Real world battery consumption from residential 12v fridge

[Quadna71]

Can anyone give us some real world experience regarding how hard our 12v fridge will eat at a battery? The label in the fridge says 11 amps and the chart I was referencing said to multiply that times the hours of use for a total. But that can’t be a true realistic expectation since the fridge isn’t cycling non-stop, right?

Our current battery, a 24 group 450 cca marine dual purpose battery, is shot and needs to be replaced. I’m leaning towards getting a new charger/converter that can handle lithium and then putting at least a single 200ah lithium battery under the bed. Seeing how very little time we were able to run the fridge on the OEM battery, I’m hoping someone can chime in and let us know if the significantly larger battery can keep us boondocking for a solid 2 days or maybe even 3. I do have the same Renogy 100w solar suitcase that a lot of other folks have so we can sometimes extend our time a little but nothing significant. I also don’t see adding panels to our roof in the immediate future, so I’ll be relying heavily on just what the battery bank can do for us when we start at 100%.

Thanks for anything you can offer!

Everchill - model #WD-282FWDC
Volume - 10.7 cu feet
Rated voltage - 12v DC
Rated current - 11 amps
LED lamp power - 1 watt

[bikendan]

Originally Posted by Quadna71

Can anyone give us some real world experience regarding how hard our 12v fridge will eat at a battery? The label in the fridge says 11 amps and the chart I was referencing said to multiply that times the hours of use for a total. But that can’t be a true realistic expectation since the fridge isn’t cycling non-stop, right?

Our current battery, a 24 group 450 cca marine dual purpose battery, is shot and needs to be replaced. I’m leaning towards getting a new charger/converter that can handle lithium and then putting at least a single 200ah lithium battery under the bed. Seeing how very little time we were able to run the fridge on the OEM battery, I’m hoping someone can chime in and let us know if the significantly larger battery can keep us boondocking for a solid 2 days or maybe even 3. I do have the same Renogy 100w solar suitcase that a lot of other folks have so we can sometimes extend our time a little but nothing significant. I also don’t see adding panels to our roof in the immediate future, so I’ll be relying heavily on just what the battery bank can do for us when we start at 100%.

Thanks for anything you can offer!

Everchill - model #WD-282FWDC
Volume - 10.7 cu feet
Rated voltage - 12v DC
Rated current - 11 amps
LED lamp power - 1 watt

I've never heard of a 12v "Residential" fridge nor such a thing in a house.
Residential fridges in RVs, are 110v AC, like a house fridge.

[boondocking]

Originally Posted by bikendan

I've never heard of a 12v "Residential" fridge nor such a thing in a house.
Residential fridges in RVs, are 110v AC, like a house fridge.

Many off grid (in home) residential fridges are 12V.

[Ballistic]

We just bought wolfpup 18to a month ago and we have the same fridge along with two Interstate group24 batteries(HD24-DP). I too was wondering how long it would last so I performed the following test. The TT was in our shop with an ambient temperature of 40F (4C). While connected to shore power I ran the fridge/freezer to get it to the proper operating temp (32-40F). Next, I topped off the batteries with an external battery charger and then let them rest for one hour. I turned on one light and set the furnace thermostat to 65F. With this configuration at these ambient temps (meaning the batteries are at 40F) the batteries had a voltage of 12.20V; 50% SOC at 48hr.

I performed the same test using two group27 batteries and their voltage was 12.35V which came to 65% SOC. I've used this chart for temperature compensation.

[Quadna71]

Originally Posted by bikendan

I've never heard of a 12v "Residential" fridge nor such a thing in a house.
Residential fridges in RVs, are 110v AC, like a house fridge.

Sorry about the confusion. I’ve noticed that in some of the RV forums folks were describing the 12v fridges in their RVs as “residential” likely due to their larger size compared to the dual ones that are typically smaller and run on propane or 110v AC. But rest assured it is a regular fridge that runs on just 12v with no cooling option via 110v AC power nor propane.

[Quadna71]

Originally Posted by Ballistic

We just bought wolfpup 18to a month ago and we have the same fridge. I too was wondering how long it would last so I performed the following test. The TT was in our shop with an ambient temperature of 40F (4C). While connected to shore power I ran the fridge/freezer to get it to the proper operating temp (32-40F). Next, I topped off the batteries with an external battery charger and then let them rest for one hour. I turned on one light and set the furnace thermostat to 65F. With this configuration at these ambient temps (meaning the batteries are at 40F) the batteries had a voltage of 12.20V; 50% SOC at 48hr.

I performed the same test using two group27 batteries and their voltage was 12.35V which came to 65% SOC. I've used this chart for temperature compensation.

Since the second test that used two group 27 batteries yielded better results, would I be safe in assuming your original test was with two group 24 batteries? Would you happen to know what the amp hour capacities are for either of your batteries (group 24 or 27)? Sometimes it is hard to try to equate a group 24 or 27 dual purpose lead acid battery to a lithium battery. It seems the dual purpose batteries are rated for cold cranking amps and not amp hours. No matter what thanks for your reply with your test results - very helpful!

[Ballistic]

Oops, yes they. Two interstate HD24-DP. They're not even close to being a "deep cycle", they a dual purpose battery. I've edited my post.

[Quadna71]

Thanks again. It is surprising how our dealer would only provide us with a single group 24 battery (and a pretty bad one at that) considering the demand we can put on it between the fridge and maybe running the water pump here and there when camping off-grid. Almost shameful once you start thinking about how much we pay for these things too. Forest River should dictate dual group 27’s for anything with a fridge like ours. Oh well..enough complaining on my part.

I think running the cables to under the the bed will be a pain but worth it in the end to keep new lithium batteries both secure and warmer than outside on the tongue. But if I end up just going with a pair of group 27 lead acids, I’ll likely leave them on the tongue for simplicity.

[Ballistic]

These Interstate group24 batteries I'd put around 70Ah on a good day and the group27 I have state 100Ah on the label; they're OEM'd by Exide. They too are not a deep cycle, but I had them laying around and I'd figure I'd give it a test. The downside is added tongue weight.

It takes a bit of Kentucky windage to calculate RC and/or CCA into useable Ah. IMO it's far from accurate and not meant for RV use.

[Ballistic]

Originally Posted by Quadna71

Thanks again. It is surprising how our dealer would only provide us with a single group 24 battery (and a pretty bad one at that) considering the demand we can put on it between the fridge and maybe running the water pump here and there when camping off-grid. Almost shameful once you start thinking about how much we pay for these things too. Forest River should dictate dual group 27’s for anything with a fridge like ours. Oh well..enough complaining on my part.

I think running the cables to under the the bed will be a pain but worth it in the end to keep new lithium batteries both secure and warmer than outside on the tongue. But if I end up just going with a pair of group 27 lead acids, I’ll likely leave them on the tongue for simplicity.

I feel there are a number of more affordable lifepo4 batteries, however most of these affordable units don't have low temperature charging integrated into their BMS. I too have been mulling over lifepo4 batteries as well as relocating them under the bed as you've stated. Less weight, more AH and higher C-rates across the board...what's not to want about them. The way I see it is it will only take one trip to be ruined when the LA batteries die and there will most likely be similar trips in the future where power requirements will be more than the LA batteries can provide. I'm going lifepo4, but I haven't decided which one yet.

[Quadna71]

Agreed. I grew up in Minnesota where CCA was near and dear to our hearts. Even with a block heater, it can sometimes be a challenge starting your truck when it is -25F (ambient) outside. Here in Delaware that no longer is a problem.

I’m currently leaning towards the SOK 12v battery - high/low temp protection and serviceable. Not sure if I should go for a single 100ah and then maybe add a second later in the season if one isn’t enough. Or maybe go for a single 200ah right from the start and then likely be good. I know you can run them down significantly further so a 200ah lithium already has a huge advantage over two 100ah lead acids, you know?

I know that Battleborn is the hot name everywhere and for very good reason…but I just don’t want to spend that sort of money.

[JimM2109S]

Originally Posted by Quadna71

.....Not sure if I should go for a single 100ah and then maybe add a second later in the season if one isn’t enough. Or maybe go for a single 200ah right from the start and then likely be good. I know you can run them down significantly further so a 200ah lithium already has a huge advantage over two 100ah lead acids, you know?....

Something to consider in the two 100ah v one 200ah LiFePO battery decision. Two 100ah batteries, each with a 100a BMS, will provide up to 200a of power when connected in parallel. The 200ah battery would likely only have a 100a BMS and thus only be able to supply 100a of power.

Also, with two 100ah batteries, should one fail (cell or BMS), you still have the second battery to rely upon until you can replace the bad battery. If the same should happen to the 200ah, you're basically out of luck energy wise.

[tomkatb]

Math is simple.

Your fridge can consume 10 ah running full tilt. That is what it would during the summer in the Midwest during the summer.

100 ah dc in your car battery is limited. If you use over 50% then you cause the battery to die early.

Thus, after 5/hours crossing tTexas the fridge will be done!

It has everything to do with the indoor temp of the rv. Plus what ever other loads you put on the battery! Lord help you if you need to use the furnace. You would not have made midnight anywhere.

The single battery in the trailer was for the brakes. A legal requirement, not to run the fridge. You are supposed to be on shore power to use it.

The more batteries you have, the better. A 300 ah dc lithium battery is about $1200. That would allow you to be off shore power for days, not hours.

[Quadna71]

Originally Posted by JimM2109S

Something to consider in the two 100ah v one 200ah LiFePO battery decision. Two 100ah batteries, each with a 100a BMS, will provide up to 200a of power when connected in parallel. The 200ah battery would likely only have a 100a BMS and thus only be able to supply 100a of power.

Also, with two 100ah batteries, should one fail (cell or BMS), you still have the second battery to rely upon until you can replace the bad battery. If the same should happen to the 200ah, you're basically out of luck energy wise.

You make two very good points. While I don’t see us in a position where we would likely need anywhere near 100 amps of continuous consumption (small RV, limited features, and no power inverter for other appliances), it really would be a bummer to have a single battery be the point of failure.

[Quadna71]

Originally Posted by tomkatb

Math is simple.

Your fridge can consume 10 ah running full tilt. That is what it would during the summer in the Midwest during the summer.

100 ah dc in your car battery is limited. If you use over 50% then you cause the battery to die early.

Thus, after 5/hours crossing tTexas the fridge will be done!

It has everything to do with the indoor temp of the rv. Plus what ever other loads you put on the battery! Lord help you if you need to use the furnace. You would not have made midnight anywhere.

The single battery in the trailer was for the brakes. A legal requirement, not to run the fridge. You are supposed to be on shore power to use it.

The more batteries you have, the better. A 300 ah dc lithium battery is about $1200. That would allow you to be off shore power for days, not hours.

Even out here in Delaware the summers are brutal - often hovering around the 100 degree mark and high humidity. But you won’t find us in any sort of situation like that without shore power to run our A/C….those days of roughing it are long gone! That’s why this whole scenario for us is just a night here or there while on the way to a good location with reliable power.

It goes against my thinking that you would think the fridge is only to be used when on shore power. Why would they even have it powered by 12v and not straight 110VAC if that were the case?

300ah of battery, eh? That would be frickin’ awesome!!! Sure wish the LiFePO4 batteries weren’t so spendy!

[boondocking]

Originally Posted by tomkatb

Math is simple.

Your fridge can consume 10 ah running full tilt. That is what it would during the summer in the Midwest during the summer.

100 ah dc in your car battery is limited. If you use over 50% then you cause the battery to die early.

Thus, after 5/hours crossing tTexas the fridge will be done!

It has everything to do with the indoor temp of the rv. Plus what ever other loads you put on the battery! Lord help you if you need to use the furnace. You would not have made midnight anywhere.

The single battery in the trailer was for the brakes. A legal requirement, not to run the fridge. You are supposed to be on shore power to use it.

The more batteries you have, the better. A 300 ah dc lithium battery is about $1200. That would allow you to be off shore power for days, not hours.

According to your calculations of the fridge running at 10 amps, a 300ah lithium battery would not last days, it would be closer to 30 hours.

[W5CRE]

Originally Posted by boondocking

According to your calculations of the fridge running at 10 amps, a 300ah lithium battery would not last days, it would be closer to 30 hours.

That's 10 amps when the compressor runs. Most of the RV 12vdc refrigerators consume between 2 to 3 amps per hour. I would plan for about 60 ah from a battery bank per 24 hours. That is if you aren't running any solar or charging with a gen set during the day.

[FFred]

"24 group 450 cca marine dual purpose battery,"

These are made for small fish boats that want to run on an electric moor for hours , and have enough kick to start the outboard.

A better choice is a true deep cycle batt.

For much boondociking you will probably need at least a pair of AGM to last overnight and have a useful service life.

Freezing containers of water before camping can help.

[NMWildcat]

The goal of most boondockers I hang out with is to have enough battery so that fully charged they will last through the night. Then you recharge them the next day via solar, generator, etc.
Lithium is great, but still too expensive.
You need at least 2 deep cell or marine type batteries and a way to fully recharge them daily if you plan to boondock several days.
This is one area where you can easily overthink it and make it much more difficult and expensive than it needs to be.

[18LT]

Originally Posted by Quadna71

It goes against my thinking that you would think the fridge is only to be used when on shore power. Why would they even have it powered by 12v and not straight 110VAC if that were the case?

300ah of battery, eh? That would be frickin’ awesome!!! Sure wish the LiFePO4 batteries weren’t so spendy!

Your thinking is correct, in that the 12-volt refrigerators are not specifically to be powered from shorepower via the onboard converter.
Yeah, a 300 amp-hour lifepo4 battery is freakin’ awesome! I bought one in late summer and it’s a noticeable improvement when compared to my two 100ah lifepo4 batteries.
I’m buying a second 300ah battery today while the price is still under $1000. Also buying a 3000-watt inverter/charger to replace my trailer’s 1000-watt unit. A couple of Merry Christmas gifts to myself.
P.S. it appears that almost all of the 200ah and 300ah batteries utilize the same case and the same bms (200 amp continuous discharge).