How long will a 12 volt fridge run on battery?

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How long will a 12 volt refrigerator run on battery?

We just wrote about a bunch of fridge stuff. And so I thought I'd chat about this just for a couple of minutes, because it's such a common question. It's all over the web. So it's a people also ask in Google search it's on forums and Facebook, and it's one of those questions that everybody has on their mind.

I think even experienced vanlifers are often wondering; what's my fridge going to draw on this trip or whatever, or with this battery, et cetera.

And mostly I'm here to say that it's complicated and there is no easy answer. You can't just say a 100 amp hour lead acid battery will run a fridge for X hours because every fridge and every user are different

And so what I want to do is just run down the checklist that we made here. And, by the way, you can just go to vantage.com and type in fridge. And you'll, you'll see three or four articles about 12 volt refrigerators and things like power use and runtime, et cetera.

We did a bunch of research on this just to make sure that we had it covered thoroughly and that we could offer a solid response to this question.

There are several factors impacting how long a 12 volt fridge will run on a battery and those factors include the size of the battery, obviously in amp hours. And then quickly we get right to battery chemistry.

So. Consider that a lead acid battery should not be run below 50% of charge because below that they start to break down or, they break down more quickly.

You shorten the life of the battery and batteries are expensive. And so the more you run the thing below 50% of charge, the sooner it will die and you'll have to replace it and this is one of the reasons that, with the newer chemistry out, specifically, lithium iron phosphate or LiFeP04, and even lithium ion in the form of the solar generators that are out available.

I don't think it makes sense to buy lead acid batteries. Now I'm not here to rag on anybody who owns lead acid batteries. I've owned them in the past. They're wonderful things.

Obviously they solve power problems for people. And if you’ve just spend a bunch of money on lead acid batteries, don't think that I'm telling you to run out and replace them.

No, use them till they're used. Or until you're annoyed with charging, recharging them at 50% or whatever, and you can afford to upgrade to lithium iron phosphate.

And even the lithium ion solar generators are spectacular. You can run them down to nothing. You get 2,500 to 4,000 recharges on them.

And I'm not sure what it is for lead acid. I think it might be a thousand or 2000 recharges, but again, that you have to cut that in half because you only get to use 50% of it.

So that's enough about that except to say that when you're calculating how long of 12 volt fridge will run on a battery, you have to consider that the lead acid has to be recharged at 50%. So half as long as the lithium chemistry options.

Uh, then there's another factor; the operating amps of the fridge compressor motor. Now that tends to be in the two to six amp range, and that will be directly impacted by the some other factors.

It's it's funny because some of the higher average fridges will run longer on battery because maybe they're slightly smaller or they have much better insulation or the compressor motor is variable speed instead of consistently running at the same speed.

The newer ones tend to be variable and therefore use power as needed instead of just being binary on off. So keep that in mind as well. And when you go to buy a fridge freezer or upgrade your fridge freezer, make sure that that the compressor has a variable motor.

Then there’s your thermostat setting. Obviously, if you're freezing down to 30 degrees, the fridge is not going to run as long.

then there's ambient temperature, and this is a big one because insulation can only do so much if it's 110 degrees outside and your fridge is sitting in direct sunlight.

Some of the people who do very serious testing on the various 12 volt fridge freezers do set them in direct sunlight as part of their testing protocol.

Others keep them in a vehicle or they'll do both. And I'll give you a resource for someone who's done a very wide range of testing protocols in our article, “How long will a 12v fridge run on battery?”. If you go look at the site, you can see a blog I linked to with some testing protocols on it for fridge freezers.

So the ambient outdoor temperature, if it's 30 degrees outside and your fridge is set to a higher temperature, then it's going to use very, very little power.

Those thermostat settings have a direct impact on how long a 12v fridge will run on battery.

And then there's the temperature in your van. You've got your fridge in your van and you're keeping the interior at 70 degrees with your nifty Webasto diesel heater, so your fridge is going to work a little harder to keep your food down around 36 degrees.

So it isn't that funny how we're, to keep ourselves warm, we're working against the efficiency of our refrigerator. It's a small price to pay. Let's face it.

And then there's the issue of how often the fridge door is opened and for how long.

If you've got a kid running around flopping that door open every 20 minutes to grab another soda or some ice water or something, then your fridge is going to be very inefficient. It's going to use more power, still be efficient, just the circumstances have caused it to use more power.

And then how the fridge is built is a factor. As I mentioned, insulation (and we just did a review on the iceco iCooler) And that thing is built with roto molded plastic and really thick insulation. So all, all bets are off with that. It's much more efficient than most of the stuff on the market.

although it's been pointed out to me that for example, the Dometic fridges are super efficient and they take up less room and Dometic just does such a fabulous job of insulation and construction that their fridges are more efficient with less insulation than some others.

So that's cool. I'll give you a kind of rundown. You can expect some kind of parameters with regard to runtime on battery.

A 12 volt refrigerator in size 30 to 50 liters, the lowest use, that is, lowest power use in colder ambient temperatures in wintertime will use less power. So it's going to use maybe 25 amp hours in that temperature range.

And then the average power use may be 65 to 70 degrees Fahrenheit, it might use 35 hours of power, so a bit more.

And then it at higher ambient temperatures above 80 degrees, maybe 45 amp hours.

But again, there's so many factors involved.

So you have to kind of do your own experimentation, and you can do that. You can just plug the thing in and stick it in the sunlight and run it for 24 hours or run it during the day and clock the power use and then run it all night and clock the power use, then run it while you're cooking, et cetera.

And it is helpful to know just how much power your fridge is using, because if it's using an Inordinately high amount of power, then there might be a problem. You might have a draw somewhere, a short, you might have a very leaky door, maybe your 12 volt refrigerator is old and worn out and it's time to replace it. There are a number of reasons that your fridge might be inefficient.

You also might surprise yourself and find that it's super efficient and it does a great job.

And you know, if you've been using one fridge for years and you switched to a new one, you don't want to assume it's more efficient. You want to actually test it and check it out. So those are my suggestions with regard to how much power a 12 volt fridge uses.