# Smaller Generator with Capacitor

1 Posts
Jun 16, 2008 09:57 am
Smaller Generator with Capacitor

Hey folks,
Newbie here.  First post.  I am moving into an off grid home that currently uses a 7.5KW Diesel GenSet to power all her needs.  The smallest light bulb in the house is 100 watt because the manual said to load Genny right up so it doesn't carbon up.  Normally all the lights are left on in order to accomplish this.  With compact fluorescent lights, I can cut the load (which is currently 2400 watts of lights!) down to 240 watts - if they are all on.  Fridge, stove, water heater are all propane, so I primarily need a genny for lights.

I wish to buy a small honda for the time being - until stream surveys are complete anyway.  Problem is, the water pump delivers a 1012 watt hit when it first starts up.  I wish to use a 240V inverter on a car battery to run this pump when it kicks in occasionally.  Then charge the battery with little generator.  The generator will always be running when the pump is, so the battery will never be dead, only act as a capacitor.

Perhaps I should run the entire place like this?  Recommendations?  The new Genny will only be 120V, so but thats ok cause the only 240V item is the water pump.  I did the calculations and I will save 520 bucks a month using a small Genny. (\$580 vs. \$62) at 400 watts continuous.

Jun 22, 2008 09:40 am
Re: Smaller Generator with Capacitor

"A car battery"
As in 12 volt nominal "cranking" battery?
1012 / 230 = 5 amps
1012 / 12 = 85 amps
That might work.
http://www.howstuffworks.com/question219.htm
Although I wouldn't try it with the battery still in my car.
If a problem occurs with the inverter or pump motor... well, there are probabilities and then there are possibilities.

Probabilities - A measure of how likely it is that some event will occur; a number expressing the ratio of favourable cases to the whole number of cases possible

Possibilities - The fact or state of being possible.

Even though someting will probably not happen it is possible.
All I can honestly tell you is what I might do, and that is, keep what you have for now and invest my money in a large, true deep cycle battery bank and a 120/240 inverter with charger. Then as time and money allowed, invest in PV, and or wind, and or water genny's. Gradually weening myself off of the ICE (Internal Combustion Engine) genny. Eventualy shutting it down for good one day or, at least having it ready for those short, gloomy days, one after another, during the Winter months.

As for sizing the battery bank and inverter. You would have make those calculations based on your power usage.

Jun 22, 2008 05:28 pm
Re: Smaller Generator with Capacitor

I need to add to this, that, while the car battery in the above proposed scenario would be "acting" like a capacitor, it is not a capacitor.
http://electronics.howstuffworks.com/capacitor.htm
It is the intent of a lead acid battery to convert electric energy into a chemical energy and store that energy until such time as it is needed as electric energy again.
To give you an example, I have read stories about off-roaders welding broken axles with nothing but battery power supplied to a welding rod, as a quick fix to get back to camp. Like wise, to much of a load placed on a battery, forcing it to give up to much power to fast, can be like putting a steel wrench across the positive and negative terminals of the battery. Kaboom!

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