Solar, Batteries and Fridges...oh my

[gusdog]

I upgraded to a Block Island 40 this past fall and it will be moored in Midcoast Maine. It has an installed and working Norcold de0051 refrigerator, but I don't have the juice on my 12V system to run it on battery. The label on the fridge says nominal DC 12/24V 3.0/1.5A
I was thinking of setting up a 3 bank battery system: start, house and fridge. I would like to have the fridge always on so that I can leave a few things behind and not have to always drag everything to the boat for every trip. I was thinking of 2 50W panels, a Victron Cyrix battery combiner, and a Victron Charge controller and of course a few batteries. I did get recommendations from the folks at Victron NA, but that was before I had the idea of having a 3rd bank just for the fridge.
I know the fridge will not run 24/7, but how much it runs depends on many factors such as temp, how much is in the fridge, how many times my 4-year-old opens the fridge, etc.
So, my questions are 1.) has anyone set up a similar system? 2.) is having the fridge on its own bank a silly idea? I have pressurized water, a mix of different lights (LED and incandescent), circulation fan on new Airhead composter and I don't want to not have enough power to run everything. 3.) what size battery should I be putting in for the fridge and how many? 4.) is the dual 50w solar panel setup enough?

be easy on me, I am a noob to solar and am comfortable with electrical, just not super knowledgable.

Let the beatings begin

[djousset]

Following this thread.

[hlev00]

Separate battery banks aren't necessary though you might consider a low voltage disconnect. The Victron MPPT controllers have one built in. It does cycle the load on and off as it learns the load characteristics. Or you can install a dedicated disconnect. One example - https://www.bluesea.com/products/763...age_Disconnect Some food might go bad but better than ruining your batteries.

Some quick calculations, I think in Maine you will be short on solar but there are so many variables that a lot more information is needed. Will they be mounted horizontal? What shading problems might arise with their location? Are you on a mooring (shading more likely)? What months do you need this to work? When you are on board using more power, can you run the engine to make up for shortfalls? Then you mostly need to size the solar to account for sustaining the fridge and bringing your batteries back up to 100% while you are away.

You might contact Ocean Planet to help with the sizing as assessment.

Harry

[Shanachie]

I run my Dometic Cold Machine with similar draw 24/7. Depending on the time of year and what we're doing, it will draw somewhere between 35 and 80 amps a day.


I use two 160 watt Renogy solar panels with a Renogy MPPT controller. (Plus two 30-amp maxi fuse blocks, one just after the panels and the other between the controller and the batteries.)


This provides plenty of power in Florida to the point where I haven't even activated 110 power at my dock. I can cruise indefinitely without plugging in.



There's no reason to go small or cheap on solar. You can buy the panels for about $400 (get the rigid ones), the controller (NOT PWM) for less than $100, the fuse blocks for $60 and 10-gauge wire for $30 or so.


I built a frame of SS tubing that connects to the stern rail, the two backstays and the bimini frame for support. That was a couple of hundred dollars.

[Lost Horizons]

Originally Posted by gusdog

2.) is having the fridge on its own bank a silly idea?

Yes. Serves no purpose and makes things more complex.

Expect 300-350 watt-hours from two unshaded 50 W panels per day in a summer, 150-200 watt-hours in winter. Your refrigerator will need about 800 watt-hours a day if 3 A is the average current, or approximately 400 watt-hours if it is a maximum current with 1/2 duty cycle.

[moseriw]

That is why everyone believes to put in a few Watts and drive a 160KW E-car.
Wont work and it does not matter if yur boat is 11 or 14m you should calculate a daily consumption of 150 to 180 Amps / 24 hrs and the posibility to regenerate the required power.

DO NOT THINK you will use the fridge only 2 hrs a day. Reality is if you col down you will need 5 Ah for 6 hrs. If you keep it on standby it will need 1,5 - 1,8 Ah.

So better keep it on standby. Same with every other unit like Autopilot etc. You think you will run the AP only 2 hrs a day? OK and then?

[Adelie]

Originally Posted by hlev00

Separate battery banks aren't necessary though you might consider a low voltage disconnect. The Victron MPPT controllers have one built in. It does cycle the load on and off as it learns the load characteristics. Or you can install a dedicated disconnect. One example - https://www.bluesea.com/products/763...age_Disconnect Some food might go bad but better than ruining your batteries.

Some quick calculations, I think in Maine you will be short on solar but there are so many variables that a lot more information is needed. Will they be mounted horizontal? What shading problems might arise with their location? Are you on a mooring (shading more likely)? What months do you need this to work? When you are on board using more power, can you run the engine to make up for shortfalls? Then you mostly need to size the solar to account for sustaining the fridge and bringing your batteries back up to 100% while you are away.

You might contact Ocean Planet to help with the sizing as assessment.

Harry

Maine is not going to be a problem. When it’s warm out the days get really long. When the days get short it also gets cold. Issues may arise in March and more likely Sept. near the equinoxes. Sun is relatively low in the sky but days haven’t gotten long enough to make up for it.

I would go with 1 or 2 banks.

With house and fridge on a single bank the batteries in the bank will actually produce more power because the average load for each battery will be lower.

If you decide to have a separate starter battery, I’d toss out a 10-20W panel with a PWM controller to keep it charged. Unless you have a monster engine each time you start the engine you use less than 1Ahr of power.

100W is marginal for keeping the batteries up. Rule of thumb for a solar panel on MPPT controller is average daily production in Ahr is 1/3 the nameplate capacity in Watts. That’s 33Ahr for 100W of panels.

Rule of thumb is 50Ahr/d for a fridge. Will vary with insulation, box size, system efficiency.

[MJH]

Originally Posted by gusdog

I upgraded to a Block Island 40 this past fall and it will be moored in Midcoast Maine. It has an installed and working Norcold de0051 refrigerator, but I don't have the juice on my 12V system to run it on battery. The label on the fridge says nominal DC 12/24V 3.0/1.5A
I was thinking of setting up a 3 bank battery system: start, house and fridge. I would like to have the fridge always on so that I can leave a few things behind and not have to always drag everything to the boat for every trip. I was thinking of 2 50W panels, a Victron Cyrix battery combiner, and a Victron Charge controller and of course a few batteries. I did get recommendations from the folks at Victron NA, but that was before I had the idea of having a 3rd bank just for the fridge.
I know the fridge will not run 24/7, but how much it runs depends on many factors such as temp, how much is in the fridge, how many times my 4-year-old opens the fridge, etc.
So, my questions are 1.) has anyone set up a similar system? 2.) is having the fridge on its own bank a silly idea? I have pressurized water, a mix of different lights (LED and incandescent), circulation fan on new Airhead composter and I don't want to not have enough power to run everything. 3.) what size battery should I be putting in for the fridge and how many? 4.) is the dual 50w solar panel setup enough?

be easy on me, I am a noob to solar and am comfortable with electrical, just not super knowledgable.

Let the beatings begin

Every in-depth article I have read on successful refrigeration has started/mentioned the need for maximum insulation of the refrigerator/freezer boxes for the intended use. It is something most don't want to even think about but without it the system is just chasing an impossible target. Don't assume the boat manufacturer did this as most if not all boats have inadequate refrigeration insulation.

I would take some accurate measurements and determine exactly what insulation material and how much of it (inches) has been used. With that information you should be able to get some idea whether successful refrigeration is possible with what you have or if you will be chasing an elusive goal without a significant upgrade of the box.

Good Luck.

~ ~ _/) ~ ~ MJH

[Martkimwat]

It is interesting to read the various responses on here, there seems to be some odd misconceptions about refrigeration, one being that because a unit has a 3Amp draw, its current usage will be 3x24=72 Amps in a day. I have a Dometic refrigerated coolbox that draws 4.5~5Amps when running, however because it only runs for about 1 minute in four or five, its average daily draw is only 25~30Amps. I have theoretically 150W of solar panels on my boat but not all can see the sun at the same time so typically half that (75w) or less. they keep my coolbox, lights (LED) and sensible use of an FM radio going indefinitely UNLESS there is a long period (several days) of heavy overcast when the batteries start to get down to 70%SOC.I have two 115Amp SLA house batteries and one 55Amp start battery. They are connected to a smart charging system that will connect all the batteries once the the house batteries are topped off (usually around midday on sunny days).

The biggest variable as MJH has said above, is the size and insulation that you have on your fridge. I am in the process of changing my setup to a built in refrigerated cool box. the box is 65 litres (as opposed to the 25 litre Dometic coolbox ) but most importantly I have insulated it with 25mm VIP panels which have the same R value as 200mm of normal bluefoam. It will be interesting to see what my average current draw will be when it is all up and running. I am hoping it will be similar or even better than the Dometic cool box which only has 30mm of normal foam insulation around it. When I took the coolbox out of the boat to check the insulation, it had an average of 30mm of spray on foam around it with it being as little as 15mm in places. Due to the confined space, there was no room to put any more insulation around it hence the High tech VIP panels. (used to transport human organs and frozen or refrigerated vaccines (think the Phizer Covid vaccination).

[joelhemington]

Originally Posted by gusdog

I upgraded to a Block Island 40 this past fall and it will be moored in Midcoast Maine. It has an installed and working Norcold de0051 refrigerator, but I don't have the juice on my 12V system to run it on battery. The label on the fridge says nominal DC 12/24V 3.0/1.5A
I was thinking of setting up a 3 bank battery system: start, house and fridge. I would like to have the fridge always on so that I can leave a few things behind and not have to always drag everything to the boat for every trip. I was thinking of 2 50W panels, a Victron Cyrix battery combiner, and a Victron Charge controller and of course a few batteries. I did get recommendations from the folks at Victron NA, but that was before I had the idea of having a 3rd bank just for the fridge.
I know the fridge will not run 24/7, but how much it runs depends on many factors such as temp, how much is in the fridge, how many times my 4-year-old opens the fridge, etc.
So, my questions are 1.) has anyone set up a similar system? 2.) is having the fridge on its own bank a silly idea? I have pressurized water, a mix of different lights (LED and incandescent), circulation fan on new Airhead composter and I don't want to not have enough power to run everything. 3.) what size battery should I be putting in for the fridge and how many? 4.) is the dual 50w solar panel setup enough?

be easy on me, I am a noob to solar and am comfortable with electrical, just not super knowledgable.

Let the beatings begin

Why limit yourself to 50 watt panels if energy is your concern? Higher wattage panels don't cost that much more per watt and are usually about the same size. You do want to parallel wire each panel to it's own controller to reduce shading reductions - and do use at least size 10 wire as low voltage items are extremely susceptible to voltage drop over runs of more than 20'. Cooling devices like fridges and freezers are more efficient if there's less air space to cool. Plastic jugs full of water are a good way to fill up space - I prefer to use beer for that (at least in the fridge).

[4eyes]

I don't know nuttin' from nuttin' about solar or refrigeration.

BUT I do have a solution to a four year old fanning the refrigerator door.

We bought our grandkids their own cooler and let them decorate it with stickers as they saw fit. We fill it with a cold-pack and juice boxes, water bottles, fruit etc. in the morning and top it off in the afternoon.
They think that they are hot stuff for having their own cooler and stuff inside. We don't have to worry about the fridge door being left open, or the ingredients for dinner spilled onto the floor.

[GoneDiving]

I'm not a fan of multiple small house banks as one large one give lots of head room for one item to have a high usage day and recover with out flattening its battery.

Eg load a fridge with new shopping on a cloudy day. Everything will still run and be recharged when the sun comes out vs flattening one battery while others could have provided power.

Obviously, no charging for long enough will see the whole boat go dark but if the bank is sized appropriately to start with that should be a rarity

[jackjb53]

I can't help you with the solar info...just starting to look at solar myself. I do have a suggestion about leaving your food in the fridge/freezer. A delivery captain advised me to leave a cup of ice cubes in the freezer portion of the fridge. If on your return to the boat the cup is filled with a solid mass of frozen water and not cubes, you can surmise that the power to the fridge was off long enough for the cubes to melt and the food to spoil.

[Don C L]

Welcome aboard gusdog! As you can see the crowd here is a pretty gentle lot.

[stormalong]

Get as many solar panels that you can fit in the place you have to mount them. Choose the dimensions of the solar panels to make maximum use of that space.

If you have a bimini and your boom does not extend over it that is an ideal place to locate solar panels.

Solar is inexpensive these days and you will never regret having some extra capacity for those reduced output cloudy days. MPPT charge controllers will cost more than the panels.