Success - Batteries instead of gas generator

As Hurricane Jeanne was on it's way to South Florida and I already had
a power loss from Frances, I decided I needed an emergency power
source.  And, knowing how gas became very scarce after Frances, I
decided to experiment with batteries.  I went with the following
design based more on cost than figuring out the power requirements and
I was sucessful, BUT I was wondering (1) how long I could expect this
to provide power, and (2) the best way to charge my system for future
use?
1 1500 inverter (MAXX by Vector $150)
4 Deep cycle marine batteries, each with 105 AmpHours ($50 each).

Yes, it was about the same cost as a generator (with obviously less
power) but it was very quite and I think it was safe in my garage.  I
kept the batteries off the cement (someone recommended this) on 2x4's
and had the batteries in parallel.  All I powered on this system was a
20W florescent light, a 16" oscillating fan, and a laptop to watch
DVDs (Starskey and Hutch was a great distraction!).  I used 4 gage
wire for the batteries in parallel.  Anyway, I didn't try and run my
fridge cause I thought I'd drain the batteries too quickly, but I
really wasn't sure.  The inverter was only used at night, but it was a
nice surprise to wake and have the fan still blowing on us.  Again, I
really wasn't too sure what to expect, and I didn't have time to test
it out and get the batteries recharged.

Does anyone have any thoughts on the efficiency of this system?  How
long would I be able to power a full size fridge?  Would there been a
better way to use the batteries and inverter setup?  And, of course,
what is the best way to recharge these marine batteries?  Should I get
a trickle charger?  As I know I'm not the only one in this situation,
any (helpful and not flamed) comments would help others, too.  By the
way, I checked my batteries and, in parallel, they still have a
no-load voltage of about 13.5V.

Thanks and sorry for the long explination.

Dave

I'm no expert... and can't really answer your questions, but will
attempt to help you answer the question yourself.

in parallel you then had 420 AH @ 12V = 5040 WH total.

Take your load and divide into this, and you'll get an approximate run
time for the setup.

your 20W lamp would run 252 hours!

How long will your fridge run? well, it's not running 24/7.... the
runtime will depend on the insulation of the fridge, how often you
open it, and the ambiant temperature.

What can you do to make this work better?
use appliances designed to run directly off 12V.
There is some inefficiency in the inverter.

Think about solar... you've got the sun!

glad you had some comfort in an otherwise nasty situation!

--
be safe.
flip
Ich habe keine Ahnung was das bedeutet, oder vielleicht doch?
Remove origin of the word spam from address to reply (leave "+")

     I have almost the identical system, but it is actually only part of the
whole.  My 4 batteries also serve as the starting battery for my generator and
are kept charged by a 90-watt PV system .  The inverter allows us to have
limited power without running the generator 24/7.  After the hurricane (I just
got power back 10 minutes ago!) we ran an extra charger on the battery while the
genny was running, and ran limited loads with the genny off.

     The efficiency is fine, but you are only storing vaguely the amount of
energy that is contained in one gallon of gasoline.  You still need a way of
recharging the battery for an extended outage.  Consider adding a small
generator for intermittant battery charging.

I would not even try, you will drain your batteries in a very few hours.

     You need a special "float" charger.  If you leave a regular battery charger
on them, they will probably be stone cold dead in 6 months from being
overcharged.  Do not trust a charger just because it says "automatic" on the
case, it must be a special float charger.  Take this advice from someone who
ruined way too many batteries before learning.  Pep Boys sells a good 1 amp unit
for about $50.00.

Vaughn

I hope your inverter has an automatic low voltage disconnect.

Thanks for your suggestions.  I will certainly get a 'smart charger'
that has a float on it unless someone can recommend a solar method
that isn't too expensive.

Another option, though I don't know yet how to do this, is to charge
it with one of those UPS that I have that now have a dead battery.  I
imagine the UPS charging system is fine and it sure sounds like a
float charge.

I did notice that BatteryMart.com sells both "battery tenders" and
"battery minders"  Which would be applicable in this scenario.  They
do have some that sound like I could keep all 4 in parallel while
charging.

That brings me to another question: storage.  Should I store them (in
the garage I think) wired in parallel or should I disconnect the
cables and rotate the charger every month?  I was thinking of building
a little cart for the battery bank where it would get enough air but
some screen material (extra from the screen enclosure that the
hurricane destroyed) would keep fingers and dropped things out of.
Then I could mount the inverter and a voltmeter on it.

And, as an update, I checked and I actually have about 15 no-load
volts (when measured in parallel).  Is this an indication that I
didn't use any charge up?

Finally, when they say I have 105AH (or 420 for 4, or 5000+WattHours)
does this mean until the battery has absolutely NO CHARGE left?  My
inverter has the following features:
- Automatic overload and over-temperature shutdown and manual reset
(activated if AC output exceeds 1500- watts for more than a few
seconds)
- Automatic AC short-circuit shutdown and manual reset
- Automatic low voltage audible alarm and reset (sounds at 10.6 volts
input)
- Automatic low-voltage shutdown and manual reset (activates at I 0.0
volts DC)
- Automatic high-input voltage shutdown (activates at above 14.7 volts
DC) and manual reset

Thanks for all your help.

the

charger

unit

Success - Batteries instead of gas generator - any thoughts?