Solar required to run fridge

oldbloke · Guru

Solar required to run fridge

Peter_n_Margaret · Guru

Don't expect much.
That appears to be a very power hungry fridge! May be worth adding some good quality insulation around the sides, base and top.
Cheers,
Peter

Whenarewethere · Guru

Your CF40 uses basically the same power as my CF28

https://thegreynomads.activeboard.com/t65059593/extra-fridge-insulation-wattage-test/

A few additional comments. I would never run a fridge off the starter battery.

I now have 4 X 26ah gel batteries, I would prefer one 100ah battery but there is nowhere to put one in my car.

I charge via DC-DC when driving. 120 watts of solar with Victron MPPT 100/20, is enough for my setup but it is extremely efficient. I can now even use my jumper leads on my solar panels.

I have also rewired inside my fridge with 12awg & reduced voltage drop by 0.17 volts.

Probably 160 watts minimum if your setup is not optimised & 120ah battery would be my suggestion.

Don't use the controller on the back of pre made panels. Put a controller near the battery. Use 6awg cable where you can.

Whenarewethere · Guru

My solar panel setup which fundamentally is to run my fridge.

https://thegreynomads.activeboard.com/t65231112/custom-6x20-watts-solar-setup-with-mppt/

Jaahn · Guru

oldbloke wrote:
I have a dometic CF40 fridge i use camping. Have used it a few times and the ute battery struggles after 2 days. So i bought a 40 watt solar panel to plug unto the anderson plug. The panel in theory should provide about 2 amps. The fridge pulls 6 amps when running.
I know there are a lot of variables but is the panel likely to help much? Will move it 3 or 4 times a day. What can i expect?
-- Edited by oldbloke on Tuesday 24th of December 2019 06:23:58 PM

Hi oldbloke smile

You can expect it to work better that it did but not as good as it would with a bigger solar panel. The fridge uses about 80Watts so having more than that for a panel seems to be a good idea. As you do not get 100% out of the panel perhaps 100W might be good or even more. Then it charges the battery a bit when the fridge is not running. After all you need to charge up the power lost during the night too. furious

I would not use my vehicle battery as running it down low regularly does kill them. I have done that in times past. If you have a bigger panel you can get the battery charged faster to get the ute started again to get home. hmm

Obviously moving the panel around during the day to face the sun makes more power. Do not lay it flat on the ground, but have it angled so it keeps cooler with the air circulating. Much better.

Jaahn

oldbloke · Guru

I have a 120watt portable but its bulky. Hence the smaller 40w for a rew days camping. My guess was since the fridge pulls 6 amp when operating and has an additional insulating cover will generally run say 15-20 minutes every hour. So 2 amps from the panel would provide about 50% of power required?

Edit. I only go camping for up to 5 days so Im just trying to ensure I dont get a flat battery if i dont drive for a couple of days. It was never intended to provide 100% of the fridge requirements.

-- Edited by oldbloke on Wednesday 25th of December 2019 09:20:36 AM

Whenarewethere · Guru

Have you measured the fridge's current while it's running & measured the solar panel current?

oldbloke · Guru

No mate. All i know is the panel is putting out some volts. An old battery its currently charging voltage rises by about half a volt when i hook up the panel. But the battery is buggered.
Not an electrician.

I think the simple answer is to take it away and try it. Just want to ensure i dont get a flat battery if i dont drive for a couple of days. And im a fair weather camper so dont go away if its going to be 40 deg or freezing.

dogbox · Guru

start car an run for 30-40 minutes might keep battery alive

oldbloke · Guru

dogbox wrote:
start car an run for 30-40 minutes might keep battery alive

Yes, only need to go for a 20 min drive each day i reckon. But dont always do that every day.

First time i went away with it, car parked 2 1/2 days and then started ok.

Second trip, I didnt open the ute cover, and warm weather went 1 1/2 days and not quite enough to start in the battery. :(

Sooo, Im inclined to think this 40watt will give me some insurance. I like to travel light so dont take a lot of gear.

Whenarewethere · Guru

We travel light & usually sleep in the back of the car so everything has to fit on the front seats. Every piece of equipment multitasks! We can jumpstart ourselves if required.

White towel on fridge to cover it from sun & use it for drying.

Bicyclecamper · Guru

When we first stated out , didn't have a battery in our second van, so only used the battery in the car, for the portable fridge, also did not have a solar panel, but what I did have was a jump start battery, What I also did do was start the car, every 4 hours and ran it for 20 min. and this kept the car battery in good nick. I also used the jump start battery to run the lights at night in the van. So if you are going to do it the way you have commented, I would buy a jump start battery, a decent one, an agm battery type, as a back up if you flatten your car battery, not one of those little lithium style ones not bigger than a pack of cigarettes, as you can't really use the extra power in them to do anything other than to start a flat battery.

Jaahn · Guru

oldbloke wrote:
dogbox wrote:
start car an run for 30-40 minutes might keep battery alive
Yes, only need to go for a 20 min drive each day i reckon. But dont always do that every day.
First time i went away with it, car parked 2 1/2 days and then started ok.
Second trip, I didnt open the ute cover, and warm weather went 1 1/2 days and not quite enough to start in the battery. :(
Sooo, Im inclined to think this 40watt will give me some insurance. I like to travel light so dont take a lot of gear.

Hi oldbloke smile

You do not need to actually drive the car. You can start it and let it run parked. I always get a piece of wood and put it on the accelerator to rev the engine up a bit to about 2000 revs, equal to doing 60Ks or so, and it charges well. Leave the bonnet up to keep it cooler. I have a jump starter too as Bicyclecamper suggested. Insurance ! disbelief

It is not a good idea to run the battery down low as it shortens the life of a normal car battery. hmm

Good luck

Aus-Kiwi · Guru

Get more solar run a regulator . A 100AH deep cycle is best and VSR between the two battery systems . This keeps both batteries charged and prevents motor battery going flat . So your not stranded, better for this type of battery as its not designed to be used for deep ( long ) cycles .

Peter_n_Margaret · Guru

Aus-Kiwi wrote:
So your not stranded, better for this type of battery as its not designed to be used for deep ( long ) cycles .

Please explain.....

Cheers,

Peter

oldbloke · Guru

This is not for extended use. Just a few days camping 4,5 times a year. Soo, most days i drive if i go camping. It has run ok fo r up to 2.5 days without starting the car, then ute started ok. The 40w panel is only intended for insurance.

I found 5.5 meters of decent cable in shed so replaced the thin stuff it come with and added an anderson plug as well this morning. The charging voltage seems to have jumped by about 0.6v. So thats a good sign.

If it provides about half t h e power the fridge demands it should do the job. I will suck it and see.

-- Edited by oldbloke on Tuesday 31st of December 2019 11:30:41 AM

Whenarewethere · Guru

Wrap the fridge in a doona or sleeping bag, anything for than matter, but make sure vents are not blocked. It will use a lot less power.

swamp · Senior Member

HI
Use a 160watt panel if u are on a budget or want to travel light .

U really need to no how much power used in 24hrs . Called Ah [amp hours ] Typically usage will be in HOT weather 40-60Ah in moderate weather half that .

160 watt will generate about 38ah in 24 hr period
200watt will generate about 48ah in 24 hr period

Mppt will add to this but cost $$$ and is unreliable to measure accurately
Ah generated is calculated on 100% sun . Sun at 99% is hard to measure . But it does happen = bonus .

4x4 supa centre
160watt under 200$ delivered

REMEBER a car battery is between 50-75ah U can use this but good 100% solar charge is an ABSOLUTE MUST .
Your current setup is under done . This WAS the case for most when solar was expensive . ******Its not now .*****
Car battery will have a short life if u keep discharging it and not recharging it .

Yes we all have done what u have done when starting out but nobody goes back to that situation .

stoney123 · Senior Member

If its just a few days camping then get an evakool Esky, ad says 7 days but I easily do 4-5 before ice melts. I freeze coke bottles (lots). I also have solar and battery and Engel which I run as a freezer and swap coke bottles and food so no big draw on battery. Only open freezer every 2-3 days.

stoney123 · Senior Member

As Tim the toolman always says "more power" Never run fridge off car battery Get at least 1 X 200 watt panel you can get 350 panels I have 2x200 Get two AGM batteries I am running 2x160. But I run a few other this things. Sometimes no sun, cloudy or smoky as we had during summer.