Temperature in controller shed

[dgd]

Agreed. +1 for including that in the manual. Of course from a marketing perspective it kinda contradicts the "point" of high voltage controllers, and to a lessor extent mppt.  Id really like to see a full set of efficiency curves, to enable users to make good decisions about their array configuration.

-1 Don't agree with that suggestion. There are just too many variables where temperature is concerned
and ambient temperature is IMO the most important.
The Classic does produce heat and its important that the heat can be removed or vented or wicked away from the Classic.
This applies to just about all heat producing electronics, thats why air-con computer rooms exist.

I personally use a 24v bank with C150 and PV input of 90v mpv from 5s 18v PVs. When the Classic unloads these in Abs and Float this rises to near 110v.  (40m twin #4 from Classic to PV frame)
Even with 80+ Amps the Fets and pcb stay below 60c, fans running BUT then the ambient in power room is about 24c despite 30c+. outside in garden.
WIth average power making 45 to 60A the temps seem to stay about 50c

I'm convinced the fact the power room is below house, below ground level by 1.5metres and hence never gets above 25c or below 15c is the real solution to keeping Classics running cool or within their designed temp range.

Lowering input voltage seems counter productive to me, why then bother having 200v and 250v input Classics if the answer to Classic heating is to reduce input voltage to nearer battery voltage *2 (or whatever)

dgd

[Vic]

Removed for now   Vic

[BobWhite]

sory Vic can't see the pdf!

walt

[Vic]

Hi Walt,

SORRY,  I was busy deleting my post,  and the .pdf,  because I had guessed wrong on too many things ....

And,  I had too many PVs.

SO,  I should just ask  Isunell for the Specs on the PVs being used,  and the number of PVs per string,  and the total number of strings.

Sorry for the mis-post.   Thanks!   Vic

[BobWhite]

Hi Walt,

SORRY,  I was busy deleting my post,  and the .pdf,  because I had guessed wrong on too many things ....

And,  I had too many PVs.

SO,  I should just ask  Isunell for the Specs on the PVs being used,  and the number of PVs per string,  and the total number of strings.

Sorry for the mis-post.   Thanks!   Vic

NP just glad I didn't continue with further questions as you answered all. This is a great subject of interest to me! you all are helping me see the reality of it all! thank you!

Walt

[russ_drinkwater]

Thanks Kurt,
Yeah I had a look after the post and it was around 86 amps which the PV array would never put out anyways.
My solar array at the reg shows 48.6 volts and the max I need is 31.0 volts for equalize.
So I can not get it any better for what I require with the 24 volt system.
Have get off my dot and get the other 12 panels up and forget about the extension to the roof out the back. It can wait a while.
I have concerns with the trojans as they show good charges, but the SG is never up to 1275 at any time. (On float at 10am most days)
The max input I get is 30-35 amps. With only 435 amp hour @ 24 volts it should be enough to keep the batteries well charged.
The highest consumption I have had on the standalone system is 5kw a day, 7am till 4pm when I switch it back to grid tie.
I am guna die with the heat and humidity here atm.
Sold some cattle today and it was 38 deg C and 85% R Humidity, crazy weather, worse than the Phillipines!
I do not want to hear about those lithiums mate! Lol. (green eyed monster)

[zoneblue]

>The thing is if you lower the input voltage you will have more loss in the cables but only at full output. If you increase the input voltage you will have heat in the controller at all output levels. In fact it's actually worse under light load.

Exactly right. If you have to kill 100W do it in the cable not the controller.

[dgd]

>The thing is if you lower the input voltage you will have more loss in the cables but only at full output. If you increase the input voltage you will have heat in the controller at all output levels. In fact it's actually worse under light load.

Exactly right. If you have to kill 100W do it in the cable not the controller.

'have to kill   

So this is all to do with Classic working temperature control, Now temperature is more important than efficiently generating power - to the point of seriously recommending reduction in input voltage despite the fact that the Classics are operating within their designed temperature range AND they have thermal shutdown capabiity if they get too hot.
And this is coming from people who are concerned about tare loads > 10 watts on other RE components.
(computers, inverters etc)

Has anyone lost a Classic due to sustained running hot within its allowed temp range?
Has thermal shutdown failed? Has MN rejected a warranty claim due to running near or at MAX power output resulting in a burnt out Classic?

What about a temperature controlled current Clipper controlled by an AUX to SSR that inserts a burn-off-power resistor into the input (PV) when a certain FET/PCB temp is approached or reached?
or using a pair or more cables in the +ve PV input and as Classic heats up an SSR disconnects one of the cables leaving the remainder to burn off power because of greater losses?

Or why not just solve the problem properly by cooling the Classic's environment, keeping the ambient operating environment at normal room temperature of 20c ?

Sorry couldn't resist this post and no offence intended toward anyone

dgd

[russ_drinkwater]

Wasan me!
Mine runs as close to usable voltage as possible.
I did see it peak a few times today at 57 volts, lol.
Reflection from passing clouds I suspect adding to intensity.
Personally not that worried about small losses atm.
Maybe if we were totally standalone it would be a different story!
Even today the hottest I saw at the reg temp was 48deg C around mid-day and putting in 35 amps.

[zoneblue]

dgd, all i  know is that the archiles of all electronics is electrolytics. And they hate heat, the hotter it gets the shorter their life. MMPT controllers rely on them. Ive replaced power caps in many a consumer item, that didnt need to be tossed, just because im stubborn. The cost effectiveness of RE isnt particularly flash as it is, and so longevity of the gear is a must.

[dgd]

zb,
I agree with you and it seems MN do too as they provide field replaceable parts for the Classic which no doubt includes the electrolytic caps board as well.
I figured that because I do diversion to water heating at the PV side of the Classic then this definitely helps it run cooler, more so now that I can divert 1400 watts of my 2800 watt pv array.
Maybe if I run all power through the Classic then I would see heating issues such as ogQ does.
I thought he was onto something with the pumped water heat exchanger on his Classics but he seems to have given that idea away 

dgd

[offgridQLD]

It's not like i don't cool my classics. They are in a insulated block wall room small power room about 2.5m x 1.5m with a 2.5kw Samsung inverter split system air conditioner blasting freezing cold air at them all day every day from 1.5m away.





Both classics have 4000w of PV on them each. Even in a refrigerated room the classic that had 3s on it was a toaster. Its that inductor in the classic that gets hot and heats the inside of the classic up.

Like others and myself have mentioned. Caps and so on last longer with cool temps. Yes I know you can buy new caps (if they didn't take something down with them when they go) but I want a system that is living a easy life and will last a long time reliably.Yes I know the classic will be ok running hotter and it can handle it but Why give it a hard time.

I didn't buy the classic because it can handle high voltage input I purchased it because I realy like the reliability and charging features, WBJ, online monitoring , support and so on.

I see little difference in production at 2s vs 3s  so its not like you are giving up much. PV is inexpensive CC are expensive and a pain if they are down for mantanance when your 100% offgrid.


Anyhow I guess we can just let people find out for them self. I just see some one who isn't informed might place a classic in a less than ideal location (hot location or confined location) then try and take advantage of some PV that they just happened to have (that is high voltage) and run 12V system. Then we get the post on the forum.....why do my fans run all the time why is the controller hot. If the input voltage vs battery voltage - heat correlation was at least mentioned this might be avoided.

One analogy could be purchasing a truck that is rated to tow 3 tons. In the manual there would be a mention that towing at full capacity is harder on the truck and it will require more mantanance and stress on the cooling system. This is common knowledge and a easy thing to understand..(weight = stress) most people get that. Though voltage conversion doesn't always  register to people that it's hard work and the higher the discrepancy the harder the job.

[zoneblue]

Its that inductor in the classic that gets hot and heats the inside of the classic up.

That confirms what i always observed, that the left side of the classic is (counter intuitively) hotter than the right ( mosfets being on the right). I guess that means that larger gauge windings would help, right?

[Vic]

Couple of things;

After running our off grid system for about one year (this was eleven years ago),  installed a window A/C in the power room,  as the OB MX-60  CC's fan would run,  often.  The A/C reduced the MX's fan run time to almost zero.   Really,  a major reason for the A/C in the power room,   was an effort to try to keep the batteries as cool as possible.

This system has run a 106 String Vmp,  since day one,  so is less efficient than a lower string voltage on this 48 V battery.  This I did know during system design,  bun wanted a fairly high String Vmp,  to allow directly heating water with PV.

Here,  the Classic's fans run often,  even when ambient temps are 50 F or a bit below,  mostly because of the high Vin to the Classics.  But the power room is 225 feet from the residence,  so it is not a problem in the living space.

To me,  the Classic is the Swiss Army Knife of Solar electronics  --  it does so many useful things that many/most other CCs simply cannot do,  or need expensive options to do,  less well than does the Classic without any options at all.  And,  many of us use these added functions that the Classic provides.  All of this added functionality adds complexity,  cost,  and some added power consumption.

And,  regarding the Classic Inductors  ...   There are several types of losses in switching system power inductors  --  losses in the magnetic cores,  losses in the conductors that create the required inductance,  and some other parasitic losses,  etc.

The magnetic materials in the cores have become very,  very expensive,  so there is a large pressure to minimize the size/amount of the magnetic material.   AND,  when the conductor becomes larger,  a larger core is required to establish the required inductance,  so,  this is an additional factor in the quest to try to minimize core size,  with the trade-off of higher losses (heat) in a somewhat smaller inductor.   This economy allows MidNite to Include so many of the other functions that so many of us rely on.

Believe that the conductor in the Classic's main inductors is flat copper tape,  which helps minimize losses in the inductor,  and best utilize the more of the core.

Believe that a considerable amount of the heat from the inductor is sunk into the rear of the enclosure casting,  and the fans try to circulate heat out of the enclosure,  and stir the air inside to help more of the casting  radiate and convect heat into the air surrounding the Classic.

In looking at the KID,  is seems quite obvious that considerable effort was made to try to sink its inductor's heat into the casting.   MidNite Engineering seems on top of Thermal Management in its products.

MidNite seems confident that the Classic will be a long-term performer,  by backing it with a five year Warranty,  with the ability to extend this warranty several years (IIRC).

The latest manual for the Classic that I've seen,  DOES have the Classic Power Charts (or Graphs)  which plot available maximum output current verses Input voltage to the Classic.   This really does give one a fairly clear indication of the effect of high String Vmp on Classic output capability.   Perhaps there should a bit of text that points the system designer to these charts,  and some of their implications.

Have noticed that so many folks are DIYing their systems,  often without any previous experience.   So,  perhaps a bit more explanation of the Vin tradeoffs might be in order.

I am not a MPPT CC designer,  so some of the above may be a bit off target ...
But,  am one of those BEGGING  MidNite to get the Classic done and shipping,  and  the Classics have been a great improvement in the off grid power systems here.  Am a bit of a MN Cheerleader,  which is obvious!

Thanks  MidNite!!
Just Opinions,   FWIW,  Vic

[offgridQLD]

Yes not knocking that things are the way they are. I know from personal experience what the effects are and Just work with the +&- to find a balance that works for the particular installation. Personally I'm pedantic about keeping power electronics and lithium batterys cool so I will go beyond the norm to see that happen.

If I am after another 3rd controller it will be another classic so I'm happy with the product.

Remote Battery voltage sensing is about the only thing I would like to see in the future on the classic if i had a wish list.

Kurt