Apartment fridge install

[Sabatical]

Although i wanted to use that Morningstar inverter, it's 300w capacity was not enough for the initial start surge. It kept popping the 3 amp fuses on the ac output side.

Currently using a Bestek 1000w modified sine wave inverter feeding the camper's ac distribition center.

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[tx2sturgis]

Although i wanted to use that Morningstar inverter, it's 300w capacity was not enough for the initial start surge. It kept popping the 3 amp fuses on the ac output side.

OH!

Lol

Ok, how about using a 3 or 5 amp slo-blo fuse?

That SureSign is rated for 600 watt peaks...should handle it fine.

 

[jimindenver]

I wanted a Morningstar 300 watt inverter for a long time and then I saw one at NA W&S. It is not little by any means, in fact it is nearly as big as my 1250w Trip-lite. That is the price to be paid for a fanless inverter.

As far as how much battery and solar is enough? Knowing your average load is only half of the equation. Knowing how to produce the power needed reliably in the worse case scenario is the other half. Plan for short low sun days in the winter. Plan for 6 week monsoons where the sun is gone by mid day everyday and that is if you are lucky enough to see it at all. Plan as we see in another thread for forest fire smoke reducing your output. Plan for heat waves that cause the fridge to run more. In any of those cases I think 300 watts falls short and they are just the tip of the iceberg. The only way to hit a must run situation is with excess and even then have a back up means of charging. It sounds like a pain in the ass but so is making a 100 mile round trip to pay mountain town prices when the plan fails.

 

[GotSmart]

Man....we could sure use SW's expertise in the math department right now...but I'm not sure he's talking to us anymore...



Sternwake, HDR, John61CT, IGBT, GotSmart, jimindenver, anybody? 

Help out please....

(crickets).....

:-/

It s been made clear that my years of training and exprience are unwanted here by the powers that deliete, as well as others.  Not going there again. :dodgy:

 

[Sabatical]

Wife and i were gone last night and i didn't get an exact 24hr snapshot. I took pics before and after. I did some math but as always you can double check because you all will have the numbers.

First two pics are after 19 hours with 0.51kwh used. Second set of pics is after 27 1/2 hours with 0.74kwh used. I took the kwh and divided by the time then multiplied by 24 for both sets and came up with 0.639 & 0.645. Without a third to average, i split the difference and decided on 642 watts for a 24 hour period. Following the equation on the forum thread link i posted, the number is approximately 25% of battery bank capacity. If i add in the inverters draw (to be confirmed still but advertised as 0.8 amps) i get another 230wh. Adding the two i came up with 32% of total battery bank capacity.

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[John61CT]

Knowing how to produce the power needed reliably in the worse case scenario is the other half. Plan for short low sun days in the winter. . .

Yes, I state that for myself even for an efficient Danfoss style setup, 2 pair GCs and 600W is what I recommend as a starting point.

In another Aussie forum people go nuts!

But there most are close to shore power anytime needed, few boondock for long periods, and they do get lots of sun. . .

 

[jonsun]

So if your killowatt is measuring a mere 600-700w how do you explain other claiming they couldn't run on 400-600w of panels and destroyed 350+ah of batteries? Or that a 120v fridge can't be done generally?

 

[Sabatical]

Here's another lesson i've learned so far. I haven't spent time sitting in front of the charge controller so this is just theory but i'll explain.

When i started this project i set a rebulk voltage on the charge controller. I never needed one before, but i reasoned that with the heavy load, i needed it now. I set it for 12.4v. As i learn more, i may need to adjust this number.

Anyway, either the cc is not getting through the bulk phase or it's going back to it quickly. Based on the time of day that i'm seeing the bulk phase, and knowing from experience with this system that it should be in absorb, my guess is that the fridge is robbing too many watts from those available and not enough are getting to battery charging. I think the solution is to get the second panel back on the roof and try again. 260w, i believe, with the amount of sun available, is not enough.

Last night i shut the inverter off. The voltmeter was at 12.2, and although i know that number was not accurate (short rest time), and the soc meter read good, i decided to give it a rest. At some point today i will check specific gravity and also the no load amp draw on the inverter.

I could move the camper to give more ideal sun exposure, but we won't always have it anywhere else so let's make adjustments for what we have. We want to know if it will work in average conditions not perfect conditions.

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[Sabatical]

Thinking over what i just wrote, i'm gonna do it a little different. A lot of folks here won't have 520w of solar panel available. If you do awesome but if not you should benefit from this too. After checking specific gravity, i'll move the camper to allow for a couple more hours of direct sun, i hope, and remove the rebulk setting. Let's see what happens.

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[Sabatical]

So if your killowatt is measuring a mere 600-700w how do you explain other claiming they couldn't run on 400-600w of panels and destroyed 350+ah of batteries? Or that a 120v fridge can't be done generally?

If you're asking me, i can only explain what i'm seeing and i provide pics so you can see it too. There are many variables, maybe theirs were different from mine

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[Sabatical]

Yes, I state that for myself even for an efficient Danfoss style setup, 2 pair GCs and 600W is what I recommend as a starting point.

In another Aussie forum people go nuts!

But there most are close to shore power anytime needed, few boondock for long periods, and they do get lots of sun. . .

I totally agree John.

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[John61CT]

The charge source has no control over when the transition from bulk/cc to absorb/cv takes place.

Bank SoC and chemistry (resistance) determines that.

 

[Sabatical]

The charge source has no control over when the transition from bulk/cc to absorb/cv takes place.

Bank SoC and chemistry (resistance) determines that.

Sure. I was surmising that fridge draw may be keeping chemistry down enough so as not to switch to absorb. I doubt it's soc due to the controller's internal meter (whiz bang jr.) stating it is near capacity.

On the full end of absorb i have end amps set to switch to float.


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[John61CT]

That's a great setup! So the wbj keeps voltage up at Absorb until amps **going into the bank** drops to what, 2A?

But of course if the fridge is drawing off most of the solar power it can take a long time to get there, or worst case not at all by sunset, depends on other loads, the weather. . .

 

[tx2sturgis]

The charge source has no control over when the transition from bulk/cc to absorb/cv takes place.

Bank SoC and chemistry (resistance) determines that.

Oooops...

Nope. Try again.

The 'smart' algorithms in the charge source DO determine when it switches from CC to CV (or CV to CC) and then we assign a fancy name (bulk, absorbtion, float) based on the 'stage' the charger has switched to and the voltage and current flow measured at the battery.

All smart chargers regulate current by reducing or increasing applied voltage, based on the measurements it takes.

From Wikipedia: 

"A smart charger is defined as a charger that can respond to the condition of a battery, and modify its charging actions accordingly."

If this were not the case, then why would we need 'smart chargers' in the first place?

IF the battery resistance and SoC (resting voltage) were all that were needed to determine the stages, then smart chargers are a total waste of money...since they have 'no control' anyway.

Two, three, and four stage charging are 'features' of a smart charger, not simply the result of chemistry and resistance changes.

The measured SoC and the chemistry settings on the charger (flooded, AGM, etc) determine the voltage being sent to the battery, and the charger intermittently measures the current being consumed to set the voltage level.

Your assertion would only be correct in the case of a 'dumb' charger like we all grew up with...a sheet metal box with Sears or Schauer printed on it, that had a 120v to 15v AC-to-AC transformer in it, and a simple diode rectifier to provide half- or full-wave rectified (but not filtered) DC.

On those, you selected 2 amp or 10 amp or 25 amp, (which tapped 3 different windings in the transformer) then hooked up the clamps to a low battery, and watched the meter slowly taper (at a very linear rate) from a high reading to a low reading over the course of a few hours.

The applied current from these simple, constant voltage chargers tapered down because as the SoC voltage increased, the applied voltage more closely matched the battery voltage. Those WERE dependent on the battery to 'control the rate of charge'.

But those were not smart chargers. And we don't use that technology much anymore.


More info:

https://www.batterystuff.com/blog/3-stages-of-smart-chargers.html

 

[John61CT]

Sorry, but you're wrong.

And for proper deep cycle bank usage most so-called "smart" features are just marketing BS and just get in the way.

The Absorption setpoint voltage* is just a target aimed for during Bulk, which is defined by the fact it is pumping in max current* but hasn't hit that voltage yet.

As the SoC has risen, voltage has been rising, resistance increasing, causing amps acceptance to be falling. When the charge regulation detects that the Absorb volts setpoint* has been reached, it prevents voltage from rising further.

Note this is the **first** "decision" requiring any "smarts".

From now on the charge source is in Absorption, and the only thing it is regulating is continuing to limit the voltage.

The current amps will continue to fall rapidly, not regulated by the charge source, but due to increasing resistance as SoC approaches full.

Now the key need for intelligence is determining "full", keeping charge flowing at Absorb voltage* until Amps has fallen to a tiny percentage of C, 20-hour AH capacity.

*which on a good charge source can be customized

Far too many "smart" charge sources fall down on this, and premature infloatulation murders your expensive bank early.

Hope this helps.

 

[Sabatical]

That's a great setup! So the wbj keeps voltage up at Absorb until amps **going into the bank** drops to what, 2A?

But of course if the fridge is drawing off most of the solar power it can take a long time to get there, or worst case not at all by sunset, depends on other loads, the weather. . .

The end amps are set at 3.5.

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[tx2sturgis]

When the charge regulation detects that the Absorb volts setpoint* has been reached, it prevents voltage from rising further.

{snip}

Note this is the **first** "decision" requiring any "smarts".

{snip}

From now on the charge source is in Absorption, and the only thing it is regulating is continuing to limit the voltage.

{snip}

Now the key need for intelligence is determining "full", keeping charge flowing at Absorb voltage*

John, you just plainly agreed with me in four paragraphs. The smart charger is actively changing (and controlling) what it does to get the battery to full charge in a fast, yet safe manner.

So if *I* am wrong, we BOTH are wrong.

But I was correct, and now you are also.

Thank you sir!

 

[John61CT]

The end amps are set at 3.5.

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IMO you could go to 2, or even 1 with no harm done.

Unless you've precisely calculated based on mfg specs for thatbatt.

 

[John61CT]

John, you just plainly agreed with me in four paragraphs.

Sorry, I thought you were claiming the charge source decides **when** to transition from CC to CV.