How do you feed oddball voltage back into a battery

[Donald Tyson]

Perhaps I don't know a bit of what I'm talking about but hear me out... If I have a solar panel and the sun is brighter or less bright varyingly all day long what converts it to exactly the 12 V that your battery can store, providing you're using solar to recharge your batteries? Is there some sort of transformer that helps the current re-enter storage at a safe Amperage?

Is there any advantage to using an inverter aboard such a small boat as a CD25 or 22? After all, there are 12v versions of almost everything used onboard these days...coffee perculators, high speed chargers for cell phones and computers, Refridgerators/freezers and so much more. Why not just work 12v appliances and be done with it on small vessels?

Are AC appliances and chargers somehow more efficient than 12V?

Is an automatic cutoff available for the protection of lead acid storage batteries?

What should I be asking that I'm not?

[ssobol]

You need a MPPT solar charge controller between the solar panels and the battery.

One problem with 12v appliances is the current demand. This can require heavy duty wiring. Sometimes 12v versions of things cost a lot more than the 120v versions because of the laws of supply and demand.

[Robert H. Wilkinson]

ssobol answers most of your questions - controller, wiring size(and cost), and cost of appliances. Also availability - if your coffee maker bites the bullet on a cruise a 120v can be replaced most anywhere while 12v items are harder to source.

Most inverters will have a low voltage cutoff or alarm at about 10.5v

Rob

[Donald Tyson]

I understood the wire size but had always thought that the 12V appliances were less expensive. Never thought about how tough replacement could be while out on the run.
Okay, I'll be back on this subject when I finally get a boat. I see that it can be an easy thing to get all this right with all the help offered here.

[thataway]

Truck stops, like Pilot or Flying J are a good source of 12 volt appliances. However many of the newer trucks come with an inverter and can use off the shelf appliances. For pure resistive loads, like a cooking pot, the 12 V. is less expensive to make--but the volume also figures in on costs. There are also warming ovens in 12 volts.

The 12 V microwaves and induction burners are few and far between. Many use a built in inverter to give the 120 volts AC.

I have been using inverters for over 50 years---the first was power a portable organ on a boat for a Christmas parade. It worked, except an objectionable hum. I had to build a filter to get rid of that. Inverters have come a long way. The Victron Multplus series is my favorite--it has a PSW inverter, a high powered battery charger, a voltage and power booster (at the end of the dock you may see 90 volts, it converts this to 120 Volts, and also if there is an over load it can put out additional power to correct that. It is an autommatic switch from mains power to battery power.

[Tom Hruby]

If you are a heavy power user (say hot pot and electric cook stove, hot water heater) I would not plan on using solar power to provide your only source of power. A solar panel laying on a relatively flat surface (not oriented to the sun) will produce about 10 watts/ square foot. Thus, over a day here in the mid-latitudes I can expect a maximum of about 80 watt-hours per square foot per day. I have about 12 square feet on cabin top on my 22' C-dory, so I can expect a maximum of about 1kWhr of solar energy per day. Appliances that use resistance to heat (hot pot, water heater, stove) usually run at 1200 - 1500 watts. Thus, your solar input would allow you to run your appliances no more than about 35 minutes a day total (assuming your inverter is at least 90% efficient). This does not account for the other electrical needs (lights, fans, etc.)