How to get Inverter electric Power without a generator

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A 24-volt inverter
A 24-volt inverter (Image: http://www.4lots.com/ , http://www.westmarine.com/, http://www.cumminsonan.com/)

Whether due to a winter ice storm or severe summer thunderstorm, chances are your electric power will eventually fail. If you don't have a generator, you can have quiet, inverter electric power without sleep disturbing noise.

Things You'll Need

  • Eight 6-volt golf cart batteries
  • Twenty feet of 4-0 gauge welding cable.
  • One 12-volt or 24-volt inverter
  • One circuit breaker panel
  • 200 amp DC fuse
  • Two bank battery disconnect switch
  • 2x6 lumber to make a battery workbench or shelf

Learn the theory of operation.

When line power is normally on, it travels through the inverter to the designated house circuits and the inverter charges the battery bank. When the line power goes off, battery power is inverted into AC and is sent to the designated house circuits.

Do the calculations.

Add up all of the power you will need ---all of the lights, motors, fans, microwave etc., you will be powering. Make sure they add up to 10% less than the rated watts of your inverter. This will leave a reserve for electric motors starting up.

Choose your inverter.

There are many brands of inverters out there, generally you get what you pay for. For our example set-up I will be using an inverter from Trace Engineering. Why this company? Because I have used their products for many years without any trouble. Heart is another good company that you may want to check into.

The Trace SW-2512 would be my choice for a home emergency power back-up system. It uses 12 volt DC input power and will output 2500 watts AC power. Or you can choose the Trace SW-4024, it uses 24-volts to produce 4,000 watts of AC power. It all depends on your needs and finances.

Trace  SW-4024
Trace SW-4024

Choose your batteries.

Depending on the inverter you choose, this system uses 12 or 24 volts DC as a power source. For this there is none better than 6-volt golf cart batteries connected in series, and one of the best brand for this is Trojan batteries. Other brands include: Interstate, US, Sam's Club, Exide, and MK.

Trojan 6-volt battery
Trojan 6-volt battery

Make storage space for your batteries.

One option is to build a small workbench out of 2x6 lumber (or what you have) for the battery bank. Make the top of this bench about 12 inches below waist level. This will make it easy to service the batteries as their tops will be at your waist level.

Mount the components.

On a 2x2 foot piece of ¾ inch plywood, mount the battery disconnect switch, the 200 amp DC fuse, and a 2-1/2 inch long 3/8 inch bolt (ground terminal). Screw this board to the other end of your battery workbench (end opposite the batteries).

Mount the inverter directly above the switch board, on the bench. You might want to make a partition, on the bench, between the batteries and the inverter. Keeps acid away from inverter.

Another option is to mount the inverter and switch board on a wall in your garage next to the auxiliary circuit panel, and to make a rolling cart for your battery banks. Some people use shelves to stack their batteries on. Arrange your batteries in whatever best suits your situation.

Place batteries in a safe location.

Place your bench or cart in a well ventilated area away from open flames (water heater) or sparks. When batteries charge and discharge, they produce hydrogen gas. You don't want to ignite this gas (ever hear of the Hindenburg blimp?) and cause an explosion. If you use a fan to ventilate, make sure it has an induction motor ---one with no sparking brushes.

Cable end connectors
Cable end connectors

Make-up battery bank.

Buy eight of your favorite brand 6-volt golf cart batteries and place them on one end of your battery bench. Using a 4-0 (0000) gauge cable, connect each set of two batteries in series (positive terminal of one to negative terminal of the other). You will end up with four sets of 12-volt (6v + 6v) batteries. If you choose a 24 volt inverter you will have to connect four 6-volt batteries in series, and will end up with two sets of 24-volt (6v+6v+6v+6v) batteries.

Battery disconnect switch
Battery disconnect switch

Connecting the positive (+) DC circuit.

Connect, using 4-0 gauge welding cable, all four battery pair positive terminals together with one cable and connect the end of the cable to the 200 amp fuse block.

Connect a cable from the other end of the fuse to the power terminal of the battery disconnect switch. The switch will make it easy to turn-off the power and will allow you to add an additional battery bank at a later time if you wish.

Make sure the DC disconnect switch is turned to the OFF position. Connect a 4-0 cable from the inverter DC power (+) terminal to the #1 terminal of the disconnect switch. This completes the positive DC circuit connections.

200 amp DC fuse
200 amp DC fuse

Connecting the negative (-) DC circuit.

Once you have the positive DC circuit connected you can connect the battery pair negative terminals together. Connect the cable end to the negative post (3/8" bolt) on the switch board. Connect a 4-0 cable from this post to the negative DC terminal of the inverter. This completes the negative DC circuit connections.

4-0 (0000) gauge welding cable
4-0 (0000) gauge welding cable

Connect to AC power.

Install an auxiliary circuit breaker panel next to your existing house circuit breaker panel. See my eHow article: "How to Connect a Manual Transfer Switch" for a more detailed way to do this.

Use 10 gauge wire to connect the positive, negative, and ground inverter output terminals to the corresponding terminals on the auxiliary circuit panel in your house.

Using 10 gauge wire, supply the inverter with line power by connecting the positive, negative, and ground input terminals of the inverter to the corresponding terminals in the main circuit panel in your house. Use a new 30 amp circuit breaker in your house main circuit panel to supply line power (black wire) to the inverter.

Main circuit breaker panel
Main circuit breaker panel

Make sure all is well connected.

Double check all of your connections with the inverter installation manual. If all is well, then turn on the main panel circuit breaker. No sparks? Good. Turn on the inverter to start charging the batteries. Once the batteries are charged, your system is ready to power your designated circuits in an emergency situation.

Consider adding generator power.

If you feel the need later on, you can connect an auxiliary electric start generator to this system. When the power goes off, the inverter will start your generator, wait for it to warm-up, connect itself, and begin to charge the batteries. One more thing, if you're using your computer when the power goes off, it will instantly switch on the inverter ---you'll not lose any data.

Add a generator for extended emergency power.
Add a generator for extended emergency power.

Now you are done, you can be sure that come what may, your critical need circuits are ready to run on quiet emergency power.

Tips & Warnings

  • Some suggested circuits to power, subject to inverter and battery bank(s) size:
  • Refrigerator
  • Computer
  • Lights
  • Furnace
  • Medical life support
  • Check your city hall for building codes and permits.
  • Use caution when using batteries, do not smoke near them.
  • AC power can kill you, inverters produce AC power ---watch where you put your fingers or tools.

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