Phocos CML20 controller and 200w Tenesol panels

South Africa
South Africa Solar Expert Posts: 295 ✭✭✭
in Solar Beginners Corner #1
What am I missing now?

Batteries are bubbling when they are charging, controller shows a red warning light, and is warm to the touch. At the time the actual incoming volts, this afternoon, was 29.5 incoming reduced to 15.5 by the controller. Batteries was also 15.5 v.

2 x 102ah batteries, 12v bank.
2 x 200w panels, parallel, specs are:
Attachment not found.

Phocos Controller specs are:
Attachment not found.

System function: Power lights, using a pure sine wave inverter, at night only.

Panels are 12v, controller is 12v, volts in is less than 30v, but have been measured to show 31.5v mid day, but controller limits that?
5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Phocos CML20 controller and 200w Tenesol panels

    Not an MPPT controller: no down-conversion of Volts to Amps. It does not reduce Voltage at all, it merely passes current.
    Maximum input Voltage is for Voc, not Vmp. In essence you're putting about 8 more Volts to it than would be expected.

    Your panel Voltage reading would be wrong at 29: you are seeing high bursts recorded when the PWM switches off (i.e. Voc). Panels with a Vmp of 26 can't produce 29 unless it's very, very cold. Panel Voc is 32. That's about 50/50 on/off pulsing.

    Notice the over-Voltage protection rating on the controller is 15.5 - just where you're at.

    No surprise here really. The controller is being stressed.
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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #3
    Re: Phocos CML20 controller and 200w Tenesol panels

    I want to swear: $#(*@&!!!!! Another(!) part for the 'shed'.

    Now I HAVE to get a http://www.morningstarcorp.com/products/sunsaver-mppt/, connect them in series for 24v system.
    If you wire in series, the controller will work fine although at peak output from your panels (which depending upon your location can be very rare) may produce over 15A, this is no problem for the SSMPPT controller. We designed the SSMPPT controller to operate at full output power (we have already taken into account the stress of running at full power indefinitely).

    This controller is able to self-limit how much power it pulls from the solar panels so that if the panels ever had the ability to produce more than 15A, the controller will simply adjust so that it only pulls 15A from the panels.

    It is actually fairly common practice to slightly oversize the solar array with an MPPT controller, as would be the case in your system.
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
    Re: Phocos CML20 controller and 200w Tenesol panels

    actually due to the imp being at 7.5a each pv that alone says you need over 15a capability on the controller for mppt. an mppt in its conversion will bring the current up beyond 15a. you need a 30a mppt cc.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #5
    Re: Phocos CML20 controller and 200w Tenesol panels
    South Africa wrote: »
    What am I missing now?

    The highest average voltage the controller is supposed to apply to the batteries is 14.8V when it is equalizing (page 36). So sounds like:

    "Battery voltage too high (>15.5 / 31.0 V)
    Check if other sources overcharge the battery. If not, controller is damaged."

    Unplug it before you ruin your batteries.

    I am available for custom hardware/firmware development

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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #6
    Re: Phocos CML20 controller and 200w Tenesol panels
    niel wrote: »
    actually due to the imp being at 7.5a each pv that alone says you need over 15a capability on the controller for mppt. an mppt in its conversion will bring the current up beyond 15a. you need a 30a mppt cc.

    Note: I want to match the panels to a controller.

    To this effect, on another thread here, can look for it, and direct from Morningstar, as well as Morningstars array calculator, there are consensus that the panels and controller are indeed a match, one little caveat being it is not used consistently in extreme cold temperatures, and for the few times year here in Cape Town where it may be +-11deg midday in winter, the controller can handle it comfortably.

    So now I am confused, again. :-)
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #7
    Re: Phocos CML20 controller and 200w Tenesol panels
    jonr wrote: »
    The highest average voltage the controller is supposed to apply to the batteries is 14.8V when it is equalizing (page 36). So sounds like:
    "Battery voltage too high (>15.5 / 31.0 V)
    If not, controller is damaged."

    Unplug it before you ruin your batteries.

    No other sources, and yes, I am worried it is damaged, even though the lights are all green if it is not midday.
    I do not suppose there is a way to test it, other than taking it in?

    Cariboocoot wrote: »
    Not an MPPT controller: no down-conversion of Volts to Amps. It does not reduce Voltage at all, it merely passes current.
    Maximum input Voltage is for Voc, not Vmp. In essence you're putting about 8 more Volts to it than would be expected.

    So a non-MPPT Controller is the same as connecting panels direct to batteries? :-) I have to respectfully disagree. :-)
    It may not be a efficient as a MPPT controller but Phocos controller are quite good at charging batteries, and to do that, they need to limit what the panels produces.

    Cariboocoot wrote: »
    Your panel Voltage reading would be wrong at 29: you are seeing high bursts recorded when the PWM switches off (i.e. Voc). Panels with a Vmp of 26 can't produce 29 unless it's very, very cold. Panel Voc is 32. That's about 50/50 on/off pulsing.

    I checked the voltages with a multimeter with controller disconnected. Once before I saw them at 31.5v when they where assisting the main system.
    Cariboocoot wrote: »
    Notice the over-Voltage protection rating on the controller is 15.5 - just where you're at.

    No surprise here really. The controller is being stressed.

    It was a temp measure for a few weeks until I could finalise the 2 systems.

    If controller is broken, so be it. It was in any event a misguided buy at the time, a stopgap that worked for nearly 2 years.
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #8
    Re: Phocos CML20 controller and 200w Tenesol panels

    12v battery system.
    Panels show 31.1v incoming.
    Then I connect the Phocos to the panels ...
    - Phocos drops the array voltage to 15.4v.
    - And drops outgoing to batteries to 14.7v.
    Phocos is DEFINITELY over worked, bit not faulty ... yet. :-)

    I think, for now, I am going to put the batteries back to 24v and use a UPS inverter till I can sort this mess out. It is only for lights at night. :-)

    My other system, 24v batteries, 3 x 310w panels
    - 41.4v incoming from panels with no controller connected.
    - When Tristar is connected, incoming drops to 26.8v and batteries are kept fully charged.
    Lekker spare power to run the inverter with no drain on the batteries. :-)
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Phocos CML20 controller and 200w Tenesol panels
    South Africa wrote: »
    So a non-MPPT Controller is the same as connecting panels direct to batteries? :-) I have to respectfully disagree. :-)
    It may not be a efficient as a MPPT controller but Phocos controller are quite good at charging batteries, and to do that, they need to limit what the panels produces.

    You are respectfully disagreeing with reality, then.
    PWM controller is an electronic switch that connects the panels directly to the batteries. It regulates Voltage by turning on and off as needed, very rapidly during Voltage regulated stages (Absorb & Float). An MPPT controller in fact does the same, but has the added feature of the buck converter which can reduce higher input Voltage and turn it into greater current.

    If the Phocos controller is so good, why are you having a problem?

    The MS MPPT 15 is good for about 200 Watts on a 12 Volt system: 15 Amps * 12 Volts = 180 Watts (plus a margin). Niel is quite right when he says it will not do for 400 Watts on 12 Volts. As he said, just add up the Imp of the two panels and there's the 15 Amps. MPPT function has the potential for increasing this: 400 * 0.77 / 12 = 25 Amps peak current potential. You would be wasting about one whole panel.
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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #10
    Re: Phocos CML20 controller and 200w Tenesol panels

    Wait wait wait ... I am getting lost. Does a non-MPPT controller regulate the incoming voltage, or not?

    You first said, which I respectfully disagreed with, for I tested it, this statement is wrong: :-)
    It does not reduce Voltage at all, it merely passes current.
    and the you said this, which I agree with:
    It regulates Voltage by turning on and off as needed, very rapidly during Voltage regulated stages (Absorb & Float).

    Cariboocoot wrote: »
    If the Phocos controller is so good, why are you having a problem?

    It is having a problem because I took the Voltage at max. power ... and it was way more. Luckily my cheap car battery monitor buzzed its speakers little head off when it went above 15.4v. Phocos is not designed for these panels on 12v .. no fault of Phocos controller. :-)
    Cariboocoot wrote: »
    The MS MPPT 15 is good for about 200 Watts on a 12 Volt system: 15 Amps * 12 Volts = 180 Watts (plus a margin). Niel is quite right when he says it will not do for 400 Watts on 12 Volts. As he said, just add up the Imp of the two panels and there's the 15 Amps. MPPT function has the potential for increasing this: 400 * 0.77 / 12 = 25 Amps peak current potential. You would be wasting about one whole panel.

    I agree. The MS MPPT15 is for a 24v battery bank with the 2 x 200w being slightly over specced as I was advised is good?

    Changed the original setup because of an idea you put in my head :-)
    You said the Phocos on 24v batteries and 2 x 200w panels is a waste when working with a Tristar 45 controler and 3 x 310w panels charging the same bank. So now I am splitting the systems: Lights on the the 200w panels and rest on the 310w panels.

    I am now short +-400w daytime AFTER the batteries are charged ... so no wonder my system is working shorter hours ... and then I thought, how can I fix it using as much of the exiting stuff I have ... and each way I turn there are issues. :-)
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: Phocos CML20 controller and 200w Tenesol panels
    South Africa wrote: »
    Wait wait wait ... I am getting lost. Does a non-MPPT controller regulate the incoming voltage, or not?

    That depends on how you define "regulate Voltage". Charge controllers aren't really Voltage regulators, they are current switches. All they do to 'regulate' Voltage is turn on and off.

    This is why you can have one Voltage reading on the output and another on the input: the 'switch' is a semi-conductor. The output Voltage is equal to battery Voltage plus whatever increase is caused by the amount of current flowing from the panel at any given time. The input Voltage is equal to Voc less whatever drop is caused by current flowing to the battery at any given time. The time is regulated by the pulsing, which can be thousands of on/off switches per second. Your meter can't sample that high so it reads an averaged Voltage.

    This is not the same process as with a Zener diode for example which constantly 'bleeds off' any Voltage over a given value by shunting it to negative (controlled short).
    Phocos is not designed for these panels on 12v .. no fault of Phocos controller. :-)

    That is correct. Because it does not regulate or adjust Voltage.
    I agree. The MS MPPT15 is for a 24v battery bank with the 2 x 200w being slightly over specced as I was advised is good?

    On 24 Volts the MS MPPT 15 will handle 400 Watts with no problem. Even 460 Watts. They you get into a range where you're wasting power potential because it simply is not going to pass more than 15 Amps.
    I am now short +-400w daytime AFTER the batteries are charged ... so no wonder my system is working shorter hours ... and then I thought, how can I fix it using as much of the exiting stuff I have ... and each way I turn there are issues. :-)

    That pretty much defines life. :D
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #12
    Re: Phocos CML20 controller and 200w Tenesol panels

    In reality--For off grid power (including cars, trucks, etc.) the battery bank is the real voltage regulator for the system.

    For most inexpensively designed charging systems, they will over volt/shut down if there is no battery in the system.

    Your ~30 Volt panels are simply being "shorted" to your 14.x volt battery bank. The battery (when less than full charged) is simply taking all the current the solar panels can supply when the PWM switch is "closed" (current flowing).

    Since solar panels are "current sources"--That is OK. The panel will output Imp at 14.5 volts and at ~24 volts (panel Vmp?). However, it is not efficient.

    For a Solar Panel with a Vmp~24 volt panel and 10 amps (just making up numbers)
    • Power = Vmp*Imp= 24 volts * 10 amps = 240 Watts

    On a PWM controller:
    • Power = Vbatt*Imp = 14.7 * 10 amps = 147 Watts from panel (not 240 Watts)

    On a MPPT charge controller, using the "real world" derating of panels+controllers (hot panels causes Vmp to fall by ~20% and controller takes ~5% for MPPT operations):

    Power = Vmp*Imp*derate = 24 volts * 10 amps * 0.77 panel+controller derate = 185 Watts (typical hot weather performance)

    So--Two controllers, two setups:

    • 147 W / 240 W = 0.61 ~ 61% efficient
    • 185 W / 240 W = 0.77 ~ 77% efficient

    Both controllers work, and the PWM is probably a whole lot less costly system. For a single 240 Watt panel, is it worth paying ~$200 USD or more for an additional 38 Watts more power? Or would it be cheaper to just get a second 240 Watt panel in parallel and keep the PWM controller?

    The prices / realities of solar--That is why for smaller systems (call it under ~400 Watts), PWM controllers are usually a better deal. And, as you see here, the greater the miss-match between Vmp and Vbatt on a PWM controller, the more "losses" you have in system performance.

    And for larger systems (over ~800 Watts), why MPPT controllers are better (plus the ability to use "high Vmp voltage" arrays that can be installed farther away from the charger/battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
    Re: Phocos CML20 controller and 200w Tenesol panels

    Curiously this seems to be a case where the controller can't handle the higher Vmp not because of V specs on internal components but because the panels are pushing the battery Voltage over the max for the controller's output - triggering the over-Voltage warning. It sounds like the controller can't switch fast enough to keep it from happening; the panels actually stay connected long enough for that V rise to occur on the output terminals.
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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #14
    Re: Phocos CML20 controller and 200w Tenesol panels

    Explanations of MPPT vs PWM would make more sense to me if they clearly separated two concepts. 1) operating the panel at its MPP and 2) the current amplification that buck converters provide. For example, I could use a dumb DC-DC converter and get the latter but not the former.

    I am available for custom hardware/firmware development

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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #15
    Re: Phocos CML20 controller and 200w Tenesol panels
    BB. wrote: »
    ... the PWM is probably a whole lot less costly system. For a single 240 Watt panel, is it worth paying ~$200 USD or more for an additional 38 Watts more power? Or would it be cheaper to just get a second 240 Watt panel in parallel and keep the PWM controller?

    Ditto! So true.

    Found out today, Yingli, whom has a near exact 200w panel to match my 200w, only imports them per container.

    But THAT is not a problem ... anymore. :-)

    A MS MPPT15 will do these panels a lot of good! Call it a perfect match, thanks to you guys. :-) And it is not that expensive either, yet it sorts out a whole lot of issues for those extra few bucks.

    And Yingli, has a close as damn match for my 310w panels ... YIPEPEEEE, and they are in Cape TOWN!:-)

    After asking about Grid tie and then Victron EasySolar inverter combo, with Yingli suggesting Victron MPPT controllers due to wide range of options and prices, the Victron Easysolar is a real option. But Cariboocoot did voice a note of caution. :-)

    But ... a Outback Flexmax 60/80 is THE cheapest option to go IF Yingli says their panels are ok with the Outback.

    And the Flexmax one ... I can work towards that ...

    What route would you guys suggest I go with the panels I already have and a 24v inverter?
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #16
    Re: Phocos CML20 controller and 200w Tenesol panels

    An MPPT charge controller is a "smart" DC to DC converter.

    The reason it is "smart" is because its output power is based on the converters available input power.

    More or less, you can make a "semi intelligent" DC to DC converter if you assume that the Vmp of the array is a fixed value (say 80%-90% of Vmp-stc). The DC converter simply varies the output current (remember the battery bank is really the "voltage regulator") such that if the panel voltage is over Vmp-setpoint, it increases output current. And if Varray is less than Vmp-setpoint, it drops the output current.

    The older Bluesky MPPT controllers did this (fixed Vmp-array assumed, as I recall) and you can get "sort of MPPT" charge controller chips that work this way (and add battery charging voltage feedback too). Some discussion here:

    Charging a Anker 20,000mAH battery pack with solar question?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #17
    Re: Phocos CML20 controller and 200w Tenesol panels

    Make sure you get the Remote Battery Temperature Sensor option--From what I have read (here), this controller really needs the RBTS to operate optimally. It tends to over correct (reduce battery charging voltage) too much with the internal BTS.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • South Africa
    South Africa Solar Expert Posts: 295 ✭✭✭
    #18
    Re: Phocos CML20 controller and 200w Tenesol panels
    BB. wrote: »
    Make sure you get the Remote Battery Temperature Sensor option--From what I have read (here), this controller really needs the RBTS to operate optimally. It tends to over correct (reduce battery charging voltage) too much with the internal BTS.

    I you are referring to the MS MPPT15, yes, I will get the temp sensor also. Thank you.
    5kVA Victron Multiplus II, 5.2kW array, 14kWh DIYLifepo4 bank, all grid-tied.


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