Wow! Thanks, Larry. That was more information than I could ever have hoped
for.

After reading your post, I checked the battery I'd be using to run the
inverter. It is a Seavolt 550 Marine **STARTING** battery. Got it from
WestMarine for $65.00. I don't know much about batteries (although I now
know more than I could ever thought possible - thanks again) but the folks
from WestMarine said this was a gel cell battery. Based on your post, I'm
not so sure that it is in fact a gel. Doesn't say so anywhere on it. Also,
based on your post, this battery will die a quick death from my use with an
inverter and recharging each time.

Against advice from those responding to this post, I did buy a Seavolt 400W
power inverter from WestMarine yesterday. The cost was $40. I looked for
power inverters at Wal-Mart and Kmart but you ask the clerk in either one of
these stores for help in locating one of these in their own store and you
get a blank stare followed by the question "You want to do WHAT with your
battery?" So I chucked the frustration, went to WestMarine and got the
inverter.

The 550 is a spare battery so I guess I don't have a problem with the
recharging of it. When you get down to it, this might be acceptable.I'm not
going to power a microwave or anything like that. A portable boombox, cell
phone charger or the like.

Thanks for all the info!

Bob
"Larry" wrote in message
...
"Robert Burkard" wrote in news:PXfwg.1390$K94.136
@trnddc01:

(800 cold cranking
amps)

First off, there are two types of lead-acid batteries. One has lots and
lots of very thin plates designed to create and immense current for a
very short period of time called a "starting battery". It's rated in
Cold Cranking Amps, like your 800CCA. If you discharge these types of
batteries, the acid soon eats holes in the very thin plates and simply
ruins them as holes cannot be replaced by charging. For your inverter
use, they are worthless.

Secondly, the other type is called a "deep cycle battery". It has a much
smaller plate surface area because the plates are much thicker so we can
allow the acid to eat away at the lead, releasing lots of electrons in a
much smaller current stream over a long period, normally 20 hours. This
is the type of battery you'll want for the inverter. It's normally not
suitable for starting because its plate surface area is much smaller so
it cannot maintain voltage during large amperage drains, like starting an
engine. It is rated in ampere-hours, normally at a 20 hour rate. If the
battery were rated at 200 AH, divided by the 20 hours, you get a standard
discharge current of 10 amps. Discharging it harder reduces its AH
rating. Discharging it at 2 amps increases its actual AH rating at that
current drain.

You'll see a compromise battery called a "deep cycle starting battery".
The keyword is "compromise". It has more thinner plates, making it more
susceptable to being unrechargeable when deep cycled but can produce
starting current. Don't buy one.

Batteries don't go "dead" because they run out of lead. They are
designed to save the lead so we can recharge them. Batteries run out of
acid, which creates the chemical release of electrons. Never add more
acid to "rejuvenate" an old battery. That just eats holes in the plates.

Your other problem is arithmetic, something many don't think about until
they've killed a few batteries. Manufacturers can now create immensely
powerful inverters...1KW, 2KW, 4KW are common. Here's where the math
problem comes in. Let's look at our 200AH deep cycle battery, again. A
4KW inverter, being very efficient, would draw 4.2KW at full load. At
full load the battery voltage will drop under the very heavy load to
around 12V, maybe less. 4200 watts divided by 12V = 350 amps!...far in
excess of any deep cycle batteries 20 hour rating your boat can float. A
deep cycle battery that can produce 350 amps is taller than you, about
4' x 3' and you'll need SIX of them, total weight around 12 tons.
Obviously, this isn't gonna plane well..(c; So, don't be too impressed
and go "overboard", so to speak, buying some huge inverter you think is
going to run an air conditioner, fridge, heaters, etc. It isn't going to
happen. The 200 AH battery will probably power it for 20 minutes before
the lights go out....assuming it doesn't EXPLODE when its electrolyte
boils from all that current. I think the ideal inverter size is 800W to
1KW as this lets you power the microwave for a couple of minutes to heat
lunch, without destroying the house battery. Ours on "Lionheart" is from
Radio Shack. Shhh....geez, don't let them find out it doesn't have a
ships wheel and flags on it and those thousand dollar pricetags. The
best inverters say TRIPPLITE on them, without the nautical crap. I've
been abusing a 500 watt one for 10 years. It's fine. 520 watts divided
by 13 volts (lower drain current= higher output voltage) = 40 amps, a
much more realistic discharge value. Two 330 AH 6V golf cart batteries
in series powers it for hours. See the reasoning?

The "standard" size 12 volt marine deep cycle you can nearly carry two
handed is 130AH. Deep cycle batteries are heavier. Sorry. You won't
want to carry it far. You'll soon tire of swapping it out every time you
use it. Guest makes this really nice little DUAL output 10A charger.
It's a plastic brick with a couple of LED lights on it to show you when
it's charging. It cuts off at 14V, cuts back on at 13V to maintain the
batteries in peak condition without boiling away the electrolyte. It
would be perfect in that Wellcraft. Don't buy a huge charger promising
to recharge the battery in 5 minutes. Batteries charge SLOWLY. Sales
hype doesn't change battery chemistry. The BEST house batteries, all
around, are 6V golf cart batteries from Sam's Wholesale or Costco. They
produce around 230 AH, are very rugged because they are made to bounce
around in an electric vehicle that may overturn so they also don't leak
out their caps if you turn the boat over. Their BEST feature is they are
around $70 each! You get much more power for lots less money. Buying a
130AH 12V gelcell or AGM battery for $350 from some boat store is absurd.
Just hook one battery's + terminal to the other battery's - terminal with
a #4 jumper you can buy at any car parts place. The open terminals are
12VDC. I like to put a safety fuse, available at the expensive boat
shop, in series with the jumper between the batteries, just in case the
wires get shorted. You end up with a blown fuse, not an exploded battery
distributing acid throughout the boat. If a cell shorts, it'll explode
anyways, but the fuse protects the battery from human errors.

Well, I can see you're getting ready to go to Costco to measure the
batteries and plan where they're going to be stowed so I won't hold you
any longer. Don't buy the automatic chargers from Costco. They shut off
after the charge and DON'T turn themselves back on when needed, not a
good idea.

Don't forget to take the teenage boys so you don't have to haul them to
the car....(c;