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EMERGENCY POWER – PART 2

How Do I Get the Power?

There are two main sources for emergency power; generators and battery balks. Each has pros and cons. If you have a screw that needs to be screwed in, a screwdriver is the best tool to do the job. If you have a nail that needs to be driven in, a screwdriver may work by grabbing the blade and beating the nail with the handle but a hammer would do a much better job.

 

Generators – Generators produce power. You can have a generator that runs on gasoline, diesel, propane or natural gas. You have to store fuel to run your generator during an emergency. Gasoline and diesel have to have stabilizers added to them if they are stored for over a year. Propane and natural gas are more storage friendly but the generators are more expensive.

The biggest pro for a generator is that it produces a lot of power quickly. The biggest con for a generator is that it is an all-or-nothing power producer. Generators are either on or off. If you have a 4000 watt generator and all you need to power is a 5 watt cell phone charger, when you turn on the generator it will produce 4000 watts even though you needed only 5 watts. It will also gobble up fuel to produce 4000 watts even though you only use 5 watts.

The some thinking would tell us not to buy a bigger generator than needed. If the most you would ever use at one time is 2000 watts, then don’t buy a 5000 watt generator. You’ll only waste money when you buy it and again every time you run it.

Look for peak rating and constant rating. Many appliances require a power surge (peak) when started and then use a lower amount if power to run (continuous). Be sure to buy a generator based on continuous wattage not just peak wattage. Buy a generator with 25% more watts than you calculate. It is my experience that manufacturers tend to overstate the power of their generators. Using a 25% – 30% fudge factor, if 2000 watts is the most you would ever use at one time then buy a 2500 watt or 3000 watt generator to make sure you are covered.

Conclusion – Buy the smallest most efficient generator you can. Generators are best used to run high wattage items like coffee makers, microwaves, furnace motors, well pumps, sump pumps, etc. It is a waste to run very low wattage items off a generator unless they are being rub at the same time as some high wattage items.

 

Battery Banks – A battery bank is one or more deep cycle batteries along with some type of battery charger and an inverter to convert the 12 volt battery power to 115 volt house power.

The biggest pro for a battery bank is that it allows you to use only the power you need. If you only need to run a 5 watts cell phone charger you can sip 5 watts from a battery bank and leave the remaining power untouched. The biggest con for a battery bank is that a battery bank with 1 to 3 batteries cannot run high wattage items for very long. A battery bank with 3 125 ah batteries would run a 750 watt furnace motor for 3 hours then it would take 5 hours to recharge it.

 

Batteries – For home battery banks I like to use deep cycle marine batteries. Batteries have Amp Hour Ratings. I buy 125 amp hour batteries from Sam’s Club for $90. To calculate the watt storage of a battery, multiply the amp hours of the battery by the voltage of the battery. In my case, 125 ah x 12 volts = 1500 watts. To insure long battery life, don’t discharge your batteries more than 50% of their capacity. If we only use half of the battery power before recharging, then we have 750 watts of usable power in the battery.

 

Inverters – Inverters convert 12 volt battery power to   115 volt house power. They are sized just like generators. They have a peak watt rating and a continuous watt rating. Be sure to buy an inverter based on continuous wattage not just peak wattage. Buy an inverter with 25% more watts than you calculate. It is also my experience that manufacturers tend to overstate the power of their inverters.

 

Battery Charger – It is important to keep your batteries fully charged when not in use. This will keep your battery healthy and will extend the life of the battery. It is important to have a “Smart Battery Charger” or a “3 or 4 Step Battery Charger”. These chargers read the condition of your battery then apply the appropriate charge to fully charge your battery and then to maintain it fully charged without overcharging it.

It is important to have a charger that can charge your battery bank in about 5 hours. If you have a single 125 amp hour battery, normal 50% use is 62.5 amp hours. A 12 amp charger would be able to recharge it in about 5 hours. A three 125 ah battery bank normal 50% use is 187.5 amp hours. A 35 amp charger would be able to recharge it in about 5 hours. My favorite high amp chargers are Schumacher smart chargers. Why recharge in 5 hours? I’ll get to that later.

In Part 3 we’ll talk about exactly what you should get for a Minimum System, Moderate System and Close to Normal System.

 

Ed Rogers
Copyright “Keep It Simple” 2013. All Rights Reserved.

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