Max Burton fridge/freezer

[regis101]

But ya know what? I can't remember if I was taking total amp readings , solar and draw, or just off the load draw. Daymn.
Oh well, back to the campground.
Daymn.

 

[John61CT]

I've seen cheap little shunt-based "battery monitor" logging ammeters online, I wouldn't trust my bank's health to, but would probably be fine for logging a Load like this' usage over time, let you do real apples-to-apples on amps consumed under different conditions regardless of charge source.

You are saying 3A load around 20% of the time, or under 15AH per 24 hours right? As a fridge ~33°

Any idea how that changes when you keep it right down to 2° ?

 

[highdesertranger]

nice report Regis. highdesertranger

 

[regis101]

You are saying 3A load around 20% of the time, or under 15AH per 24 hours right? As a fridge ~33°. Any idea how that changes when you keep it right down to 2° ?

Uh,  I dunno.  Am I?   Still learning the Ah/day calc vs battery capacity.  Is what you're saying good or bad or at least calculable for daily loads.
If I had to round 'er off , I'd say one ten minute cycle per hour at ~3 amps.  How does that calc out to a 24 hr period?
That was at ~90* during the day.  When it cooled off outside , I was getting the seven minute cycle every hr and fifteen to hour and a half.  Dunno how it ran in the dead of night since I was snoring off some Zzzz's.
No idea of run  time(s) at colder temp settings since I was trying to keep it as a fridge vs freezer and the three day meat supply was already frozen.  
That opens up discussion for chest freezers vs fan aired fridges.  Another thread on that.
The other thing I was trying to obtain was control panel temp setting vs interior setting.  I used three fridge/freezer mechanical / mercury thermos.  Had one in the bottom of the basket.  One stuck to the lid .  One laying loose in the upper compartment.

Not to fret.  I'll be doing more lab work in the near future.  Just my hang up.  It's gonna be in the 100's for a week coming so maybe next month or so after I notice a cooling trend or at least comfortable trend.

Now also, with this fridge/freezer, as constructed, and in my environment, there might be , and I know there is, a sweet spot and I just have to find it.  Maybe 30-38* is too high, maybe 02* is too low, as it pertains to efficiency.  

I'll work on that before I start building extra exterior foam boxes and blankets and whatnot.

 

[Silver6gen]

I agree there is a sweet spot, my fridge likes to live in the 22-24* range. I just want to prolong it's life any way I can hence the fans and extra insulation.

@john61CT Regis is seeing a 20% load per cycle to maintain 33* at an ambient of 90*, today I tried to go negative and it stalled out at 2* with an ambient of 94*. So it was 100% load/cycle trying to get into the negatives, perhaps if I set it at 2* it would cycle ~95%.

In reality there is really no need to go down to 2* for a portable freezer. If you have frozen meats at the start of your expedition and your freezer is maintaining even 10* you'll keep them mostly frozen for at least a week. If you have frozen meat past that on a trip then there are other issues.

 

[regis101]

We're supposed to be in the 100's this weekend.  I think I'll try to take more info during the cooler mornings with regard to scrolling the LCD controller readout to observe the load amperage with it still in the van.
 I will then remove the fridge from the van and put it in the garage and take more readings using shore power and a clamp on amp meter.  
I want to determine actual fridge load vs fridge and solar load.

 

[John61CT]

> Still learning the Ah/day calc vs battery capacity.

> If I had to round 'er off , I'd say one ten minute cycle per hour at ~3 amps.  How does that calc out to a 24 hr period?

7 min out of 60, 7÷60=11.7%, of 24hrs = 2.8 hours, 3A for 2.8 hours = 8.5AH per 24 hours

10 min out of 60, is a sixth so 4 hours = 12AH

Super efficient AFAIC.

 

[John61CT]

> In reality there is really no need to go down to 2* for a portable freezer.

Perhaps for your use case, but

I want to freeze polar tubes to rotate into a super-insulated cooler, so colder the better.

But you're right, I don't want to draw 72AH per 24 hour cycle when it gets hot.

Just gathering data at this point, but meat is not part of my scenario in any case.

"The street finds its own uses for things."

— William Gibson

 

[Silver6gen]

So I had it set to 2 degrees over night. It has a full gallon of water, three ice packs, various other frozen food bags so I'd rate the freezer compartment as 90% full. Since everything spent the night in the freezer everything was sufficiently frozen. Hopped in the car for my drive to work and clicked it down to -7, when I pulled into the office it was showing -4. IMO that reinforces the fact that efficiency and run times will vary based on ambient temps (62* ambient this morning) and the initial temp of the items you are trying to freeze.

In your case I would freeze tubes overnight and set the freezer to the lowest temp it will sustain at <50% cycle. Then in the morning cycle the tubes before the day gets super hot to take advantage of the cooler morning air's affect on the freezers ability to cool. As the day gets hotter I would slowly adjust the set point up stopping at 18* ish.

Also note that the unit runs more efficiently as voltage increases, so if you have your engine on and your alternator is floating your batteries at 14 volts thats what the cooler is operating on. Your amp draw will be slightly less at 14v than 12v. I've always noticed that it works better/faster at 14v. This has led me to seriously consider setting up an isolated solar charged 24v supply for the unit, also 24v would be easy to knock down to charge voltage of 19.5v for my SAR laptop.

I would be very interested to see duty cycle graphs showing the (if any) difference between running these units on 12v vs 24v.

 

[Silver6gen]

FYI!
Wow 53qt Max Burton for $250... I might have to grab a second one!

http://www.ebay.com/itm/Max-Burton-...883897?hash=item212d1e5739:g:C2wAAOSwRLlZpc6~

 

[Silver6gen]

couldn't pass the opportunity.  Hell I paid 300 for my 37qt.  

 

[regis101]

I would be very interested to see duty cycle graphs showing the (if any) difference between running these units on 12v vs 24v.

Sounds like you have a project waitin' fer ya

 

[regis101]

FYI! Wow 53qt Max Burton for $250... I might have to grab a second one!

Wowza!!

 

[regis101]

I had a little bit of a burp yesterday. I went out to the van to plug the MB into its designated ciggy socket for an amp reading off the controller. Ok, wait. There were a few cocktails during a prequel to all this. So, I plug 'er in and nothing happens. I plug it in to the outside ciggy socket and it worked. What the..??? Unplug. Replug into the inside ciggy? Nada. Oh man, maybe I messed up the wiring. Nah. Cant be. There's only two wires.
The Rover 20a load LED is blinking. Short or overload, according to the trouble shooting page of the manual. Can't stop the light from blinking. Unplug the PV and the battery leads. Rehook and everything is normal. Test. Test. Test. Got juice to everything. Polarity is correct. What the...??
Ends up I wasn't pushing the plug into the interior socket far enough and it wasn't making contact.
I did mention the cocktails earlier, right?
So what happens is after fifteen minutes of, What the...'s??, things calm down but I'm noticing that the fridge, now running, is pulling 5 amps. 4.5-5 maybe a 5.1. And the, What the...'s? start up again.

I can only surmise at this time that the numerous plug and unplug exercise was making the thing want to lock up or act like a high pressure cut out. Stoopid me.

 

[John61CT]

As quickly as possible, eliminate ciggy plugs from your life, they are an abomination.

​Blue Sea has a nice socket design that twist-locks with the matching plug, but will also accept standard ciggie plugs for smaller (<10A) loads.

Also the BMW/ Hella/ Merit/ Powerlet "Euro-style DIN" (ISO 4165) style is very robust.

Anderson plugs for high amps. If you standardize on one of the last two types, there are adapters for devices with ciggie plugs.

 

[regis101]

I'm hearing ya. The ciggy plug on the MB isn't that bad. When it fits, it fits. The marine grade 12v sockets I'm using are good quality.
This mishap was totally human caused. I'm an idiot sometimes.
I will, however, under your heed and voices from others, pay some attention to more betterer tie points.

 

[John61CT]

For low-amp usage, twist-lock is OK.

Andersons much better though

 

[regis101]

So. I leaned on it today using just the batteries, before the sun came up, before the controller noticed the PV.
The interior of the van was 72*. The fridge showed 69* and the set temp is 33* and the basket was empty except for the 120v power cord and a nylon strap.

Amp draw started at 2.2 and went to 3 amps at the 2:30 mark. It hit 4 amp at the 3:30 mark.
Bounced around from 3.8 - 4.5 until the 16:00 mark. From the 17:00 - 26:00 mark it was at 3.8 - 3.1 and then it shut off.

I used a clamp-on meter also and it pretty much backed up the readout on the controller. One thing about the clamp-on was that I'd read ~4 on the pos and ~3 on the neg, or 5 and 2 or whatever. This was at the controller.
I'll have to study about using amp probes on DC circuits.

The average draw was 3.35 amps, under my test conditions. I'm not going to sweat over this anymore. It's a three hun dollar portable chest style fridge/freezer that works as well as I'd expect. The run cycle time is the learning curve as it pertains to ambient and relative conditions. Kinda makes, YMMV, a true statement.

Thanks for reading.

 

[Silver6gen]

53qt showed up.  Just for everyones reference, the 37qt fridge will hold one standard one gallon milk / water jug in the basket with some room for extra goodies, the 53qt will fit four...  pretty huge differeance.  Also the 53qt has a much larger compressor as one might expect, current draw was measured at 4.2amps peak.  I've also installed an exhaust fan on the case that runs whenever the unit is powered, its .09 amp draw and is like 19db so its way quiet. 

Additionally my dometic 40 insulation case came in and fits the burton 37 pretty well.  Couple things, the power port is on the wrong side.  Its also a but wider than the burton 37.  But it allows for a couple 3/4" foam boards to be wedged in .  

Also I added a small fan (5 cfm) to the lid of the 37qt to push air to three outlets, the fan only runs when the condenser is on.  I used a 3/4" foam board inset in the lid then carved air ducts into it, covered with duct tape.  The three outlets are at each corner of the freezer compartment.  

I can say that the interior fan has done an excellent job at keeping the interior temp uniform and I feel that it's reduced the duty cycle.

In this photo you can see the reveal of the channels I cut in the foam

This setup at peak draws a hair over 10 amps when both units are in max cooling mode.  Which is rare, I have the 53qt set to 35 degrees (interior measured at 32*) and the 37 qt is set to 10*.  I've found that adding  the interior fan has made the displayed temp much more accurate to the actual temp in the compartment.  My solar panel has still kept the batteries at float voltage through the day, in the morning the main battery is at 12.2.  I'm very happy with the two fridges.

 

[Silver6gen]

So I've been data logging the voltage of my 3rd battery which is charged by solar and runs the fridges. It will charge from the alternator when running but for the purpose of the test I locked it out. The last two days have been overcast and dark so not much solar has made it into my 3rd battery.

As to not wander off into the weeds I'll come straight to the point. The battery monitors on these fridges were set to 'Hi'. Which means they should shut off when the battery gets to 11.8v and restart when it comes back up to 12.6v.

They didn't. Both ran past 11.8 and took the battery down to 11.6v (measured when both units were in standby). Both units would still cycle and when on the battery measured 11.4 v.

This isn't good, deep cycles can handle occasional discharges to 11.6 but any more than that can cause permanent damage to the cells. I will be looking for an adjustable low voltage disconnect.