How much solar for small ice-box conversion?

[toddster8]

Just a note on some of the calculations described above.
My Isotherm icebox conversion draws around 2.5 amps, BUT it only runs about 25% of the time in hot weather, and less in cold weather.
Even without solar, the batteries can handle that for several days without charging.

[Rohan]

Originally Posted by Pete7

I would like to explore why you think this. There are lots of us running hybrid battery systems quite happily, so why not mix LFP and FLA?

Because in this previous thread from 2021 I started here, I asked that same question and the overwhelming response was that it wasn't a good idea.

https://www.cruisersforum.com/forums...es-235439.html

That video you provided was interesting, yes, it can always be done with a complicated setup, but that's the problem. It's complicated.

[newhaul]

Originally Posted by Rohan

Because in this previous thread from 2021 I started here, I asked that same question and the overwhelming response was that it wasn't a good idea.

https://www.cruisersforum.com/forums...es-235439.html

That video you provided was interesting, yes, it can always be done with a complicated setup, but that's the problem. It's complicated.

Not complex just place a b2b in between the different chemistries.

[Shoalbay]

I had a 40 qt Engel fridge/freezer that was used
as a fridge only. It’s average draw was 1.5A.
A 260w panel sufficed to charge two 125Ah
house batteries and one 125Ah engine starting
Battery for all onboard requirements during
Extended offshore passages with no engine use
For charging purposes.

[realem]

I think you have a couple of options. I had an ice box and converted the ice box to a fridge with a danfoss db 35 and the correct size evaporator plate for the box. Total cost was about $600.00. Works great. I did add insulation to the converted box to ensure it would keep cold since iI do have an old boat. I also have 2 100 watt solar panels on the boat and it runs the fridge plus fans and electronics and fully charges the batters (2 100ah AGM) Batterys are down in the morning but again fully charged by mid-day. The second option is I have an Engle 40 on the boat that I can use as a fridge or freezer. I did have an engle drop in but it died which is why I converted the ice box. I found the Engle to be very efficient and the 40 is a decent size. It will also run on 110.
It is pretty easy to convert an old ice box to fridge. Since I had the drop-in I did cut out the old box and when the engle drop-in died I installed an igloo cooler in the same spot and refrigerated the igloo.. The igloo is now built-in and you would never know it is an igloo cooler from Home depot as the countertop for the galley covers the box with a top just like the built in had

Hope this helps

[Rohan]

Originally Posted by newhaul

Not complex just place a b2b in between the different chemistries.

Oh boy - I hear that so much on this forum. Maybe if I hire a professional it's simple. But Murphy's law always kicks in and there are unplanned problems because every boat is different. Is it the right type of unit to handle these batteries, is it hooked up in the right direction, how do I hook it up and still use my battery selector switch, how do I secure the electronics inside the small space of a boat, is there a danger of water getting in, am I using the right type of wire, do I need another fuse, how do I do this safely without ruining the batteries or starting a fire? Just a few off the top of my head. When it comes to electronics, one incorrect setting or connection can make the whole system useless. You want to keep things simple, not just so it's easy to install but so it's easy to repair when something goes wrong, and it will go wrong.

Getting back to the topic at hand - OP if you aren't a pro, you want your setup to be as simple as possible.

[bensolomon]

Your solar is more than adequate. I, too, would recommend either maximizing your battery to a group 31, or buy an additional battery and connect in parallel.

Also, get a 12 volt, air cooled evaporator plate like the frigoboat Capri 50. When I bought my boat 10 years ago, she did not have any refrigeration and this is what I've added. I have been very happy with this setup.

Ben

[MikeHoncho]

As mentioned, 800w is overkill for your current needs. Assuming that your needs will increase though. Your shortchanging your system with your battery, assuming it is a 100amp/hr battery. You'll be making plenty of power during the day and running your single battery down significantly. I have an icebox conversion with excellent insulation and once cooled down it runs about 2.5 amps when cycleing. I can't guess on the total amps used in a 24 hr period. I have 2 125watt panels and a 8D Lifeline AGM rated at 220amp/hours I believe. Perfect for all my needs given the lack of consistent sun in the PNW.

[newhaul]

Originally Posted by Rohan

Oh boy - I hear that so much on this forum. Maybe if I hire a professional it's simple. But Murphy's law always kicks in and there are unplanned problems because every boat is different. Is it the right type of unit to handle these batteries, is it hooked up in the right direction, how do I hook it up and still use my battery selector switch, how do I secure the electronics inside the small space of a boat, is there a danger of water getting in, am I using the right type of wire, do I need another fuse, how do I do this safely without ruining the batteries or starting a fire? Just a few off the top of my head. When it comes to electronics, one incorrect setting or connection can make the whole system useless. You want to keep things simple, not just so it's easy to install but so it's easy to repair when something goes wrong, and it will go wrong.

Getting back to the topic at hand - OP if you aren't a pro, you want your setup to be as simple as possible.

There are many many videos on YouTube that show how to do it . Not to mention the directions that come with the unit . It's not rocket science .

[akopac]

Many posts have mentioned battery and solar panel size. You really need to take a few more steps back and look at this as a larger system picture though.
To begin with, your major power draw while not under way is the refrigeration system, HOWEVER, that draw comes from whatever heat (conducted, radiant, or convective) is leaking into the frig. box and needs to be removed by the refrigeration system. Insulation is cheaper than solar panels, controllers, batteries, and refrigeration systems.
I started a thread that has a spreadsheet to calculate the insolation and system requirements. You can do a search for it. The homework and calculations are very rewarding. These are what my system calculation final parameters were and my system seems to be matching them so far. I’m in Mazatlan now where as summer progresses water temp. and air temp will be peaking for the final true test.

[jen1722terry]

On our older and therefore narrower Cape Dory 31, we managed to insulate the existing top-loading icebox with closed-cell canned foam and installed a small NovaKool compressor. It runs well off our single, 130W, 15 year-old solar panel and two house batteries (grp. 31 AGM) and uses very little energy. Unless we get a few foggy days in a row, we never run the engine to top up the batteries. We can even turn up the thermostat a bit to make ice cubes or store ice cream if we wish, though that may require sunny days or some motoring.

With proper insulation of a top-loading ice box, you'll probably not have to motor all that much to keep the batteries topped up.

A couple other thoughts:

1. Front loading fridges spill a lot of cold air each time you open the door, so converting to a top loader will save energy in the long run.

2. You'll need a space for the compressor. We mounted ours on a small shelf in a cockpit locker and installed a small vent into the cabin for good air circulation.

3. Keep the fridge full. The food holds the cold. Even some large jugs of water help to get the fridge thru the night without using much power.

The first summer after we converted our ice box to a fridge, we thought we had gone to yacht heaven. We can take off for a few weeks with no marina stops and not return until the food runs out. We always have cold drinks. Nice.

Best of luck with the new solar panel.

[Bill O]

Originally Posted by argosail

So I have a boat under contract, turns out she does not have a fridge. I was looking at either a ice-box conversion (12V) or portable fridge/cooler (12V). There is only 12V on the vessel.

I guess I'll come at this form a different angle and ask the question, do you really need a full time fridge?

It will really depend in how and where you will use the boat in the near future. If you are working full time and will only get long weekends or a couple of weeks of vacation on the boat, why not just get an extreme cooler to handle the fridge needs. Typically an extreme cooler w/2 gal. water jugs frozen will handle a good hot week in the Chesapeake (assuming Ches. since OP lives in Philly). Since it will be a decent drive from Philly (~1.5 hrs.), you most likely will already have a good cooler to transport your food from home.

Until you own your new to you boat for a while, would take a better look at your needs vs. nice to have. While a cooler isn't ideal nor sexy, it works well w/no modification of your present electrical system and may be enough to meet your current needs.

[valhalla360]

Originally Posted by jen1722terry

A couple other thoughts:

1. Front loading fridges spill a lot of cold air each time you open the door, so converting to a top loader will save energy in the long run.

3. Keep the fridge full. The food holds the cold. Even some large jugs of water help to get the fridge thru the night without using much power.

In the old days when solar was very expensive and it was difficult to power, a top loader's better efficiency was an advantage. Of course, when you had to leave it open for 5 minutes and pull half the stuff out onto the counter in the warm air while digging for items near the bottom...not sure how effective it was in practice. The one we had was certainly a pain.

With the OP's small system, he can easily power a front loader and the ease of access with a front loader is easy to justify.

I do agree, though keeping it full really helps. The food is much more dense so it holds more "cold" and there is less cold air to escape.

[Pete7]

Originally Posted by Rohan

Because in this previous thread from 2021 I started here, I asked that same question and the overwhelming response was that it wasn't a good idea.

That video you provided was interesting, yes, it can always be done with a complicated setup, but that's the problem. It's complicated.

Actually having done it and run a hybrid system for a year its not complicated.

DC/DC charger between engine start battery and the hybrid LifePO4 (LFP) and the flooded lead acid ((FLA) battery bank. Solar MPPT re-directed to the hybrid batteries and an inverter wired off the bank. An after market fuse box made the connections simple.

In use the FLA doesn't do much, perhaps providing 10% if there is a heavy load like boiling the kettle. The rest of the time its on float. Should the LFP BMS disconnect then the FLA will continue to provide power for the VHF, chart plotter etc.

When leaving the boat we drop the LFP down to 70% or so and leave the solar on to keep the FLA charged and run the bilge pump.

Works nicely and on a smaller yacht means we don't need a huge battery bank.

Pete

[dmkkeng]

You don't mention the capacity of your existing battery however I think you will need a 2nd battery. Flooded cell and AGM batteries have a working capacity. For Flooded cell batteries it is approximately 30%. This is based on rarely get batteries charged beyond 80% and not letting them discharge below 50%. AGM batteries have a slightly higher working capacity perhaps up to 40%. So if your AGM battery capacity is 100 AH, for example, your working capacity will only be 40 amp hours.

If you fridge draws 2.5 amps and operates at a 50% duty cycle that equates to 36 AH (12 hours X 2.5 amps).

You should have 2 - 3 days capacity, that is 108 AH, this would require total battery capacity of 270 AH.

Thats an efficient fridge, my fridge/ freezer is over 4 amps.

Also keep in mind you have other electronics, a vhf radio will draw .5 -1 amps at idle, more when recieving or transmitting.You need determine your total capcity requirements.

As far as solar requirements, 800W is a lot, you likely need somewhere between 100 and 400W. Get a good mppt controller to maximize the output of your panel. Someone else mentioned 250W that sounds about right.