Isolated solar set-up for fridge. questions / help needed.

[blackohio]

I have a bed rack with dual rotopax mounts on each side, I want to move one set to the drivers side and in its place make a plate and articulating arm to mount the 100watt rigid solar panel to it.

My goal is to have something I can move around to follow sun when needed. I'll make clasps to hold the panel stationary with retracted.

Do you guys think a magic arm will be strong enough, I dont see myself driving with it unlocked from its stationary position.

I've used magic arms before when using camera rigs on rolling vehicle shots and know it'll support a DSLR / Vert Grip and prime 28-ish lens.

I figure I can make a brace between the 2 mounts with a locking box that the arm is concealed within, so inorder to access the arm the box cover needs to be unlocked and access from the side or behind, so someone cant get to the mount to loosen and remove.

Thoughts.

Along with that, I'm planning on running an optima yellow, 100 watt panel mppt controller on a
sno master ex85D specs are, do you guys think that'll be sufficient? My intended purpose is to have the fridge isolated from the trucks electrical system. (reason being im running a switch pro system thats ACC powered and no sure how to deliver constant power to the fridge using this system and a dual battery set-up) I also like the idea that the fridges draw is away from anything vehicle related and never needs any true running to charge. I dont know much about solar at all so calculating needs is a little bit of an unknown to me.

RENOGY SOLAR SPECS
100W Eclipse Solar Panel Renogy 20ft 10AWG MC4 Adaptor Kit (A pair)
Maximum Power: 100W Lenght: 20ft
Maximum System Voltage:600V DC AWG: 10
Open-Circuit Voltage (Voc): 21.2V Rating Voltage: 600/1000V
Short-Circuit Current (Isc): 6.10A Temperature: -40°F to +185°F
Optimum Operating Voltage (Vmp): 17.7V
Optimum Operating Current (Imp): 5.70A
Weight: 15.0lbs
Dimensions: 40.8 X 20.7 X 1.4 inches

Commander 20A MPPT Charge Controller Commander 40A MPPT Charge Controller
Nominal System Voltage: 12V/24V Auto Recognition Nominal System Voltage: 12V/24V Auto Recognition
Rated Battery Current: 20A Rated Battery Current: 40A
Rated Load Current: 20A Rated Load Current: 40A
Max. Solar Input Voltage: 150V DC Max. Solar Input Voltage: 150V DC
Max. Solar Input Power: 260W (12V), 520W (24V) Max. Solar Input Power: 520W (12V), 1040W (24V)

FRIDGE POWER SPECS
12/24 V DC 120 V AC
Model: EX95D 95D
Size: 32.48 x 18.50 x 25 Inches, 825W x 470D x 635H mm’s
Capacity: 89.81 Quarts, 66 Liter (37/48 Split)
Running Current: 2.5, 5 or Variable @ 12 V DC, average run time 12 hours in 24
Power Consumption: 66 watt
Weight: 83.77lbs, 38Kg
Features
12/24 V DC 120 V AC
Temp Range 50F to -8F, 10c to -22c
Running Current: 2.5, 5 or Variable Amps @ 12 V DC, average run time 12 hours in 24
66 Watt Snomaster compressor
Cut out Voltage 3 settings: 10/10.7/11.8 Volts @ 12 V DC
Interior LED Light
3 min delay protection start up
On / off Switch
Power Consumption: 66 watt
Battery Monitor
Free Bottle Opener
Weight: 83.77lbs, 38Kg

 

[john61ct]

I'm planning on running an optima yellow, 100 watt panel mppt controller on a sno master ex85D specs are, do you guys think that'll be sufficient?

No.

First off you want true deep cycling battery, not dual purpose with a CCA rating.

Easiest choice best value is 2x 6V GC2 from Sam's Club (East Penn/Deka, labeled Duracell).

Each pair is 200+AH, for a largish fridge like that I'd say three pairs, but less is OK if you can charge high amps off dino juice mornings to supplement solar.

If you're trying solar only then as much wattage as you can physically fit, at least 600W if possible, forget the fancy mount flat will do.

Best efficiency is a big dedicated House bank for all non-vehicle uses, not separate ones dedicated to a single appliance.

Carrying a small genny to run in the morning, or HO alt set to pump big amps from fast idle, ideal for morning Bulk stage run when solar isn't enough.

All charge sources direct wired to that House bank, dedicated voltage sense wire and temp compensation.

Small ACR/VSR, Echo Charger or DCDC charger to keep the barely used Starter topped up.

SoC battery monitor to make sure House never pulled below 50%, and back to 100% full every cycle.

 

[jonyjoe101]

As long as you keep the fridge set to 40 degrees and you have a lot of sun you might be able to do it.
I google the optima yellowtop and the biggest one was 55 ah. That barely can do the job 50 percent of the battery is 27 ah. You don't want to go below 50 percent to extend the life of the battery.

My fridge when I set it to 40 degrees consumed 26 ah in 24 hours.

The 100 watt solar panel will give you about 5 amps when pointed directly at the sun. By comparison the 120 watt panel I had max out at about 6 amps.

Since your 100 watt panel is only a 20 volt panel it won't benefit from the mppt controller you have, mppt needs a high voltage panel (30 volts or higher) to see any boost in the amps. It will still work with your panel but will only give you 5 amps.
With a bigger panel like a 240 watt 36 volt panel, that would definitely benefit from your mppt controller, it would give you close to 15 amps.

Myself I use to run a fridge on solar 100 percent of the time with a 120 watt panel and a 75ah agm battery, But in cloudy days the fridge would disconnect every night because of low battery. But in perfect weather I could run it months at a time with no problems.

 

[blackohio]

No.

First off you want true deep cycling battery, not dual purpose with a CCA rating.

Easiest choice best value is 2x 6V GC2 from Sam's Club (East Penn/Deka, labeled Duracell).

Each pair is 200+AH, for a largish fridge like that I'd say three pairs, but less is OK if you can charge high amps off dino juice mornings to supplement solar.

If you're trying solar only then as much wattage as you can physically fit, at least 600W if possible, forget the fancy mount flat will do.

Best efficiency is a big dedicated House bank for all non-vehicle uses, not separate ones dedicated to a single appliance.

Carrying a small genny to run in the morning, or HO alt set to pump big amps from fast idle, ideal for morning Bulk stage run when solar isn't enough.

All charge sources direct wired to that House bank, dedicated voltage sense wire and temp compensation.

Small ACR/VSR, Echo Charger or DCDC charger to keep the barely used Starter topped up.

SoC battery monitor to make sure House never pulled below 50%, and back to 100% full every cycle.

I wasn't deadset on the Optima nor did I buy yet, and had thought of using the blue top rv/marine battery. I know exactly a little above zero so please excuse the novice questions when it comes to power needs.

You're saying I'd need 6 of those cart batteries to run the dual door fridge based off specs? what kinda run life could I expect if fridge is running at 40º and freezer to 32º. Any transit time I will run fridge off trucks bed outlet and let battery charge. The fridge doesn't remain in the truck constantly and I will prerun it at home prior to using. Trips are in the neighborhood of 2-3 days average.

Is 600 watts of panel absolutely necessary? thats alot of panel, I cant mount to top of bedrack as RTT is there.

What could I expect from a 280 or 320 watt mono panel and a 200AH battery stand alone. If I understand correctly a 66watt fridge at say 5amp would run for 40 hours on 430ah batteries?

If that is correct what 600 wats of panels would be then required to feed it back? This is confusing as I know so little.

 

[john61ct]

Forget any "top", batteries used for deep cycling should be explicitly designed for that purpose, renewable energy rated.

The actual AH consumed by a fridge per 24 hours is subject to lots of variability, but if shooting for mostly solar input your bank should be enough to carry for at least 2 full days without going below 50% SoC.

As I said a small genny can help reduce the panels needed. Also a big (60+Amps) mains charger; run it in the AM until your bank monitor says 85% full, then let 6+ hours of solar top it up to 100%.

Obviously the load of the fridge needs to be lower than the solar input for any power to go into recharging the bank.

If you're really only away from mains for three days max maybe forget the charging while you're away, just get a big enough bank, maybe four pair? and the mains charger for when you can plug in.

 

[OCD Overland]

I know it's late and I did have a few glasses of wine tonight but I swear I just saw someone recommend 600Ah of batteries and 600W solar plus a generator just to run a danfoss fridge for a 3 day camping trip.

 

[blackohio]

Forget any "top", batteries used for deep cycling should be explicitly designed for that purpose, renewable energy rated.

The actual AH consumed by a fridge per 24 hours is subject to lots of variability, but if shooting for mostly solar input your bank should be enough to carry for at least 2 full days without going below 50% SoC.

As I said a small genny can help reduce the panels needed. Also a big (60+Amps) mains charger; run it in the AM until your bank monitor says 85% full, then let 6+ hours of solar top it up to 100%.

Obviously the load of the fridge needs to be lower than the solar input for any power to go into recharging the bank.

If you're really only away from mains for three days max maybe forget the charging while you're away, just get a big enough bank, maybe four pair? and the mains charger for when you can plug in.

Would I just be better off with say a small generator and let it do all the heavy lifting when not driving? Let it run the fridge when parked and just altogether forget the solar/battery when weighing cost for 4 pairs of the batteries. It sounds like any amount of panel banks below 600 watts is effectively useless as it cannot supply enough juice back as compared to draw.

If budget were an issue what avenue would you suggest.

 

[blackohio]

I know it's late and I did have a few glasses of wine tonight but I swear I just saw someone recommend 600Ah of batteries and 600W solar plus a generator just to run a danfoss fridge for a 3 day camping trip.

holy ****, thats alot of juice.

 

[john61ct]

Yes, genny = generator but good one like Honda not cheap, all of them are IMO annoyingly noisy, def wouldn't want it running all the time.

As I said 3 days max changes things.

Big enough bank full to start, no charge source needed at all.

Load also depends on temps.

 

[blackohio]

Realistically 3 days would also be a stretch for dog the wife and dog.

Man I'm torn about what to do the last trip I went on we ran the fridge alone (smaller than this arb) off a single battery that charged while running truck. Same guy ran his fridge for a full day and night with the battery and small solar panel. Maybe 100/200 watt for 2 days.

You think 6 of those golf cart batteries fully charged would survive we could then charge when back home.

 

[dwh]

Since your 100 watt panel is only a 20 volt panel it won't benefit from the mppt controller you have, mppt needs a high voltage panel (30 volts or higher) to see any boost in the amps. It will still work with your panel but will only give you 5 amps.

Sorry, but this is a pretty common misconception. MPPT does not require, nor gain anything from, a higher voltage panel.

100w in to the controller is going to be 100w out to the battery, no matter the voltage.

100w ÷ 33v = 3a in
100w ÷ 12v = 8a out
(5a "boost")

100w ÷ 20v = 5a in
100w ÷ 12v = 8a out
(3a "boost")

Higher input voltage doesn't change the output amps. It just makes it seem better because you see a 5a "boost" (difference between input amps and output amps) instead of a 3a "boost".

I put boost in quotes because it's pure marketing BS. An MPPT controller doesn't boost, it just converts the voltage. When you lower the voltage but keep the same watts, amps goes up.

 

[dwh]

So let's see..

Fridge specs say 66w, 50% duty cycle.

33w ÷ 12v = 2.75a
2.75a x 24hr = 66 amp*hours

So to keep the battery above 50%, you'll need 132 amp*hour battery capacity.

Battery charging is only around 80% efficient, so if you draw out 66ah, you'll have to supply 66 x 1.2 = 79.2...call it 80 amp*hours to get the battery back to 100%.

If you got 8 hours of full power out of the solar (you won't), then you'd need 10a per hour.

10a x 12v = 120w
But, you need to get up above 14v to charge the battery so...
10a x 14v = 140w

So you'd need 140w solar (minimum) in a perfect world. But it's not a perfect world. I'd say 180w might get it done, 200w is more like it.

Plus 3 of the 55ah Optimas.

 

[dwh]

Oh, and I just noticed. It's not a 20v panel. That's Voc. Vmp is 18v.

 

[blackohio]

So it sounds like if I ran a renogy 270watt 24v panel, 40a controller and say 2 6v 225ah batteries should do the trick for shorter trips.

You guys are actually helping me understand this without being condescending which in a forum is totally amazing

 

[swduncan]

I'm in a similar situation. I've got an ARB 63qt fridge, 3-5 day trip coming up with the fam. 3 days if it's too hot, 5 if the weather's good.

There are lots of folks who've posted here and other places about going 3 days on the vehicle's battery alone. Personally, in my life, if my wife and kids are along the likelihood of them not driving somewhere for something in 24 hours is pretty slim. But for a trip to Cape Lookout, and being a geek, using the vehicle battery and carrying a jump pack is very attractive, and by reports, working fine for many folks. There are gobs of threads on this subject.

However, to consider a very small battery, for a moment...

The fridge draws a nominal 5.3a at 12v, which goes between 4 & 6 in real life. I have two 50w 12v panels in series going into a Victron 75/10 mppt controller. I also have an 18ah SLA battery that I bought for another purpose,but have been using with the fridge just to experiment. The panels and batt kept the fridge at 31F all day yesterday, on a partly cloudy day. This morning I rose to find the fridge at 36, power error indication on and the battery at 12.25 V give or take. The fridge's low voltage cuttoff was set to high. Setting it to low didn't allow the fridge to run. The 18ah battery is so small that the current the fridge needs drops the voltage so much that it won't run even though there should be 40% ish capacity left.

It's overcast now (about 0730), and the sun's been up and hour, and the system is putting 3w into the battery. Fridge is still 36. I figure the fridge will be running again in about an hour when fog burns off. If it was going to be an overcast day and I was in the boonies, well, that'd suck. I'd have to plug it into the truck. But for now the stuff in the fridge is still cold, and it will be at least 2-3 hours before anyone else is up. If the sun shows itself all will be good for another 24h.

So an 18AH SLA battery could work, in ideal circumstances. But clearly it's an edge case even then.

Based on all of this I'm planning to get either a 35AH or 55AH AGM. The former is $70, is light enough one of my kids could carry it, and has 3 times the usable capacity (50% dod for sealed lead acid vs. 80% DOD for absorbent glass mat). I'll go to 80%DoD if the battery will and if I get 150 cycles out of the battery that's like 10 years of trips for me.