Fridge w/out solar?

[ValerieP]

I'm curious, and I'm sure someone knows. I want an ac/D.C. Fridge, but I don't have solar yet. I can plug into shore power from 5pm- 6am daily and I drive about 30 minutes a day- the rest of the time the van sits. Could I run the fridge off a battery during the day and re-charge it with the shore power? 
Thanks!

 

[Bohemian scout]

I have a small 12v fridge with a house plug in adapter. If I have house power available I plug in if not I have an agm battery in my van hooked up to a 12 volt plug. I can camp 3-5 days without recharging the battery but then I need to drive the van to recharge the battery. What I need is a way to charge the auxiliary battery without driving. I’m trying to figure that out now and planning on getting solar soon. This is stuff I don’t understand at all so I’m trying very hard to learn. I love my fridge, it makes a big difference if you’re trying to eat healthy and I don’t throw away money on ice.

 

[ValerieP]

Thanks- so there is a way to do that! I will get solar at some point, but not until I figure out how and where I want it. In the meantime, I want a fridge. I think I'll get a battery that will go with the solar, and the thing that measures its level to start. This business is quite confusing- there was a ton of great info on your thread- I'll read it again!

 

[user 37446]

If you have a 12v compressor fridg (Dometic, ARB, Engel, Whynter type) that is on the smaller side (less than 35 quarts) and you have it insulated with either polyiso or blankets, the duty cycle (how often it needs to run to maintain temperature) is about 15-25% of the time (keep it out of the sun and ventilated).  They draw 2-5 amps per hour average, according to what I have read in the forums, depending on where the thermostat is set.

A larger house battery (100 amp) that can be drawn down to no more than 50% (good rule of thumb for a deep cycle) allows you 50 amps in 24 hours, so if you are running the fridg during the day you should be ok (say 15-25 amps drawn off).  As long as you recharge your battery fully off that shore power that you have available, and cool your fridg down to just above freezing during the night, I think you will be fine.

Key think is insulate the fridg more, and don't block the cooling port (fan).

Here's a recent review from a Dometic 34 quart user:

Updated 4/1/17
=====================================
The results of the cool down test are chilling.

"Cooling 2.5 gallons of water from 39 to 33 took 5 hours and used 4.75 amps or about .95 amps an hour. That is not linear by the hour. It varies. More in the beginning less at the end. But if you run this out for 24 hour you are going to need 25 amps. + what you use in the trailer – In my case 31 amps. BUT that is not the case since after the food reaches the desired temp the energy consumption drops to about a half amp. My two solar panels will have no problem with full sunshine and even clouds. BUT this is no substitute for real world testing. The 55 amp hour batty (25 useable amps) might work with the two solar panels I did would not feel comfortable with that setup. With 115 (50 useable amps) I would be using 31 amps and still have about 20 amps left with no charging. With the solar panels limping along at half capacity on a cloudy day I would be fine. Under trees on a really shadow less day I might need a third panel – time will tell. But I am confident I can do fine with 2 panels. Keep in mind this is the cool down mode. Maybe the first 12 hours after the food purchase. I use very thin solar panels and I could easily carry a third panel with my controller.

For the second test I want to verify the battery drain after the water was cooled to 33 degrees and find how much electric it takes to keep the food there overnight. I am trying to simulate after the restock food and is chilled to the right temp. I am thinking I can get by for several days with the food and want to know what is the drain over 24 hours. For this test I set the fridge temp to 33F I started with the battery freshly charged and ambient temp of 65F

Over 12 hours the fridge used ,47 amps an hour to keep th3 water at 33F. That is truly amazingly low energy consumption. 24 hour consumption would only be 11.28 amps (in my living room).

So under ideal stable lab conditions (I rounded up) at 12 hours of daytime @ one amp an hour - 12 amps consumed. At night 6 amps consumed @ ½ amp an hour. 18 amps is a good starting estimate (for me) until I can get outside in some hot weather."

 

[Trebor English]

I can plug into shore power from 5pm- 6am daily 

Can you put a couple of 2 liter bottles of water in the fridge?  If you plug it in over night, let it get cold, and then keep a blanket on it during the day that might work.  

I have mine set to shut off at 30 degrees so the water freezes.  It only runs when the sun is shining.

 

[HumbleBeginnings]

If you have a 100Ah battery and you charge to full on shore power every day, you're absolutely golden. You could probably get by with less battery, but then you're narrowing your margin for error and things like ambient temp will become more important.

What is your current battery?

 

[Almost There]

I'm curious, and I'm sure someone knows. I want an ac/D.C. Fridge, but I don't have solar yet. I can plug into shore power from 5pm- 6am daily and I drive about 30 minutes a day- the rest of the time the van sits. Could I run the fridge off a battery during the day and re-charge it with the shore power? 
Thanks!

That will depend on the size of the battery and also the battery charger you  use.

If it's a smallish battery and you're using something like a trickle charger, no! If you're using a decent sized battery and a charger matched to it (not one of the 'Smart Chargers' (which should be called 'stupid chargers'... then you should be good to go.

 

[ValerieP]

That will depend on the size of the battery and also the battery charger you  use.

If it's a smallish battery and you're using something like a trickle charger, no! If you're using a decent sized battery and a charger matched to it (not one of the 'Smart Chargers' (which should be called 'stupid chargers'... then you should be good to go.

Could you recommend a battery and charger- one that is sealed? I've been reading several threads but haven't found any thing solid- I would like to use the battery as part of the solar later- I'm thinking of 200-300 of solar before next summer.

 

[frater secessus]

I want an ac/D.C. Fridge, but I don't have solar yet. I can plug into shore power from 5pm- 6am daily and I drive about 30 minutes a day... Could I run the fridge off a battery during the day and re-charge it with the shore power? 

Daily shore power is what's going to make this work.  Getting back to 100% charged regularly (daily is preferable) will really help the battery last.  

What do you mean when you say AC/DC?  Some of the compressor fridges have both power inputs and choose AC when available.  They are quite expensive.  Dorm type AC fridges can be run off an inverter but will likely require more battery bank.

For daily connection to shore power I would encourage you to install a shore power port.  Makes [dis-]connecting quick and easy, and elminates running cords through cracked windows or open doors. Keeps bugs and rain out.  Drilling a "small" hole like that is also a great way to get used to the idea of hacking on your new van.    

[img=200x133]http://www.overlandtrailer.com/wp-content/uploads/2012/01/IMG_0412.jpg[/img]

As far as chargers, I'd consider installing a converter since you are going to be on shore power so much.   It's about $160 for a 30A Progressive Dynamics converter with the charge wizard doodad that adds in three-stage charging.  You could get one with more power but:

1. you are on shore overnight, so 30A is plenty; and
2. you will be adding in solar which will help keep the bank up during the day.  

I made a very small 10A DIY converter for about $100 because I am both cheap and a control freak.  But that size and approach is not for everyone.  

A few forum members (including Trebor and Sternwake) run combined starter/house banks.  From memory, Sternwake used a high end AGM battery and manually charged with a power supply from shore power + solar.  Trebor runs a marine-type battery that is augmented with 100w of solar.  And of course in a setup like that the battery is also being charged when the vehicle is driven.  Again, not for everyone but an elegant solution where appropriate.

 

[Bohemian scout]

Thanks- so there is a way to do that! I will get solar at some point, but not until I figure out how and where I want it. In the meantime, I want a fridge. I think I'll get a battery that will go with the solar, and the thing that measures its level to start. This business is quite confusing- there was a ton of great info on your thread- I'll read it again!

I have a dometic 18 quart fridge. I get it cold using shore power and everything I put in is cold. It’s tricky figuring out the right setting because things will freeze! I keep mine set very low, just 2-3 notches up. I keep the fridge covered and I’m getting ready to make a reflectic cover for it. If the weather is nice it rarely comes on.

 

[John61CT]

Absolutely yes, not just fridge but **anything** you can power off solar (and more) will work of daily overnight access to shore power, just need a powerful quality charger and batteries.

Don't even worry about tapping into the alternator while driving, as long as you're getting to mains power every night for 8+ hours no worries at all.

Only limit is weight/space and expense of the battery bank; going to LFP will give you a quarter the weight half the space, maybe 5-7x the cost.

 

[ValerieP]

Absolutely yes, not just fridge but **anything** you can power off solar (and more) will work of daily overnight access to shore power, just need a powerful quality charger and batteries.

Don't even worry about tapping into the alternator while driving, as long as you're getting to mains power every night for 8+ hours no worries at all.

Only limit is weight/space and expense of the battery bank; going to LFP will give you a quarter the weight half the space, maybe 5-7x the cost.

Is the cost worth the expense and will the battery pair well with the 200-300 watt solar I plan? Also, is any one brand of lithium battery better for the price than another?  
Thanks for your input!

 

[John61CT]

Post the LFP question separately, but only if spending thousands on a bank is something you'd actually consider

Will otherwise derail this thread completely.

 

[John61CT]

> Is the cost worth the expense?

Only you can answer. For advice budget out specific alternatives.


> will the battery pair well with the 200-300 watt solar I plan?

Depending on latitude and weather, 100-300AH in size.

Type depends on lots of variables. Cheapest is a pair of FLA 6V golf car batts, maybe $190?

 

[Trebor English]

A completely different approach:  
(1) Get a cheap very small "dorm" fridge  
(2) Put ziplock bags half full of water in the freezer compartment.  
(3) Plug it in and set the thermostat cold enough to freeze the water.  

For $80 for a cheap fridge and $20 for an extension cord you have a fridge.  12 hours plugged in is plenty to make a block of ice 8 to 10 pounds.  That will keep the fridge cold for 12 hours.  When you get solar and batteties and inverters and all that stuff give the fridge away, sell it, or pitch it.  It's only $80, cheaper if bought used.  Meanwhile you get a fridge now without any foreign technology.  

This will work with a tiny fridge that has a freezer compartment to put the water / ice in.  

I recommend a quart of water in a half gallon heavy duty "freezer" ziplock bag.  Get the plain zip, not the one with the little plastic slider.  They all leak, extra specially in the corners.  A couple of drops of Dicor roof sealant carefully spread across the length of the zipper works.  That's what I have.  Something that stays flexible would be better than something that gets brittle.  Tar would be better than super glue.  Vaseline might work paryicularly when cold.  It is hard to seal up a quart of water trying to exclude air.  Don't let perfection be your enemy, some air just wastes a little bit of space.  My Haier 1.7 cubic foot easily holds 4 bags each holding a quart.  Each quart is about 2 pounds.  

If you add warm drinks only when plugged in it might keep food cold better.   I regularly buy frozen foods.  They thaw and keep ok refrigerated until eaten.

 

[ValerieP]

Great ideas! Thanks!

 

[Trebor English]

We are curious.  Let us know what you end up doing and how that works.

 

[ValerieP]

I'm still thinking- I need to learn more about batteries, and weigh the cost. I would really like to spend money on something that will stand the test of time, but....

 

[John61CT]

The best battery value by far is Duracell (actually Deka/East Penn) GC-2 from BatteriesPlus or Sam's Club deep cycle golf cart batteries, 2x6V, 200+AH @ less than $180

 

[John61CT]

IMO better than ziplocs, not expensive

Google "polar tubes", just glue-capped 2" PVC, cut to the right length and filled 85% full with seawater.

Will likely stay cold 6-8 days in a well insulated box, longer in super Yeti style cooler.