Simple MPPT solar panel charge controllers

Discussion in 'OnBoard Electronics & Controls' started by BillyDoc, May 21, 2009.

  1. Buckiller
    Joined: Dec 2010
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Alabama

    Buckiller Bryan W Buckley

    Against the rules to resuscitate old topics?

    I found this topic from Google when I was building my website. I'm an undergraduate ECE major and MPPT was our senior project. I haven't totally finished the website, but the MPPT project page is mostly finished: http://bama.ua.edu/~bwbuckley/mppt.html

    Very cool to read the progress you're making BillyDoc, wondering if you ever finished?
     
  2. scruffy.mogwai
    Joined: Apr 2011
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Zealand

    scruffy.mogwai New Member

    MPPT in Laymans terms

    This is for gonzo and any others that are struggling with the claim that MPPT can increase your energy yield by up to 30%. This is NOT getting something for nothing. A sacrifice is made within these devices.

    Disclaimer: Some facts and definitions are modified to help me explain the concept at a reasonably simple level.

    Just say you usually get 12V from your panel(s) at full sun. In less sun that value drops. what a MPPT controller can do is keep the voltage at 12V (it has limitations though) at the sacrifice of current.
    This is because that voltage and current are inversely proportional, that is, for the MMPT controller to keep the voltage at 12V when the panels are at <12V, the current is decreased to provide that extra increase in voltage.
     
  3. scruffy.mogwai
    Joined: Apr 2011
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: New Zealand

    scruffy.mogwai New Member

  4. Redtick
    Joined: Jul 2009
    Posts: 21
    Likes: 7, Points: 0, Legacy Rep: 82
    Location: usa

    Redtick Junior Member

  5. anilpaulbaby
    Joined: Jan 2012
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: bangalore

    anilpaulbaby New Member

    Hi, am new in forum.i am waiting you finish this project
     
  6. powerabout
    Joined: Nov 2007
    Posts: 2,904
    Likes: 61, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    except the only way to raise the voltage of a lead acid is to push more current in till you have enough to raise it to that voltage
     
  7. BertKu
    Joined: May 2009
    Posts: 2,478
    Likes: 42, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    I just inquired about and ordered the very simple but effective LTM8062. It only needs 4 external components and it allows you to charge up to 20 ampere by paralleling 10 devices (LTM8062s). Would anybody need 100 Ampere, just keep on paralleling. Input is a 36 cell solar panel charging either 4 cell li-Ion , Li-Poly , 5 cell LiFePO4 or 6 cell lead acid batteries. Will let you know when I received the product and have tested it.
    Bert

    P.S. The pin layout is a nightmare, 77 of them centre to centre 1.33 mm ( 0.0523 " !!!) One could make a small through hole printed circuit board and solder wires from the other side. The question is , how stable will it be. I have never seen sockets for 77 pin BLGA package. Alternative one could use maybe watch strap pins which has a little spring section and solder those ones in a pcb.
     
    Last edited: May 15, 2012
  8. WindyOne
    Joined: Dec 2012
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: OHIO

    WindyOne Junior Member

    BillyDoc,
    This was a very interesting thread! It took me many hours to read and understand what you had designed. You appeared to follow the Maxim APP Note in message #5 of this thread. Your schematics were difficult to understand because I needed to reference the documentation for each chip since you only provided Pin #'s. I can tell this project took a substantial amount of design time. The $64,000 Question is: "Did you actually build this circuit?" And if you did build the circuit, did your PV YIELD increase by "up-to" 30%?

    Also, on a hot day with less sun your Max Power Point voltage will be significantly lower than your FIXED Turn Off Voltage. But your circuit will never know that since it is not a True MPPT because it does not track the actual Max Power Point Voltage, ever. The "T" in MPPT means tracking. So really, this circuit is an FPP, a "Fixed Power Point" circuit that works well only under Maximum Sun Radiation and one specific Temperature (77 F). Given less than maximum solar radiation levels (very likely) and temperatures other than 77 Degrees (very likely) then your circuit will not be at Max Power Point.


    Suggestions:
    Hysteresis on the Input Turn On / Off voltage.
    Temperature Compensation for the Input Turn On / Off Voltage.
    Fast Charge cut-off by sensing low amperage into the battery vs a FIXED Voltage (15v ?).
    Use of the BOOST PWM Charger when the PV Voltage is below the Turn-On Setpoint otherwise that power is just wasted - which lowers your overall efficiency.

    It is questionable if there is actually a net increase in PV Yield with this circuit since the MPP Voltage of your PV panel is already nearly the same as the battery voltage, in the first place. Now, if the MPP Voltage from the PV array was significantly higher (like double) than your battery voltage then this circuit could help increase PV Yield.
     
  9. BertKu
    Joined: May 2009
    Posts: 2,478
    Likes: 42, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Sorry for it, the supplier returned my deposit and payment. For whatever reason they could not supply. Would it not be much easier if one take medical stainless steel plate and shine/reflect the sun onto the solar panels. Would we not get more than trying to achieve with Maximum Power Point Tracking. Look I am also an electronic hobbyist, but one sometimes has to be practical. The same surface area Medical stainless steel folded over the solar panel will protect the surface of the panel when not in use and if folded open, get you most likely more than 30% more output power. Heat may be of a problem. Although I have deep respect for the work put into this marvelous design. Bert
     
  10. WindyOne
    Joined: Dec 2012
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: OHIO

    WindyOne Junior Member

    Heat would be big problem. Heat lowers the maximum power available from a PV array. Lower temperatures increase the maximum power from a PV array. Also, the logistics of constantly adjusting the stainless steel plate to reflect the sun direcly on to the PV array is not practical, otherwise that idea would be widely implemented by now. MPPT is very effective when the Max Power Voltage of the PV array is significantly higher than the battery voltage but MPPT is not nearly as effective when the Max Power Voltage of the PV array is already near the battery charging voltage, which unfortunately is BillyDoc's case.

    A good example of where MPPT does capture a 30% increase in Power: I have 2.58 Kilowatts (12 x 215 Watt) of PV panels wired in series at my home. The voltage at Max Power can vary from a low of 175 volts to a high of 315 volts, depending upon the temperature and solar intensity. My MPPT constantly searches for the highest POWER, which is the product of the Volts times the Amps. Sometimes, the MPPT will allow the PV volts to increase which will decrease the amps but by a lower percentage, which means more power from the PV array. Sometimes, the MPPT will allow the volts to decrease which will increase the amps but by a higher percentage, which means more power from the PV Array. The MPPT always searches for the maximum Power Point near the "knee" of the Amps vs. Voltage curve of the PV Array. The knee of the I-V curve changes significantly for different temperatures and solar intensity. I would hate to only yield 1.8 kilowatts (70%) with a Fixed Voltage Inverter, when I could be getting 2.58 kilowatts (100%) by using an MPPT Inverter.
     
  11. BertKu
    Joined: May 2009
    Posts: 2,478
    Likes: 42, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Fully agreed. Often the panels are to close to the roof installed and does not get enough air / cooling air circulation.
    If your panels are not tracking the sun, your argument of using reflectors are not valid. Except if you, also continuous shift your panels, to the optimum angle of the sun. But that is not the case. I was more thinking of the sun late in the afternoon or early making use of a reflector. The heat created is then less. But I am NOT going to argue, I think your design is marvelous and next year I will certainly copy and try it out. Bert
     
  12. BertKu
    Joined: May 2009
    Posts: 2,478
    Likes: 42, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    I am just wondering, whether MPPT will not work better with Lithium LiFePo4 batteries. A lithium battery start already charging at 2 Volt, although the nominal Voltage is 3.3 Volt and maximum allowed battery voltage of 3.65 Volt. This in contrast to Lead Acid Batteries, which start only charging at 2,1 Volt and needs 2.4 Volt to charge properly, a higher voltage with higher temperature creates gassing. Thus by low sun and low power, Lithium batteries are being easier charged and Lead Acid batteries not. Thus 4 Lithium batteries in series start charging already at 8 Volt, while Lead Acid needs 12,5 Volt. (6 batteries in series) Bert
     
  13. WindyOne
    Joined: Dec 2012
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: OHIO

    WindyOne Junior Member

    Yes, an MPPT circuit will increase yield whenever the Charging Voltage of your batteries is significantly lower (different) than the PV Voltage at Max Power Point.
     
  14. WindyOne
    Joined: Dec 2012
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: OHIO

    WindyOne Junior Member

    "If your panels are not tracking the Sun ..."
    I could not justify the additional cost of Solar Tracking vs a Fixed Mount design.
     

  15. BertKu
    Joined: May 2009
    Posts: 2,478
    Likes: 42, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Then I think, you could benefit early in the morning and late at night with a reflector. Try it and let us know. Bert
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.