Parallel Morningstar Charge Controller issues......Float

Muskoka
Muskoka Solar Expert Posts: 103 ✭✭
Hi all,

Don't want to get into the nity gritties of my system, don't see the need. Just trying to wrap my head around a programming issue with these controllers.

I have 2 Morningstar controllers, a Tristar 60, and Tristar MPPT 60. The MPPT controller has no problem transitioning to float, the other stays in bulk, and or pwm mode for hours (sometimes) after the other has transitioned. Yesterday we had full sun all day, the batteries were charged by noon, SG's were pushing 12.7 on all 12 cells. The MPPT controller had gone to float, 13.2v was it's target voltage, the other was still in bulk mode 45 minutes later and pushing the system voltage to stay at 15.5v, with no loads on the system, none, I shut them all off so I could test. So in other words, the MPPT controller had been at 15.5v for 2 hours and was happy that the batteries were full and went to float. Why is the other controller not going to float as well?

The MPPT controller is set for 15.5v abs for 2 hours, battery manufacturer specs. The PWM controller is set for 15.5v abs, transition to float when duty cycle is 30% or less for 2 hours. I'm assuming this is supposed to be the same as or close to the MPPT settings? Why didn't they just use voltage / time on the PWM like the MPPT?

What can I do programming wise to get the PWM controller to go to float? Do I want to change the abs voltage set point, make it lower by a few tenths, so it goes to float sooner? Or, do I change the pwm duty cycle percentage to a higer value than 30%? Even when the PWM controller goes to pwm mode, it seems to take far too long to get to down to 30%. Even when the loads are on, their only about 10 amps, and I saw charge amperage yesterday around 87 amps from my system. The duty cycle shouldn't stay above 30% on that controller for too long with that much charge current versus load. The PWM controller is capable of 45-50 amps current. I saw 51 amps yesterday on that controller, still a lot of snow on the ground and cool temps. It's full cloud today so I won't get to test today, just looking for a plan of attack for when the sun is out again.

Battery voltage sense and temperature compensation is installed on both units, and gives roughly the same readings, within a few tenths at best.

Glen

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,606 admin
    Re: Parallel Morningstar Charge Controller issues......Float

    You might need to call MorningStar tech support... I believe there was an issue with some versions/date codes of their controllers not working correctly (?).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Muskoka
    Muskoka Solar Expert Posts: 103 ✭✭
    Re: Parallel Morningstar Charge Controller issues......Float

    Hi Bill, I have sent an email, no response yet, hopefully sometime next week. Phone service is not great here, might loose connection, so email is about it. I have the latest firmware on the units, hope it's not more than that. They really need to do away with that duty cycle parameter, and just go voltage / time. A firmware update would be nice, and I can't imagine it would be that hard to change, what do I know though?

    Glen
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Parallel Morningstar Charge Controller issues......Float

    Glen, are you comfortable with the charging your batteries are getting?
    If not it looks like your idea to knock back the PWM CC is the best fro an interim action until MS get back to you, better safe than sorry with your bank. The MPPT CC should just run a bit longer if needed if you cut back the PWM CC.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Muskoka
    Muskoka Solar Expert Posts: 103 ✭✭
    Re: Parallel Morningstar Charge Controller issues......Float

    Yes, quite comfortable. U.S. Battery is pretty aggressive with their recommended voltages for these batteries, so a little extra time in bulk / abs has not hurt, not that I can tell.

    I tried yesterday to knock it back a bit with the voltage, and the duty cycle setting. What "bothers" me is the duty cycle doesn't seem to represent the physical state of the batteries or system load very well. When the MPPT controller goes to float, the other should as well in a reasonable amount of time. Forty five minutes and still climbing doesn't seem reasonable to me. With no load on the system, and one controller in float, the other shouldn't have a duty cycle of 50+ on a continuous basis. What's causing the controller to keep the voltage at abs / the duty cycle up? If there was a "larger" load I could understand, but then the MPPT would be coming out of float as well, per my float settings, and it doesn't until the voltage drops below float for half an hour.

    If I recall correctly the duty cycle did come down when I changed the abs voltage on that controller (I think it was 2 or 3 tenths below the MPPT), but that shouldn't affect the duty cycle, nor should one have to "mess" with the voltages. If the abs voltage is being met, which it was, and there's no load on the system, the duty cycle should be down around zero or dropping at a nice steady rate? The controller should basically not be working at all, no duty, other than maintaining the float voltage? Do I have it straight in my head?


    Glen
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Parallel Morningstar Charge Controller issues......Float

    when you see this happening what are the voltages at both ends of the wires connected to each CC?
    Have you checked all the connections? Retorqued?
    It seems that there is misread/parameter setting(s)/ programming that is not in sync on each CC. Have you tried disconnecting each CC to see how it performs solo?
    Best i can think of right now...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Muskoka
    Muskoka Solar Expert Posts: 103 ✭✭
    Re: Parallel Morningstar Charge Controller issues......Float

    The voltage is slightly lower on the PWM controller, but only a tenth at the most. The voltage sense wires are at the same location, and the same length. Neither one of the controllers ever measures the voltage exactly to what my "expensive" digital clamp meter reads. The controllers are always a bit higher in voltage. The RTS is also a little lower on that controller, 1 degree celsius is pretty normal. They are also in the same location, attached to the side of one of the batteries, covered in insulation.

    All connections are tight, kind of anal about that stuff. The controllers have basically identical settings, other than the fact that the transition to float is done totally different between the two. The MPPT is 15.2v abs, for 2 hours, temperature compensated. The PWM is 15.2v abs, duty cycle 30% or less, for 2 hours.

    It's the controllers measuring of the duty cycle that's the issue. Lowering the PWM controllers abs voltage by 2 tenths down to 15.0 volts seems to be working, the sun was out for a bit and it transitioned to abs before the MPPT controller. Now I just need a full day of sun again to see what happens come float time, and whether the PWM controller gets to float first.

    It's interesting, and kind of like a game trying to get everyone working together, man I need to get a life.

    Glen
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Parallel Morningstar Charge Controller issues......Float

    Those ever so slight adjustments for whatever reason can be quite irksome, especially when you find out it is just a 1/10volt or 2 off.
    Soem people on the Midnnite forum have found similar issues with identical CC's not behaving the way they should.. due to a slight difference in 'pot' adjustments... let us know when you get a sunny day.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada