[VAC] Re: DC TV's

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Brian,
 Nearly all of the "solar" sites have an AH chart similar to the one you
found at RVSolar. Pick one and go with it.

Before charting your usage, you need to actually measure the consumption
of your various appliances and lights, then estimate how many hours/day
each will operate. Your DVM, set on the 10-amp scale will work fine to
measure the draw, just be very careful to run only one device at a time.
Simply disconnect one of your main battery leads and connect the meter
in series, then turn on each light, the pump, the furnace, your small
inverter (both loaded and unloaded), etc., ONE AT A TIME, and record the
number. Round to the nearest .1 amp, closer than that is not necessary.
This will require no more than 30 minutes of your time, believe it or
not, and you'll be WAY ahead of the folks who are guessing, discussing,
rehashing, and so on.

Put your numbers in your chart, just as shown in the examples on the Web
sites.

Now, put the AH output from your solar panel(s) in the chart. A 100-amp
panel will have a peak output of slightly more than 5 amps, and you can
expect to see that much for a maximum of 4 hours per day, plus half that
for another 4 hours. That's a total of 30 AH/day. Although that's my
estimate, it's actually pretty close to personal experience. Note that
we're assuming sunny days, it'll be next to nothing on a dreary day.

If you're exceeding 30 AH/day in usage, your battery has to make up the
difference. But, let's put that into the chart also. Your 3 batteries
will give you about 250 AH max, or 125 AH if you try to never draw them
below 50% charge. Let's say that you're using 60 AH/day, giving you a 30
AH/day deficit. You can still operate for 4 days before running your
battery bank lower than is prudent, twice as long as without the solar
panel. You might well look at your camping lifestyle and figure out that
4 or 5 days is the maximum time you will spend away from shore power and
realize that you're all set. Of course, an eMeter or equivilant will
help you track usage and give you a real-time readout on the state of
your batteries.

You might consider adding a good 3-stage charger/converter to your
setup, especially if you plan on being out for a long time and using
your generator to charge the batteries. A regular converter will charge
the batteries so slowly as to be almost useless in this situation, but a
3-stage charger can put a very useful amount of juice into them in 4 or
5 hours of run-time. The small 1000-watt Hondas with the inverters are
very quiet and very fuel-efficient and should do the job nicely.

We use about 30 AH/day, being wastrels next to Sherry, but frugal
compared to many others. Our 2, 75-watt panels can easily provide that
amount of power and more. The eMeter has proven out the system, showing
the batteries as "full" by shortly after noon most days. The one thing
that could hurt us is if we had to run the furnace very much and the
days were dreary. The furnace draws over 4 amps and runs quite a bit, so
it really contributes to the AH consumption. Our TV is tiny, but draws
only 1 amp. The 9" TV that I'd kinda like to have draws 4 amps, so would
add at least 9 AH/day to our usage if we watch it for 3 hours/day.
That's nearly 1/3 more total than at present!

It sounds to me like you're all set in the power department. If you're
interested, I'll tell you about my solution for the water problem. :-)

                                         <<Jim>>