100 Watt solar panel testing - Goal Zero, Rock Pals, Aims Power, and another cheap Chinese one from Amazon.

[ArnieC]

Holy smokes - disappear for a day and everyone gets busy!

To answer a few questions:

To run the ARB Elements and most refrigerators, you need a battery. Just a solar panel and controller can not supply enough amps during the initial spike when the compressor turns on, you would likely burn out the controller, fridge, or something else. Or it just wouldnt start because the voltage would drop low enough the fridge would not turn on due to battery protection.

To address the concerns about not running through the night, I had run approx 4PM Friday to (sometime Sunday morning) on solar/battery, keeping my fridge below freezing because I had some delicious brandy slush in the bottom I wanted to keep cold. Due to Newton's law of Cooling, it takes significantly more energy to maintain approx 60F temperature differential (80 Ambient to 20 Fridge) than it does to maintain a 50F temperature differential (80 Ambient to 30 Fridge). We had also put in a whole warm 30 pack of Coors Light on Saturday AM to take advantage of the solar we had through the morning on Saturday. Saturday afternoon was cloudy so we had minimal solar energy.

Lastly, I am running just a single OEM Toyota starter battery, so I don't want to run it too low. I am pretty aggressive with the battery voltage protection to keep some life in my starter battery.

My ARB elements fridge while running (after starting, compressor operational) draws less watts than my 120W panel puts out in good conditions. This means that during the daytime in direct sun, the fridge is essentially "free" - it does not consume any battery energy to run. Because of that, if you are around camp, you can use some strategy to cool heavily during the afternoon when you have good solar, then raise the temp during the evening to minimize battery impact. Also a good plan if you are in the midwest where the weather tomorrow could be totally different than the weather today. I am going to maybe try wrapping my fridge in a blanket or similar for time periods where the vehicle is not running but I am not using the fridge to help maintain the cooling best I can.

I can appreciate the food temp discussion, but we are taking things like beer and cheese and temp swings from 20 up to 35. Whenever we go with something like raw meat we keep it in the bottom of the fridge and load it in frozen. That way even with the fridge running in the 30s it takes days to thaw out.

 

[shade]

Lastly, I am running just a single OEM Toyota starter battery, so I don't want to run it too low. I am pretty aggressive with the battery voltage protection to keep some life in my starter battery.

Add a good jump pack, and consider upgrading the battery. A single Group 31 battery in my Tacoma can power my Indel B fridge (similar performance to yours) for 2-3 days without any additional charge.

If your battery is incapable of running your fridge for 24 hours, it's probably time for a new battery, but there may also be a need to improve the wiring between the battery and fridge to reduce voltage drop.

 

[ArnieC]

Battery is less than 1 year old OEM Toyota, fridge is run off 8 gauge wiring from the battery to a distribution block in the back of the land cruiser to 12 gauge wiring approx 3-4 feet total length.

I can get 2-3 days off of the fridge in 60 degree weather no worries, not so easy in 90 degree weather. The Delta T makes a huge difference. Damn those laws of physics! An Indel B is a whole lot smaller than an ARB Elements, the largest unit they offer is 2/3 the size at approx 40 liters so not sure what they do for power consumption.

When my battery goes tits up I will replace it with a bigger one but for now I am doing great. Thanks for the tips.

 

[shade]

Battery is less than 1 year old OEM Toyota, fridge is run off 8 gauge wiring from the battery to a distribution block in the back of the land cruiser to 12 gauge wiring approx 3-4 feet total length.

I can get 2-3 days off of the fridge in 60 degree weather no worries, not so easy in 90 degree weather. The Delta T makes a huge difference. Damn those laws of physics! An Indel B is a whole lot smaller than an ARB Elements, the largest unit they offer is 2/3 the size at approx 40 liters so not sure what they do for power consumption.

When my battery goes tits up I will replace it with a bigger one but for now I am doing great. Thanks for the tips.

My Indel B is 51qts, and uses refrigeration components on par with ARB fridges, but ARB models are usually a little more efficient due to better insulation. I've run my fridge at 34*F in Death Valley heat with no battery issues.

I don't see any benefit to chilling the fridge as cold as you do, but you'll need a new battery soon if you keep discharging it so deeply. It's also possible that it's already performing poorly, even if only a year old.

 

[DorB]

Me included. I would look as voltage as an indicator of the batteries state of charge. Would a lower voltage also indicate a batterie's lack of amp output potential?

When your battery is in its prime, then yes, the volt is a common easy indicator for its status.
Good indicator to the battery status is when it’s fully charged, left a night to rest without anything connected to it.
After 12hr it should be no less then 12.5v.
If it drops from that, it mean that it has internal discharge.
It’s doesn’t mean immediate replacement, but take notice.
It won’t hold as good as new.

Does this vary between battery chemistries? I have seen some Lithium battery claims of crazy amp outputs.

Deep cycle and lipo batteries can discharge better then regular lead-acid batteries.
A 100amp lead battery gives you in real world about 40practical amp before it’s damaged and too weak to start your engine.
Deep cycle can discharge as low as 80% and recover.

Is bacteria a concern even in the near freezing temps? My wife is a chef and talks about the TDZ (temperature danger zone). 'between 40 and 140 degrees for 2 hours'

We’re far from sterile when off-road camping and travel, but I found that in hot weather, if I pre-freeze some of the products at home, (what I don’t need for immediate consumption) and setting the fridge to 32fr, it’s a good balance between keeping the food healthy and reasonable energy consumption.
Frozen products de-frosts slowly, and everything is still fresh, and the beer is ice cold.

Our life has become simpler when we realize there is no room for a fridge in our rig. We are just going to rely on ice or dry ice. Although on a camping trip in July we had a heat wave and a cooler in the cab of the truck the ice was keeping the cooler cold but the top layer of the cooler above the ice felt as hot as the rest of the truck.

For an ice cooler you need ice, which is bulk volume that is used for products in a fridge.
So you have less useable volume and insufficient cooling ability.

If your food demands are ok with that, maybe you don’t need a fridge.
Actually, most of us don’t “need” a fridge, rather then “want” one.
Because it’s easier to keep your food fresh longer.
You can carry bigger verity then an ice-box, the volume is better managed and you’re able to chill new supply all the time without warring they will heat up the icebox.

A good electric system for a fridge in a vehicle is practically one-time setting and that’s it.
If you don’t mind the noise when camping, you can even skip the solar panel and run your engine to charge the battery.

 

[DorB]

A single Group 31 battery in my Tacoma can power my Indel B fridge (similar performance to yours) for 2-3 days without any additional charge.
..

Sounds exceptional.
What type and size battery?
What was the climate?

I did a test once, with a new 72amp lead battery, fridge set to 32fr (about 90fr ambient temp) and after 23hr, the battery ran flat and damaged, and did not charge properly anymore.

 

[shade]

Sounds exceptional.
What type and size battery?
What was the climate?

I did a test once, with a new 72amp lead battery, fridge set to 32fr (about 90fr ambient temp) and after 23hr, the battery ran flat and damaged, and did not charge properly anymore.

Group 31 AGM battery, parts store house brand; "Super Start" brand. I believe the battery was rated at 110-120 Ah new. Nothing special about it or my fridge. My truck has a 130A alternator, and the long fridge run times have occurred after 15-20 hours of driving, so I'm confident the battery was at 100% state of charge.

In Death Valley, highs were around 100*F, dropping to around 60 at night. In Canyonlands NP, highs were around 90*F, lows around 60. I keep the fridge in my truck's cab, with the windows open a little for ventilation, and I put a white towel or Reflectix cover on the fridge. I went 2.5 days in Canyonlands without starting the truck. In Death Valley, probably more like 16 hours parked, with 6-8 hours running per day.

I'd post power consumption numbers, but I don't have any. I don't think the performance I've seen is particularly noteworthy.

 

[DorB]

What size fridge and what temp setting?

I run a fridge in my truck’s bed (well ventilated and shaded all time), for the past 6 years and didn’t get even close to these results, even with a good 90apm battery.

Even the best fridges don’t go down to less then 1.7amp/hr average consumption (night/day) ,and for a 2.5 days it’s minimum 100amp, so the numbers don’t adds up if there wasn’t any power supply(solar?) during all that time .





Slowly..

 

[shade]

What size fridge and what temp setting?

I run a fridge in my truck’s bed (well ventilated and shaded all time), for the past 6 years and didn’t get even close to these results, even with a good 90apm battery.

Even the best fridges don’t go down to less then 1.7amp/hr average consumption (night/day) ,and for a 2.5 days it’s minimum 100amp, so the numbers don’t adds up if there wasn’t any power supply(solar?) during all that time .





Slowly..

51qt Indel B fridge set to 34*F on Economy mode, filled with food & drink, with a white towel over it, and the truck cab passively ventilated. I only open the fridge briefly a few times a day when the truck is parked, since I'm away backpacking.

Whatever the math, the fridge ran 2.5 days off of the battery without any charging, the low voltage protection never kicked in, and my truck started fine. I know I've probably shortened the life of the battery some by cycling it so deeply, but I don't do it often, and it always gets a long charge back to 100% on the drive home.

I also carry a jump pack in case things don't work out, but I haven't needed it.

 

[ArnieC]

Those 60F lows are a huge help to keep battery consumption in check, and only going to 35F indicated, which in reality is probably a bit closer to 40F average, unless monitored with a standalone thermometer in the center of the fridge in still air, still makes it a bit hard to believe 3 days - the 16 hrs on battery alone is much more realistic and inline with what most are seeing.

Keeping the lid closed is a big help, we are in and out every 30 minutes sucking down beers, and practice "1 in 1 out" during peak solar so always adding room temp liquid back to the fridge which also requires more power to cool down.

I for one love my fridge, the wife said it changes the way we camp and I agree. So nice to not have to worry about ice, dig around for waterlogged vegetables, etc. Plus its certainly a talking point.

 

[shade]

the 16 hrs on battery alone is much more realistic and inline with what most are seeing.

If someone is only seeing 16 hours of endurance from a 100Ah battery, the fridge (or something else) is consuming far more power than mine.

 

[DorB]

If someone is only seeing 16 hours of endurance from a 100Ah battery, the fridge (or something else) is consuming far more power than mine.

A 100ah battery is not delivering 100ah rather then close to practical 40, if it’s not a deep cycle battery, and your is not as you mentioned.
Remember that the cutoff kicks in about 11v, which is far from using all the battery capacity.


I did more then one testing of fridge energy consumption to plan my dual battery system, and the most optimist number I got was average 1.7ah consumption.
With a sufficient solar panel, you can compensate for the night amp draw, and the day use.

I still don’t see how you managed 3 days without any energy source except the battery.





Slowly..

 

[shade]

A 100ah battery is not delivering 100ah rather then close to practical 40, if it’s not a deep cycle battery, and your is not as you mentioned.
Remember that the cutoff kicks in about 11v, which is far from using all the battery capacity.


I did more then one testing of fridge energy consumption to plan my dual battery system, and the most optimist number I got was average 1.7ah consumption.
With a sufficient solar panel, you can compensate for the night amp draw, and the day use.

I still don’t see how you managed 3 days without any energy source except the battery.





Slowly..

I explained the conditions and the performance. If you don't believe what I've said, that's fine.

Was there a reason you quoted what I said about not getting 16 hours of endurance from a 100Ah battery?

 

[DorB]

Was there a reason you quoted what I said about not getting 16 hours of endurance from a 100Ah battery?

Yes,
Because it’s not accurate to relate to a 100ah battery as 100ah capable for static energy source for a fridge.

It will be insufficient for the spike needed to start the fridge’s compressor even when the volt is within cutoff values.

It’s not just the volt, but the current is more relevant.

That’s another issue why I’m trying to understand how you manage these great results from a standard battery.

 

[luthj]

I have worked with a number of DC fridges. My largest 120L unit would use an absolute max of 80AH per day. That was with a closed up van, and temps over 100F inside. On a cooler day, with highs in the 80s, in the van, it would use half that. On a day where it rarely got over 70s in the van, it could use as little as 25AH per day. Direct sun incidence, ventilation around the battery, etc all make a difference. A fridge on a slide out with poor ventilation around the condenser will use 20-30% more power than a fridge in the shade with good ventilation. There is also a big difference between various fridge models insulation. Take note that fridges with a dedicated freezer section will cycle more often to keep the freezer cold enough. This increases power draw over a dedicated fridge, or a unit that only monitors fridge temps.

Part of the equation is the vehicles own parasitic draw. This can be as high as 200mA, or about 5AH per day. Things like phone chargers and lights can easily eat up 10AH per day.

A 100AH battery can supply about 50AH over 24 hours, but at lower current rates it could be as high as 60AH over 36 hours (peukert effect). At that point it should still start a typical V6 engine, assuming the weather is not super cold.

Starting batteries not intended for deep cycling may only deliver about 100 cycles to 20% SOC before they are end-of-life (about 70-60% of new capacity).