Multiple tiny or one large inverter?

jmb
jmb Registered Users Posts: 42 ✭✭
in General Solar Power Topics #1
At our cabin I have a 1.5Kw Samlex true sine inverter to handle all of our AC needs. It's quite a bit larger than we need but I wanted to be able to grow a little as more PV capacity comes on line. Once I get a larger array up I will also invest in a larger battery bank when my current one bites the dust but hopefully that is a ways into the future.

We currently have 24 VDC lights and water pump is 24 VDC so the only thing we use AC for is 3.1 Cu ft fridge, 26" LCD TV, couple of fans, and my CPAP.

I was wondering if I mothballed the Samlex inverter (until I needed it) and go with 2 or 3 "tiny" inverters if my DC consumption would be less. My total AC load is about 350 watts and the fridge suck an additional 30 watts when it starts up. What I have right now works fine but I use about 20% of my 300 AH 24 volt battery bank over night which doesn't leave me much "padding" if the sun was to go away for a while.
Justin B.
Cabin - 9 Mission Solar 310 watt panels, MidNite Solar Combiner, Iron Ridge mounting, 4 Speciaized Power 200 AH 24V LiFePO4 batteries, Samlex PST-1500-24 inverter, MidNite Solar Classic 200SL CC

Barn - 9 Renogy 100W panels, Generic Chinese 40A MPPT CC, 6 Universal 12V 100 AH AGM batteries, Reliable 3KW 12V PSW inverter

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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    What is the idle consumption of the Samlex? Usually they are pretty low.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Your refrigerator starting surge usually defines the minimum battery bank size (AH @ volts) and the minimum AC inverter size (typically around 1,200 to 1,500 watts is a good minimum for a standard AC refrigerator with compressor). Even the "bar fridge" size units have a compressor that draws similar to a full size fridge.

    The newer "inverter' type AC refrigerators have almost no surge (although, the auto defrost heater can take upwards of ~600 Watts).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #4
    The idle consumption rate of the 1500 watt inverter is 18 watts. The 700 watt unit is only 3.5 watts less, at 14.5 watts less, really only saving you less than 100 watt hours over 24 hours. Really not worth the effort in my opinion.

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited October 2018 #5
    The CPAP is something of concern, if ones life is dependent on it, most, if not all, inverters, are not listed to provide such life support, be it alone or in combination with other devices, it would be a real bummer if the refrigerator turning on, turned you off.....so to speak
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #6
    I don't know if you are going to find 3 small inverters that will use less standby power than the samlex.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • jmb
    jmb Registered Users Posts: 42 ✭✭
    #7
    BB - Our fridge pulls about 130 watts (AC) when starting and a little over 100 watts running - unless my Kill-A-Watt just can't catch the surge adequately. It's a 3.1 Cu ft Frigidaire not frost free.

    mcgivor - The CPAP just helps me sleep better but my life doesn't depend on it at least on a short term basis.

    raj and oil pan - I've pretty much came to the same conclusion now that I'm awake! I posted this up last night sorta thinking out loud so to speak.
    Justin B.
    Cabin - 9 Mission Solar 310 watt panels, MidNite Solar Combiner, Iron Ridge mounting, 4 Speciaized Power 200 AH 24V LiFePO4 batteries, Samlex PST-1500-24 inverter, MidNite Solar Classic 200SL CC

    Barn - 9 Renogy 100W panels, Generic Chinese 40A MPPT CC, 6 Universal 12V 100 AH AGM batteries, Reliable 3KW 12V PSW inverter

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    edited October 2018 #8
    Unless you have a true peak hold meter, it is difficult to measure peak starting current with standard meter or kill a Watt type Meter.

    More solar panels will address a bunch of issues... When you have a chance to install more.

    Otherwise, your system sounds pretty balanced.

    Eventually a bit larger battery bank would be nice for longer term, deeper into winter and poor weather.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • jmb
    jmb Registered Users Posts: 42 ✭✭
    #9
    I have 9 100W Renogy panels in series-parallel at present (three strings), 60A MPPT controller, and 6 100 AH AGM batteries in series-parallel for a 300 AH battery bank. I now realize having three parallel strings of batteries is less than optimal but I guess that's all part of the learning curve. Next spring I would like to add 4-6 300 watt panels and another charge controller. It would be really nice to be able to run a small widow unit during the heat of the day.
    Justin B.
    Cabin - 9 Mission Solar 310 watt panels, MidNite Solar Combiner, Iron Ridge mounting, 4 Speciaized Power 200 AH 24V LiFePO4 batteries, Samlex PST-1500-24 inverter, MidNite Solar Classic 200SL CC

    Barn - 9 Renogy 100W panels, Generic Chinese 40A MPPT CC, 6 Universal 12V 100 AH AGM batteries, Reliable 3KW 12V PSW inverter

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #10
    3x parallel strings properly wired:

    http://www.smartgauge.co.uk/batt_con.html

    And you use a DC Current Clamp DMM to monitor the heavy charging and discharging current for each string and that they, on average, reasonably share current. Also check each battery's voltage to ensure that they are reasonably similar state of charge.

    As long as all looks OK, there is no reason to change out/upgrade the bank before its time.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #11
    Another way, is to use a tiny PSW inverter only for the CPAP machine & a light, and leave the other inverters off.
    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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  • jmb
    jmb Registered Users Posts: 42 ✭✭
    #12
    Bill - I have the strings hooked to a solid copper bus bar. I will be heading back up to the mountains next month and will scrub my bus-bars and cable ends and apply no-ox. While I am doing this I will check all battery voltages.

    mike - Unfortunately the fridge needs juice, too.
    Justin B.
    Cabin - 9 Mission Solar 310 watt panels, MidNite Solar Combiner, Iron Ridge mounting, 4 Speciaized Power 200 AH 24V LiFePO4 batteries, Samlex PST-1500-24 inverter, MidNite Solar Classic 200SL CC

    Barn - 9 Renogy 100W panels, Generic Chinese 40A MPPT CC, 6 Universal 12V 100 AH AGM batteries, Reliable 3KW 12V PSW inverter

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  • jmb
    jmb Registered Users Posts: 42 ✭✭
    edited October 2018 #13
    Here's what I have... Next spring I plan on cementing in a more permanent panel mounting structure.











    Justin B.
    Cabin - 9 Mission Solar 310 watt panels, MidNite Solar Combiner, Iron Ridge mounting, 4 Speciaized Power 200 AH 24V LiFePO4 batteries, Samlex PST-1500-24 inverter, MidNite Solar Classic 200SL CC

    Barn - 9 Renogy 100W panels, Generic Chinese 40A MPPT CC, 6 Universal 12V 100 AH AGM batteries, Reliable 3KW 12V PSW inverter

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