MPPT charge controllers vs PWM for very small systems?

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #32
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    Re: MPPT charge controllers vs PWM for very small systems?

    140w of PV is not even a trickle charge for a 1,000a battery.

    By the time it's de-rated for shadows, poor sun angle and everything, it may not be worth trying to figure out where to mount it and run the wires:cry:
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #33
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    Re: MPPT charge controllers vs PWM for very small systems?

    I said that the extra Ah produced by the MPPT controller over the course of one year, would equate to about 1,000 AH.

    My terminology was wrong, the controller produces Amps, not the Amp Hours-my Bad.

    The idea is the same, less than 3 Amp a day, extra, provided by MPPT vs. PWM controller, contributing extra power during it's life cycle(bar accidents, acts of god, insect damage, etc.), so that the work it produces would pay for itself.

    I never wrote anything about a 1,000Amp battery.
    mike90045 wrote: »
    140w of PV is not even a trickle charge for a 1,000a battery.

    By the time it's de-rated for shadows, poor sun angle and everything, it may not be worth trying to figure out where to mount it and run the wires:cry:
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #34
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    Re: MPPT charge controllers vs PWM for very small systems?

    bmet; it was singleprop who has the 1,000 Amp hour battery bank and 140 Watts of panel being referred to (post #29).

    Everyone please try to stay focused on the topic. We are discussing flying hippopotami and their effect of the spaghetti harvest in outer Bangadingle.

    Or something. :p

    When these threads get long it's really easy to get confused, especially as similar numbers will be mentioned in respect to different aspects: id est bmet's 1000 Amp hour gain for MPPT over the course of a year and singleprop's 1000 Amp hour battery bank.

    Not pointing fingers, just pointing out how easy it is to confuse things. I do it all the time myself. So far I haven't started wearing socks on my ears, so I'm good.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #35
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    Re: MPPT charge controllers vs PWM for very small systems?
    singleprop wrote: »
    ..The battery bank is 24 V, 1000 Amps/hours.
    The PV system is only used to keep up / top up the batteries.....

    Someone wrote this, and 140 w won't do squat for it.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • System2
    System2 Posts: 6,290 admin
    #36
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    Re: MPPT charge controllers vs PWM for very small systems?

    Thanks,
    The battery bank for this yacht is about 1000 Amps/hours as mentioned and the idea was to use a generator/alternator to bring the battery bank up to about 85% of full charge and then let the PV panels do the rest when the yacht is NOT used - this would save the generator from being underloaded when the batteries cannot accept the full charge.
    So this top-up could easily take a couple of days..
    Would the suggested system b able to do this? If not - then how much bigger?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #37
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    Re: MPPT charge controllers vs PWM for very small systems?
    singleprop wrote: »
    Thanks,
    The battery bank for this yacht is about 1000 Amps/hours as mentioned and the idea was to use a generator/alternator to bring the battery bank up to about 85% of full charge and then let the PV panels do the rest when the yacht is NOT used - this would save the generator from being underloaded when the batteries cannot accept the full charge.
    So this top-up could easily take a couple of days..
    Would the suggested system b able to do this? If not - then how much bigger?

    If you want to trickle charge a battery bank you need about 1% current. That's 10 Amps in this case. On a 24 Volt system that works out to around 384 Watts of panel.

    If you want to maintain or "finish charge" with solar you'll need about 5% current potential: 50 Amps. That's nearly 2kW of panel.

    Frankly I'd be looking at why the battery bank is so big. It's 3X the size of what I use to run the whole cabin. 12kW hour potential? What is it running? An electric stove? Normally with that amount of power potential you'd go up to 48 Volts, but I suspect 24 is used because that's the electrical for the yacht motor(s). Definitely a case for trying to find was to reduce consumption and shrink that bank as I can't see putting a 2kW array on a yacht. Not even a big one.
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  • System2
    System2 Posts: 6,290 admin
    #38
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    Re: MPPT charge controllers vs PWM for very small systems?
    Frankly I'd be looking at why the battery bank is so big. It's 3X the size of what I use to run the whole cabin. 12kW hour potential? What is it running? An electric stove? Normally with that amount of power potential you'd go up to 48 Volts, but I suspect 24 is used because that's the electrical for the yacht motor(s). Definitely a case for trying to find was to reduce consumption and shrink that bank as I can't see putting a 2kW array on a yacht. Not even a big one.

    Yes, there is an electrical stove.......unable to reduce the consumption any further as every single light on the yacht is LED's and controlled by timers.....

    So the way forward with the offered system would be to double the size of the PV panels to 340 Watts and reduce the battery bank size, say 700 Amps/hours?

    You say 48 volts - That would be done by connecting the panels in serial to get the higher input voltage for the MPPT controller?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #39
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    Re: MPPT charge controllers vs PWM for very small systems?
    singleprop wrote: »
    Yes, there is an electrical stove.......unable to reduce the consumption any further as every single light on the yacht is LED's and controlled by timers.....

    So the way forward with the offered system would be to double the size of the PV panels to 340 Watts and reduce the battery bank size, say 700 Amps/hours?

    You say 48 volts - That would be done by connecting the panels in serial to get the higher input voltage for the MPPT controller?

    When I say 48 Volts I mean the system Voltage, not the array Voltage. Increasing the array Voltage will gain you nothing in particular. But on the system side the same Watts supplied by 48 Volts are 1/2 the current than if supplied by 24 Volts. This makes recharging the battery bank a bit easier: 500 Amp hours @ 48 Volts instead of 1000 Amp hours @ 24; a need for 50 Amps charge current (can be handled by one charge controller) instead of 100 Amps (needs two charge controllers). In either case you end up needing the same massive array, as the Watts work out the same.

    Even with a 700 Amp hour battery bank you're looking at 1.4kW of array for 5% "finish" charge.
    Possibly the best you can hope for is to install as much PV as you can fit and hope it helps offset some of the usage. Of course it's going to produce mid-day which is probably not when most of that usage occurs.

    340 Watts will give you about 8 Amps @ 29.6 Volts charging. That's barely 1% of a 700 Amp hour bank.

    So about that propane stove ...
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  • demobanjo
    demobanjo Registered Users Posts: 5 ✭✭
    #40
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    Although this thread is quite old. I am new to the solar energy world. I am working in Nigeria where the average temp is usually very hot (28degrees centigrade), would it be better then to get an extra 200Watt panel rather than upgrading my solar charger from PWM to MPPT?
    Solar Know How - Panels and Gadgets
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #41
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    demobanjo said:
     would it be better then to get an extra 200Watt panel rather than upgrading my solar charger from PWM to MPPT?
    Maybe... depends on the rest of your system.  What do you have now?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • demobanjo
    demobanjo Registered Users Posts: 5 ✭✭
    #42
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    vtmaps said:
    demobanjo said:
     would it be better then to get an extra 200Watt panel rather than upgrading my solar charger from PWM to MPPT?
    Maybe... depends on the rest of your system.  What do you have now?

    --vtMaps
    I have a 200 Watt Panel, a 30A PWM solar charger, a 3000Watt Inverter and a 200AH deep cycle battery!

    Solar Know How - Panels and Gadgets
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #43
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    What voltage is your system?

    Does your current 200 watt panel meet your system voltage requirement? if 12 volt does the panel have a VMP of 17.5-19 volts or 24 volt system is the VMP 35 - 38 volts?

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • demobanjo
    demobanjo Registered Users Posts: 5 ✭✭
    #44
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    Thanks Photowhit!
    I really don't know how to measure the voltage after the panels have been installed. What I read when connected is 12.5Volts which I think is the voltage of the battery. I know it's a 12volt system though. How do I measure the VMP?
    Solar Know How - Panels and Gadgets
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #45
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    There should be a label on the back of the panel with the electrical information (or at least, brand and model number).

    You can also count the number of "cells" on the front of the panel (if crystalline solar panel and not thin film). A panel made for charging 12 volt batteries should have ~36 cells for Vmp~18 volts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    edited May 2016 #46
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    BB. said:
    There should be a label on the back of the panel with the electrical information (or at least, brand and model number).

    You can also count the number of "cells" on the front of the panel (if crystalline solar panel and not thin film). A panel made for charging 12 volt batteries should have ~36 cells for Vmp~18 volts.

    -Bill


    It might also have 72 cells, if we're talking about a single 200 watt panel. I think the Evergreen Cedar 12 volt panels had 72 cells wired for 12 volts systems (@18 VMP)

    I went and looked, actually 108 (36 x 3)

    http://pdf.wholesalesolar.com/module pdf folder/evergreen-es-a.pdf?_ga=1.90066011.1760799724.1454822746

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • mike74820
    mike74820 Registered Users Posts: 44 ✭✭
    #47
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    well since this discussion is about what im using on my system. i would say go with and adjustable pwm controller for your small system, they make all the diffrence to me. i have the xantrex c35 and 300 watts of solar panels and a 105 ah battery and the pwm controller i got keeps the battery charged just fine, even on cloudy days itll get it darn almost top off
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #48
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    I guess I've never addressed the question. I'm fine with PWM controllers, so long as you can find panels at a reasonable cost.

    It's getting more difficult to find panels that have a VMP in the 17.5-19 volt range, and I haven't seen large panels, above 140 volts, for a long time.

    Until 4 years ago I had a 1500 watt system at my cabin that ran fine on a PWM charge controller and continues to do so, at least last I heard about a year ago. It was a 24 volt system though, you can still find 35 volt vmp panels at a reasonable cost.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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