How to Install Inverters With Dual Input/Output Terminals

Some manufacturers use 2 positive and 2 negative leads on 12-volt power inverters. They do this because the internal wiring would be very large if they only ran one lead for each. This is a shortcut that saves them design time and money, but causes a bit of headache if installation instructions are not included.

Option One – Bridge the leads together forming one input.

If you’re handy enough, you can bridge the leads together forming single inputs. You’ll bridge the two positive leads with each other, and the two negative leads together. You can do this with sufficiently sized copper stock available here.

Just drill 2 holes for the inverter leads to mount, then drill a seperate hole for your main input lead and mount accordingly. It’s important that the main input lead is in between the two inverter leads. If it’s not, then it’s possible that the input leads receive unequal power flow, in that case resort to option 2.

Option Two – Dual input/output with dual fuses

Or you’ll need to use two cables that when combined, are large enough to handle the inverters current draw. Each cable will need it’s own appropriately sized fuse. If you’re not sure which size fuse to install remember, the fuse is there to protect the wire, not the inverter. The inverter will have it’s own internal fusing.

Both cables will need to be roughly the same length, this helps ensure equal power flow. Since we’re dealing with a power inverter, it’s best practice to keep cable length as short as possible. This will cut down on unneccesary resistance between the inverter and battery bank.

Since we’re using dual leads, there is always the chance of unequal power flow, meaning one cable will carry more current than the other. If powerflow is too unbalanced, this will cause one fuse to trip thus sending all power through the second cable, causing the second fuse to trip aswell.

To prevent this from happening you can oversize you’re cables, just always use the appropriate size fuse for each cable.

How to determine cable and fuse size.

Option One – Bridged Terminals:

1. (Inverter wattage) ÷ (Battery voltage) = ___Amps (expected amperage)
2. (___Amps) + (25%) = Cable Minimum Ampacity
3. Find your cable from the chart below
4. Select a larger cable if inverter is more than 3 feet from battery bank
5. Read our article on wire sizing for more information.

Option Two – Dual Cable Input/Output

1. (Half of Inverter wattage) ÷ (battery voltage) = ___Amps (expected amperage)
2. (___Amps) + (25%) = Cable Minimum Ampacity
3. Find your cable from the chart below
4. Select a larger cable if inverter is more than 3 feet from battery bank
5. Read our article on wire sizing for more information.

Selecting Fuse Size

To calculate the required fuse size:

1. Fuse size = (___Amps) + (25%)
2. Fuse size must fall under cable maximum amperage
3. If fuse size is to close to max amperage, choose next larger size cable
4. For more information on fuse selection read our guide here.

Here’s a list of cable and fuses for your project