Running refrigerator on solar alone

S

Sealeggs

Well-known member
Joined
Sep 8, 2016
Messages
57
Fluid Motion Model
C-26
Hull Identification Number
Fmlr2521a414
Vessel Name
SeaLeggs
Stayin temporarily at marina with no shore power
Will solar maintain the refrigerator without draining the house battery on our R 25 SC
 
I don't have any direct knowledge of how long the batteries will stay charged by solar, but what i was told during the factory delivery and from word of mouth from others is the single solar panel would only keep the fridge going a few days. Not worth killing your batteries finding out how long you will get without power available.
 
It all depends on how much sun you have. I joined my thruster battery to the house and I am good for a couple of days.
 
Like Mike we were good for a couple of days if the batteries were topped off when we docked. If you're staying longer then that you could always untie and go for a ride to let the engine alternator charge the batteries back and or run the generator if you have one.

Jim F
 
My experience is the same as Mike and Jim’s, just two days for me with one panel. I did find, with sunny days, I would run the fridge during the day and shut it off at night. That would extend power for another day or two but with the refrigerator you are dealing with diminishing returns for recharge with just the house batteries.
 
I am running two fridges and a small freezer (no wine cooler). I switched to an MPPT type of solar charge controller and have had no issues. I tested the setup by docking with no shore power.
 
Hi, Sue

We have a new C28. Could you tell me more about your switch over, and how it differs from the original setup.

Please assume minimal knowledge and experience on my part.

Thanks, Bob
 
I've been running a bunch of tests this spring with the fridge running (in a hot buttoned up cabin) with no shore power charging. I've gone easily the past 5 days on solar power only (during rather rotten overcast and rainy days) and my house batteries are at 13+ volts.

Early on, I was told that the solar power was supposed to do that so you could leave the boat at a mooring and leave the fridge stocked and running.

I do know that the solar panel (while covered with shrink wrap) was still, easily able to keep the batteries happy.
 
rpmerril,

Yes, It is possible.. but be careful, Our fridge plus ancillary items draws about 2.5 amps on average.

2.5 amps x 24 hours = 60 amp hours per day usage.

If you have a single solar panel from the factory you can expect 10 amps at best during the middle of the day in direct sun with no obstructions. Given the varying sun angle and daylight hours you are likely getting less than 5 amps charge on average from the solar panel over 12 hours. Over 24 hours that averages to 2.5 amps or

2.5 amps x 24 hours ='60 amp hours of charge per day.

There you go! Charge maintained. However, this assumes a clear day. Given the cloudy conditions you describe I suspect you are getting even less charge than this, but you are also getting more hours of daylight this time of year so let's go with it.

If you are seeing 13+ volts on the batts they are likely under solar charge and thus that is not a reliable indicator of state of charge (SOC). You need to check the batteries when not under charge (after the sun goes down) and when the refrigerator has been off for at least 30 minutes (turn the breaker off to check). If you are still above 12.6 volts you are probably good to go. Less than that and you are slowly depleting them each day due to variation in the assumptions above. It doesn't take much to make these numbers go the other way!

I agree that in the best conditions it may be possible that the refrigerator could be left on with nothing else turned on in the summer (no one on the boat using stuff). However, I would confirm, what your average draw is, what sort of average charge you are getting from the solar panel, and what your actual SOC is before counting on it. The numbers can go the other way quickly!

Curt
 
All good points.
I recently got a nice clamp on ammeter and I should check the amp draw.
I doubt if it draws full amperage 24 hours a day. My manual on the fridge doesn't even quote a number. I'll guess it is on the nameplate somewhere. The other thing to document is the run time under several conditions, bright sun, dim sun and no sun, plus hot cabin and cool cabin.

I do have a couple other items that are enegized continually. All I can think of is radio memory, TV memory (I think) charger for a flashlight, gas valve/detector, CO detector and bilge pumps (God forbid).

Fun stuff, our little hobby, eh?
 
Yes, the amp draw for the fridge is on the label. Ours draws about 4 amps when on and cycles about 50% of the time so I used 2 amps. We have about a .5amp draw with all the switched items off so I added that to get 2.5 amps.

If you are averaging 5 amps of charge over 12 hours you are doing much better than we ever do out here in the NW. I can only count on about a 3 amp average throughout the day (40 amp hours total if I am lucky) and worse than that of it is cloudy.

I have added a second solar panel this year and I will report back on how it does over the summer.

Curt
 
I want to reinforce Mike's approach (which we borrowed from him on our 27): wire the house and thruster batteries together and you get a 50% boost in available amp hours. We found this really reduced drama over leaving the fridge on.
 
Not such a crazy idea! I like it too.
 
No question that Mike's approach is the simplest way to increase storage capacity. I suspect I will be making that mod soon!

However, it doesn't change the the numbers for usage vs. generation. Even with more storage you will eventually run out of juice if you can't get them recharged. In my case I am trying to get close to a balance between generation and usage such that the boat can be off the grid with both our fridge and freezer running (about 5 amps continuous). Yes, we could run the engine every several days but I'd like to not bother for several reasons. We often visit friends for several days. We just anchor the boat and leave it and need to keep the fridge and freezer running. We also often go to the state parks in the San Juans for several days and I don't like to run the boat at the dock and disturb others (Better now with reduced smoke on start up due to new SW!) I want to know that the batts will not be stressed in these situations (went through one set of AGMs already) and to ensure this over many days means increased generation. Having said this, the more storage capacity means a higher SOC overnight and happier batteries. Given this I will be adding in the Thruster battery soon to the house set.

The question remains. Does anyone know why the factory wires the boat with a separate thruster battery? What are the negative implications to combining it with the house set? The only reasons I can think of are 1) ensure you have thrusters when you leave the dock/anchorage, and 2) maybe the house lights flicker or equipment is affected when you use the thrusters when they are combined? Are either of these a real concern?

Mike and Hydraulicjump, do you ever disconnect the thruster from the house? If so, why? If there are no negatives I can't see any reason to not just connect them permanently. If anything, I think I'd rather have the option to switch the thruster to the start battery to get off the dock if the house is dead. Maybe a switch to just switch the thruster between the house and the start?
 
The thrusters can/do take a lot of juice and suspect this is why RT wires the thruster battery to be a standalone. If I recall, the thruster(s) have a 150 amp fuse 😱 .

I guess you could always add an additional battery for your needs.
 
I have the switch so I can isolate the thruster if I want to. I keep it connected all of the time. Never had an issue. I look at it this way, the thrusters are used when the engine is running, so you are getting a charge from the alternator anyway. Chances are the extra amperage from the house helps the thrusters.
Curt, You may seriously want to look at an MPPT controller. It will deliver more amperage from the solar panel. I can't remember, did you add a second panel? I would say with a second panel and the different controller you should be much better off. On that note. Morningstar has an MPPT controller, but I believe it will only do one battery bank. I don't think that is really an issue. I don't see a need to have a charge going to the engine. And quite frankly I think the battery relays join them at any given time anyway.
 
FYI. Regarding my question on why the thruster battery is wired independent I received an answer from RT. When the thrusters are activated there can be a significant voltage drop due to the high current draw. This voltage drop can cause the Garmin GPS to lock up. I don't know if any of you who have combined it with the house have experienced this but that is the concern.
 
Red Raven":3e0cd9b0 said:
FYI. Regarding my question on why the thruster battery is wired independent I received an answer from RT. When the thrusters are activated there can be a significant voltage drop due to the high current draw. This voltage drop can cause the Garmin GPS to lock up. I don't know if any of you who have combined it with the house have experienced this but that is the concern.
Click to expand...

This response makes sense to me and was what I would expect given the thrusters take a lot of juice. 🙂 I for one do not mess with the RT stock battery setup for reasons like this.
 
As I said, I can isolate the thruster battery from the house any time I want to. However, I have left the switch in the on position all of the time and have had no issues. As you think about it usually the only time one uses the thrusters is while docking, if the Garmin were to lock up because of the draw, I doubt you would get lost. 😀
 
Mike: Thrusters are also used for un-docking and getting ready to cruise shortly after. 😱
 
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