Is there anyone here doing this? I have a 26' cruiser with a Mermaid
Marine A/C unit (6500) btu. I only want to use the air on the water for
about 4 to 6 hours a day and maybe an occasional over night stay. I am
looking at a Prosine 2.5 and will probably use 2 or 4 optima batteries.

Any input would be appreciated

Ronny

Ronny:

You will need more and bigger batteries, probably more than you can
reasonably stow. At the current draw necessary to start the compressor on
that unit, you will get maybe 60 usable amp-hours out of a 125 amp-hour
battery (typical group 30 wet cell), or about 1 hour of use. I have a 1500W
modified sine-wave inverter (not quite as "clean" as a pro-sine, but 90%
efficient) with two group 30 dual-purpose wet cell batteries and a 3 stage,
140A alternator to charge them while under way. Just out of curiosity, I
tried running my A/C from the inverter, and got not quite two hours before I
got a low-battery alarm while the compressor was running (not just at
start-up). As to the Optima batteries, AGM is good technology, but the
storage capacity is not all that high. Their biggest single deep cycle
(DM31) is 75AH, and about $200.00. You might get 50AH out of it at the
current draw necessary, for about 50 minutes of use on a modearately warm
day. You would need 8 batteries for an overnighter. Sorry to burst your
bubble.

Soft water in Michigan soon!

Terry

it was tried a number of years ago by quite a number of vendors. None stayed
in business. To this day, have not heard of anyone doing it successfully.

On Wed, 17 Mar 2004 18:52:35 GMT, Ronny wrote:

Is there anyone here doing this? I have a 26' cruiser with a Mermaid
Marine A/C unit (6500) btu. I only want to use the air on the water for
about 4 to 6 hours a day and maybe an occasional over night stay. I am
looking at a Prosine 2.5 and will probably use 2 or 4 optima batteries.
================================================== ====

The Prosine 2.5 is a good unit and it will definitely supply enough
starting current *IF* you have a big enough battery bank, and *IF*
your battery cables are properly sized.

There are two big IFs there.

First the battery bank: Your A/C draws about 7 amps at 120 volts.
That will translate to 70 amps at 12 volts. 70 amps for 6 hours is
420 amp-hours, which will require a deep cycle capacity of 840 hours
in order to follow the 50% maximum discharge rule. You will need 8
golf cart batteries in series-parallel, weighing about 500 pounds,
and costing about $500 USD. That is the cheapest way to get the kind
of capacity you need, but not necessarily the best way because of
technical issues with 8 batts in series-parallel. You are also going
to have issues finding that kind of space on a 26 foot boat, not to
mention the weight implications. Anything less than 500 pounds of
lead acid batteries will be inadequate regardless of type or
configuration.

The second IF is easier to resolve but frequently overlooked. You
will need BIG cables between the inverter and battery, or voltage drop
will be excessive during the high current compressor start. I'd
recommend something like 2/0 cable with professionaly crimped and
sealed end connectors. West Marine has the cable at about $6 per foot
but it's a bear to work with.

If you continue to think about the AC or just to have a good house bank
consider using golf car batteries.

Hi Ronnie,

I have an 8000 btu ac/heat unit. I did not have enough room in the
engine compartment for a built in generator, so tried the inverter thing.
Its ok if you are underway and have a 100 amp alternator constantly
charging. At anchor, my 2 group 27 house batteries will run the unit on the
inverter for about one and a half hours. Don't forget besides the a/c you
also have the 115v circulating pump drawing amps.

My solution was to set a Honda EU2000 suitcase genny on the swim platorm
and plug in the shore power (via adapter cord) The unit is very quiet, and
does not shake the boat like a built in diesel genny. It runs the a/c almost
all night without a refill.

The Honda 2000 is a little under powered wattage wise. If I am charging
batteries or cooking I have to shut off the a/c. Since little Honda was
stolen in a break in last month, so I plan to replace it with a larger unit.

EU3000. It is a little heavier and a little quieter, and has an electric
starter. I plan to set it in a "dog box" on the swim platform to keep it out
of the weather.
The EU units put out very stable, spike free, electricity, so you can even
run your lap top or DVD staright off the genny. Thay also have a number of
"user friendly" features like low oil shut off, GFI, and overload
protectors. They are easy to refuel too.

It just depends on your (or your wife's) power needs. My wife likes a/c
and amenities so.....

--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"Ronny" wrote in message
8...
Is there anyone here doing this? I have a 26' cruiser with a Mermaid
Marine A/C unit (6500) btu. I only want to use the air on the water for
about 4 to 6 hours a day and maybe an occasional over night stay. I am
looking at a Prosine 2.5 and will probably use 2 or 4 optima batteries.

Any input would be appreciated

Ronny

If you continue to think about the AC or just to have a good house bank
consider using golf car batteries.

do NOT continue to think about it. no one else has made it work.

, my 2 group 27 house batteries will run the unit on the
inverter for about one and a half hours.

considering that 2 group 27's will put out about 100 amps in an hour and a
half, or about 1,200 watts or about 3,600 btu's, you a/c unit ain't putting
out but about 1,000 btu's per hour of cooling.

not a hell of a lot.

Huh?
--
Capt. Frank

__c
\ _ | \_
__\_| oooo \_____
~~~~|______________/ ~~~~~
www.home.earthlink.net/~aartworks
"JAXAshby" wrote in message
...
, my 2 group 27 house batteries will run the unit on the
inverter for about one and a half hours.

considering that 2 group 27's will put out about 100 amps in an hour and
a
half, or about 1,200 watts or about 3,600 btu's, you a/c unit ain't
putting
out but about 1,000 btu's per hour of cooling.

not a hell of a lot.

don't understand your question, but will try to explain what _may_ have been
your question.

An a/c unit will use about 1,400 watts electricity input to remove every 1,000
watts of heat.

1,000 watts = 3,012 btu's(according to the figures used by th HVAC industry [I
have family in the business long term])

A group 27 battery usually has aboout 100 amp-hour capacity, of which about 50%
is usuable. 2 grp 27's will give about a total of 100 amps before going dead,
as in unusable

100 amps at 12 volts = 1,200 watts = 3,600 btu's

across 1-1/2 hours that makes for about 2,400 btu's per hour INPUT (about 800
watts, about 65 amps).

Which makes for about 1,800 btu's of cooling.

sorry I used the 1,000 btu figure as I was just doing the numbers quickly in my
head.

btw, 1,800 btu's is about the cooling capacity of 12# of ice melting.

In other words, for drawing your 2 grp 27 batteries to their knees in an hour
and a half you will get about the cooling capacity of throwing about 18 pounds
of ice on your cabin sole.

, my 2 group 27 house batteries will run the unit on the
inverter for about one and a half hours.

considering that 2 group 27's will put out about 100 amps in an hour and
a
half, or about 1,200 watts or about 3,600 btu's, you a/c unit ain't
putting
out but about 1,000 btu's per hour of cooling.

not a hell of a lot.