High Load interferes Drops Charging Voltage?

[John61CT]

Very bright and cold can do it with tracking.

Not counting snow reflection

 

[frater secessus]

Cloud edge effect occurs anywhere it is partly cloudy. That effect + altitude has smoked (overvolted) at least one controller here on the forum.

 

[tx2sturgis]

Cloud edge effect occurs anywhere it is partly cloudy.  That effect + altitude has smoked (overvolted) at least one controller here on the forum.

Then that controller was probably undersized for the application...as with anything in electronics, there should always be some provision for out-of-tolerance operation. Which, after all, is what we are talking about when you spec ALL of the components in a system.

 

[frater secessus]

No argument there, but that isn't what John and I are talking about. We are pushing back on your statement that:

> Max power actually produced is always less than the rating of the panel.

 

[tx2sturgis]

No argument there, but that isn't what John and I are talking about.  We are pushing back on your statement that:

> Max power actually produced is always less than the rating of the panel.

And I understood that. I also said 'in the real world'...meaning that in our calculations for overall, average, day-to-day power generated for the average vanner or RVer, we have to assume, always, that we will get LESS output than the panel ratings. If I had said that 'instantaneous power can never exceed X watts' then you would have a valid issue. But I did not say that.

In the original context, I am correct.

Can panels occasionally exceed ratings, sure. But do you size your solar system and expected loads based on the panels being able to do that day-after-day? Of course not.

(Maybe if you park year-round at high elevation with cold year round temps and high levels of direct sun and movable panels. But that was not presented as the situation we were dealing with.)

But you DO need to spec the parts downstream for occasional over-performance...but that is off the original topic and was not being discussed.

 

[John61CT]

Then we are agreeing.

"Real-world power actually produced always averages less over a period of time than the rating of the panel."

is 100% true, and is in line with my statement about sizing for suboptimal conditions

"Max power actually produced can sometimes and for short periods be greater than the rating of the panel."

is also true, and means that even with good quality controllers, the panels purchased should be sized say 10% below the SC spec'd maximums.

In the case of the Victron 75/15 for example, max amps (20A lsc input) aren't ever going to be a problem, since most people don't want to throw money away exceeding the 220w max **output**.

However, the max **voltage** (Voc) I would attach to each SC would be 65V.

 

[DLTooley]

I haven't gotten an ammeter yet, but I should definitely move the charge controller to the battery bank. It is currently located near the starter battery close to the hood mounted solar and everything is connected at the terminals of the starter battery.

There was a benefit to this set up with a FLA starter battery as it help keep that topped off and extended the life of same. With my AGM starter I don't see any benefit at all and the higher voltages on the run to the house battery will be a plus.

I am thinking a MPPT controller is NOT worth the expense as my system is 12v and not likely to increase.

Also, in warmer months I am typically at 8-10k feet. Could there be something else causing the excessive voltage readings?

 

[John61CT]

With your now increased understanding, it would be helpful if you re-state any problems you still feel **aren't yet accounted for or explained**.

In full, as if starting a new thread.

 

[jimindenver]

Living and testing my gear at a mile high the numbers I saw from my panels always exceeded what people at sea level reported. I camp close to two miles high and on a cold sunny day your panels wear Superman's cape. A MPPT controller will clip the amps but not the Voc.

 

[DLTooley]

With your now increased understanding, it would be helpful if you re-state any problems you still feel **aren't yet accounted for or explained**.

In full,  as if starting a new thread.

Thanks.  I haven't done the rewire yet, nor purchased an ammeter.

I have done additional research.  One benefit of PWM charging is that it has some de-sulfation benefit over a period of time.  I think I've now observed this twice on this same battery.

Would you have any recommendation for a lower cost shunt based BMS or ammeter?

 

[tx2sturgis]

I camp close to two miles high and on a cold sunny day your panels wear Superman's cape. 

This kinda skews the numbers on 'real world' applications.

In a good way tho....

 

[John61CT]

I have done additional research.  One benefit of PWM charging is that it has some de-sulfation benefit over a period of time.  I think I've now observed this twice on this same battery.

I don't see how. MPPT vs PWM is about extracting power from panels, no inherent difference in charging output algorithms, that woyld depend on the regulation, and all good SCs let user program those anyway.

Equalization / "conditioning" to **prevent** sulphation should only be done manually, never allow a charger to automate the process.

And marketing bulldust about chargers desulphating abused batteries is just that, hooey, stay away.

Link to your "research" sources?

Would you have any recommendation for a lower cost shunt based BMS or ammeter?

Sinometer UT207 https://www.amazon.com/gp/offer-listing/B005VUBGZW

Cheaper dunno if good http://m.sears.com/product-details/p-03482369000P?partNumber=03482369000P

BM: Victron 702-BMV

There's lots cheaper Chinese stuff on eBay

 

[DLTooley]

I was looking at this clamp ammeter, same manufacturer as the Sinometer, for a clamping meter.  No specific details on accuracy for either.

$38.00

https://www.amazon.com/dp/B005HOPRRK/_encoding=UTF8?coliid=I197P022VMQYTL&colid=FGV5GIUXY8RP
https://www.amazon.com/dp/B005HOPRRK/_encoding=UTF8?coliid=I197P022VMQYTL&colid=FGV5GIUXY8RP
Shunt based systems are more accurate, but $200 is definitely out of budget.

 

[DLTooley]

I don't see how. MPPT vs PWM is about extracting power from panels, no inherent difference in charging output algorithms,  that woyld depend on the regulation, and all good SCs let user program those anyway.

Equalization / "conditioning" to **prevent** sulphation should only be done manually, never allow a charger to automate the process.

And marketing bulldust about chargers desulphating abused batteries is just that,  hooey,  stay away.

Link to your "research" sources?

Page 3 of this Morningstar PDF has a section on the subject with two cited studies.

https://www.morningstarcorp.com/wp-content/uploads/2014/02/8.-Why-PWM1.pdf

I have observed same on two occasions when I thought the battery was dead - it took maybe a month to get back to green on my current 5 LED battery box meter.

 

[John61CT]

I was looking at this clamp ammeter, same manufacturer as the Sinometer, for a clamping meter.  No specific details on accuracy for either.

$38.00

I'm not that au fait on ammeters, pretty sure the UT207 was a Maine Sail reco.

Look at DC amps measurement range and resolution.

Measuring inrush and true RMS seem to be important.

This forum is good for diving down that rabbit hole

https://www.google.com/search?q=site:eevblog.com+UT203

 

[John61CT]

Again, resurrecting abused near-dead batteries is an edge use case, nothing to do with mainstream considerations for normal day-to-day usage.

Sulphation needs to be prevented, not "cured".

And that marketing sheet was produced well over 20 years ago, when PWM was the new hotness.

And