RV Inverter

An inverter converts DC battery power to AC power. The RV uses 120 volt power to charge a computer, run small appliances like the microwave or the refrigerator instead of using gas. If the batteries have enough power an inverter can be used to supply 120v wattage to several of these appliances. If the batteries are not going to be recharged soon it may not be a good idea to start the inverter as it will run batteries down very quickly. Lithium batteries hold more power to run down as they can be discharged to about 10% power while lead acid batteries should only be discharged to 50%.

Capacity of lead acid vs lithium
Capacity of lead acid vs lithium

I installed 210 ah of lithium batteries. When fully charged they should provide 2200 watt hours of electricity before the voltage drops too low to run the inverter. I wanted an inverter capable of running the microwave for a few minutes. I decided on a Samlex as the brand is used for many RV’s and it was less expensive than the Victron. It is a pure sine inverter which is the best for electronic equipment.

Samlex PDT 3000 Pure Sine Wave Inverter
Samlex PST 3000 Pure Sine Wave Inverter

Although our microwave delivers 900 watts of power, it takes a little more than double that to run. The inverter is about 85% efficient so loses some watts converting 12 volt DC to 120 volt AC electricity. That 2200 watts minus 15% is 1870 watts that could possibly run the microwave for about an hour.

RV microwave
RV microwave

We don’t run the microwave that long so we can get plenty of warm up microwave time from a full battery bank. We also run the coffee pot and toaster in the morning. These two use about 1000 and 1200 watts. But they could be added to the microwave for 10 to 15 minutes before the battery voltage drops too far.
The advantage to adding an inverter to the electrical system is that these appliances can be run silently without the use of the generator. Later in the morning we can start the generator or let the solar panels recharge the batteries.
Another device that is necessary when adding an inverter is a transfer switch. This switch turns off power to the charger when the inverter is running. It lets the batteries run the 120 volt system without also trying to charge the batteries with the battery power. A waste of power and possibly dangerous.

Go Power Transfer Switch
Go Power Transfer Switch

The switch goes between the power to the charger on one line with the inverter on the other. It automatically switches depending on whether the 120 volt power is originating, either the generator/plug in or the inverter.

Transfer switch either charger or inverter
Transfer switch either charger or inverter
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