posted on May, 4 2008 @ 10:41 AM
First thing to consider is the amount of power you will be needing, both peak (everything on) and average (for recharging). Based on what you just
A small TV will pull about 500 watts when on. When off, it will pull maybe 50-100 to maintain internal voltages.
The laptop will pull about the same, say 400-500 watts.
A fan, depending on size, will pull about 100-150 watts maximum. I am assuming a pretty large fan, such as a window unit, to be conservative.
The heater is a wild card. Since we're talking batteries, I am assuming electric heat. A heater can easily pull 2000-3000 watts, depending on its
So all together, we're talking about 4100W peak. That's a HUGE inverter to run these off of a 12V battery system, but they are available. Expect to
spend about $300 - $400 dollars for the inverter itself, but the good news is it simply connects to your battery and has plug-ins right on the box.
At peak load, you will be pulling 4100/12, or about 340 amps out of that battery. That's almost what a starter pulls, so you will need multiple
batteries. They can simply be wired together, (+) to (+) and (-) to (-). Your wires will need to be large enough to handle the amperage, so figure on
using small starter cables.
As far as average, for a day, the TV will be on about an hour, so that's 500W-Hr. 20 hours of the fan is about 20Hr * 150W = 3000 W-Hr. How long will
you have the laptop on? The heater? Figure them the same way, time on during one day multiplied by the wattage used. Add all these figures up and that
will give you the number of watt-hours used.
Now take that number and divide it by the number of hours each day that you expect to receive solar power (sunshine). That is the number of watts of
charging power you need to maintain your battery charge, and will vary some based on your geographic location and time of the year. Take that and
divide it by 12 (the voltage) to get the number of amps of power you will need. With that information, you can calculate how many solar panels you
will need to install on your rooftop to maintain your batteries. Simply gang the solar panels together in a 13.8V array (charging voltage for a 12V
battery) using series connection for the voltage and parallel for the amperage.
Even though I understand you are looking for quiet operation, since you will be in an RV, I would look into a dual-charging system for backup. This is
simply a special type of regulator that allows two different batteries to be charged simultaneously from one generator/alternator, while maintaining
one battery to be the primary starting system. They are reasonably priced and will allow you to charge your auxiliary batteries while you drive
without worrying about the main battery when you are parked using the auxiliaries. It will allow you to use gasoline (or diesel, depending on your RV)
as a backup for those days when the sun isn't shining, or when you need to overuse that heater past what you had figured.
If your RV is diesel, you might want to look into a bunk-heater unit. This thing uses a small burner to provide heat directly from the diesel supply
without the noise of a motor. From what I understand, they are a bit pricey, but not so much so as to prevent them from being used in semi's to make
it cheaper to maintain heat than idling the truck. That will remove your biggest power drain from the battery system and use smaller components and
less solar cells.
I hope this helps.