Nova Kool RFU7300D Fridge battery usage

[MT45]

For the newer Airstream Interstates GT and GL that come with the 12 volt only Fridge and freezer (upright stack). Does anyone have some real world data on battery consumption?

Assume AGM batteries, not lithium; assume door kept closed.

Would really want to know:
Driving down the road consumption, and also, does alternator charge the house batteries, so that the fridge then pulls from the batteries? If so, does it “keep up?”


Boondocking consumption, just sitting, no generator running

Lastly, as the fridge is 12v only, I’m assuming if I run the generator then it is charging house batteries, then the fridge pulls from those?

Thx

[WBB]

I just installed a shunt in my van and "played" with it a little. From what I can tell, the house monitor and multiplex, etc. draw about 2 amps. Turning on the fridge and freezer, so at max power, they seem to draw 10 amps. Note, they do not run 100% of the time, but when they are running, I am showing a max draw of 12 amps total (10 for fridge and freezer and 2 for "other stuff".) You can verify the amperage of the fridge in the manuals.

As you know your fridge runs off the batteries and the batteries can be replenished / recharged with solar, shore power, the generator or the alternator. Solar will vary with weather and is not available at night, but I believe all the other charging sources will more than 12 amps to fully offset the consumption and what ever excess there is will charge the batteries.

For example, on shore power, say your battery charger puts out 24 amps and the fridge and freezer are both running, the "house" consumption might be 12 amps, so the excess over consumption is charging the batteries (12 amps). If the fridge and freezer reach the target temp and shut off, your consumption might drop to 2 amps and 22 amps would be available to charge the batteries.

Your question about consumption when boondocking is a little harder to answer. Without getting into the numbers, the short answer is - in our experience- with 200 Ah of lithium and no solar or other charging, we wake up the second morning of boondocking with the batteries almost totally used. This means we are using about 100 Ah per day with conservative power use and, say 80 degree weather. As you may know, since AGM/Lead acid batteries can only be discharged 50%, you would need 400 Ah of AGM batteries to have the same power available as 200 Ah of lithium batteries.

If we have very good solar production, I am guessing we will receive between 50-75 Amps in a day from our 300 Watt panels, so if our consumption is 100Amps per day and we get 50 amps from solar, our net "use" is 50 amps (100-50), so we could conceptually boondock for four days (200 Ah battery/ 50 Amps pre day).


Hopefully this helps.

-Bill

[StogieMan]

I'm sorry but I really don't pay too much attention to it but I think WBB has it about right at around 10A. I don't pay attention to it as we have 600Ah's of lithium and on any given night with everything running- refrigerator/freezer, Starlink, microwave, air fryer, lights, cell phone & laptop chargers, water pump and I mean everything - we drop down from 100% to 80% every single time that we've gone out per night. We don't hold back and use everything without a care in the world.

Obviously we have solar, generator and alternator charging to charge up our batteries but lately it's just been the two Orion XS DC to DC charges doing the bulk of the work.

[uncle_bob]

Hi

Per the spec on the fridge, there are two compressors and they each pull a max of 5.5 amps. If it's really hot out, they both will run full time. When you get down to the 60's they drop back to about 30 to 40% run time. How you set the internal temp and how often you open the doors has an impact on the numbers.

The modern vans have a DC/DC converter that charges the batteries while you are going down the road. It's rated at 50A. They throttle it back to keep from overloading the van alternator. Ours puts out about 30A as we drive along.

As noted by others, you have about another 1 to 2A of this and that most of the time.

The inverter / charger will also put about 30 to 40A into the batteries if you are on shore power or if the generator is running.

If you are lucky (as in really lucky) you might get 40AH a day from the solar on the roof.

So how does that all work out?

Absolute worst case, you have maybe 12A and that *could* be 24 hours a day. In that unrealistic / insane situation, your 200AH batteries would last for about 16 hours if they are the only power source.

In a far more realistic case, you are around 5A and burn off about 120AH in a day. If you drive for about 4 hours, you could top them off. It would be even faster if there's enough sun to be useful.

Yes, this assumes you are frugal with power usage. If you like running the inverter to power this or that .... yikes !!!!

Lots and lots of variables.

Bob

[Hermes]

Originally Posted by uncle_bob

Hi

Per the spec on the fridge, there are two compressors and they each pull a max of 5.5 amps. If it's really hot out, they both will run full time. When you get down to the 60's they drop back to about 30 to 40% run time. How you set the internal temp and how often you open the doors has an impact on the numbers.

The modern vans have a DC/DC converter that charges the batteries while you are going down the road. It's rated at 50A. They throttle it back to keep from overloading the van alternator. Ours puts out about 30A as we drive along.

As noted by others, you have about another 1 to 2A of this and that most of the time.

The inverter / charger will also put about 30 to 40A into the batteries if you are on shore power or if the generator is running.

If you are lucky (as in really lucky) you might get 40AH a day from the solar on the roof.

So how does that all work out?

Absolute worst case, you have maybe 12A and that *could* be 24 hours a day. In that unrealistic / insane situation, your 200AH batteries would last for about 16 hours if they are the only power source.

In a far more realistic case, you are around 5A and burn off about 120AH in a day. If you drive for about 4 hours, you could top them off. It would be even faster if there's enough sun to be useful.

Yes, this assumes you are frugal with power usage. If you like running the inverter to power this or that .... yikes !!!!

Lots and lots of variables.

Bob

You know what all this reminds me of? Managing the power of your electric vehicle (EV). The automobile industry is figuring out now that for many buyers, hybrid is the way to go; you are running on electric for most of the vehicle's use, but you have the engine when you run out of electric power.

Airstream, with its 100% electric fridges, is forcing the "full electric" option on airstreamers, no hybrids, no choice. With the equivalent of "range anxiety" when aistreaming which is the last place we want anxiety!

Not cool (no pun intended)

[StogieMan]

Originally Posted by Hermes

You know what all this reminds me of? Managing the power of your electric vehicle (EV). The automobile industry is figuring out now that for many buyers, hybrid is the way to go; you are running on electric for most of the vehicle's use, but you have the engine when you run out of electric power.

Airstream, with its 100% electric fridges, is forcing the "full electric" option on airstreamers, no hybrids, no choice. With the equivalent of "range anxiety" when aistreaming which is the last place we want anxiety!

Not cool (no pun intended)

In a van you kinda want the fridge/freezer to run on 12v as to not pay the conversion tax over to AC. When not tied to shore power, generator or if the sun is not out, the refer is running off our inverter. The batteries are using more power to convert power from DC to AC via the inverter.

On the older Nova Kool fridges & Freezers, you had a choice of running them on either AC or DC but many of us just unplugged the AC side of it and ran them strictly on DC.

[uncle_bob]

Originally Posted by Hermes

You know what all this reminds me of? Managing the power of your electric vehicle (EV). The automobile industry is figuring out now that for many buyers, hybrid is the way to go; you are running on electric for most of the vehicle's use, but you have the engine when you run out of electric power.

Airstream, with its 100% electric fridges, is forcing the "full electric" option on airstreamers, no hybrids, no choice. With the equivalent of "range anxiety" when aistreaming which is the last place we want anxiety!

Not cool (no pun intended)

Hi

If you dig a bit: The EU outlawed the sort of "propane fridge" that we all used to have. Since the folks that make them are all over there, that pretty much was a death blow. They will stop making them within the next year or three. When they do, there are no more warranty parts to be had from them.

AS actually dragged their feet on moving over to full electric. I'm guessing they bet on the rule being revised or amended. That didn't happen. Most of the other RV outfits completed the conversion before they did.

Can you maybe buy this or that from a tiny little shop that makes a few dozen fridges a month? You probably can. That sort of "supply chain" isn't going to keep the RV industry fed with fridges. Also the RV's with those fridges will be off the list for sales in Europe (and likely other places that follow the same set of rules).

So no, this was not something that the RV folks *wanted* to do.

Bob

[MT45]

Great feedback so far - thank you all!

[Hermes]

Originally Posted by uncle_bob

Hi

If you dig a bit: The EU outlawed the sort of "propane fridge" that we all used to have. Since the folks that make them are all over there, that pretty much was a death blow. They will stop making them within the next year or three. When they do, there are no more warranty parts to be had from them.

AS actually dragged their feet on moving over to full electric. I'm guessing they bet on the rule being revised or amended. That didn't happen. Most of the other RV outfits completed the conversion before they did.

Can you maybe buy this or that from a tiny little shop that makes a few dozen fridges a month? You probably can. That sort of "supply chain" isn't going to keep the RV industry fed with fridges. Also the RV's with those fridges will be off the list for sales in Europe (and likely other places that follow the same set of rules).

So no, this was not something that the RV folks *wanted* to do.

Bob

Thanks uncle-bob for the info, makes sense.

So I supposed for those of us who will want to keep their absorption fridge at the end of its life, we will have to count on the Amish for new replacement parts! (I've read good reviews and experiences with their offering -- I image they naturally tend to stick to the tried-and-true)

[uncle_bob]

Originally Posted by Hermes

Thanks uncle-bob for the info, makes sense.

So I supposed for those of us who will want to keep their absorption fridge at the end of its life, we will have to count on the Amish for new replacement parts! (I've read good reviews and experiences with their offering -- I image they naturally tend to stick to the tried-and-true)

Hi

If you drive around here, you can work out which farms are Amish pretty easily. They are the ones with no electric feed from the power company. They have nowhere to plug in a compressor based fridge.

Just how long they will be able to keep making these fridges .... who knows.

Bob

[pboomerx]

Originally Posted by MT45

For the newer Airstream Interstates GT and GL that come with the 12 volt only Fridge and freezer (upright stack). Does anyone have some real world data on battery consumption?

Assume AGM batteries, not lithium; assume door kept closed.

Would really want to know:
Driving down the road consumption, and also, does alternator charge the house batteries, so that the fridge then pulls from the batteries? If so, does it “keep up?”


Boondocking consumption, just sitting, no generator running

Lastly, as the fridge is 12v only, I’m assuming if I run the generator then it is charging house batteries, then the fridge pulls from those?

Thx

Fwiw, the fridge in my 2021 Classic pulls 8.5A. With two AGM you have about a day. You can pack the freezer and turn it off at night…stretch about an extra day.
Yes, the trailer charges off the tow vehicle while driving with your lights on.

Imho, any boondocking will require changing to lithium

Good luck

[uncle_bob]

Hi

Ok, here's the battery side of the math:

Two flooded lead acid cells, 80AH labeled capacity. You get 50% of that "usable". Net is 80AH from fully charged (8 hours of charging) to "stop using".

Two AGM's, 100AH labeled capacity. Same deal. Net is 100AH usable.

Two lithiums, 100AH labeled capacity. You now get to use that all, 200AH usable capacity.

The fridge isn't the only thing in these modern trailers. You probably have another amp or three of drain running around.

80 AH (flooded cells) / 8 amps is 10 hours. Not going to work.

100 AH (AGM's) / 8 amps is 12.5 hours. Not going to work.

200 AH (Lithium) / 8 amps is 25 hours. Just barely makes it across the one day line. It's going to work in the real world.

400 AH (4 x Lithium) / 8 amps is 50 hours. Probably the minimum to do anything off grid.

Yes this all *assumes* an 8 amp total drain for everything in the trailer. It also assumes it's a cloudy day and you have no input from solar.

Bob

[MT45]

Originally Posted by uncle_bob

Hi

Ok, here's the battery side of the math:

Two flooded lead acid cells, 80AH labeled capacity. You get 50% of that "usable". Net is 80AH from fully charged (8 hours of charging) to "stop using".

Two AGM's, 100AH labeled capacity. Same deal. Net is 100AH usable.

Two lithiums, 100AH labeled capacity. You now get to use that all, 200AH usable capacity.

The fridge isn't the only thing in these modern trailers. You probably have another amp or three of drain running around.

80 AH (flooded cells) / 8 amps is 10 hours. Not going to work.

100 AH (AGM's) / 8 amps is 12.5 hours. Not going to work.

200 AH (Lithium) / 8 amps is 25 hours. Just barely makes it across the one day line. It's going to work in the real world.

400 AH (4 x Lithium) / 8 amps is 50 hours. Probably the minimum to do anything off grid.

Yes this all *assumes* an 8 amp total drain for everything in the trailer. It also assumes it's a cloudy day and you have no input from solar.

Bob

Best. Details. Ever!