classic 150 12 volt 96 amp limitation work around?

[new2PV]

Hi I am stuck with a 12 volt inverter, and i want to use more panels than (12 volts x 96 amps)=1152 watts. I plan to use 5x 295 watt panels at 8 amps each in parallel 36Vmp  this will put me at 102 amps according to the sizing tool using 12 volts.  Could I not install a few more panels in a different location so as the sun moves from one set of panels to another I always will get the  max 96 amps?  I would trigger this with the aux ouput some how?  Looking for ideas on this.

[Vic]

Hi new2,

Generally,  it is not a good idea to expect to run any CC at or very near its maximum output current for extended periods of time,  IMO.

Your plan for 5 ea 295 W PVs will just about max out the Classic.   Adding more PVs with a somewhat different azimuth will increase the number of hours that the Classic will be laboring at/near its maximum output.

It is a bad idea to place a load on a portion of a series string of batteries.

We do not know the AH capacity of your batteries,  but there are limits to the amount of charge current that batteries will accommodate without damage.

Is it time for you to consider getting a 24 V inverter?

What is the AH Capacity of the battery bank?
Are your batteries Flooded,  AGM,  or ??
What is your application,  or ..  what is it that you expect your system to do?

Thanks,   Vic

[new2PV]

I want the system to provide as they call it as self-consumption and backup power. It will always have some type of load on it, one fridge, one freezer, and the furnace blower motor, and a few lights(led 6w bulbs).  They are cyclic loads, but all 3 could be on at once. The furnace is a soft start motor which would eliminate big surges.  During the day I would run the devices off the solar output and as the sun sets the batteries would come into effect, until the voltage would drop and then the whole system would auto-transfer back to grid, with a contactor.  The batteries will not get charged by the grid, only the next day via solar, to repeat the whole thing over again.  To start the bank will be a northstar AGM rated at 12v 170AH only telcom battery. I will contact the manufacturer to get the max amp charge rate, but most of the time the battery wont see the high charge rate as it always will have some type of load on it when the solar is active.  Looks like the classic will derate at 40C to 80 amps automatically.

[TomW]

I would have to concur with Vic:

Generally,  it is not a good idea to expect to run any CC at or very near its maximum output current for extended periods of time,  IMO.

That is a recipe for disaster, running anything full bore.


The Classic will protect itself but you will likely lose power over time as it dials back throughput to keep itself safe.

Much better to run 2X controllers at partial rating than one full bore.

Your mileage may vary.

Tom

[Vic]

Hi new -

Thanks for the added detail.  Many AGM batteries can tolerate quite high charge currents.  Although Telecom batteries may be a bit different,  so it is good that you will be checking the manufacturer's specs.

It is also good that you will work to have significant day-time loads.  But,  as you know,  all of the current to run these loads will be produced by the Classic.

There is a secondary effect of having an over-PVed CC,  is that when the loads are lighter,  the PV input voltage to the CC will rise to a value closer to Voc.  This rise in voltage can make the CC run warmer than it might otherwise,  even though it is producing  less current.  With your 36-ish volt Vmp this effect may not be as large as it would be with a higher string voltage.

As you also know,  running the Classic at 24 V,  will double the amount of power that a given output current,  verses a 12 V system.  Too bad that you are "stuck"  with that 12 V inverter.

Out of curiosity,  what is the make and model of 12 V inverter that you are using?

Thanks,   Vic

[new2PV]

I am running a pro sine 1000w with built in transfer switch, 120 volt output, and its 1000W rating is continuous, and 1500 W surge. I may have to sell it, but It works really well on the auto-transfer.  Could I add extra cooling to the classic 150 using aux 2?

Thanks for the help.

Norb

[Vic]

Hi Norb,

Think that the Prosine is a nice inverter.

A few users have tried added cooling for the Classic,  but believe that it has some value,  but perhaps not a huge improvement.

Mounting the Classic on an Aluminum plate (or even a large heat-sink)  that is spaced away from a wall might help a bit.   Just make sure that the Classic is mounted vertically,  as convection also helps cooling.

There are three fans in/on the Classic.   The Inductors inside the Classic case get fairly warm,  and the two internal fans help cool those.  The FETs are mounted on the right side of the case.  Convection and the Turbo Fan cool those.

It is fairly difficult to add extra cooling for the inductors,  short of a blower that forces air into one or two of the Conduit Knock-outs,  or perhaps after part of the Classic case is removed.   This is not recommended,  IMO.

The Engineers that designed the  Classic have designed-in Thermal management.   Sometimes efforts to improve thermal performance (for example)  can actually make things worse.

And,  boB and the MN hardware crew do not seem too worried about the thermal characteristics of the MN CCs,  with the possible advice that it is often not good to run system components at or near maximums for extended periods of time.

All of this is just my opinion,   YMMV!   Good Luck,   Vic

[new2PV]

If the classic can;'t handle the load, I won't buy it.  I may buy an off grid 4000 W hybrid pv inverter for $1000. I don;t think it has a 110 volt output though and not for North American use, but still doing research...Thanks for your input..

[Vic]

Hi again Norb,

PLEASE do not misunderstand what I am TRYING to say.

Would guess that you are looking at the Classic just because of its capabilities,  like having the max rated output current of 96 Amps.  The Classic CAN handle this on a 12 V battery system.   BUT,  just my opinion,  that one should not run ANY power electronics at or near its maximum for hour after hour -- not the Classic,  and not any other MPPT CC that I can think of.

Charging batteries often requires hours and hours,   and,  if your is looking at trying to run a number of day-time loads,  it is not just the current required to charge the battery,  but the current to run these loads  that will go on for hours and hours.

The Classic is just about the largest,  most capable CC that you will find.  It can protect itself,  but  this protection will reduce the amount of power that will be produced.   This protection is no different on the Classic than any other CC that I can think of.

It is good that you are thinking about the design of your system,  and asking questions about design trade-offs.   But,  really seems that you are trying to extract too much power from a 12 volt system,  when going to 24 V would make much more sense  (or perhaps even 48 V,  if you have plans to grow your system).

Hope that if you are looking at getting a different inverter,  that it will be at least a 24 V unit.

FWIW.    Vic

[new2PV]

I have been studying the classic for 2 weeks now, and it has many nice features that i really like.  All the other controllers max at 60 amps and cost comparable, or even more.  I know it looks like its pointing to change the inverter, or run 2 classics. Just looking at all the options right now for cost vs output.  Stand alone grid is nice, but I want to reduce my electricity bills as its scheduled to go up 50% within 5 years. All those loads are cyclic so it might work, or might overheat.  The battery manufacturer says 100A is not a problem if the voltage is 13.4-8 volts, not higher, really stuck between a rock and a hard place as the saying goes..

[Jacotenente]

FYI - I am running the Classic 150 nowhere close to it's max with a 24v battery bank, grid "connected". Flawless performance. I hooked my "Kid" back up to my system and it runs near it's max (30 amps) quite a bit. However, it runs much cooler since I converted to 24v.

Classic 150 solar array - 1.3KW Sunpower e20 panels
Kid array - 1.2KW Renogy panels. Note: with weird angles and 4 panels at 45 deg angle facing west

My batteries (24v 342 amp/hrs) go into "Absorb" on both controllers at about 11 am, then "Float" 3 hours later. Both are set the same. However, it seems I am not using the excess PV power I am harvesting/charging with or could be selling back. 

The only thing I don't like about the Classic 150 is mating up with the Optics RE communications software with my Outback Power inverter.

Good luck.

Chris

[new2PV]

Thanks everyone, I will maybe re-think the 24v option, maybe the best solution.

[mike90045]

..... To start the bank will be a northstar AGM rated at 12v 170AH only telcom battery. .....

NOOOOOOooooooooo!
This will be a very short lived system  Telcom batteries are designed for a half dozen deep discharge cycles.  They are not off-grid deep cycle batteries.

During the day I would run the devices off the solar output and as the sun sets the batteries would come into effect, until the voltage would drop and then the whole system would auto-transfer back to grid, with a contactor.  The batteries will not get charged by the grid, only the next day via solar, to repeat the whole thing over again.

And the point is to do what ? Cycle batteries till they die and you buy new ones ?   This will cost you hundreds of dollars in batteries, to save mere dollars in electric grid rates.

[mahendra]

FYI I have successfully used my classic 150 with extra panels ,not the best idea, but it worked and its is good to constantly monitor the system. Amp out limit kind of assisted but ideally its should not be pushed to work there. Also 12v nominal is not advisable especially when power has to be feed in to a house I have noticed that the inverter has to work harder as compared to connecting an equipment directly.
I should also add that I am very sceptical of magnum and xantrex/Schneider products ,reason I was operating a t 12v nominal and that inverter failed got another one just because I didn't have the money to get a nice outback ,Sadly it didn't last a day mainly because of poor quality components ,I also compared the built of the very same model of xantrex sw2000 both were of poor quality but the later was of alarmingly poor quality I can confidently say its like the Chinese version but just with the brand name xantrex.

AS ADVISED BEFORE GET A HIGHER VOLTAGE INVERTER AND SAVE YOURSELF SOME MONEY AND STRESS.

I SHOULD SAY I HAVE SEEN SOME LATE MODELS OF MAGNUM AND XANTREX INVERTERS AND THEY ARE NOT IMPRESSIVE WHERE QUALITY IS CONCERNED

FOR SOME REASON SCHNEIDER INVERTERS ARE BETTER BUILT BUT I AM STILL SKEPTICAL SINCE THEY ARE THE SAME PARENT COMPANY AS XANTREX.ITS IS ETHICALLY UNHOLY TO CHARGE SUCH MONIES FOR POORLY BUILT PRODUCTS.
IF YOU AL DO SOME RESEARCH YOU WILL FIND THAT ALL LINES OF XANTREX INVERTERS ARE CLOSELY COMPARED TO THE LESSER BRAND RECENTLY E.G COBRA,SAMLEX,ETC,GO POWER,POWER BRIGHT,AIMS,KISAE

[mahendra]

OH IF ANYONE IS HAS A NICE 48V INVERTER FOR SALE I AM INTERESTED SINCE MY SYSTEM IS DOWN I NEED A GOOD QUALITY INVERTER SO I CAN SWITCH TO 48V, THANK YOU . I AM ALSO DESPERATE SINCE I DONT HAVE THE KIND OF CASH FOR A BRAND NEW OUTBACK. I WILL CONSIDER OTHER BRANDS ALSO.