About clouds -- could someone explain?

raindog · November 2019

My batteries are not healthy; new ones on the way. But, if bad batteries are not the cause, could someone explain to me why, on a mostly bright, sunny day, when a cloud passes over and then the sun reappears in full brightness, my controller gives alarm and shuts down?

This appears to happen, even when there is no load on the batteries other than the controller.

I suspect that there is a sudden change (surge?) that trips the controller. Can this be fixed?

MichaelK · November 2019

Which brand of controller do you have? I've heard about problems with cheap Chinese controllers that have poorly written firmware.

BB. · November 2019

Are you talking about the Charge Controller or the AC Inverter or some other controller shutting down?

Did you get a volt meter so you can monitor the battery bus voltage?

-Bill

raindog · November 2019

Sorry -- made a mistake; I meant the inverter : 24volt MicroSolar 1000/2000 Pure Sine Wave Inverter.

@Bill -- sorry, again, haven't gotten there yet. Could you recommend one, since I know nothing? Perhaps I can get one here, but will not have a selection. If I order it quickly, it can come over on the boat with the batteries. I'll check with the neighbors too.

BB. · November 2019

It sounds like the batteries are not charged, and probably by this time, they are not in very good shape. Both of those would cause the AC inverter to low voltage fault, especially when there is no sun on the panels (shade/night/etc.).

Here are a couple examples of DC Current Clamp Meters--(really AC+DC Current Clamp digital multimeters)--A current clamp is really nice and easy to measure current flow through any wire in your system. Note, there are AC Current Clamp DMMs too... They are perfectly good meters, but don't measure DC Current (they do measure AC+DC voltages, so the description can be confusing). The prices for DC clamp meters run from $50 to $350+ (Fluke professional meters).

https://www.amazon.com/gp/product/B019CY4FB4 ($100 meter that will do about anything you need)
https://www.amazon.com/gp/product/B07546L9RT (inexpensive $50 meter that is "good enough" for our needs)

The above are suggestions for starting points in your search. I have the first meter, and others here have the second meter...

DC Clamp meters are a bit "different" when measuring DC current vs other functions... You have to "ZERO" the meter (current flow off, or no cable through clamp) first, then measure current... DC current clamp meters do need to be reset every so often (minutes) for accurate readings. Drift in DC current clamp readings is just how they work.

Even a $10 DMM would be helpful for you to measure battery bank and other voltages in your system. You need to see what is happening.

Are the panels not charging, is the charge controller set wrong, are the batteries now bad--But having been under charged/over discharge) shortened their life, using non-distilled water for refill cells, bad electrical connections (loose, corroded, etc.)....

-Bill

Estragon · November 2019

It could be a "cloud edge effect"?

When a cloud passes, the panel temp drops, current is reduced, and voltage rises. Depending on conditions (breeze, sun angle, etc), when the cloud passes there's a sudden increase in current at the cool panel voltage, lasting maybe a minute while the panel warms.

What may be happening is a short spike in voltage beyond the inverter spec. Some inverters have pretty low high-voltage cut-outs (which can be a real pain for those of us in colder climates).

The controller should prevent the pv voltage spike getting to the batteries for more than a few seconds, but may not be. Bad batteries and/or connections could make this worse.

icarus · November 2019

Additionally, “edge of cloud” insolation spikes are very significant. The reflection of the sun off of the edge of clouds serves to magnify the amount of light . Panels that have been in cloud (and as Estragon points out) are somewhat cooler, all of a sudden are hit with not just say 100% of available sun, but possible as much as 150% (WAG), leading to a huge, short lived spike in current. I know that my of grid system will plug away at around 20-25 amps all day in full sun, (with a 30 amp MPPT controller), but an edge of cloud will drive it over the limit, forcing the controller to clip the current for a few seconds quite often on puffy cumulous days. I’ve seen ~38 amps during these events. I have to breaker the panels for 40amps to allow for that surge. (With proper sized wiring)

If your controller or inverter can’t handle those spikes it may be shutting down. Possibly poor batteries cannot absorb the spike, leading to a quick spike in apparent battery voltage causing the inverter to shut down? Try this experiment. Next time you have puffy clouds producing the event you describe, try loading the battery significantly when the sun is just about to come out again and see if this drops the apparent voltage enough to stop the surge trip.

Tony

raindog · November 2019

It is charging, I think : I cannot run the fridge after dark, but I can run the laptop and smartphone all night, it seems

.

I have a blinking, green light on the inverter 'til abut noon, then it turns to solid green.
The alarm sounds and shuts down the inverter when the sun reappears from behind a cloud and there is a sudden blast of full sun. I do not have this issue on cloudy /overcast days and can still run the fridge/laptop/smartphone-hotspot in daylight. This was occurring before I began having battery troubles, and when the refrigerator would also run day & night without issue.

I don't know about the settings on the controller (Schneider C60); it doesn't appear to have any settings.

Batteries are are PVX-1040T Sun Xtender (about 5 years old).

Yes, I suspect I hastened the demise of the batteries by knowing virtually nothing about off-grid living when I moved here. But, I expected to need more power than was present here before I came, so no surprises there. I need to learn as much as I can before installing a new system. I admit, it's a little steeper learning curve than I thought it would be.

Estragon · November 2019

If this is your inverter;
http://thepowerinverter.com/microsolar-1000w-peak-2000w-pure-sine-wave-inverter/

It lists DC overvoltage as 15v (presumably a 24v version would be 2x that), which is not far above a typical 14.x volt absorb voltage. That wouldn't work at all for me, as my banks are cool/cold enough for much of the year to need 15.x volt absorbs.

Some inverters will restart when voltage drops back down.

raindog · November 2019

@Estragon : It is this one : https://www.amazon.com/MicroSolar-1000W-Peak-2000W-Inverter/dp/B01ALI9QIW/ref=cm_cr_arp_d_product_top?ie=UTF8

Looks like it's no longer available and there's not much information available on it either, it seems.

If I get scattered clouds tomorrow, I'll try putting a load on the batteries just before the sun re-emerges and see what happens.

I was able to borrow a multimeter (Fluke III) from a neighbor, so I'm studying a bit how to use it. Should I disconnect the batteries to get the information needed? I have to say that, since I don't know much about batteries, I am a little shy about touching them, but I need to get over that now.

icarus · November 2019

You really need to take a step or two back and do some reading. Read up on the battery FAQs. Understand how batteries work (and don’t work!). The biggest thing to worry about when working with batteries is make sure you use insulated tools. With the voltages we are talking about, you don’t have to worry about shock, but dropping a wrench across the terminals can (and will) result in an explosion! Depending on chemistry, battery electrolyte can cause severe burns and blindness.

You don’t have to disconnect batteries to read them with a meter, but understand that readings are pretty meaningless if you don’t understand when a d how you are measuring them. (See also battery FAQs). Somewhere there is link to the above mentioned FAQs.

Tony

mcgivor · November 2019

As lead acid batteries age they loose capacity, the voltage will climb rapidly with current dropping correspondingly, if for example a 100Ah battery has lost 80% of its rated capacity it would then be a 20Ah battery, this would explain the rapid drop off after sundown. Voltage readings alone may create the illusion that everything is normal when there is no load, but once loaded the voltage drops rapidly due to diminished capacity, this will be more obvious when there is no charging.
These are some specs on the linked inverter

24V 1000w (Peak 2000w) pure sine wave inverter.

Input under voltage activation: 21.2V.

Input under voltage protection: 20V.

Input over voltage protection: 30V

Conversion efficiency: 90%

Here is the link to the learning center https://www.solar-electric.com/learning-center/batteries-and-charging/

softdown · November 2019

A quick perusal of that inverter leads me to believe that it is not a proper inverter for a user employing sensitive high tech computer equipment. Not hardly worthy of even a back up role. I'd go quality 48 voltinverter/charge controller with the new system, this will double your wiring efficiency and charge controller capacity while properly allowing for almost any reasonable growth.

raindog · November 2019

So, I waited 'til the Schneider indicated the batteries were fully charged (~11:30AM); then I switched on the fridge (as I don't want to wait another ~3 hours to let the batteries "rest"; I need the fridge on at this point after no fridge all night) for 10 sec. and then, shut the system down. One battery gives a reading of ~12.4; the other battery hovers around 10v, but fluctuates down. I see considerable fluctuation.

We cleaned the terminals not long ago, but since I didn't know to coat them with, say, petroleum jelly (not having any CRC available), there is rust on them (everything subject to rust, rusts here). Is it OK to clean with baking soda and wire brush? Then I will test again.

@softdown : I was thinking of keeping this system operational just to run a fridge. I'm trying to determine whether this is possible, what the cause of the cloud quirk is, and whether we can fix it. It is not nice to go to town (~25 mi one way) and come home to a fridge in meltdown because a cloud passed over.

It is always a good idea to have a possible backup for everything here. This system has run the little laptop just fine for a year and half now, charges other devices (clippers, small battery chargers) OK, etc.

706jim · November 2019

A fridge and a laptop are two entirely different loads. The fridge never sleeps. If a cloud shuts your inverter off with the fridge as the only load......You need a larger system!

Aguarancher · November 2019

Your one battery at 10V is dead and dragging your whole system down with it. Either remove from system an replace it or you could try charging it with a car charger by itself.

raindog · November 2019

Hello, 706jim, it does not appear to be the shade of the cloud that is the culprit, as I can run fridge and laptop, etc, on completely overcast days without issue. It is the reappearance of the sun from behind the stray cloud on bright, sunny days that is causing the problem. The second the sun reappears, the inverter alarms and shuts the system down. And it does this whether there's my typical load on the system or whether everything is unplugged from the system.

See Estragon and icarus (above) think this may be an "edge of cloud" phenomenon. I am waiting for proper conditions to test their hypothesis. Because I frequently meet this condition (once, so far this AM) -- at least several times a week, for most of the year -- it may be relevant for building the new system as well.

Just to add, for the sake of clarity, this does not happen if there is a gradual shift (over several seconds) from cloud/shade to sun.

My remark about the laptop was in reference to softdown's comment (above) concerning the inverter, which, I would admit, is probably not a very good one. And the system is small for my needs, so we have a new system in the planning stage. But this current system runs all the things I mentioned, plus the fridge, and has for more than a year, despite the quirky behavior with scattered clouds. I would like not to just trash the little system if it is still functional; it's a matter of principle.

Are we on the same page?

Aguarancher · November 2019

FYI basic state of charge chart:

Image: https://us.v-cdn.net/6024911/uploads/editor/vi/grbdb4pvtq1i.jpg

icarus · November 2019

Your batteries are DEAD!!!. The cloud “issue” is just confusing things for you. Get your batteries sorted, then get the charge regimen sorted. In fact...start from scratch, do the load calcs to determine system component sizes, work backwards from there to determine the battery bank size, then the pv to keep that battery healthy, and then a generator shore charge regiment for back up.

Anything else is simply spinning your wheels and costing you time...and money. You need to learn and understand the basics, and that all starts from understanding the loads, and how to power them. I’m not meaning to sound snotty, but I don’t think you get the basics...We are here to help however,

tony

BB. · November 2019

At the very least, your 10 volt battery is severely undercharged (basically dead).

You may be able to recover by charging it with a 12 battery charger, but the reality is that there is a 99% chance it needs replacing (and you should replace both/all batteries in the back at the same time (of they are all 2 or so years old or older).

Battery FAQ

https://www.solar-electric.com/deep-cycle-battery-information-faq.html

Beside volt or clamp+volt meter for tools, you need a hydrometer to measure battery specific gravity:

https://www.solar-electric.com/search/?q=hydrometer

Before putting the hydrometer away, rinse with a couple draws of distilled water (or the float can get sicky).

Hydrometers are only used with flooded cell lead acid batteries. Not for AGM, gel, lithium, or other battery chemistries.

Batteries are groups of cells connected (most of the time for lead acid batteries) in series. They are "matched" cells (voltage, capacity etc.).

You can have all cells go bad at the same time, or one cell fail (open or shorted).

It does sound like your system is charging, but too small for your loads (a refrigerator usually moves a solar system from small to medium capacity).

Details matter (loads, exact battery your configuration, solar array panels and configuration, location free of shading, etc.).

If your batteries lasted for 5 years or more, the system may be ok. If the batteries failed in 2 years or less, too much loading, not enough solar panels, incorrect configuration).

In you case, I think you have 2x 250 Watt @ Vmp=31 volts in parallel. That is not high enough voltage to properly charge a 24 volt lead acid battery bank. And the batteries will not last very long, and will not operate your expected loads very well (low battery voltage, AC inverter shutdown).

Bill

softdown · November 2019

I have considerable experience with dead batteries showing ~ 10-10.5 volts. It has a bad cell and is severely damaging the other batteries capacity as well. With a specific gravity meter you would find that you have what measures out at as water in one cell. Any battery that doesn't show at least 12.6 volts when fully charged is absolutely doing more harm than good.

Everybody kills their first battery array it seems. Chronic undercharging usually.

raindog · November 2019

@Estragon & @icarus : a little reading suggests the "edge of cloud" phenomenon occurs only in cold weather conditions, but everything else fits. Do you think my proximity to the Atlantic may make it possible for this to occur despite the warm, ambient temperatures here? The DC system does not do this. Today, at ~2PM, the ProStar controller is showing 13.7v charge with fairly bright sun and hazy clouds without sharp edges.

raindog · November 2019

The current Sun Extender AGM batteries are 5+ years old and I have purchased replacements for them.

I thank you all for your help and patience. I have learned much, but still have much to learn.

icarus · November 2019

raindog said:

@Estragon & @icarus : a little reading suggests the "edge of cloud" phenomenon occurs only in cold weather conditions, but everything else fits. Do you think my proximity to the Atlantic may make it possible for this to occur despite the warm, ambient temperatures here? The DC system does not do this. Today, at ~2PM, the ProStar controller is showing 13.7v charge with fairly bright sun and hazy clouds without sharp edges.

It have been my experience that edge of cloud effect is not dependent on temperature. Cold temps may make the phenomenon more pronounced however. Your proximity to the Atlantic should have nothing to do with it.

One more thing...you are equating the Prostar showing 13.7 volts as necessarily a good thing. Absent any other information, like current (amps) charging duration (bulk/absorb/float etc) it is a number that is largely meaningless.

About clouds -- could someone explain?

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