Fridge freezer issues

[Sunshine Coast]

We've purchased a secondhand power cruiser and are having some issues with the 220ltr fridge freezer. When on shore power it works a treat but when we are "off grid" and running the generator for two hours morning and evening it slowly starts to loose its cool (if you know what I mean). We currently have two x 110ah AGM batteries and were wondering if we need to bump that up to help the fridge. The fridge is 23 years old. Our intention is to be off grid as much as possible so a working fridge/freezer is going to be vital.

[Uncle Bob]

Originally Posted by Sunshine Coast

We've purchased a secondhand power cruiser and are having some issues with the 220ltr fridge freezer. When on shore power it works a treat but when we are "off grid" and running the generator for two hours morning and evening it slowly starts to loose its cool (if you know what I mean). We currently have two x 110ah AGM batteries and were wondering if we need to bump that up to help the fridge. The fridge is 23 years old. Our intention is to be off grid as much as possible so a working fridge/freezer is going to be vital.

Hi, not being physic here but I kind of see a set of batteries in your future, if you want the best bang for your buck then 6 volt traction batteries wired in series/parallel will provide good volt storage . Six of these will provide for your needs for years to come.

[owly]

Originally Posted by Uncle Bob

Hi, not being physic here but I kind of see a set of batteries in your future, if you want the best bang for your buck then 6 volt traction batteries wired in series/parallel will provide good volt storage . Six of these will provide for your needs for years to come.

Not being psycho either, I too see an array of batteries in your future. But it has reached the point where a self assembled bank of lithium ion batteries is ultimately far cheaper than the so called "traction batteries", which I assume refers to deep cycle flooded lead acid batteries, also known as golf cart batteries.

The lithium batteries may seem pricey, but when you consider the fact that they can be safely discharged far lower, they should be looked at as having roughly triple the nameplate capacity as compared to flooded lead acid batteries which do not tolerate being discharged below 80% without reducing life. Thus a 100ah lithium would provide the same capacity as a 300ah lead acid battery. The number of discharge cycles is many times more than lead acid, so many that your long term cost is far less. It is important with all batteries to have proper charge and discharge control, and this is if anything more critical with lithium batteries due to their long projected life and higher initial cost, but the equipment to manage these batteries is not expensive or difficult to use.
There are quite a few Utubes on how to assemble and manage your own battery bank, and where to get the batteries economically, and the net up front cost can be close to equal.
With solar power cost dropping like a rock, it makes sense to invest in panels and a fairly substantial lithium battery bank. In addition to running refrigeration and the usual stuff, it would be foolish not to use electric power for at least some cooking. There are a number of technologies that greatly reduce the amount of power needed.


In a perfect world...... I would design a refrigeration system for a boat such that it produced ice when there was solar or wind power. That ice would in effect be a battery, keeping the fridge cold without the need to constantly cycle the compressor on a dumb thermostat. Not all thermostats are "dumb", but even the sophisticated PID thermostats that learn and anticipate take into account ONLY the temp in the system, not other conditions such as power being generated at that time. Refrigeration is the highest power draw most of us have unless we are heating and air conditioning or motoring with electricity, so it makes sense to use ice as a virtual battery. To my knowledge, this system does not yet exist. Another way to store surplus energy is to make fresh water.... if you use a watermaker. As the farmers say "make hay while the sun shines"


H.W.

[Cpt Mark]

At a minimum I'd say new battery bank is #1 and a much larger battery bank.

More information would help too. Do you know how many amps it is drawing when powered up? How many hours in a day it is using power? What else is drawing power on your boat? Lights (LED or not?) radios, inverters, computers, charging etc. There is a lot to designing a battery system.

Let's not forget your refer box. How much insulation do you have? 23 years old is pretty old, the insulation foam may not be good anymore.

Once you're out at anchor, how do you recharge your batteries? Solar? Wind, engines, genset?

AGM batteries on a good day you get about 30% of the total capacity of the battery bank before you start to damage them. And this is not in hot climates or batteries in hot locations. LiFePo4 batteries you can use 80% of the capacity without damaging the batteries. On the negative side is you will need to revamp your charging systems including your shore charger most likely. If not, you'll destroy them fast.

I rebuilt my fridge/freezer box. A huge job. 6" of foam on the bottom, 5" on all sides and 4" on top. My box is not against a hull being in the middle of my catamaran. All of this and I still go through 100 amps a day. My stuff is all low energy and brand new.

A lot for you to think about and consider.

[Gudgeon]

Need some more information. 1. While on shore power how many hours is your fridge operating while on shore power?
2. Do you have an inverter that your fridge can operate off of correctly? Is the inverter a square wave or sine wave inverter if square wave the fridge compressor may not operate correctly.
3. How well insulated is the fridge?
You fridge may be operating more than you know while on shore power and the 2 hours in the morning and evening may not be enough time to keep it cold. With the older fridge I would ensure the insulation is not waterlogged.