fuse each circuit independently. It also makes future troubleshooting much easier since you can isolate one circuit without disturbing the others.
If you have not set up a busbar yet, it is worth doing before you run the inverter cable. See our walkthrough on wiring a clean 12V system with busbars for the layout I use in most builds.
Grounding the inverter properly
Inverters typically have two separate grounding requirements, and conflating them is a mistake I see constantly. The DC negative terminal connects back to your battery negative or busbar, completing the low-voltage circuit.
Separately, the inverter chassis usually has a ground lug that bonds to your vehicle frame or vessel bonding system. This chassis ground protects against a fault putting stray voltage on the metal case.
On the AC output side, most inverters have an internal neutral-to-ground bond that should only be active if the inverter is your sole AC source. If you also have shore power or a generator feeding the same panel through a transfer switch, you need to make sure only one neutral-ground bond exists in the system, or you risk nuisance GFCI trips and, worse, a genuine shock hazard. Our article on grounding a 12V camper system covers the DC side of this in more depth, and it is worth a read before you finalize your ground scheme.
Mounting the inverter and managing heat
Inverters need airflow, and most units want at least a few inches of clearance around the vents. Mounting one directly against plywood in a tight cabinet without ventilation is a common way to trigger thermal shutdown during a long high-load run like running a microwave or space heater.
Keep the inverter close to the battery bank to minimize cable length, but not so close that cable bend radius becomes a problem at the lugs. I generally aim for a 2 to 4 foot run when the layout allows it.
Warning: Never mount an inverter directly above or touching the battery bank. Battle Born and other manufacturers recommend keeping heat-generating equipment away from the batteries themselves, since elevated temperature affects both battery lifespan and BMS behavior.
A real wiring walkthrough
Here is the sequence I actually follow on install day, using a 2000 watt inverter on a single 100Ah Battle Born or Li Time battery as the example.
- Mount the inverter with clearance for airflow and cable bend radius
- Run 2/0 or 4/0 positive and negative cable based on distance, per the manufacturer’s chart
- Crimp lugs with a proper hydraulic or ratcheting crimper, never a cheap hand crimper that leaves a loose joint
- Install a Class T fuse on the positive cable within 7 inches of the battery or busbar
- Connect negative to the busbar or battery negative terminal
- Bond the inverter chassis ground to the vehicle or vessel ground
- Torque every lug connection to the manufacturer’s spec, usually with a torque wrench in the 15 to 20 ft-lb range for larger lugs
- Turn the inverter on with no load first, confirm output voltage, then test under a real load like a hair dryer
A mistake I see constantly on forums and in other people’s vans is skipping the crimp quality step. A properly crimped lug should not pull off the cable when you tug hard on it, and a poorly crimped one is a resistance point waiting to overheat under sustained load.
Testing the installation before you trust it
Once everything is connected, run the inverter under its heaviest expected load and measure voltage right at the inverter’s DC input terminals, not just at the battery.
A voltage drop under 3 percent from battery to inverter under full load is the general target used by most marine and RV electrical references. If you are seeing a full volt or more of sag, go back and check your cable size, your lug crimps, and your fuse holder connections before you assume the battery or inverter is at fault.
If you have not yet installed a shunt-based monitor, doing so before your inverter test gives you a much clearer picture of what is happening under load. Our guide to installing a battery monitor shunt explains the placement that gives you accurate readings.
Once your inverter is wired correctly, it becomes one of the most reliable parts of the system, quietly converting DC to usable AC power for years. If this is your first time wiring a full lithium system rather than just adding an inverter to an existing setup, our guide to installing a lithium battery bank safely is the better starting point, since it covers battery-side decisions this guide assumes are already settled. Take your time on the crimps and the fuse placement, because that is where nearly every inverter wiring problem actually lives.
