Nova Kool R3800 AC/DC Refrigerator

[RossWilliams]

"Bottom line is you need a shunt based monitor and that is just a starting point. "

Why does he need a "shunt based monitor" to run his refrigerator? Mine seems to run just fine without one.

"Install your system and then tell us how well it works."

Actually he seems to be doing the smart thing which is hiring a professional to install his system rather than trying to become an expert himself. He seems to be asking questions to make sure he has a clear idea of his real needs.

[GeorgeRa]

81 posts and no progress. Is 2 plus 2 to equal to 5?, no - it is 4, why not 5, 4, 5, 4,.............................

[Bud]

"Install your system and then tell us how well it works."

Good idea Ross, probably all agree.

"Actually he seems to be doing the smart thing which is hiring a professional to install his system rather than trying to become an expert himself. He seems to be asking questions to make sure he has a clear idea of his real needs."

You serious? Recall the Literally Unbelievable onan story? Plus the other stories......

Bud

[booster]

Originally Posted by GeorgeRa

81 posts and no progress. Is 2 plus 2 to equal to 5?, no - it is 4, why not 5, 4, 5, 4,.............................

Yep, yep, and yep.

Why ask for opinions and guidance just so you can argue that they are all wrong, continually, on many topics?

[RossWilliams]

Here is a discussion of battery monitor options. The bottom line is they all only provide an estimate of remaining power if that is your concern. The article provides examples of what additional information you might get from the different options.

With the refrigerator is seems that there are two concerns. One is that the refrigerator will drain the battery to a level that damages the battery. The other is that, to avoid that, you will be forced to turn off the refrigerator and your food will spoil. Almost any battery monitor can be used to avoid those two things if you have immediate access to a generator to replenish the batteries.

[booster]

Originally Posted by RossWilliams

Here is a discussion of battery monitor options. The bottom line is they all only provide an estimate of remaining power if that is your concern. The article provides examples of what additional information you might get from the different options.

With the refrigerator is seems that there are two concerns. One is that the refrigerator will drain the battery to a level that damages the battery. The other is that, to avoid that, you will be forced to turn off the refrigerator and your food will spoil. Almost any battery monitor can be used to avoid those two things if you have immediate access to a generator to replenish the batteries.

IMO, that article was written by someone who knows only enough to about batteries and charging to give incomplete at best information on the topic, including how battery monitors work and are kept accurate, especially when teamed with correct charging methods, which is also not understood or just being ignored in the article.


Perhaps you should start a new discussion on that, and we can go over exactly what the author does not understand very well and how this stuff actually works, even though there is a ton of information on both the charging and monitoring already on this site. It might be interesting for those who weren't here for the very extensive examinations into charging and monitoring that have been done. Do you understand how a shunt based monitor system works, what the settings do, and how to use one?



Shunt based battery monitors are the most accurate way to determine if you are getting a full charge and then how much power you use, and as long as you get to a complete charge periodically so they recalibrate to full reference point will be very precise, IMO.


That said, there are significant numbers of users that choose to not use a monitor and have developed a "feel" for how much power they have used over time. Some, especially those with very consistent charging and use patterns, are just fine that way. Nearly everyone ran that way for decades before monitors became readily available. For people considering a compressor frig without having a huge battery bank and worried about losing food, a monitor is the best way to go for peace of mind, IMO.

[hbn7hj]

There is a whole 'nother world of power management out there for those that want or need it. If you don't need it, fine. With sat TV, cold temps, and moderate solar, I do, and I don't have a compressor fridge.

On another topic a Dometic RM 2663 ran at 10680ft for two weeks in June. I could hear it struggle to light but it always did.

[SteveJ]

Originally Posted by hbn7hj

On another topic a Dometic RM 2663 ran at 10680ft for two weeks in June. I could hear it struggle to light but it always did.

I spend one to two months per year camping at 8-10,000. My RM2551 seems to have no issues with that altitude. It has electric spark start up, not the old hi/lo flame with push button spark. The old push button start also seemed to have no issue with.

I have never run across anyone that has had a problem with higher altitudes, not to say it never happens, just never heard or read about it.

[RossWilliams]

"There is a whole 'nother world of power management out there for those that want or need it."

Want and need are different. Some people want to manage their power and spend a lot of time at it, the more new gadgets the better. Others see it as a necessary chore to be avoided beyond that.

But you don't need a "'nother world" fancy power management system to use a compressor refrigerator in an RV. You just turn it on and go. At less than 40 watts, its not a big load even when running. Not when the inverter needed to use 120 volts for things like TV or microwave draws 100 before you turn anything else on or plug it in.

[booster]

Originally Posted by RossWilliams

"There is a whole 'nother world of power management out there for those that want or need it."

Want and need are different. Some people want to manage their power and spend a lot of time at it, the more new gadgets the better. Others see it as a necessary chore to be avoided beyond that.

But you don't need a "'nother world" fancy power management system to use a compressor refrigerator in an RV. You just turn it on and go. At less than 40 watts, its not a big load even when running. Not when the inverter needed to use 120 volts for things like TV or microwave draws 100 before you turn anything else on or plug it in.

I don't know what inverter you have, but the small one that runs everything except the microwave or hairdryer uses about 4 watts and only on when in use. The big inverter for the other items use 17 watts and is only on for minutes at a time. The frig uses double that 24 hours a day, minus duty cycle, so certainly is a significant power user unless you have some very high use items elsewhere, like davydd's ARV does.


I think is time for you to start a thread on this to discuss power systems needs or wants including monitors which is where this all started because of the link provided that badly misrepresents their usefulness, IMO.

[avanti]

Originally Posted by SteveJ

I spend one to two months per year camping at 8-10,000. My RM2551 seems to have no issues with that altitude. It has electric spark start up, not the old hi/lo flame with push button spark. The old push button start also seemed to have no issue with.

I have never run across anyone that has had a problem with higher altitudes, not to say it never happens, just never heard or read about it.

My old push-button unit never had issues at altitude, either. Maybe there is an issue specific to certain models.

Nonetheless, I would never even consider going back to an absorption fridge.

[hbn7hj]

Originally Posted by avanti

Nonetheless, I would never even consider going back to an absorption fridge.

I would prefer one, too. Just can't bring myself to part with the 40+ amp hours daily. The next time the absorption one craps out I'll probably make the change.

[SteveJ]

Originally Posted by hbn7hj

I would prefer one, too. Just can't bring myself to part with the 40+ amp hours daily. The next time the absorption one craps out I'll probably make the change.

Agreed. That is the thinking on my end.

[GeorgeRa]

I had absorption fridges since seventies starting with a portable Dometic still in operation at my daughter family beer parties. Never had issues at elevations from 10K’ or less but did pay attention to keep it a reasonably levelled. Keeping trailer level was very easy with an electric tongue jack. Being free from levelling has value for us, so going back to absorption is not a likely scenario. Huge majority of RVs worldwide use absorption fridges with LPG being the main energy source. An absorption fridge can likely run for a month on a large RV LPG tank.

[SteveJ]

Originally Posted by GeorgeRa

...................

Huge majority of RVs worldwide use absorption fridges with LPG being the main energy source. An absorption fridge can likely run for a month on a large RV LPG tank.

Actually 152.5 hours per gallon at 100% duty cycle. At least for most smaller fridges. Based on the claimed 600 BTU input for the burner per Dometic on my RM2551. I think most small fridges use the same size burner.

[Winston]

RoadTrek Adventurous RS1,

After reading the 11 pages (on my screen) of this thread, we couldn’t decide between smiling and ‘walking-away’ or adding to the continuum . . . .

RARS1, to many of the electrical gurus who attempted to contribute to this thread, you didn’t help yourself by not understanding the important difference between 1) Energy (i.e. a measure of the amount of work we can do in the future [or the amount of work that was done to collect this Energy in the first place]); and, 2) Work, itself, (i.e. a measure of the rate or speed at which we’re adding to, or subtracting from our ‘pile’ of Energy.)

Let’s put it in a different light. Let’s say we have a 224 gallon fresh water tank and a pump that can deliver 9 gallons a minute. Would anyone be able to answer the question: “If we turn on the pump, how much water will we have in the tank?” Even were we to disclose how much was in the tank when we started, hopefully it is apparent that the question is missing important information . . . namely, how long is the pump to be left on?

We doubt Zamp told you that your solar panels output 9 amps per hour, or even 9 amp-hours. If they did, they misspoke. More likely, they said: “Under optimum conditions, these 100 watt panels can output 9 amperes.” (By the way, the best we’ve seen, even when new, from our now 3 year old Kyocera poly-panels has been 7.5 amps (per 100 watt panel)). And, do you know whether that “9 amp” quote from Zamp corresponded to horizontal panels (flat - the normal way most RV’ers use fixed panels) or does it represent the output when the panel is tilted perpendicular to the sun?

Yes, it is true that if you subject one of your panels to optimum conditions for a full hour, the 9 amp output (the RATE at which you are producing Energy, alternatively, the Work that your panels are doing each minute of that hour) will result in your collection of 9 amp-hours of Energy.

While it may seem like nit-picking to make this distinction between amps and amp-hours . . . the truth is that since, in designing and discussing RV electrical systems, we are constantly jumping back and forth between the Work we are doing (i.e. the rate at which we are consuming or replenishing our Energy) and how much Energy we have, or can store, it is important to not inadvertently mix these two concepts. And the same dichotomy applies to watts (the rate at which we are transferring Energy) and watt-hours (the amount of Energy we have used, or have left to use).

In our analogy, your 224 gallon fresh water tank is your storage of Energy. And your pump that can move that water at a 9 gallon/minute rate is equivalent to our electrical Work, or amps (amperes). The Work we do to move/pump that water multiplied by the Time we spend pumping/moving the water tells us how much water we have moved/collected (or used).

Now, let us attempt a response to your question. We start with our own observations - - that after more than 500 days of use, the most Energy we’ve ever collected in a calendar day (per 100 watts of solar) is: 560 watt-hours). As our lithium system typically operates above 13 volts, this is equivalent to ~43amp-hours (in one day). Now, as the peak current (at noon) is 7.5 amps, this translates into 5.73 hours of Perfect Panel Sun Illumination. Thus, we question, first, your 9 amp output (per 100 watts) and the equivalent number of hours you will obtain this maximum current in any one day - - it is far less than 8 hours.

As you have 160 watts of solar, the best you can expect (based on our poly-panel experience) is: 896 watt-hours (in a given day).

If we assume an AGM system operating at 12.5 volts, even if your frig were to run 24/7, the most you would be consuming is 2.2 amps x 12.5 volts x 24 hours = 660 watt-hours. And since you’ll have to park in the hot-sun in order to have a chance at that “best” 896 watt-hours, you may have to run the frig at ‘full tilt’ during at least the middle of the day!

Our experience shows us that we rarely get our maximum . . . and between tree shading and bad weather . . . we think you’d be lucky to get 50% of that peak (we won’t address how you schedule your travels for all sunny days . . . yes, we too, like to camp in good weather, but we’re not that great at weather prognostication.)

And we’ll avoid the discussion of whether you must have a shunt-based SOC system. We’d say yes if you were running lithium, but we ran AGM’s for awhile with just a voltmeter - - so we’ll avoid the hypocracy of suggesting that your solution is inadequate.

The bottom line seems to be, anyway, that with your alternative charging methods, you should not have a problem keeping your system charged (of course, we haven’t considered your other loads).

And we’ll take issue with the comment that you don’t need additional solar . . . whether you need it or not, you could benefit from it. We have over 800 watts of solar for 500 ah of lithium and find that solar must be supplemented by shore or engine generator power not infrequently.

Good luck.

[avanti]

Heh... a few days ago, I sat down and started to write a post using the water flow analogy to try to help him understand what is being said (it is the golden path to clarifying this mirky topic). I quickly concluded that I would be wasting my time. Some people just don't WANT to understand. which I guess is ok--sort of.

[RossWilliams]

More likely, they said: “Under optimum conditions, these 100 watt panels can output 9 amperes.” (By the way, the best we’ve seen, even when new, from our now 3 year old Kyocera poly-panels has been 7.5 amps (per 100 watt panel)).

Since he said his panels were 170 watts, it seems unlikely that ZAMP gave him a number for 100 watt panels. Here is what ZAMP actually says on its website which he linked to:

170-Watt Panel Specs:
24.25 lbs
58.3” x 26.4“ x 1.5”
170-Watt Power Output
Generates 9.4 amps
25-Year output warranty

"You didn’t help yourself by not understanding the important difference "

He didn't seem to confuse the two

'While it may seem like nit-picking to make this distinction between amps and amp-hours"

The distinction between the two isn't nit-picking at all, its important. But nit-picking the language used when the meaning is clear in context is almost the definition of nit-picking.

BTW this analogy is wrong:

In our analogy, your 224 gallon fresh water tank is your storage of Energy. And your pump that can move that water at a 9 gallon/minute rate is equivalent to our electrical Work, or amps (amperes). The Work we do to move/pump that water multiplied by the Time we spend pumping/moving the water tells us how much water we have moved/collected (or used).

In the water/electricity analogy, volts are the water pressure, amps are the size of the pipe and watts are the flow. You don't have 9 gallon pipes. That solar panel generates 170 watts at 9.4 amps and 18 volts. So if there is universal confusion here it is between watts and amps.

Amp-Hours is a rating of battery capacity that is useful only when comparing batteries of identical voltage. It is standardized as the steady amperage that will fully drain the battery in 20 hours. With lithium batteries the voltage doesn't change much for most of that time. But with AGM and other lead acid batteries the voltage changes continuously as the battery drains and the wattage it produces will change accordingly.

[tgregg]

winston,

thanks for trying to educate a fellow member.

just confirms what I already thought that you're not such a bad guy.

Tom and Charlotte

[markopolo]

Originally Posted by Roadtrek Adventuous RS1

My Zamp Solar is a pretty sophisticated integrated system with my rig ....I have a battery isolator and the charge controller will stop adding additional amps to the batteries when they reach full capacity....

Here's some pictures of this.....

If you look closely at the picture showing 0.0...in small print it says 100 percent....

Again, I don't know what others have done.... my system was professionally installed and the solar panel is mounted right on the roof.....SO...in full sunlight it gets the maximum amount of power.... and Stops to prevent "overcharging"....

See pictures..... all lights are green...full charge and fantastic fan is still running. .. never had to turn on the engine... batteries are doing well at full capacity...

I don't think you appreciate how much money, time and effort I put into this.... unfortunate.

Maybe you have a better system??? I don't know.

Sorry to break it to you but that is a pretty basic PWM controller IMO. It's similar to the type of controller I'd buy at around $20 or so but I wouldn't buy that one because the float voltage is too high for any batteries I own and I have a wide variety of batteries (over 1,000Ah managed over three applications).

The 4 hour absorption timeout is another reason why I wouldn't buy it.

The float voltage on your appears to be 13.7V. (published specs for that model are 13.6 +/-0.2. Your display shows 0 amps in and 21Ah total for the day at the time you took the photo.

Think back to the day when you took the photo to know what the 21Ah was used for. What was using power that day? Some Roadtreks have a separator that uses (aka wastes) a lot of current just to operate.