Classic 150 Maximum input power

[Bryan]

Does a classic regulate it's output power to a safe level regardless of the solar input power available?  For example if the power graph indicates the maximum output power is 2700watts for a 24 volt battery at 90 volts input, what would happen if there happened to be available 4000 watts of solar power available.  Would it burn itself up?  Or would it simply output the 2700watts and "waste" the rest??

[dgd]

Does a classic regulate it's output power to a safe level regardless of the solar input power available?   

yes.

[zoneblue]

Would it burn itself up? 

No.

[Halfcrazy]

So to clarify. Some controllers CAN be way over driven and some can not. The Classic CAN.

A controller will actually raise the input voltage to make the arrays MPPT voltage less accurate to maintain its rated current limit. So it is not having to dissipate the extra heat it simply de-tunes the array.

Think of it like the accelerator peddle in the car. You have 300 horse power if you mash it all the way down but you don't need it so you back off the throttle and the fuel is not burned.

BUT beware as I said only a few controllers work this way. Some will just keep going and damage themselves or blow breakers etc, But everything MidNite makes can be over driven and will simply limit to its max current

[Solar trucker]

Interesting Info on the max input power Halfcrazy. Got a very pertinent question, I'm running (4)-327watt
panels in to a classic 150..2 strings of 2 in series..The Panels have a VOC of 67.6 ea so my input volts is
134 volts, Used #10-AWG to controller which computes to 0.96% voltage drop to the controller...12 volt battery bank made up of 6-6volt batteries...2/(00) cabling from controller-(8ft) to the battery bank also
gives me about 0.88% voltage drop which I'm also very pleased with...I'm relatively new to the operational idiosyncrasies of the classic 150..The last couple of days all the cells in the 4 panels have been
getting full direct sun and my controller is rocking around 86 amps!  I know the classic is capable of 96A
The controller feels quite warm and the fans are running BUT I can still leave my hand on it with no discomfort (so the controller is not super hot..(just quite warm)..Question is Can the classic run at this level for a few hours at a time? should I be concerned? Also I'm thinking of adding (1) 315 watt panel with a similar VOC..When I add another classic, should I also remove one of the other strings and add it

[Westbranch]

Well, that 86A is about 89.6% of the max so you are hitting the Classic pretty hard, but they are tough... I keep an eye on the FET and PCB temps when the panels are givin' 'er.  boB has a post somewhere here about their max temps...

Issue I see is you have conversion losses in the Classic , evidenced by the heat being given off, that is coming from the step down from > 120 Volts to 12 V. 
Have you considered a 24V battery for the inverter (120V) loads plus a 12V battery for those lights etc that need native 12 V? Still 6 cells...

For the added panel, a Kid is probably a better cost effective alternative.

[Vic]

Solar trucker,

FWIW,  the SunPower PVs appear to really be 96 cell modules.  The Vmp of two of these PVs in series is about 111-ish volts:
http://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/ds-e20-series-327-residential-solar-panels-datasheet.pdf

This is a very high Vin to the Classic,  and as Wb mentioned this is a large step-down ratio,  and causes the Classic to limit its output current due to heating (probably).

AND,  you might find that if you travel to cooler climates,  that the Classic might spend some time in HyperVOC  --  producing no power at all when the PVs are cold.

Running strings to two of these PVs is probably not the greatest idea ...

How about rewiring them as four of these PVs in parallel  ...  you would need to add a Combiner if you do not currently using one.

FWIW,   Keep Cool,   Vic

[Solar trucker]

Thanks to both of you for your advice on the Heat issue on the Classic!  Just got off the phone with my friends at Northern AZ Wind & Sun in Flagstaff...They have been supplying me with Equipment for many
years and I talked to a fellow who says he's quite informed re: Midnite controllers!  He tells me that I'm
right up there in terms of hitting that controller with that input voltage!  He says the saving grace here
is that I won't be letting that controller see any ambient temps less than 28 degF...I'm either on RV Park
Grid Power and/or Propane when temps go below that, and I'm only using the batteries for some small
Lighting or TV use then which wouldn't require a massive Replenishment of the bank for that situation!
He says with no reservations that the classic will run for a few hours each day this time of year with no
ill effects and I should put the single Sunpower 315 watter onto the kid...That panel will hit the Kid at
75% of it's rating..I gather that should not present an issue???  I will get some info on those FET temps
and do some more research re: my classic temp situation..AS Always thanks for the Feedback!

[Solar trucker]

West Branch...I have considered the 24V Option, but in an RV there is limited Real Estate...and simplicity
sometimes has to win out over optimum design now and then!  it's always a pro and con game when
designing systems for these movable homes away from home!

One has to take into account..weight, space and usability...Are you advocating running the 4 panels and the 150 classic into 4 of my 6 volt batteries for Inverter use only??  AND 2 of my remaining 6 volt batteries just for the lights??  Would that be a much better situation than I have now?  I don't know, see
right now with 696 AH of storage, when I run my huge(1800 watt microwave) say for 3 minutes at a time,
my battery voltage stays above 12.7 in the daytime with good sunlight hitting the panels..Would I still
be above 25.4 with a 24V bank of only 464 AH storage??  I guess I could just allot the lone 315 watt panel from the kid to the 12V bank made up of 2 x 6 volt batteries? It's something to ponder I guess

[Solar trucker]

Just wondering, if I'm adding in 22 to 23 amps to that same batt bank as the classic, should that not
alleviate some of the load requirement coming from the classic??  i.e.: If my power requirements stay
the same but I add over 20 amps into the mix with the Kid...will the classic not back off somewhat from
the 86 amps to possibly a more comfortable 66 to 70 amps? At that point the classic is cruising at 75%..

[Vic]

Solar trucker,

   ...   Running strings to two of these PVs is probably not the greatest idea ...

How about rewiring them as four of these PVs in parallel  ...  you would need to add a Combiner if you do not currently using one   ...

As impolite as it is to Quote oneself,  did not note an answer to the above wonderment,

AND,  thanks for removing the reference to those SunPower 327s as being 72 Cell PVs.

Thanks for ANY reply,  Vic.

[Westbranch]

Yes I did mean what you responded ....
you have 6 x 6V cells, that would give you 4 cells = 24V and 2 = 12 V.
you would not need to change any of the wiring as it would now be over-sized compared to the 12 v setup you have now...
The benefit is you will not have 3 parallel strings in the 12 V setup, but now 2 single strings,
one string of 2 cells for the 12v and one string of 4 cells for 24V.  In this setup you will have better charging of all the cells due to eliminating parallel strings.

some good reading here if you have not seen it yet.. http://smartgauge.co.uk/batt_con.html

[Vic]

Just wondering, if I'm adding in 22 to 23 amps to that same batt bank as the classic, should that not
alleviate some of the load requirement coming from the classic??  i.e.: If my power requirements stay
the same but I add over 20 amps into the mix with the Kid...will the classic not back off somewhat from
the 86 amps to possibly a more comfortable 66 to 70 amps? At that point the classic is cruising at 75%..

Well,  let's see ...

During Bulk,  each of those CCs would be producing maximum current available.

If the CCs were each in Absorb,  then,  the current sharing is not predictable,  as each is just regulating voltage,  and the current from each of them will vary,  depending on things.

If the Classic with the two Strings of two 327 W PVs  was not delivering the maximum available current,  due to contribution of another CC (or other Charge source),  then,  its PVs would not be fully loaded,  and the String voltage into that Classic would rise,  even higher than the  Vmp for the Solar conditions  --  that is,  the input voltage to the Classic 150 would rise closer to Voc for the temperature that those PVs happened to be.  Higher input voltage,  with lower output current may produce the same amount of heating in an MPPT CC (like the Classic),  or even more heating,  even though the output power is lower.

The above is just my experience with several different MPPT CCs,  including the Classic.

In general,  it is not a great idea to load a piece of Power electronics at about 99% of its absolute maximum rated output for an extended period of time (as in some number of hours).   AND,  as the temperature of the Classic rises,  it will limit the output current to the extent needed to limit its temperature rise.  In a warm/hot environment,  this current limiting will be increased.  These effects will be seen as reduced harvest (power production),  compared to what would be harvested with a CC that is not running at full-throttle for hours at a time.

But,  these effects may not be of any significance to you (yet).
FWIW,   Vic

[Solar trucker]

Vic...I've decided from listening to you
Guys here to reword the input to the classic
To 4 parallel strings!
I will then be hitting the classic with an
Input voltage of approx 65v...This should
Help to alleviate some of the heating issues!
Also I'm thinking of reworking my 6 x 6v
12v Bank into a 4 cell-24v bank and a
2 cell-12v bank just for native 12v applications
On the RV...The 24v bank will strictly be used
For inverter AC loads!

Anyone want to buy a mint condition cared for
Magnum MS2812 full sine Inverter?
I'm looking for the same Inverter in 24v

[Westbranch]

the ''for sale - private'' is the best place to post the inverter ad 

http://kb1uas.com/mnsforum/index.php?board=59.0