Solar output during non peak hours

[akrvbob]

It's a big mistake to assume you'll not get the full amount fro the panel. While that is generally true, not always. You get up to 12,000 feet in Colorado on a cool fall day with full sun and it will produce MORE than it's rated for.

I have a friend blow his controller under those exact circumstances even though it was supposedly able to handle the rated power of the panels.
Bob

 

[jimindenver]

At 5280 feet I can't test my panels rated at 8a Isc with a ten amp meter. On a cold day I have had a panel rated for 36v go over 40 Voc. I have an acquaintance with over 900w that boast 48a with his MPPT system in AZ. Here in Denver my 750w system matches it easily and where we camp at 10,000 ft, it will push the 60 amp limit of the controller. It's lifes way of evening up what altitude does to my generator which can lose 40% of it's ability on a hot day up there.

 

[Seraphim]

Bob

When designing a system, I look at it as I look at a financial budget: plan for the worst. If you plan for the worst case scenario, and things are always better, you're a happy camper. If you plan for average conditions, or for ideal conditions, one will be unhappy the results. I planned my storage to cover four days of of usage without recharging, and the panels for as rapid a recharging rate as I could get, using realistic data provided from both knowledgeable users, technical websites and books, and info provided by the manufacturer itself. So far, I've been more than a happy camper. Of O ever get the 'full amount from the panel' I'll be ecstatic *grin*. But when I DONT, it won't really matter: what I get will do the job. That's what's important, to me.

So I think it's a big mistake NOT to assume you won't get full amount from the panel. Just different perspective, I guess....

 

[Bela's Mom]

I think Bob's point was that, if one doesn't assume that one will get full power, they might purchase a controller that is too close to the edge of what they need.

For example, Seraphim, you have panels that produce 400 watts and a 30 amp charge controller.  Your driving at altitude like Bob's friend, you drive under some clouds and then out into full sun.  From what I have read, the "cloud effect" can cause power spikes that can damage the controller.

Getting more power than the panels are rated for certainly can be good.....as long as your controller can handle it.

 

[Seraphim]

My controller is 40 amp, which is not the point of your post, I guess. But as I said, when budgeting, one assumes worst case scenarios, which the spiking would be ( and frankly, I've never hear about panels over producing before, in all the research I did). I have read one should not choose a controller with an amperage rating close to what the panel's are rated to produce; one should choose a stronger controller. I don't remember the percentage, but spiking may be the reason they suggest that margin. But that's not how I read Bob's post, and I could have taken it in a manner it was not intended. We were talking about considering what a panel could or could not produce, not what size controller was needed. Controller choice would be the next step.

 

[Seraphim]

On my 400 watt system, the panel's are rated at 5.29 amps each (IIRC). 5.29x4 is 21.16 amps, theoretically, ideal conditions. Will that spike above 30 amps at any time - is it possible? Serious question, I really don't know. But that would be about a 50% increase in power necessary for those 4 panel's to exceed 30 amps and potentially damage the controller. Again, we're discussing the amperage the panel's can produce, not what an MPPT controller can put out.

 

[Seraphim]

And I apologize - my autocorrecting iPad keeps making panels as panel's - I can't stop it... I do know the difference between plural and possessive lol

 

[Seraphim]

Last thought / question: I also notice the input limits on the controllers are listed in wattage, not amperage. So if the input to a 30 amp controller is listed at 400 watts/12v, that's actually about 33.34 amps. Again, that's input from the panels (caught it this time), not output from the controller. Im not trying to argue the point, but looking for an explanation that makes sense.

 

[Seraphim]

Apology to Bob - just re read your post about the controller being damaged. Old eyes must have missed it.

 

[Bela's Mom]

I was just using your set-up as an example; not intended to infer that your panels or controller are not matched.  There is something called the "cloud edge effect" that has been written about.  I read about it after the first time Bob wrote about his friend's controller blowing.  The panels produced more watts and voltage than they were rated for.  This can blow fuses and possible damage the controller, to which the panels are attached.  So the controller is relevant.

While this has nothing to do with the OP's question, it is interesting to read about and was related to where the discussion went.

 

[SternWake]

I've been looking at my Ammeter during a couple Edge of cloud events here at sea level, and seen a short lived double the expected solar amperage during them.


My controller is rated for 25 amps.  198 watts of MPPT solar will yield 13 amps or so on noon of june 21, and I've seen 24 amps in march during an EOC event.

The amps taper quickly as the panels heat up and the edge of cloud moves away.

How long any particular controller can handle an over amperage EOC event is an unknown.

 

[Seraphim]

Thanks Jo. Like I said, I'm curious about just how much those panel's can overproduce. Did some online research and can't find any discussions or research on the problem.

 

[Optimistic Paranoid]

Stern,

No fuse or circuit breaker between the panels and the charge controller input?

Regards
John

 

[SternWake]

OP,

I do have a 20 amp Maxi fuse in the junction box on my Kyocera 130 watt panel, but mostly as a disconnect, not to protect the 8awg wiring or controller. My unisolar pvl-68 has no fuse on the 10 awg to the controller. I do have a 30 amp circuit breaker as instructed by Blue sky on controller to battery cable.

I do not like the circuit breaker, I can measure voltage drop across it, and the Maxi fuse also causes some VD. Both of which compromise solar performance to some degree.

 

[Bela's Mom]

Thanks Jo.  Like I said, I'm curious about just how much those panel's can overproduce. Did some online research and can't find any discussions or research on the problem.

Just google cloud edge effect.  There are lots of articles, both research and forum discussions.  Here is a sample:
http://forums.energymatters.com.au/solar-wind-gear/topic1507.html.

Enjoy!  It is very interesting..

 

[blars]

The case I know of where a cotroler blew was cold, high altitude, and charged batteries with an MPPT controler. VOC was higher than the panel was rated for, and there wasn't much margin between the rated max input voltage of the controler and the rated VOC of the panel. The panel producing more power should never damage a well designed controler, it will just not use all the panel can produce under those circumstances. I've had seen the output of my 450 watts of panels exceed 500 watts for short times, but my controler is overrated for what I have.

400 watts of panels on a PWM controler will probable never exceed 360 watts to the battery, the rest is wasted by being PWM rather than MPPT.

 

[Seraphim]

I have trouble determine the wattage my panel's are putting out; my controller never enters the bulk charging cycle, as far as I can determine. We never tax our batteries., so I can't calculate what the panel's are actually producing. Is there a way to put a meter between the panels and the controller to show what the panel's are actually giving the controller to work with?

The controller only shows panel voltage, SOC, battery voltage and amps provided the battery.

 

[SternWake]

 Is there a way to put a meter between the panels and the controller to show what the panel's are actually giving the controller to work with?

The controller only shows panel voltage, SOC, battery voltage and amps provided the battery.

Put a large load on the batteries more than what the panels are capable of.  if the controller is in float already, the load will have to be big enough to drop battery voltage below the set float voltage.  At that point the controller will take everything the panels can make and your controller display should show it.

Think inverter powering an Angle grinder or something. That is about 50 to 65 amps if the grinder is actually grinding

 

[akrvbob]

Seraphim, you and I are in total agreement, we are just talking around each other. I think this will clarify my thinking and you'll see we think alike:

1) When you buy your controller, plan for the best possible case scenario of panel output when they can over-produce what they are rated for. In other words, get too big a controller and not too small.

2) When sizing your total system think worst case scenario. A weeks storm on Dec 21 in Seattle WA.

Bob

 

[Seraphim]

Seraphim, you and I are in total agreement, we are just talking around each other. I think this will clarify my thinking and you'll see we think alike:

1) When you buy your controller, plan for the best possible case scenario of panel output when they can over-produce what they are rated for. In other words, get too big a controller and not too small.

2) When sizing your total system think worst case scenario. A weeks storm on Dec 21 in Seattle WA.

Bob

That's why I apologized - I completely missed your comment about the damaged controller.  Careless reading on my part...