Solar Necessary for Boondocking w/ 12V Fridge?

[Viajeros]

Agreed Mark. But I can’t see ever choosing a propane fridge over a 12 volt compressor model. To each his own but in the Okanagan in the summer propane fridges just don’t keep up. Solar Is super cheap. Batteries aren’t bad depending on what you want and where you shop. Propane Fridges are expensive and smaller for the same cabinet size because of the cooling unit.

Generator is a different category. Handy things but not something you want your neighbour using when camping.

 

[Mark_K5LXP]

Seems if a propane fridge couldn't keep up in the Great White North there'd be no way one would work in New Mexico. Not saying propane is ideal but I would rather have a quiet fridge that works OK without a second thought than have to buy and manage a battery/solar/genset to feed a compressor fridge. But that's my choice and I get it comes down to the end use, and user. Just offering that looking at the problem from a different direction might open up options for solutions.

Mark B.
Albuquerque, NM

 

[steveblonde]

We have an 18cu ft propane 3 way 4 door fridge (the largest propane fridge available,) and it does just fine in 40c 104f temperatures. Weve gone to Southern Ontario. South Dakota, Vanvouver and the Okanagan,California and Nevada in mid August and NEVER had an issue in 20years

 

[Viajeros]

Seems if a propane fridge couldn't keep up in the Great White North there'd be no way one would work in New Mexico. Not saying propane is ideal but I would rather have a quiet fridge that works OK without a second thought than have to buy and manage a battery/solar/genset to feed a compressor fridge. But that's my choice and I get it comes down to the end use, and user. Just offering that looking at the problem from a different direction might open up options for solutions.

Mark B.
Albuquerque, NM

I hear ya. But this part of the great white North gets to 45 degrees C and hotter in the summer. Those with the DC compressor fridges are fine at those temps. The propane absorption fridges not so much.

Jmho.

 

[Gary RV_Wizard]

The fridge in our new camper is a 12VDC compressor-type fridge. Amp draw is 8.3 amps according to the manufacturer (there is a night mode that draws 6.2 amps). The 6V batteries proposed by the dealer are 230 Amp-hour GC15. I think this means that the batteries will last 230 Amp-hours / 8.3 Amps = 27.7 hours running just the fridge. Is that the right way to figure it?

NO. It is basically run-hours x amps, but the fridge doesn't run continuously, so the hours are much less. Depending on the temperature in the RV and how often the door opens, the run-hours may be only 20%-25% of the elapsed time. That cuts your amp-hour consumption way down, e.g. 0.25 x 24_hrs x 8.3_amps = 49.8 AH.

To keep a lead acid battery healthy you should avoid using every last AH, so the effective capacity of those 230AH batteries is more like 115-130 AH. That still gives you more than two days of runtime for the fridge alone.

 

[Viajeros]

NO. It is basically run-hours x amps, but the fridge doesn't run continuously, so the hours are less. Depending on the temperature in the RV and how often the door opens, the run-hours may be only 20%-25% of the elapsed time. That cuts your amp-hour consumption way down, e.g. 0.25 x 8.3 x 24 hours = 49.8 AH.

To keep a lead acid battery healthy you should avoid using every last AH, so the effective capacity of those 230AH batteries is more like 115-130 AH. That still gives you more than two days of runtime for the fridge alone.

Yes. AGM’s are a little better than flooded in this regard. You can comfortably run them down to about 30 percent regularly with little impact. I know LFP’s you can down even further but I have no experience with those.

 

[Lou Schneider]

Over the millenium I spent 2 months boondocking in Quartzsite and just before I went there the propane refrigerator in my Arctic Fox trailer failed. I replaced it with a slightly larger 120 volt apartment size refrigerator and headed south. This was a basic box that made cold, no auto defrost, etc. The refrigerator drew about 9 amps from the battery through an inverter when it was running and the parasitic load of the inverter (about 0.3 amps) when the compressor was off. A pair of 160 a/h golf cart batteries would power it and some lights, etc. for about 36 hours before I'd have to connect the generator and recharge the batteries. The low limit was reached when the compressor's starting surge dragged the battery voltage below the inverter's low voltage shutoff.

Solar was too expensive back then so I wound up running my generator (Honda EU1000i) for 3-4 hours each evening while I watched TV and that was enough to keep the batteries charged up. It used about a half gallon of gas a day.

Today, with solar and drop-in lithium batteries becoming more reasonable, it's a no brainer. For the price of a replacement propane refrigerator you can get an Energy Star refrigerator and have enough money left over to pay for a good size solar system.

 

[Alontheway]

Short answer, yes. The dealer was correct.

Marine batteries are wrong. Deep cycle batteries are correct for RVs.

Minimum 200 watts of solar should suffice, 300 or 400 I would suggest.

You HAVE to recharge the batts every day with a fridge. Solar will do this just fine.

If you plan to do a lot of boondocking then I would suggest getting true deep cycle batteries in 12 volt and getting more amp hours than the two golf cart batteries provide. 3 batteries at least, 4 would be plenty.

Running a fridge and a propane furnace will suck down the batteries, two 6v gc batts might be dead every morning. The furnace blower fan needs a lot of power.

Lights are pretty insignificant, but a fan running 24/7 needs to be part of the equation (though unlikely u run a window fan when you need to run a furnace as these are two different seasonal items).

Try to buy the new RV without a battery and get a discount.

Longer answer....
I have a DC fridge and propane furnace. The good part is that when i need the furnace it is cold outside, so the fridge benefits from this cooler air, especially if it is open to an outer wall, or vents to the outside, such that heating the RV does not heat the air that the fridge uses to cool off.
Mine is entirely inside. If I run both fridge and furnace I can make it til morning, but battery charge is much lower than I prefer, and running them low is worse than keeping them closer to full charge. My batts are over 6 yrs old (two gc 6v's).
I have 200 watts solar into an MPPT controller. I wish I had at least 300 watts, and wish I had a little more amp hours as the older batteries do not have the capacity as when new (consider this when doing the math).
With paired 6 volts I can't just add a 3rd battery, I would have to add two more paired 6 v's, and it is not good to match old batteries to new batteries in parallel. In series is fine as with two 6's, but two pair of 6's run parallel is not good if one pair is old and one pair is new. It just occurred to me I guess i could pair one old with one new then run those parallel... Has anyone tried this? If I lost you then no worries, it is not vital to understand the last part. The point being to just do it correctly right from the start and not have regrets.

If possible, add extra insulation to the fridge cabinet. This will be huge in reducing the run time of the fridge. I insulated mine and it runs less than half as much, and a side benefit is that it is very very quiet now.

 

[Lou Schneider]

With paired 6 volts I can't just add a 3rd battery, I would have to add two more paired 6 v's, and it is not good to match old batteries to new batteries in parallel. In series is fine as with two 6's, but two pair of 6's run parallel is not good if one pair is old and one pair is new. It just occurred to me I guess i could pair one old with one new then run those parallel... Has anyone tried this? If I lost you then no worries, it is not vital to understand the last part. The point being to just do it correctly right from the start and not have regrets.

That's another advantage to lithium. You can add additional batteries up to two years later. Plus they put out full power even when they're as low as 20% SOC so you need less total capacity. And they don't brown out at low SOCs so you don't have to worry about the inverter shutting down or the fan not spinning fast enough to let the furnace ignite.

You don't want to put old and new batteries in series - the capacity of the pair will be limited by the weaker battery.

If possible, add extra insulation to the fridge cabinet. This will be huge in reducing the run time of the fridge. I insulated mine and it runs less than half as much, and a side benefit is that it is very very quiet now.

Arctic Fox already had extra insulation around the refrigerator, 1" of fiberglass batting between the refrigerator and the walls of the cabinet it was built into. Not a lot but it helped. I added more insulation to the top of the new fridge. It's coils were rear mounted like the propane fridge it replaced so I kept the stock outside vents.

 

[Viajeros]

If you are starting from scratch consider asking the dealer to put on two x AGM 31 12 volts. This along with a single 200 watt panel will probably be adequate. And you can always add a second 200 watt panel later. Panels are expensive at dealers but cheap online.

 

[Gary RV_Wizard]

Just for the record... No amount of panels is "adequate" if he parks in a nice shady spot.

He can get a pair of Deka GC15's for $300 or less, but a pair of G31 12v deep cycle AGMs is more like $550+. Top-of-the-line Trojans would run $700. And he probably doesn't have space for 3 or more batteries anyway.

 

[JayArr]

Back to the original question:

We will have a gasoline generator, but I am concerned about how long we will have to run the generator to recharge the batteries every day. Do I need to install solar panels to keep the batteries charged up during the day?

The answer is NO, you do not need solar.

200W of solar will take 5 hours to deliver the same amount of power to your batteries that a 1500W genny and a 80A converter will supply in one hour.

Solar = 200w/12V = 16.66Amps per hour x 5 hours = 83.33 Ah
Genny = 1500W but the converter doesn't use all of that, the converter delivers 80A for one hour = 80Ah

And the solar setup will cost you thousands.

The easiest solution is to ask the dealer to install the highest wattage converter possible. The converter charges the batteries when the genny is running. Even a small 1500W genny will charge up GC15 batteries enough in a couple of hours to run your fridge all night if the converter is large enough.

Example: The GC15 batteries are 230Ah but let's say you only deplete them by 150aH per day, (fridge, furnace, lights pumps etc) An 80A converter with a Honda 1500 will charge those batteries back up to about 80 or 90% in a couple of hours max and that's good enough while camping. You can do it all at once or run an hour in the morning and an hour at night.

Before you spend a lot of money that could be used to go somewhere try the trailer out as is without solar and see if it's really needed.

 

[Alontheway]

200 watts in the shade recharge my two gc's back fully. I do not know how many amps the panels give in the shade, all I see is their 18 volts, but they do work in the shade. Full sun pointed directly at the sun is idea, and more panels will make up for shade. By shade I do not mean inside a garage, but under trees. Always some daylight coming through and usually short periods where there is direct sun. They work in the shade.

 

[Isaac-1]

The problem is a pair of 6V lead acid batteries can't absorb 80 amps in 1 hour

 

[MoInEd]

Stay away from 12V fridges, you won't be able to keep up with the amp draw. I have installed 3x100 solar panels and a good inverter on our previous trailer and am in the process of doing the same on our new trailer. Costs around $700.
We almost always go where there is no Poland 300w is enough to keep the two batteries fully charged but won't be enough for a fridge especially if he weather isn't fully sunny.
Get a propane fridge and install a few solar panels and you won't need a generator either.

 

[Viajeros]

So many different experiences from so many walks of life. And they are all valid. So much depends on where you camp, how you camp and your expectations. Draw a little info from everybody and find what works for you.

 

[Alontheway]

lots of knee-jerk comments. Every situation is different. Telling about things that work, and making up things that you work out on paper can be vastly different.
I do not know any situation where a battery needs to absorb 80 amps in one hour for example. Irrelevant info. What viewpoint that supports I do not know. Typically a solar system has many hours of daylight to operate at.

If DC fridge does not work for you then great. Others love their DC fridges.

Blanket statements are meaningless. Tell us your issues and your weaknesses and let the reader glean the info.

I will never go back to propane for a camper fridge, I might even go to an induction cooktop in the future. 200 watts solar is plenty parked in the woods. Two gc batts work for me. Lead acid batts are cheap and do the job. Li-ion are great and do the job also but at a price. I do not have space constraints, others do. All good info.

 

[JayArr]

The problem is a pair of 6V lead acid batteries can't absorb 80 amps in 1 hour

They actually will. We do it in the shop all the time. The German made Eltek battery chargers we repair for BMW dealerships regularly push 80A into simple car batteries so pushing that much into a pair of deep cycle golf cart batteries is no problem at all, in fact they're built with thicker plates to withstand it.

I speak from experience, I've done this, not just read about it.

Batteries will accept all the charge you can hurl at them until they start to fill up and as they fill up the voltage rises and when it gets to 14.5V the charger changes to acceptance mode which is a constant voltage charge mode. At this point they are about 80%-90% charged.

Mark has posted on battery life a few times and I have to completely agree. You can treat your batteries with kid gloves and only charge them at low rates and insist on reaching 100% every charge cycle and they may last an extra year or so but you won't have gotten the most out of them when you throw them away.

Here's an analogy: Say you and your neighbor both buy sports cars.

-You drive yours only on the weekend and you never speed or stress the engine, your car lasts ten years than it rusts out and you have to scrap it.

-Your neighbor drives his every day and takes it to the track on the weekends, he redlines it regularly and loves smoking the tires. At 7 years his engine fails and he sends it off to the wrecker.

Who got more value out of the car they bought?



Charge them like you stole them LOL

 

[Viajeros]

They actually will. We do it in the shop all the time. The German made Eltek battery chargers we repair for BMW dealerships regularly push 80A into simple car batteries so pushing that much into a pair of deep cycle golf cart batteries is no problem at all, in fact they're built with thicker plates to withstand it.

I speak from experience, I've done this, not just read about it.

Batteries will accept all the charge you can hurl at them until they start to fill up and as they fill up the voltage rises and when it gets to 14.5V the charger changes to acceptance mode which is a constant voltage charge mode. At this point they are about 80%-90% charged.

Mark has posted on battery life a few times and I have to completely agree. You can treat your batteries with kid gloves and only charge them at low rates and insist on reaching 100% every charge cycle and they may last an extra year or so but you won't have gotten the most out of them when you throw them away.

Here's an analogy: Say you and your neighbor both buy sports cars.

-You drive yours only on the weekend and you never speed or stress the engine, your car lasts ten years than it rusts out and you have to scrap it.

-Your neighbor drives his every day and takes it to the track on the weekends, he redlines it regularly and loves smoking the tires. At 7 years his engine fails and he sends it off to the wrecker.

Who got more value out of the car they bought?



Charge them like you stole them LOL

Lol. Love the analogy.

We drive and charge our Tesla like we stole it. So far so fun.

Cheers.

 

[Isaac-1]

Here is a write up on the charge acceptance process of lead acid batteries relating to fast charging, it is regarding AGM lead acid vs flooded lead acid, where AGM's outperform traditional flooded batteries, but a lot of the same concepts apply, just the actual rate differs a bit. How Fast Can an AGM Battery be Charged? - Marine How To