??? about an inverter system
 

Jim wrote in message link.net...
Larry's discussion has some very good information. I have a couple of
questions:
1) Why are you running refrigeration through an inverter?
2) Why, with the choices available today, are you running a TV through
an inverter?

I have a (one) 1,000 watt inverter for my 110 volt stuff, and just about
the only thing I run is the microwave oven.

Marine refrigeration is either dual power (110/12) or cold plate (engine
driven), lcd tvs are 12 volt (4 amp draw)

If you are running 110 volt appliances you are not being very efficient.

Opinions, please.
Jim
The answer is very simple. I use the inverter because I am using all
standard, cheap household applienaces, like a household TV, VCR,
Microwave, Toaster, Coffeemaker, Power tools ( drill, saw, soldering
iron). I expected these appliances to last maybe a year, but so far
they have been lasting 3 years with no sign of corrosion. BTW My Boat
is in San Francisco Bay and it is perfectly dry.
I also have a normal apartment size fridge which I run on shore power.
I can put the stuff in the evening before, fill up the freezer
compartment and then it keeps cold for most of the weekend. I don't
use the fridge with the inverter since the drain on the batteries is
too great and I don't use the microwave for anything but heating
something. For cooking I have a propane 2 burner stoven and oven.
Rolf


wrote:

I'm trying to learn about inverters, and how to put a
system together. I want to use it pretty much just
for my refrigerator (about 800W), and my TV/VCR
etc. It seems like it would be cheaper to get two
less powerful inverters, than one powerful one.
So far getting two of the 1200W for $120 each at:

http://store.worldstart.com/customer...=16468&cat=307

seems like the best deal for me. That would leave
me plenty of head room--especially on the TV
circuit--for including other things. Does anyone
know of a better deal?

How do I figure what size batteries to use? Should
I keep the batteries separate for each inverter, or
is it better to connect two or more batteries and go
from there? If so, how to connect the batteries
together, and then how to go from there to the
inverters?

I'm lead to believe that any inverters I can afford
would produce a square wave instead of a sine
wave. How to know what influence that would
have on my TV's performance? The TV works
great using the Generac 4000W generator I'm
using now. Can I expect it to be different using
the inverter?

Thanks for any help!

??? about an inverter system
 

"Jim" wrote in message
ink.net...



A toaster and a coffee maker? Off an inverter? WHY WOULD YOU DO THAT????

Several reasons:

1) Your stove is AC, and you don't feel like firing up the generator to make
a piece of toast.
2) Your stove is alcohol, and you don't want to risk burning up your boat to
make a piece of toast.
3) Your stove is propane, and you would rather have your bread lightly and
evenly toasted rather than charred in spots.
4) The electric coffee maker doesn't heat the cabin up nearly as much as
running the stove


I don't care if it works, it's... not efficient use of your batteries.

I installed big enough batteries so that I don't care if they are used
efficiently!

Rod

??? about an inverter system
 

"Jim" wrote in message
ink.net...


Larry's discussion has some very good information. I have a couple of
questions:
1) Why are you running refrigeration through an inverter?

Well, one reason is that you can buy a small household refrigerator for
about $200 and the same sized 12 volt refrigertor will cost you about $1200.
There are reasons that the 12 volt refrigerator is better, such as automatic
switching to 110 and likely to have greater efficiency, but I know that a
lot of people prefer to go the household route just because of the cost.

2) Why, with the choices available today, are you running a TV through
an inverter?

What choices? There are a lot of 9" TVs that run off of 12 volts, and I have
seen a couple of 13", but if you want a 25" TV it is going to be 110 volts.

Rod

??? about an inverter system
 

wrote in message
...

want to use it pretty much just
for my refrigerator (about 800W),

That is either a very large refrigerator, a very inefficent one, or the
rating is way above what it actually draws. If this is a "frost free"
refrigerator then you would be best to get rid of it and get one that uses
lots less power. Frost Free refrigerators use more energy creating heat
(directly, not counting the byproducts) then they do "cold".

and my TV/VCR
etc. It seems like it would be cheaper to get two
less powerful inverters, than one powerful one.

It is possible that dedicating a smaller inverter to the refrigerator might
be more efficient. An inverter uses power even when there is nothing
drawing AC power. This "idle" power can be significant, especially on the
larger inverters. There are advantages to a good expensive inverter,
however.


seems like the best deal for me. That would leave
me plenty of head room--especially on the TV
circuit--for including other things. Does anyone
know of a better deal?

I would go with a minimum of 1500 watts, then you can run just about
anything (coffee maker, blow drier, belnder, etc.). You can decide if it is
wise to run such things, but at least you will have the option.



How do I figure what size batteries to use? Should
I keep the batteries separate for each inverter, or
is it better to connect two or more batteries and go
from there? If so, how to connect the batteries
together, and then how to go from there to the
inverters?

One large battery bank is much better than two smaller ones.

The first step will be to establish how much capacity that you need.

The refrigerator is going to be the biggest consumer. 800 watts will force
the inverter to draw about 76 amps out of the battery system, after
adjusting for the inverter efficiency loss. I would guess that the
refrigerator would run about 50% of the time, which means that you would
need 919 amp-hours per day.

That's a lot! If you want to last a three day weekend you would need 2700
amp-hours. To treat the batteries reasonably well you don't want to
discharge them below 20%, so you really would need ~3300 amp-hours. That's
a bunch of some very serious batteries. A lot of weight, a lot of room, a
lot of cost. Since you started off saying that you were concerned about
cost I would think that this would be a major issue.


I'm lead to believe that any inverters I can afford
would produce a square wave instead of a sine
wave.

There are sine wave inverters, square wave inverters, and modified sine
wave.

A square wave inverter goes from +60 volts to -60 volts in one step.

A modified square wave would go from somthing larger than 60 volts, to zero,
then to somethng larger (magnitude) than - 60 volts. The pause in the middle
would approximate the zero crossing of the sine wave and would make
inductive loads much happier.


How to know what influence that would
have on my TV's performance?

If the TV was made in the last 20 years it probably would be very happy with
the output of any inverter. Most electronics these days use switching power
supplies that would actually have better efficiency off a square wave than
they would off a sine wave. Where you can get into trouble is with
inductive loads (some motors) and transformers.

On a sine wave AC, the peak voltage is ~1.4 times the RMS voltage. Thus, if
you had a device that uses a "wall wart" transformer it would be expecting a
" 6 volt" output to actually peak at 8.4 volts. When rectified, this would
produce a useable amount of 8 volts DC, which could be used recharge a 6
volt battery operated device. If you connected this up to a square wave
inverter than the rectified output would only be 6 volts, which might not be
enough for the circuit to operate. The modified sine wave would certainly
be better and they probably make the "modification" such that the peak is
the same.

Square wave inverters are great for running series wound motors (drill
motors, blenders, saws, etc.). They will run most electronic items that
have swicthing power supplies or that aren't too sensitive on the voltage.
They are a lot cheaper and more efficient than modified square wave or sine
wave.

There are other factors to consider for the total installation.

If you go with something like a Xantrex marine inverter you will get the
following features (which will not be available from the inverters you have
indicated)

1) Automatic AC input cross over. When you have 110 Volts available you
will not want to be running off the batteries. The Xantrex will sense the
incoming AC and pass it through, switching the load over without ever
powering it down. With the cheap inverter you will have to pull the plug
out of the inverter and plug it into the normal AC outlet. (that can be a
real hassle if the refrigerator/TV is recess mounted).

2) The Xantrex inverter includes a battery charger, suitably sized for the
job. If you install that 3300 amp-hour battery bank you will need a way to
charge it. If you don't have a really good charger it could take a week to
get the batteries recharged!

3) I have some amount of faith in Xantrex products. They have been around
for a while and I know many people who have used them. Some fly by night
company off the internet is a gamble.


My recommendations:

1) Get a refrigerator that uses a lot less power. The "old" style, where the
cooling coils are the floor of the freezer, and you have to manually defrost
them occasionally, are the best for this application.

2) Install a battery bank that will provide at least twice what you think
you will need for the length of time you will be away from shore power.

3) install a single inverter that will cover all your needs.

Rod McInnis

??? about an inverter system
 

various posters - inverters, Threat or Menace?

I'd leave all that crap ashore.

I have a cooler that kept ice for five days. Got a percolator
that sits on the stove, and if I wanted toast I guess I could
fork it over the flame. I'd fix drinks that didn't require a
blender.

And a television? Spare me.

??? about an inverter system
 

LCD tvs are 12 volt. I have a Sharp 20 inch in my salon that
runs off the cabin light circuit. I haven't checked the larger ones,
but I'll bet they are the same.

15" draws 4 amps, 20" uses 4.5, at 12 volts.


Rod McInnis wrote:

2) Why, with the choices available today, are you running a TV through
an inverter?


What choices? There are a lot of 9" TVs that run off of 12 volts, and I have
seen a couple of 13", but if you want a 25" TV it is going to be 110 volts.

Rod

??? about an inverter system
 

I'm with you. If you want to sail your living room mount
your mast on the roof of your home and never worry about
heeling over again! And imagine all the power capabilities
you could have, even surround sound on your computer.

Seriously though just the essentials keep it simple and you
will be happier in the long run.

John

"Steve Daniels, Seek of Spam" wrote in
message ...
various posters - inverters, Threat or Menace?

I'd leave all that crap ashore.

I have a cooler that kept ice for five days. Got a
percolator
that sits on the stove, and if I wanted toast I guess I
could
fork it over the flame. I'd fix drinks that didn't
require a
blender.

And a television? Spare me.