12v Battery charging options

[sailguy40]

I am hoping someone can point my in the right direction here. Ok, the only item I have onboard my boat to charge my battery is a solar panel. This is good for when I go out and just run a few lights or whatever. Now, if I am planning on going for a 4 day cruise and running a 12v mini fridge, invertor and other items, the solar panel will not be enough to keep my battery charged. So my question is, what can I use to keep a charge on my battery other then a solar panel and/or gas generator? My boat runs on an outboard so I don't have an inboard diesel motor. Wondering what my options are?

[Maine Sail]

Originally Posted by sailguy40

My boat runs on an outboard so I don't have an inboard diesel motor. Wondering what my options are?

Ice, a much bigger bank or a much bigger solar panel and lots of sun..

[Ilenart]

From your description it sounds like a gen set is the only pactical option. An inverter and portable fridge is really going to suck up the juice.

For a 4 day trip what about hiring a gas / petrol generator?

Ilenart

[sailingdog]

I run the 12 VDC Engel refrigerator on my boat all summer long on a mooring using solar power.

[hellosailor]

sailguy, you'll need to work out an energy budget to get a good answer. You need to know how many watts or amps each device draws, then multiply the amps times the hours of use every day to get how many "amp hours" your whole boat needs.

Then you sit down to figure out how many amp hours of capacity your battery has (if it is one "car" battery, that's probably 70-80 when it was new) and how many amp hours you'll need to produce every day to keep the supply and demand matched up.

You might need a generator, you might be able to tap or add one to your motor (they tend to be marginal on outboards), you very likely will need more battery. Or you might decide to use dry ice and ditch the refrigerator.

You'll find watts and amps on the label on each device.

[sailguy40]

Thanks for the advice guys! Really, the main thing I want to do is just run a small portable fridge. I want to use this to keep eggs and lunch meat cold, also a few bottled waters. Only other thing I use electricity for is a cabin fan, cell phone charger, radio and laptop. None of these use much battery and rarely are they all on at the same time. Still, I am going to pickup an extra battery and solar panel, I have plenty of room onboard for this. I see no reason not to have an additional battery onboard. I do need to figure out how much I am going to be using so I can determine the best option. I never thought about using dry ice, that sounds like another great idea. With this option, I won't need a fridge at all. @SD, how many watts is your solar panel? Living in Louisiana, we get so much sun around here so it could be a matter of just getting a much higher watt panel.

[noelex77]

Fridges use a lot of power.
Some of the small fridges work without a compressor. This reduces the cost but makes them very inefficient you will need something like 150w of solar panels to be OK if it this type of fridge.

[sailingdog]

I run the refrigerator and keep the batteries topped off on my boat using a single 130 watt panel. That's probably the minimum you're going to need, but it depends on what kind of 12VDC refrigerator you have. I have an Engel MT27 (22 qt) unit. BTW, I could run it in freezer mode with that panel, but don't.

[kwaltersmi]

Other options might include a wind generator/solar combo, towable generator, or block ice. We've found that a block of ice will last at least 3 days. You can always add insulation to your icebox if you feel yours is inefficient.

[75R20]

What about a charging circuit for the outboard ? Many manfacturers offer them, and most work reasonably well.
Best of luck
Kary
S/V Mariah
#49080