Mix'n'match array addition?

Polychrest
Polychrest Registered Users Posts: 17 ✭✭
in Off Grid Solar & Battery Systems #1
I've got an evolving 24-volt off-grid system in the backwoods of Ontario--8 220 amp-hour 6-volt batteries, a 4000 watt Magnum pure sine wave inverter, a Blue Sky Solar Boost 3024i charge controller, and on the roof....two series-wired strings of 12-volt panels: a Sharp 120 linked with a Siemens pro charger 100, and two linked Solarex MSX 60's. I'd like to boost my array power, and I'm thinking of adding something like a Sharp 224 watt 24 volt panel in parallel with the other two strings. Will this work, and is it a good idea?

Your expertise is much appreciated
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: Mix'n'match array addition?

    When you parallel panels, the array takes on the lower voltage (of the lowest panels) For charging a 24V battery, you need panels with 32Vmp spec. (or 2 series 12V panels to get at least that voltage). If you attach a 45V panel in parallel with a 33V panel, you only get 33V . So reading the stickers on the panels comes first, and then you can figure how to match them. - + 10% is reasonable.
    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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  • Polychrest
    Polychrest Registered Users Posts: 17 ✭✭
    #3
    Re: Mix'n'match array addition?

    The listed Vpm for the Sharp 224 is 29.3 V. Is this high enough to work with my two other strings, which are both closer to 34 V?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: Mix'n'match array addition?

    Just a quick glance tells me that you have way too many batteries or way too few panels.

    Ideally you would wish panel capacity to be able to push ~5-15% of ah capacity into the batteries, so your 440ah (24vdc) of batteries would like like a minimum of ~22 amps (24 vdc up to maybe ~66 amps.

    If I am reading your post correctly you have ~ 240 watts of PV. These might, on a good day put out ~ 8 amps into the batteries,,,, just barely enough to keep them in float. Depending on how you are adding a charge beyond the PV you may be putting these batteries at risk of very short life.

    Good luck, and welcome to the forum.

    Tony

    PS If you upgrade and wish to get rid of the Solarex's let me know. I currently run 5 of them and am always looking for a few more.

    T
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  • Polychrest
    Polychrest Registered Users Posts: 17 ✭✭
    #5
    Re: Mix'n'match array addition?
    icarus wrote: »
    If I am reading your post correctly you have ~ 240 watts of PV.

    It's actually 340 watts and about 10 amps on a good day, and I've got a small generator for backup/equalization duty, but I'm with you on your logic otherwise. I really do need more array, and I'm trying to figure out the best way (read "efficient" and "cheap") to do so.

    Thanks for the useful advice. I just discovered this forum and am learning important stuff that my solar dealer didn't/wouldn't tell me. I'll keep you in mind for the Solarex MSx 60's.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #6
    Re: Mix'n'match array addition?

    Where are you located?

    Just FYI, there are American suppliers who can sell panels under $2/watt. Shipping to Canada is not impossible, but shipping to the border and then picking stuff up works quite well.


    On another note, I would consider retiring the Bluesky controller, and consider going with the Rogue 2430 mppt. That would give you 30 amps into 24 vdc. Alternatively Morningstar makes a new MPPT controller. I think the BS controllers are old enough technology that your really don't gain too much advantage with the MPPT.

    Good luck and keep in touch.

    Tony
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  • Polychrest
    Polychrest Registered Users Posts: 17 ✭✭
    #7
    Re: Mix'n'match array addition?

    Hey Tony, I'm south of Magnetawan on a small island (sound familiar?). I added the Blue Sky last year and it's rated for 30 amps in 24 volts (or so I was told). My most pressing need right now, I think, is array. What I'm wrestling with is whether I should go with a 24 volt panel (cheap, simple to install, ~30 volts, 225 watts) or two more 12-volters in series (more expensive and complicated to install, ~35 volts--which is closer to what I've got now--260 watts).
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Mix'n'match array addition?

    Oh, Suburban TO,,, as we call it! LOL.

    In some ways it might be nice to start from scratch using 24vdc default, as you say, simpler and easier. Of course you could pair up your 12 volt panels and include them in an array. Or you could sell your 12 volts to defray some of the cost.

    Personally, if money were (little) no object, I would go with 24 vdc, and get the biggest controller you can envision needing. As I'm sure you know, loads grow with time, and speaking from experience, the controllers are the limiting factor. I am on my third or fourth. (Partly because I like the Rogue, not that I "really" needed it, but I really do like it now that I have it. It's limitation is that you can only wire an array for 24 vdc, rather than 48 like other bigger MPPT controllers.

    Good luck, keep in touch,

    Tony
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  • Polychrest
    Polychrest Registered Users Posts: 17 ✭✭
    #9
    Re: Mix'n'match array addition?
    icarus wrote: »
    Oh, Suburban TO,,, as we call it! LOL.
    Tony

    Quetico....that's suburban Thunder Bay, right? ;) Thanks again for the advice, Tony. Long-term, I'm probably going all-24. But right now, I'd like to add 200-300 watts to my array and do so in the most efficient way I can.
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  • dmiller
    dmiller Solar Expert Posts: 68 ✭✭✭✭
    #10
    Re: Mix'n'match array addition?
    icarus wrote: »
    Where are you located?

    Just FYI, there are American suppliers who can sell panels under $2/watt. Shipping to Canada is not impossible, but shipping to the border and then picking stuff up works quite well.


    .....

    Sounds slightly exciting.
    I think I'll be driving well out of my way to pick up panels in Northern Arizona. Not exciting.

    Polycrest, in a recent discussion here I was advised to be closer to Vmp than the sharp panels your looking at. 30 is more common than 34, but you can find the later.
    I would love to see test data on the mismatch, but I haven't found any.
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  • Polychrest
    Polychrest Registered Users Posts: 17 ✭✭
    #11
    Re: Mix'n'match array addition?

    An update: I bought 2 Kyocera KD135GX-LPU's and installed them in a series string a few days ago. They've been great so far, adding as much as 7 amps of current to my array. The new locking clips made wiring them a snap--literally. My roof has a mongrelish air to it with all the different panels, but the VMPP voltages of my three strings are all really close and they seem to be playing well with my MPPT controller.

    The panels were on sale at a new (for me) dealer I discovered recently. Just before I bought mine, he'd received a shipment of 200 cartons of 2 KD135GX-LPU's--400 panels in total. Two weeks later, he had 17 left and was looking for more. This guy was great: no "Trust me, you need this, I'm an expert" b.s., no useless value-adding overhead, no restrictive list of predefined packages with high penalties for substitutions. I still coughed up a "sold in Canada" penalty, but it was not too bad. And the price was $400 less than what a big-chain dealer asked for 2 about-to-be-discontined Sharp 130's. I'm never going back to those pirates again.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: Mix'n'match array addition?
    My roof has a mongrelish air...

    But you got your additional solar power wired in and working... What more can you ask for! :D

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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