A Forum run by Enthusiasts of MidNite Solar

Charge Controllers and Clippers => The "Classic" charge controller => Topic started by: Matrix on May 12, 2018, 09:26:45 PM

Title: The Limits Setting - In the Local App
Post by: Matrix on May 12, 2018, 09:26:45 PM
Sorry if this has been asked before,  I did a forum search and did not come up with what I was looking for.

In the Local App (and I assume from the MNGP) there is a Limits setting. 

Using the Output Limits,  I realize that would lower the CC 150s Current Output ... But does that settings ...

1.  Lower the charge current to the battery

OR

2. Lower the battery charge current AND the Loads current

Example:  Lets say I set the limits to 35 Output amps.   If I then run a load during the day that exceeds that ... so 50 amps,  would it draw the other 15 amps off the batteries even though the panels would be able to supply the load?   

Is the setting just for charging or is it for the TOTAL output of the CC 150?
Title: Re: The Limits Setting - In the Local App
Post by: ClassicCrazy on May 12, 2018, 10:10:11 PM
Yes if you set the current limit to 50 amps that will limit the battery charging but also limit current available from PV for the loads to 50 amps too.
But after many requests Midnite fixed that - there is a way to limit only the charge current to the battery but make the full current potential available to loads.

The procedure for using that function is documented on the forums somewhere . I will try to look it up .

Larry
Title: Re: The Limits Setting - In the Local App
Post by: ClassicCrazy on May 12, 2018, 10:13:14 PM
You will find the pdf file document in the first post of this forum topic  called Global Current Limiting
http://midniteftp.com/forum/index.php?topic=3796.0

Larry
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 13, 2018, 01:23:58 PM
Thanks Larry
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 13, 2018, 05:49:11 PM
 Why would the default value for current limiting be set to 30000?  Wouldn't that mean the default current value is 3000 amps?

Also, by limiting charge current does that cause the classic to build up even more heat? Even though I have my classic set on a very large 1 in heat sink, the size of the classic itself and I have a fan that comes on when aux one comes on to dump XS power to a dump load, I still get Celsius temperatures of about 62 264 degrees when fully charging and running the dump load during a full sunny day
Title: Re: The Limits Setting - In the Local App
Post by: Vic on May 13, 2018, 06:26:53 PM
Quote from: Matrix on May 13, 2018, 05:49:11 PM
Why would the default value for current limiting be set to 30000?  Wouldn't that mean the default current value is 3000 amps?

Also, by limiting charge current does that cause the classic to build up even more heat? Even though I have my classic set on a very large 1 in heat sink, the size of the classic itself and I have a fan that comes on when aux one comes on to dump XS power to a dump load, I still get Celsius temperatures of about 62 264 degrees when fully charging and running the dump load during a full sunny day

Matrix,

Yes,   a Default of 30,000,   would equate to 3,000 Amps.   Some of the Defaults in the Classic appear to just chosen to make certain that a rarely-used function is far,  far from becoming active   ...   there might be some other reason that this is the Default ...

YES,   to a certain degree,   Limiting the Classic's output current  would reduce the loading on the PVs,  causing the Vin to the Classic to rise.   This rise in Vin would reduce the CC efficiency,   somewhat.   But the  increase in CC heating should not be a large factor.

This current Limiting,  is designed to Limit the amount of battery charge current,   not the maximum output current of the Classic.   This battery charge current limit is probably more useful in systems with multiple Classics.

FWIW,   Vic
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 13, 2018, 10:59:17 PM
So if C/10 of my battery charge rate is 43amps,  but my classic can (and I have occasionally seen 63+ amps),  that is not a bad thing?   I was wanting to set a limit of 43 to keep the charge rate at or under C/10.  But perhaps with a single classic it is not that important?
Title: Re: The Limits Setting - In the Local App
Post by: FNG on May 14, 2018, 09:54:02 AM
Matrix,
It really comes down to the battery, if the battery manufacturer says do not charge over xx amps then yes you should set the global current limit to xx and make sure a WBjr is in place. Setting the amp limit on the local app or MNGP in the limits menu will actually limit the classics output based on just that value, So with some loads on the system the battery will get less. This is whats nice about the global limit in modbus, it watches the actual battery and limits on that
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 14, 2018, 11:53:46 AM
Thanks.  I am tinkering with the settings now (actually yesterday) and watching to see what it does. 

I absolutely love the Classic and the MN products.  I wish / hope they have a 4000 watt inverter at 48v when it comes time to replace my SW inverter.   My plan is to replace batteries and inverter in 2-4 years when the batteries are done.   Hopefully by then I can go all MN Solar gear. 

(well that is if code enforcement does not shut me down because I never did permit and never installed any form of Rapid Shutdown system - the $2k + addition to your system you will ever only need once ... if you ever need it)
Title: Re: The Limits Setting - In the Local App
Post by: KyleM on May 14, 2018, 01:59:51 PM
http://midnitesolar.com/pdfs/little_SOB_manual.pdf (http://midnitesolar.com/pdfs/little_SOB_manual.pdf)


I was not here ... you saw nothing.


Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 14, 2018, 03:31:52 PM
Quote from: KyleM on May 14, 2018, 01:59:51 PM

I was not here ... you saw nothing.
That reads like something printed on a B17 circuit board.  LoL !!
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 14, 2018, 09:11:46 PM
Quote from: KyleM on May 14, 2018, 01:59:51 PM

I was not here ... you saw nothing.

OK so I am seriously looking at this,   and I am seeing the array shut down receiver and I assume for off grid purposes that the transmitter shuts down all DC close the Inverter / Charge controller,  but where is the switch the fire and safety work would use to shut off the array and DC?    Does it use the bird house or something else or what am I missing? 

Also,   is there an SOB system setup for the AC side shutdown?   

Looking at the docs all I see is set up for Grid - Tie not off grid for the SOB
Title: Re: The Limits Setting - In the Local App
Post by: FNG on May 15, 2018, 05:53:34 AM
The Little SOB system is designed to shut down just the PV array, NEC 690.12 Rapid Shut Down was only intended to shut down the wires between the pv modules and the MPPT device be it a charge controller or grid tie inverter. The Little SOB takes a transmitter ont he ground and injects a signal onto the dc lines and the receiver listens for that signal. No signal then it shuts off to be safe. In the case of a grid tie inverter the transmitter can be powered internally inside the inverter so the ac disconnect can be the initiator for example
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 15, 2018, 07:57:35 AM
So for an off grid system,  it would seem that the SOBs might be able to handle the DC and then one would merely need a MN breaker and Birdhouse or some other switch to cut off the power to the inverter to power down the AC (and thus cause the SOBs to power off the Array)?    Seems for a system that is already installed this would eliminate the need to purchase a Disco closest to the array (already have a combiner) and another Disco closest to the CC?
Title: Re: The Limits Setting - In the Local App
Post by: FNG on May 16, 2018, 07:22:38 AM
Matrix,
NEC code doesnt care about us shutting down the inverter, 690.12 only applies to the conductors between the pv modules and the MPPT device.

That said IF you wanted to disable the complete system, you would want to use the birdhouse system as a complete package
Title: Re: The Limits Setting - In the Local App
Post by: Matrix on May 16, 2018, 07:40:18 AM
Thanks,  I thought the safty part of the code required the DC and the AC to be shut down.  I do have a meter as part of my house (Air/Heat, Washer, Dryer) are all on grid,  but the rest of my house is not.  If fire department pulled my meter, most of my house wiring would stay live as the batteries would still be connected to the inverter. 

So some how i would need to have some kind of switch to trigger the SOB as I think I see that it shuts down the array when the transmitter side of the SOB sense no DC power?