Classic 150 Current conundrum

[B_r_i_a_n]

I just put my system together for an off grid solar shed that I use to power a travel trailer and so far am very pleased with it. I am scratching my head over an issue though. I fired up the air conditioner and went to at the wiz bang jr to see how much it was drawing. It showed ~ -72amps or ~1725 watts which is not out of line. There was no sun at the time and I was just looking for the power draw and to make sure it didn't trip the inverter with the start up. The issue struck me as Renogy suggests no more than 40 amps of charge current. My question is how can I use all the available power during full sun and run that air conditioner and still limit the charge to the batteries when I am not running the air?

[Vic]

Hi   B r I a n,   Welcome to the Forum.

There is a neat way to Limit the battery charge current,   based on your setting in the Classic,   teamed with the WBjr.

Read about this here:
http://www.midniteftp.com/support/kb/faq.php?id=37

Good luck with the new system,   and please let us know how things are working.
Vic

[B_r_i_a_n]

Vic, Thanks for the reply. My problem is that while I would like to limit the current to the batteries for charging, I would like to be able to use all the available current the classic can put out for the inverter. My question is how can I do both?

[B_r_i_a_n]

ok, a little electronics refresher for me...lol I have 3-24v batteries in parallel, so the charge current is distributed between the 3. So my worries are unfounded. Wheew

[boB]

Of course you can do both.

If you are drawing a lot of current for your inverter load, then there won't be much left to charge the battery from the controller.

(1) Let's say you need 50 amps DC to run the inverter and the Classic is putting out 40 amps DC....  Then you only need 10 amps from the battery at that time and 40 coming from the Classic and the solar.

(2) Then, when the inverter load drops, say to 10 amps DC total input, the Classic and the solar would be supplying that 10 amps with 30 amps left over to charge the battery. 

If in this case (2) you have set the Classic to stop charging at say, 20 amps, then the Classic would be "capable" of putting out 40 amps but you would only be using the 10 amps into the inverter and 20 amps for charging and a possible 10 amps would be unused at that time.

[australsolarier]

yes , as far as im concerned brian should at least double his battery.

but as for his question there is a pdf on the midnite classic website called   " MN Global Current Limiting with Classics" which does what brian asks with a midnite classic with jr whizbang shunt. it took me an hour to program it though.

[Vic]

yes , as far as im concerned brian should at least double his battery.

but as for his question there is a pdf on the midnite classic website called   " MN Global Current Limiting with Classics" which does what brian asks with a midnite classic with jr whizbang shunt. it took me an hour to program it though.

That same info on Global Current Limiting,  IS now in the Classic Knowledge Base,   as linked in  Reply #1,   above.   That,   too,   was intended to try to answer Brian's original question..

FWIW,   Vic

[B_r_i_a_n]

I don't think doubling my battery bank will have any effect. right now I have 3 parallel legs of 24 volts. 2 -12v batteries in series. If I could get a full 96 amps out of the classic, that would only put a charge of 32 amps on each leg. That is well under the 50 amp limitation from the battery manufacture.

As far as limiting the current output from the classic, I have read how to set the limiting feature. I don't think the Classic can distinguish where the power is going. Unless It can be controlled by the wiz bang jr feedback. Meaning if the wiz bang shows a negative current flow from the battery, then that means the power is being drawn away from the batteries. The 150 could send more power, but if the wiz bang show a positive flow That means its going to the battery and would then throttle the current to whatever setting you have input. Maybe this feature is how it already works, I just have not read that in any of the literature.

I apologize if my original question was poorly worded. I do like learning about about this system. I think it was a wise investment for sure

[boB]

Ahhhh...    I think the current limit function you were looking at, if it was in the menus, was in the main LIMITS menu ?

That setting is different than the one for the WB Jr. that we are talking about here.   That setting needs to be set in the MODBUS editor which is new enough where there is not a separate menu for it and may not be in the manual either.

I'll try to dig up something already written up for this.  I remember this was done for a bunch of units in Puerto Rico.

[B_r_i_a_n]

To be clear, My system is OK. Because of the parallel strings of batteries, I am in no danger of putting more current into the battery than recommended. On the theoretical side, it is still a good question if the output of the 150 could be throttled to 40 amps if the wiz bang jr reads positive current in the shunt, but be able to run wide open if the shunt has negative current.

[Vic]

To be clear, My system is OK. Because of the parallel strings of batteries, I am in no danger of putting more current into the battery than recommended. On the theoretical side, it is still a good question if the output of the 150 could be throttled to 40 amps if the wiz bang jr reads positive current in the shunt, but be able to run wide open if the shunt has negative current.

Brian,

When set up correctly,  the Classic with a WBjr  can limit battery charge currrent,   and provide maximum available current to other loads on the system.

The WB measures the battery charge current,   and maintains that.  The Classic will provide whatever additional power is necessary for other loads,  by changing the loading on the PVs (or other input power source to it),   up to the limit of the available input power.

Here is some discussion of this:
http://midniteftp.com/forum/index.php?topic=3441.0

There is a link early in that Thread,  that is now broken,  as the MN Forum is now hosted on a different server   ...   will try to repair that Link,   And post it   ...

EDIT:  Here is the repaired Link to the Thread where there is some added discussion:

http://midniteftp.com/forum/index.php?topic=2696.45
  Later,   Vic

[boB]

Found this about how to get into the modbus editor.
You will need to edit modbus register ADDRESS   4419  or 4405...

My notes say that address 4419 was moved TO 4405 BUT the software seems to indicate this register is in both places right now for the latest software we have.  IF you have real old software you may need to update ?   I think this was here since 2016.

So go into the MODBUS EDITOR (shown below) and when the address is highlighted, (I think it starts at 4100 ?) and just go to address 4419 to star with.
Then press the right arrow to edit the value.  I think that this value comes up as 30000  which would be 3,000 amps. Disabled basically because it is
higher than any amount of current you would have available.

If you want to limit the charge current to say, 50.0 amps, change this number to 500      The last right hand digit is tenths of an amp although that is kind of an extremely small resolution for this kind of thing.

To bring the value down in steps of 256 (quicker than one at a time) hold down the upper-left key (SHIFT) while pressing the down button when the value is highlighted.

To save the value so that the Classic remember this when it resets or reboots, hold the SHIFT button down and tap the ENTER button.

It should tell you that it saved I think just like when pressing ENTER in normal menus.

Lettuce know if you this is successful.







CLASSIC - MODBUS - How do I get to the MODBUS Editor?

*** WARNING *** Changing the WRONG Register may cause permanent Damage.

Go to TWEAKS menu and press MORE once (Using the RIGHT SOFT KEY)
HOLD the LEFT ARROW and TAP the RIGHT SOFT KEY 2 Times

Use the LEFT/RIGHT ARROW KEYS to select address or value.  Change using the UP/DN Arrow Keys.
Use Right Softkey to toggle Decimal or Hexadecimal

To SAVE changes HOLD the LEFT SOFT KEY and press ENTER.
PRESS ""STATUS BUTTON" to Exit.

[B_r_i_a_n]

Got it. I appreciate all the help and patience