625ah Battery or 450ah and 400 Solar ?

[Ex-Calif]

Originally Posted by Jimbo485

............

"What did you say? Who is Ra??? No more interruptions, Watson! Please, just STFU and pray!"

Excellent!

We used to live in a house with no water mains. Storage in tanks and rain collection.

When the tanks got low near end of summer, we took weekly baths not daily. 3 boys all bathed in one tub, or went in turns with the same water.

Your point about conserving energy when you need to is not lost on me.

[Maine Sail]

Originally Posted by engele

The SAMs Club stores on the West Coast all carry "Energizer" brand batteries. So it looks like I am back to T105s.

The Energizers are made by Johnson Controls, and while not bad quality, I have a number of customers on year 6 & 7 with those, most easily exceeded 5 years, they are probably not in the same league as Deka/East Penn, US Battery, Crown, Superior or Trojan. There are lots of good options in the US for 6V golf cart batteries.

[engele]

In my case it probably isn't worth driving four hours, the $40 Sams Club membership, and then ending up with the Energizer batteries. We are planning to be out for an indefinite amount of time, anywhere from six months to five years or more depending on how much we like it. I would totally purchase a rebranded Deka for $80 given the opportunity. We have Crowne and Trojan's available in town. Both are expensive. Anyhow, I do appreciate everyone's input.

[nwdiver]

I have 480 in 12volt house bank and have 450 in solar.
I have a keel cooled frig/freezer that uses 50-75 amp a day and navigation and lights with music it adds another 25-50, but often when moving and using nav equipment I am under power part of the time (I have a 120 amp alternator).
I find on the hook for several days using my water maker is all about watching my charging, often by noon my batteries are topped, I then use the water maker to make water for much of the afternoon and my batteries stay, topped up. It doesn’t happen all the time but when it looks like it will happen, often a couple of times a week I make water not waste the solar power. I have looked at wind and realized adding another 100-120 in solar will work better and be cheaper, even in the PNW.

[engele]

This is basically what I want to be able to do. Run the watermaker, autopilot, nav gear and fridge without needed to start the engine. I think added solar will do it.

[SunDevil]

Originally Posted by engele

This is basically what I want to be able to do. Run the watermaker, autopilot, nav gear and fridge without needed to start the engine. I think added solar will do it.

I would look into finding a way to only run the watermaker when it is sunny. The fridge might be on a timer so it wouldn't come on between 1am-7am. If it is insulated enough and you don't open the door very much between that time, it shouldn't cool off too much. You would want to test this out though and adjust the time. Outside temps also play a factor.

[s/v Jedi]

Originally Posted by SunDevil

I would look into finding a way to only run the watermaker when it is sunny. The fridge might be on a timer so it wouldn't come on between 1am-7am. If it is insulated enough and you don't open the door very much between that time, it shouldn't cool off too much. You would want to test this out though and adjust the time. Outside temps also play a factor.

Ehrm no, you do not want to do this. The only way to save energy by turning off the fridge is by letting it warm up, which reduces the difference between inside and outside temperature. It's easier to just adjust the thermostat to a higher setting then. Which is all a moot point because your food will go bad much earlier so you don't want that anyway.

If the isolation is so good that the temperature doesn't go up much, then is costs very little energy to keep it where it belongs. It is, however, sheer impossible that the fridge cools off when you turn it off.



ciao!
Nick.

[SunDevil]

You aren't really trying to save power though, you are trying to use solar power when it is available instead of battery power.

It seems like an engineering problem that some college students should design the most effective way to power refrigerators by cooling them down quite low when excess solar power is available, yet uses battery power sparingly at night to keep the inside temperature below the level that would make food go bad.

[s/v Jedi]

Originally Posted by SunDevil

You aren't really trying to save power though, you are trying to use solar power when it is available instead of battery power.

It seems like an engineering problem that some college students should design the most effective way to power refrigerators by cooling them down quite low when excess solar power is available, yet uses battery power sparingly at night to keep the inside temperature below the level that would make food go bad.

Yes, these systems have been around a long time... they use holding plates to store the cold and they sense a higher than normal battery voltage to decide when to go in "overdrive". However, and here it comes, the efficiency of holding plates is worse than that of batteries combined with thin evaporator plates in the fridge. So in the end, the best thing to do is store excess energy in the batteries to be used for the fridge at night.

ciao!
Nick.

[engele]

I would totally agree with you Nick, except on one thing. Batteries die off sooner than holding plates. Using a holding plate to store energy may not be quite as efficient as storing it in your battery bank, but it is certainly a more durable place to store energy and makes sense if the fridge is smart enough to ramp up when it senses excess charge capacity. Our fridge isn't that smart though. I think I am going for the solar and maybe even lesser batteries than what I originally planned. Given we are making 225ah work currently, doubling that and adding solar should make needing to use the engine to charge less common. I hope this thread has been as useful for someone else than it has been for me. Thanks,

[s/v Jedi]

Engele,

Exactly about how big a solar array are you talking? If you want to go to solar for 100% if your energy requirements, you must understand that you will consume all you generate, regardless how much that is. This is the human character at play.

With batteries, you only need capacity for night time use which, for refrigeration, is only about 25-30% of the 24 hour energy use of the fridge. The load this gives on batteries does not change the requirements of your battery bank which you also need for other purposes. This means you need to buy them anyway removing their durability from the equation.

If you are looking into saving energy, it is better to improve insulation. If you are looking into saving money, holding plates are not the way imho.

cheers,
Nick.

[noelex 77]

Some of the Danfoss compressors are variable speed and can be adjusted.. It only needs some very simple electronics to do this.
Speeding up the compressor and decreasing the temperature should be an easy and cheap way to store "electricity" when excess power is available.
The isotherm ASU utilizes this.

Another winter project.

[engele]

My main dilemma was trying to decide if I really needed 625ah, or if 450ah would be enough after we added the watermaker usage to our energy load. 225ah has been great so far. We really don't use all that much and the 60w of solar and the wind generator almost keep up as it is. Hotter temps, the fridge, and the watermaker made me want to increase capacity. I think that going to 450ah and adding the ability to keep that 450 charged up is a good strategy.

[s/v Jedi]

Originally Posted by engele

My main dilemma was trying to decide if I really needed 625ah, or if 450ah would be enough after we added the watermaker usage to our energy load. 225ah has been great so far. We really don't use all that much and the 60w of solar and the wind generator almost keep up as it is. Hotter temps, the fridge, and the watermaker made me want to increase capacity. I think that going to 450ah and adding the ability to keep that 450 charged up is a good strategy.

It is. Scale the batteries for getting through the night and scale wind and solar generation to your minimum requirements plus some for luxuries. We can live and operate Jedi on 660W solar only and that includes fridge and freezer and anchor light etc. but not the watermaker.

cheers,
Nick.

[The Boat Galley]

We cruised the Sea of Cortez for 6 years -- 450 amp-hour bank, with 453 watts of solar, no wind generator. In the summer, we used about 7 gallons of water a day -- would have liked a tad more but 7 got us a Sunshower every couple of days and plenty to drink and cook (you say you've never used more than 4, but in a tropical summer you'll be surprised at how much water and water-based drinks you go through).

With that setup, and it's VERY sunny in the Sea of Cortez -- very few cloudy days -- but also hot and we had the refrigerator running and plenty of Caframo fans, we pretty well balanced out. The solar almost fully recharged us each day -- so if we motored in/out of an anchorage once a week, we'd top it up.

We watched our energy usage (turned off stuff we weren't using, etc.) but had a decent lifestyle -- SSB and ham, computer, e-mail, downloading photos from the camera and editing, lights, lots of fans, watermaker, refrigerator, etc. But your exact equipment and lifestyle might be different from ours and hence your energy needs different.

I'd be very tempted to go with more solar. Several years ago, I wrote an article for Blue Water Sailing with a cost analysis on our solar installation. A copy is on my blog:

Dollars and Sense of Solar Panels -- it's a PDF

Have fun wherever you go!