MorningStar TS-MPPT-60 Charging not as expected

dbriffa
dbriffa Registered Users Posts: 2
in Off Grid Solar & Battery Systems #1
Hello

I have this difficulty that hope you can help me with

So I upgraded my off-grid system from 12v to 48V nominal battery system and a new inverter.
Now I installed 3 Solar panels having 21V open Circuit and a max of 13 amps. These panels are rated as 230W panels. I tested these panels individually and the meter was reading 20V 11amps .
I connected these 3 panels in SERIES and run the wire from the controller to a breaker and than to the (MorningStar MPPT 60 + display)

With a multimeter I tested the wires before turning the breaker which then feeds the controller to check if every thing is ok. At mid-day in bright full sunshine with no clouds the meter read 59.55V which is for me OK and then switch to AMPS and it read 11.36A which is OK which when multiplied it will give 676W, and till there everything is very acceptable for me.

Now when I switch on the the breaker to feed the TS-MPPT-60 controller I was expecting to see 600 ish Watts but no only some 140W-180W It was displaying 53V and 3.3A.
Could be the battery are near full?

To check that I added a load on the connected inverter of 3.5KW to reduce the battery voltage. When turned on the battery (380AHr, 48V) went to 48.5V. The controller this time was showing 48V 5.5A (260W) but no where near the 13 amps that it should, 600w ish area.

Ideas? why is this happening?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: MorningStar TS-MPPT-60 Charging not as expected

    Welcome to the forum.

    A couple of things.

    First of all, yes the batteries will only take what they need. Just because the array is capable of pushing 11 Amps to them, for example, doesn't mean they'll take it.

    Second, you may have your array configured incorrectly. It appears you are using Voc for Voltage, and that is not right. A panel with a Voc of 21 has likely got a Vmp around 17-18. Three in series would not be sufficient for charging a 48 Volt system. So when you read the array Voltage without any load on (Voltage open circuit) is shows 3*21 or 63-ish Volts. Close the connection to the battery and the array is pulled down to Vmp or less, which would be around 52.5 - too low for proper battery charging. You may be getting full current, but not proper Voltage. To reiterate, these panels appear to be standard 12 Volt panels, for which you would need four in series to charge a 48 Volt system.
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  • dbriffa
    dbriffa Registered Users Posts: 2
    #3
    Re: MorningStar TS-MPPT-60 Charging not as expected

    Great, in fact I was thinking along those lines. Are 3 panels enough? but I was being convinced by the open circuit voltage..and for some reason I was still expecting the 11A ish even at lower voltage.
    On the controller it went up to a MAX of 58V (on load, charging) with 3 panels and still it was saying 4amps ish..but that was the peak probably it was around 53V during great part of the day.

    Checked the sticker on one of the panels, it says Uoc 21.8V and Umpp 16.9V....which is at the lower end.

    Now immediately I added 1 more panel and connected it in series with the other 3 to see the results.

    By now, during these last hours of the day already seeing some improvement. The Sweep P Max finally shown a number because the last days of testing it was always 0W and now the MPPT seems running more smoothly already.

    Hopefully I'll see some 800w ish peak by tomorrow.

    Thanks
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #4
    Re: MorningStar TS-MPPT-60 Charging not as expected
    dbriffa wrote: »
    Great, in fact I was thinking along those lines. Are 3 panels enough? but I was being convinced by the open circuit voltage..and for some reason I was still expecting the 11A ish even at lower voltage.
    On the controller it went up to a MAX of 58V (on load, charging) with 3 panels and still it was saying 4amps ish..but that was the peak probably it was around 53V during great part of the day.

    Checked the sticker on one of the panels, it says Uoc 21.8V and Umpp 16.9V....which is at the lower end.

    Now immediately I added 1 more panel and connected it in series with the other 3 to see the results.

    By now, during these last hours of the day already seeing some improvement. The Sweep P Max finally shown a number because the last days of testing it was always 0W and now the MPPT seems running more smoothly already.

    Hopefully I'll see some 800w ish peak by tomorrow.

    Thanks
    Congratulations on a quick fix (fingers crossed.) BTW, the sticker probably means Voc and Vmpp (Vmp).
    An MPPT CC may require an even higher input voltage relative to Vbat to start working when compared to a PWM CC, even though that extra voltage will not be wasted.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: MorningStar TS-MPPT-60 Charging not as expected
    inetdog wrote: »
    Congratulations on a quick fix (fingers crossed.) BTW, the sticker probably means Voc and Vmpp (Vmp).
    An MPPT CC may require an even higher input voltage relative to Vbat to start working when compared to a PWM CC, even though that extra voltage will not be wasted.

    Well, no.
    Both types of controller require only an input Vmp above charging Voltage to work. You can run an MPPT controller on a 12 Volt system, for example, with an array Vmp of 17.5 just the same as with a PWM controller. The controller itself does not require any higher input Voltage to function.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
    Re: MorningStar TS-MPPT-60 Charging not as expected
    Cariboocoot wrote: »
    Well, no.
    Both types of controller require only an input Vmp above charging Voltage to work. You can run an MPPT controller on a 12 Volt system, for example, with an array Vmp of 17.5 just the same as with a PWM controller. The controller itself does not require any higher input Voltage to function.

    Really depends on the design of the CC. It is not a logical requiement, no, but it may be seen in some implementations.
    Also an MPPT CC which can work with the same differential as a PWM controller is working effectively in PWM mode at that point. It will still be converting DC to DC internally, but may not have any room to actually do a sweep to find the MPP of the array, but instead just stays at its lowest voltage point.
    SMA SB 3000, old BP panels.
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