MPPT vs PWM controllers?

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  • VicVic Solar Expert Posts: 2,976 ✭✭✭✭
    Re: MPPT vs PWM controllers?

    AND regarding MPPT controllers, most include a comprehensive dispaly of current state of batts, voltages to tenths of a volt, and amps to the tenth as well. Furthermore, charging parameters are settable to the tenth of a volt, and there are very comrehansive mode/function adjustments, plus, the mainstream MPPT CCs also have an Aux output to add even more funcitonality. There is no need for the user to learn the Morse Code -- actually, not nearly as precise as Morse code, in an attempt to decode what SOC, mode that the CC is in, or any Faults.

    And most PWN controllers require one to set a number of DIP switches to a limited number of options, or perhaps buy an add-on meter (with limited functionality), and/or a Computer Interface to set parameters not available on the DIP switches. These often axquired over time, can make the PWM CC cost advantage less clear.

    Have seen PWM CCs at neighbor's locations that have been broken for months, damaging batteries, because the Code of blinking colored lights was undecipherable to the user.

    PWM CCs do have their place, low cost being an important one, but their limitations can make them an expensive choice for those not knowing the Code, etc.

    Regarding the MPPT functions of CCs, Of course, the CC will MPPT in EQ, and Float as well. In these charge stages, the percentage improvement of MPPT will still be higher than that of a PWM CC, but the power gain AH/WH would be fairly small.

    Realize that the OP is doing a system on a budget. It is possible the MidNite Classic CC, with ALL of its capability, will dislodge quite a nimber of early MPPT CCs, like the very venerable Outback MX-60, into the used market. JMHO, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: MPPT vs PWM controllers?

    I don't usually disagree with Vic but ...
    As far as I know, no charge controller has a built-in battery monitor for reading SOC (although the folks at MidNite have dropped hints it may be coming). The metered data that is available isn't 100% accurate, but it's better than nowt.

    And so we are left with the original assessment: The MPPT advantage is normally so small that on low-power systems it isn't worth the extra money unless there is a need to handle long wire runs or to squeeze every last Watt out. But with even a 3% advantage in Bulk stage it adds up to significant power when you get into hundreds of Watts of array: 3% of 200 Watts is 6 Watts, not much to work with and you can gain more by spending the same money on more panel. But 3% of 2000 Watts is 60 Watts, which could run something useful like your laptop - and your spouse's. The claims of "50% more power" made by some are exaggerated. Maybe in a best-case scenario, but not on average which is what counts for making the decision.
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    Re: MPPT vs PWM controllers?

    Apollo and Outback do have integrated battery monitors (optional in some cases).

    But I am not sure the can use the data as part of their charge algorithm.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: MPPT vs PWM controllers?

    I don't know about Apollo, but Outback's monitor is not integrated. Thus it's no more than having a Trimetric.

    It would be a huge improvement in controllers to have them be able to regulate charge according to the battery SOC. Probably some tricky programming, but ...
  • VicVic Solar Expert Posts: 2,976 ✭✭✭✭
    Re: MPPT vs PWM controllers?

    Coot,

    I was NOT saying that any CC had a battery monitor. was attempting to say that it is often difficult for me to decode the state of the charging process. AND, it seems difficult for most of the operators of systems using CC with blinking lights as the readout. SOC was not, perhaps the EXACT correct term of art. Not to nit pick, however. I probably should have used the SOCP Acronym -- State Of Charging Process. Is the CC in Bulk? Asorb? Float? If the CC happens to be in Asorb, I kinna wonder just how long it has been there and/or when might it complete this stage.

    And while the OP's system may be on the smaller side, it is always a shame to see batteries RUINED regardless of their size. Have seen too many battery banks serially ruined, because the manager of the system simply did not know what was happening. A CC with the ability to actually SET a charge parameter, as opposed to setting switches can be a real boon to batt health. I, do have a back-up CC that is PWM. It is made by a well-respected company. The neat thing about it, is, that even an essential item like a BTS is optional. The seemingly inexpensive CC needs many options to begin to equal many of the MPPT CCs in settability, and comprehensive readout. Believe it or not, these options add to the cost, making the cheap CC quite a lot more expensive. This what I WAS trying to say. Too often I kinna try, for the sake of brevity, use a bit of shorthand, not exhaustively laying out, .. This, can cause that, and that and sometimes THAT, and therefore ...

    Perhaps I was too nit-picky about other MPPT modes of many MPPT CCs.

    Am certain that the above has numerous things that need to be set straight. Thanks, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: MPPT vs PWM controllers?

    No, Vic; I misunderstood you.
    Which is why I said what I did because I thought others might misunderstand the same way.

    Lots of small and medium-sized (subjective criteria there) work fine with PWM controllers. The devil is in the details as always. With any component of a system there is no absolute "this is better than that" answer. All we can do is point out the various advantages/disadvantages and hope people can make the choice. Too often it becomes "information overload". We'd all like this stuff to be simple and easy to understand but in all honesty it just isn't. :p
  • NScooknetNScooknet Solar Expert Posts: 30
    Re: MPPT vs PWM controllers?
    Still have the receipt for the CT Eliminator inverter? Take it back.
    I actually tested most of their MSW inverters a few years back. I found the Wattage ratings to be "optimistic".


    I took your advice, and returned it to Canadian Tire today. It was a POS...LOL

    I have another modified sine inverter which is not near as powerful, only 1000W, and it actually is not bad, you can see a little line running through the TV screen when powering it via the batteries, but nothing major, with the eliminator inverter is is NOISY!
    Thanks for the good advice !

    Chris :)
  • SolaRevolutionSolaRevolution Solar Expert Posts: 407 ✭✭✭✭✭✭
    Re: MPPT vs PWM controllers?

    Cold and crisp today. (40 F, 5 C. cool for Northern California)

    I was working on a system with 4 Sharp 240s into an Outback FM60 MPPT charge controller and 8 L16s. With the system under C-10 load for about an hour. The peak logged PV output was 910 watts. 94.8% conversion efficiency of STC rating. There were no clouds during this time to give it an "edge of cloud" effect.

    This was a great example of having maximum efficiency when it is needed most. These PV modules would not be used for a battery sysyem without MPPT but if it were a 960Watt PWM system I would have been suprised to get better than 75% of the STC rating.
  • icarusicarus Solar Expert Posts: 5,355 ✭✭✭✭
    Re: MPPT vs PWM controllers?

    Cold and crisp? We were -33C yesterday morning! (-26F). LOL!

    Opening the water hole, throwing a dipper of water into the air, and it steamed like hot coffee, evaporating before it hits the ground.

    Tony
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