Connecting a motomaster 3000 watt power inverter to a stand alone battery
Some things to clarify:
Is the battery a 12volt or 24volt? I will assume a 12volt.
You should always have a fuse between the battery and the inverter. The fuse rating and wiring between the battery and your inverter depend upon the size of the load you will hook up to your inverter.
Inverters are usually NOT 100% efficient. Typically they are 80-90% efficient. If you run an inverter at rated load (your case 3000watts), you will most likely damage the inverter. If you run the 3000watt rated inverter at 500watts or less, you will have significant internal losses.
The capacity of the battery is important.
The type of battery is important (Flooded, Gel or GSM).
A 12volt battery is usually fully charged at 14 volts, but as it discharges, the voltage will drop. Batteries should not be operated at less than 11volts and most likely be damaged permanently if allowed to go below 10.5volts.
If a battery is rated at 100 amp/hours, that means it can supply 100 amps of current at 12volts for 1 hour, or 50 amps for 2 hours or 10 amps for 10 hours.
Now for the more important part. Assume your inverter is 80% efficient. 3000 x .8 = 2400. So the maximum load your inverter can safely handle is 2400watts. At 120volts you will be drawing about 20 amps of current at full load.
If you are going to draw full load, your battery must be able to supply the current to that inverter at an equivalent power rating (power out + power loss = power in). Therefore, 3000watts ÷ 12volts = 250 amps. If your load is only 1000watts (80%), load plus loss will be 1250watts, and therefore, the battery will need to supply 1250 ÷ 12volts = 104 amps. Why is this important? Because the wire between the battery and the inverter must be capable of carrying that current. And that becomes even more important, because if the wire carrying that current is undersized, it could start a fire. Also, with Direct Current, there is more of a loss than with Alternating Current. So if your battery is 20 feet from your inverter, it will incur twice the loss if it was only 10 feet away. You may have to use some very large gauge wire to satisfy the requirements.
on Oct 21, 2018