[Cdnbiker]

Not sure if this helps or confuses things but here's my thoughts

12V at 50A is 600W, that converter claims 92% efficiency which would leave you with about 50W being dissipated as heat.

That being said the marketing material says 92% at nominal load (70A) so your pretty much guaranteed to be less efficient at any other load (higher or lower). If you truly only need 40-50A you might be able to get a bit more efficient by using the smaller one (Orion 24/12-40) which claims 95% efficiency but then you lose the extra capacity if you ever need it and might not gain that much in terms of getting a lower case temperature. Overall buying one rated higher is likely to be less efficient and generate more heat as converters typically have a peak efficiency at the nominal load they as designed for, of course if the case is bigger the heat might dissipate more effectively and end up with a lower temp but you would get the same effect buy strapping a heat sink on the outside of the one you have.

115 doesn't sound that hot to me for a converter putting out 600W of power, so the converter is probably happy not having the fan on.

You could measure the input and output current and voltage and see how efficient it is actually operating right now?

 

[kenryan]

115 doesn't sound that hot to me for a converter putting out 600W of power, so the converter is probably happy not having the fan on.

This makes sense to me.

 

[Brandon]

Not sure if this helps or confuses things but here's my thoughts

12V at 50A is 600W, that converter claims 92% efficiency which would leave you with about 50W being dissipated as heat.

That being said the marketing material says 92% at nominal load (70A) so your pretty much guaranteed to be less efficient at any other load (higher or lower). If you truly only need 40-50A you might be able to get a bit more efficient by using the smaller one (Orion 24/12-40) which claims 95% efficiency but then you lose the extra capacity if you ever need it and might not gain that much in terms of getting a lower case temperature. Overall buying one rated higher is likely to be less efficient and generate more heat as converters typically have a peak efficiency at the nominal load they as designed for, of course if the case is bigger the heat might dissipate more effectively and end up with a lower temp but you would get the same effect buy strapping a heat sink on the outside of the one you have.

115 doesn't sound that hot to me for a converter putting out 600W of power, so the converter is probably happy not having the fan on.

You could measure the input and output current and voltage and see how efficient it is actually operating right now?

Thank you.
It just feels hot. I will just make sure I have it in a well ventilated area.

 

[gregoryx]

I have been testing my electrical system and my Air Conditioner and my 24-12v converter gets up to 115 degrees on the outside case. The fan inside it never turns on. I'm pulling about 40-50 amps 12v from it. It is rated for up to 85 amps and 70amps continuous so I'm not near the max.
BTW it is a Victron Orion 24/12-70 converter.
Does anyone know of another converter maybe rated for more power that would run cooler at 40-50 amps?

My other option is to open it up and put in in a custom case with heat sink and a larger fan that runs on a low quiet setting like a computer fan and just have the fan on anytime is it running.

Thank you for any comments or ideas you may have.

Agreed with the others: that's cool. Our same 24>12, the fan ran all the time. I killed the fan and it's been fine - placed with the lugs on bottom and fan on top so convection is in our favor. 115F is not hot.

 

[BobCollins]

Curious. If I understand correctly, you have a 24 V system and you have needs for some 12 V loads. What are you running that has significant 12 V power requirements? So far, I keep finding that many modern low voltage appliances work at both 12 V and 24 V. Examples are my refrigerator and my CPAP machine. Even my USB-PD phone charger specifies either voltage.

I am currently running a 12 V system. I am trying to decide on the trade-offs for moving to 24 V.

Thank you.

 

[Brandon]

Curious. If I understand correctly, you have a 24 V system and you have needs for some 12 V loads. What are you running that has significant 12 V power requirements? So far, I keep finding that many modern low voltage appliances work at both 12 V and 24 V. Examples are my refrigerator and my CPAP machine. Even my USB-PD phone charger specifies either voltage.

I am currently running a 12 V system. I am trying to decide on the trade-offs for moving to 24 V.

Thank you.

The main thing I have that is 12v is my RTX 2000 Air Conditioner. It pulls between 12-25amps 24v. On the 12v side it is pulling 24 to 50 amps. I wish Dometic would import the 24v version but they do not.
You are right about other items. The only other item I need 12v is the Maxxfan and my 12v puck lights for the ceiling as I could not find a 24v version. These 2 items will not pull a lot of power and will be on a different converter that will always be on. The larger one will only be on if I'm running the AC.

 

[Brandon]

Agreed with the others: that's cool. Our same 24>12, the fan ran all the time. I killed the fan and it's been fine - placed with the lugs on bottom and fan on top so convection is in our favor. 115F is not hot.

Your right 115 is not that hot. I was just out in the van and checked the outer wall temp on the inside and it was 140 on the side facing the sun.

 

[BobCollins]

The main thing I have that is 12v is my RTX 2000 Air Conditioner. It pulls between 12-25amps 24v. On the 12v side it is pulling 24 to 50 amps. I wish Dometic would import the 24v version but they do not.

Your air conditioner needs both 12 V and 24 V? Wow! That is a crappy design.

 

[Van Gogh]

@Brandon

The ideal solution is to have your battery bank and a/c at the same voltage. I realize that may no longer be an option, but that a/c is likely your largest single load, so powering it directly would be much more efficient, assuming the a/c manufacturer designed it to accept a range of input voltages (fully discharged to fully charged battery voltages).

Otherwise, improving heat dissipation via any means or a converter rated for twice the continuous load you plan to draw -- including converter derating due to temperature -- would be my advice.

Also verify your a/c amperage. Are you sure it's maxing out at 50A?

If so, a 100A+ continuous converter would be my advice. You may also want to inquire with your a/c manufacturer regarding input voltage. If it can run at 13.8V instead of 12V, you may have better luck with a 24V>13.8V converter. The a/c may draw 15% fewer amps, but you'd have to verify that with the manufacturer. They may not allow it.

I use a 48>13.8 80A converter for all of my 12V loads. There are many advantages and only a few drawbacks versus 12V. I talked DayGreen into making a larger 150A unit but I've yet to buy it (see attached). I found I didn't actually need that many amps, at least not yet.

So far that converter has been perfect. Efficient, cool, and only 1W tare loss (standby). But I rarely draw more than 10-20A. Someday when I need all my battery and tank heat pads, plumbing heat trace, and every load I could possibly turn on I might max it out. We'll see.

That being said the marketing material says 92% at nominal load (70A) so your pretty much guaranteed to be less efficient at any other load (higher or lower).

Lower loads are only less efficient due to the tare loss, which is present at all times. But a good DC converter's tare loss should be ~1-2W, so it's negligible.

An inverter on the other hand usually has a much higher tare loss, so smaller loads become notably less efficient. But even inverters operate at maximum efficiency around 66% of the rated continuous load. And that 66% still applies as the unit's output derates due to high temps.

Having an oversized converter/inverter is generally the solution to high case temps or output derating. It will dissipate heat better, helping it operate more efficiently and making the case less likely to melt a stray object (plastic/rubber). Good airflow is always important, oversized or not.

Cheers.

 

[Brandon]

Your air conditioner needs both 12 V and 24 V? Wow! That is a crappy design.

No Bob, the the Converter is pulling 12-25 amps from the 24V system on the input side and putting out 24-50 amps on the 12v output side to the AC.

 

[Brandon]

@Brandon

The ideal solution is to have your battery bank and a/c at the same voltage. I realize that may no longer be an option, but that a/c is likely your largest single load, so powering it directly would be much more efficient, assuming the a/c manufacturer designed it to accept a range of input voltages (fully discharged to fully charged battery voltages).

Otherwise, improving heat dissipation via any means or a converter rated for twice the continuous load you plan to draw -- including converter derating due to temperature -- would be my advice.

Also verify your a/c amperage. Are you sure it's maxing out at 50A?

If so, a 100A+ continuous converter would be my advice. You may also want to inquire with your a/c manufacturer regarding input voltage. If it can run at 13.8V instead of 12V, you may have better luck with a 24V>13.8V converter. The a/c may draw 15% fewer amps, but you'd have to verify that with the manufacturer. They may not allow it.

I use a 48>13.8 80A converter for all of my 12V loads. There are many advantages and only a few drawbacks versus 12V. I talked DayGreen into making a larger 150A unit but I've yet to buy it (see attached). I found I didn't actually need that many amps, at least not yet.

So far that converter has been perfect. Efficient, cool, and only 1W tare loss (standby). But I rarely draw more than 10-20A. Someday when I need all my battery and tank heat pads, plumbing heat trace, and every load I could possibly turn on I might max it out. We'll see.



Lower loads are only less efficient due to the tare loss, which is present at all times. But a good DC converter's tare loss should be ~1-2W, so it's negligible.

An inverter on the other hand usually has a much higher tare loss, so smaller loads become notably less efficient. But even inverters operate at maximum efficiency around 66% of the rated continuous load. And that 66% still applies as the unit's output derates due to high temps.

Having an oversized converter/inverter is generally the solution to high case temps or output derating. It will dissipate heat better, helping it operate more efficiently and making the case less likely to melt a stray object (plastic/rubber). Good airflow is always important, oversized or not.

Cheers.

Yes having them the same would have been idea but at this point it was not an option as they do not import the 24v system to the united States. Yes 50 amps is the max I could make it pull from the system. Even pulling 25 amps the converter hit 110 degrees and that is only 1/3 the rated capacity.

I could have purchased a 24v AC unit but the ones I found and speaking to Nomadic cooling said I would need a larger battery system to run their AC all day long. SO I went with the Dometic and it will easily run all day on my batteries. Heck I was testing it yesterday and then ran it another 9 hours today and I still have 35% battery left. I do not expect to run it that much in normal use but I can if I have too.
The AC only puts a 15amp load on the 24v system so it is not my biggest draw. My induction cooktop and wifes hair dryer will pull the most. The system is designed to handle it so I'm good.

I will find a way to move air over and thru the converter quietly.

 

[gregoryx]

FWIW... that combo of 24/12 was the implementation on the Undermount AC 24V unit initially. They were able to source some of the components 24V but not all, so the same converter that @Brandon cites was included in the 24V package to step-down whatever parts were still 24V. Not ideal, obviously... but also seems to match making as much of it 24VDC as possible?

The new one is all 24VDC. Sitting in my garage. Waiting for the van to return. And me to spend a day or two installing. 😄

 

[NW_Freedom]

I'd like to know if someone has squeeze d one of the dometic into the rear spot of the non ext where we mount the fans. It might be possible.

 

[Van Gogh]

Yes having them the same would have been idea but at this point it was not an option as they do not import the 24v system to the united States. Yes 50 amps is the max I could make it pull from the system. Even pulling 25 amps the converter hit 110 degrees and that is only 1/3 the rated capacity.

I could have purchased a 24v AC unit but the ones I found and speaking to Nomadic cooling said I would need a larger battery system to run their AC all day long. SO I went with the Dometic and it will easily run all day on my batteries. Heck I was testing it yesterday and then ran it another 9 hours today and I still have 35% battery left. I do not expect to run it that much in normal use but I can if I have too.
The AC only puts a 15amp load on the 24v system so it is not my biggest draw. My induction cooktop and wifes hair dryer will pull the most. The system is designed to handle it so I'm good.

I will find a way to move air over and thru the converter quietly.

I wouldn't count on 360W as the normal draw during hot days. It appears that unit draws 58A/700W on high and delivers max 6.8k btu per Dometic.

I had early a/c tests on 85F days with partial shade and 60F nights that made it seem like my a/c could run forever. 99F highs parked in the sun and 70F lows definitely made a difference.

Hair dryers and cook tops run for a few minutes. An a/c may run 24 hours a day.

By largest load I don't mean instantaneous draw, which can be all over the map and really doesn't matter as much in the end. I mean kWh consumed per day. An a/c will tend to dwarf all other loads combined in terms of how much power it draws from your battery bank. And all of that power has to flow through the converter in your setup, and the inverter in my setup.

For instance, my microwave draws 1100W but I only run it for 10 minutes per day = 0.183kWh per day.

My 9k btu a/c on a 99F day 71F night parked on concrete in full sun set to cool at 72F day and 68F night with the fan on high draws 4.07kWh per day = 170W/hour average including inverter loss. That's 2,200% more power per day than the microwave consumes, and 330% more power than all other loads combined (1.23kWh).

Cheers.

 

[NW_Freedom]

He has been testing it in the garage here in Boise and we are at 100 daily so the garage has to be in the 90s.

 

[Van Gogh]

He has been testing it in the garage here in Boise and we are at 100 daily so the garage has to be in the 90s.

In full shade 90F I could see that. That's still reasonable.

But let the sun hit that metal exterior and it changes everything. A 100F day can produce 140F temps inside a vehicle parked in the sun. The roof, walls, and windshield get very hot, even with insulation.

Sometimes camp spots offer full shade, but not always. Usually you have to move around if you want that. And solar output is minimal without sun, although one nice thing about a large array is that it shades the roof, which otherwise gets very hot.

Cheers.

 

[Brandon]

In full shade 90F I could see that. That's still reasonable.

But let the sun hit that metal exterior and it changes everything. A 100F day can produce 140F temps inside a vehicle parked in the sun. The roof, walls, and windshield get very hot, even with insulation.

Sometimes camp spots offer full shade, but not always. Usually you have to move around if you want that. And solar output is minimal without sun, although one nice thing about a large array is that it shades the roof, which otherwise gets very hot.

Cheers.

I ran it today non stop in my garage at 95 for 9 hours and it stayed right around 350 watts. I have camped many times in over 100 temps and I’m not expect to run the AC and sit in the van. The only way to get the AC to pull close to 600 watts was to put it in boost mode. And that 50 amp draw is still within the 70 amp specs of the converter and even at that for 2 hours and the converter maxed out at 115 with no air flow. Yes the converter is rated for 70 amps continuous and up to 85 for short periods of time.
I only started this because I thought 115 was hot but I’m learning it is not crazy hot. I also figured out it gets that hot pulling 13 amps so I guess that is just the working temp.

 

[Sams stock van]

I've often used 1/4" aluminum bar stock when mounting any device with a heat sink case.
It adds more air flow under the case and increases the mass used for heat dissipation. Easier than adding an additional fan and might be all that's needed. Good luck.

 

[njvagabond]

I've often used 1/4" aluminum bar stock when mounting any device with a heat sink case.
It adds more air flow under the case and increases the mass used for heat dissipation. Easier than adding an additional fan and might be all that's needed. Good luck.

Cut open, flatten and stack a bunch of beer cans? ... very slow and frugal.