why don't Solar controller mfg/sellers use honest ratings

[MrWizard]

example most 30amp controllers are listed at 390w of panels

and 40amp controllers at 500w of panels

but we don't charge batteries at 12.0v we charge at 14v or higher

14v*30 amps 420w output, going to need more than that input

40a*14v 560w output to batteries, controller must handle at 600w input

500w with 17.5 actual output 12v nominal panels only equals 28.57 amps into and thru Controller NOT 40 amps

so will these controllers really handle the rated amps ? which means a much larger array than the stated max

or are they just blowing smoke..uykw

30 amp ? 390/17.5v = 22.28 amps max from the array
so what is it really a 25amp controller ?

30amps charge at 14v =420watts out , 17.5 * 30 = 525 input
you need 525w panels to get 30amps out at 14.0v

this of course does not included mpppt panels although the same mfg/sellers are doing the same thing playing loose with the words

[pianotuna]

Hi Mr Wizard,

I prefer discreet devices, too, but 999 for a 3000 watt psw inverter is pretty good and having the ability to do 30 amps of solar is a definite bonus.

[Naio]

pianotuna wrote:
This looks interesting--a combo inverter/charger/solar controller.

inverter charger and solar controller It can accept 30 amps on the solar side.

Cool find. Until I saw the $9oo price tag!

Edit: OIC, that is just what 3000 psw's cost.

[MrWizard]

thats interesting, i don't think its practical for Rvs, at least not for me
AC charge is too low at 25amps,
i prefer discreet devices, easier to replace an item if some function fails

[pianotuna]

This looks interesting--a combo inverter/charger/solar controller.

inverter charger and solar controller It can accept 30 amps on the solar side.

[time2roll]

http://www.morningstarcorp.com/string-calculator/

[MrWizard]

I don't think of voltage as being a problem with controllers
In most cases your panels in series is easily under the limit or you know it's over, especially with PWM where parallel is the norm, because you want amps not volts
With MPPT you do need to check that your series arrangement is under the controller limit

[BFL13]

It is not 1.25 for voltage as such, but you do have to leave margin in your controller's total Voc input limit for when Voc is higher than rated at STC.

You can calculate that from the coefficient in the panel spec for the coldest you expect to be using it.

Mr Wiz--"working amps" with PWM is Isc NOT the lower Imp figure you would use with MPPT. You would see this if you had tracking panels and checked panel Isc (disconnected) with amps to the battery (connected) --same amps amount.

[MrWizard]

NEC says use a controller with a rating 25% more than your isc..not working amps which is less than Isc
I don't know how the output would ever reach that point
Unless maybe there was a dead short on the output at STC..?
And even then you could not exceed Isc

And morning star says the controller will handle 130% of the rated input and taper the amps
Which means NEC wants you to use 36amps Isc not the panel working amps for a 45amp controller that the MFG says will handle 58 amps input

Now I believe Morning star, I would have no qualms connecting 700w aka 41amps to that controller

But I would have second thoughts about some of these other controllers
The NEC and controller MFG are not using the same play book

There has got to be done middle ground for quality and price point
How long until the market sorts itself out

[time2roll]

With 41 amps Isc it would appear you need a PWM controller rated 51.25 amps minimum to meet NEC. That probably puts you at a 60 amp controller.

Those panels in series would need just 45 amp MPPT to meet NEC and not clip the amps. Actually if you rarely see 35 amps a 30 amp MPPT might be fine with minimal clipping. Still meets NEC.

There is no 125% applied to voltage that I am aware of.

[MrWizard]

what is the "Voltage" ?

again this is MPPT which will convert the volts to amps
for increased output
something that DOES NOT happen using PWM

all the cheap controllers are PWM, even the the 'fake' mppt are PWM
there is no 'overhead' conversion to more amps

smkettner wrote:
Yes this is on p8 of the TS MPPT manual:

To comply with the National Electric Code (NEC), the current rating of the controller must be
equal to or greater than 125% of the solar array’s short circuit current output (Isc). Therefore, the
maximum allowable solar array input to the TriStar MPPT 150V controller for compliance with the
NEC is:
TS-MPPT-30: 24 amps Isc*
TS-MPPT-45: 36 amps Isc*
TS-MPPT-60: 48 amps Isc* *Solar array Isc @ STC


My array Isc is about 8 amps and 675 watts. Maybe another reason to go series.

TS MPPT manual

[MEXICOWANDERER]

Empty Nest, Soon wrote:
I have not looked that much at cheaper controllers, but the lack of a heat sink is one obvious difference. And yes, providing a heat sink at a reasonable cost should be easy. I can’t explain why the market has not offered that.

But how about a Tri-star 45 for $161? http://www.ebay.com/itm/221681616399?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Wayne

If you believe heat sinks are reasonable take a heat sink tour of eBay, electronics suppliers and manufacturers. The price them like they are manufactured from copper. And the cheap @#$/\&!, s don't even bother to black anodize them. A heatsink for a working MOSFET is not small. I am forced to use 7 fin 50X40 mm sinks for my LED buckers. Heat sinks are the bane of the LED industry. You hear screams THIRTY WATT LED LIGHT and find out it's driven at 20 watts with a hot as hell heat sink.

Working with newer electronics and their cost structure has really given me an education about heat sinks. Devices are taxed thermally to the bitter limit and of course the fluorescent tie & paisley shirt crowd lie like hell in order to sell merchandice. Welcome to the age of B.S. There's no one out there to trim their horns.

[MrWizard]

BTW,, for those interested
the Imp? Working amps,, for my current configuration is right at 41 amps

hoping to hit 35 amps at STC during testing this Sunday

i will have to put a load on the inverter to do so
maybe run the Vacuum cleaner

[time2roll]

Yes this is on p8 of the TS MPPT manual:

To comply with the National Electric Code (NEC), the current rating of the controller must be
equal to or greater than 125% of the solar array’s short circuit current output (Isc). Therefore, the
maximum allowable solar array input to the TriStar MPPT 150V controller for compliance with the
NEC is:
TS-MPPT-30: 24 amps Isc*
TS-MPPT-45: 36 amps Isc*
TS-MPPT-60: 48 amps Isc* *Solar array Isc @ STC


My array Isc is about 8 amps and 675 watts. Maybe another reason to go series.

TS MPPT manual

[MrWizard]

That link is not working for me
But I did find this

To comply with the National Electric Code (NEC), the current rating of the controller for solar charging must be equal or greater than 125% of the solar array’s short circuit current output (Isc). Therefore, the maximum allowable solar array input to the TriStar controller for compliance with the NEC is:
TS-45: 36 amps Isc
TS-60: 48 amps Isc

$142.25

http://www.ecodirect.com/mobile/product.aspx?ProductCode=Morningstar%2DTriStar%2DTS%2D45&gclid=CM7M...