Advice on solar panels

[chuck53]

Here's the situation. I have a Catalina 34 with the basic Adler-Balbour refrigeration unit in my ice box. I believe my unit pulls about 3 amps when the compressor is running.
My house batteries consist of 4 x 6v batteries, each one putting out approx 230 amp hours.
I want to leave my icebox running Sunday night when I leave the boat and have it still on when I get back on Friday. Boat is unplugged so no battery charger is working.
I don't mind if my batteries run down some by the time I get back on Friday, but of course I don't want them dead either.
How big of a panel do I need to keep my batteries not necessarily fully charged, but still with a decent charge when I get back and turn on the charger?
When we get to the boat, it takes a good 24 hours for the icebox to get to a good temp. And then, 24 hours later, I'm heading home.

[tattoosteve]

your a.b. draws 5.5 amps while running and usually runs 50% of the time, due to charging losses you probably need 100 watts. two 50 watters would probably be easier to place than one 100 due to smaller sizes. i purchased 50's from golden sun solar in brisbane ca. for 300 dollars for two, i think that is a very fair price. i actually bought six and now my problem is i can't use all the electricity i make!

[chuck53]

Good advice, but I'm not so sure about the amperage draw. I switched off everything electrical on my boat except for my refigeration. My Zantrex monitor showed between 2.5 and 3 amps and I could hear the compressor running. Turned it off and it dropped down to 0. Turned it on and off several times and each time, my monitor showed no more than 3 amps. Is my Zantrex wrong or maybe I have a little smaller AB that uses less power than most.

[mitiempo]

At roughly 6 amps half the time your daily refrigeration draw is about 70-75 AH. You have 230 AH before your batteries are at 50% SOC. If you have 100 watts of panels you can count on up to 40 AH per day based on 5 hours of good sun per day. So on a sunny day you have a net deficit of 35 AH, as much as 75 on a rainy day. If the sun shines all week you will be ok but a few cloudy days and the batteries will be down more than 50% and their life will be shortened drastically.
Do you not have shorepower available?

[Faster]

Originally Posted by chuck53

Good advice, but I'm not so sure about the amperage draw....... or maybe I have a little smaller AB that uses less power than most.

Our A-B definitely runs between 5 and 6 amps when running, and is usually at an approx 50% duty cycle. If you have a newer one it may be more efficient. If indeed you only draw 3 amps when running you're well ahead of the game.

[mdbee]

Do you keep things in the fridge during the week? Perhaps a 7 day timer could turn the fridge on the day before you need to use it. Eliminate most of your problem. A solar panels would still be a good addition but maybe not as elaborate.

I think the twin design might be a good idea too. Easier to mount and if one gets some shade on it, the other will still be producing.

[chuck53]

Yes, I have shore power available but I prefer not to have the boat hooked up while I'm not there. The marina charges extra for boats hooked up all the time - no charge for typical weekend use.

[chuck53]

You know, that 7 day timer suggestion is worth looking into. Not sure how to go about doing that, but something I had not even thought about.

I'm not concerned about keeping food cold while I'm not on the boat. Just looking to have a cold (or semi-cold) ice box when I get there on Friday night.

[tattoosteve]

even in the s.f. bay i usually get more than 5 hrs. charging location is important of course but even at less than optimal you should get more than 40 amps per day from a 100 watt panel, having said that it is always better to have more, i have 300 solar and an airex wind generator so i could probably run an arc welder, but as a full time liveaboard/cruiser i want complete independence from shorepower. which means i would guess your needs aren't the same as mine, also just because your monitor says 3 amps doesn't make it so. practical sailor tested the a.b. and they say it draws 5.5 amps while running i would trust their estimate.

[GeorgeB]

Chuck, what year (and sail #) is your Catalina? Mine is a MkII model (2000 - #1476). My A-B cycles @ 5 Amps/50% of the time as measured on my link 1000. My average electrical consumption is 2.5 Amps/hour. I'm wondering if your system isn't fully charged with freon? That could explain the "low" power draw of your compressor and that it takes 24 hours to cool down the refridgerator. Mine is cool after several hours. To accelerate the cooling process we do take a sack of ice down to the boat to get things started.