Off-Grid Solar Test

lzhomelzhome Registered Users Posts: 39 ✭✭

Moderator, please remove if posting my video is against forum policy.

I have performed a test of my off-grid 800w system in the video link below. I know my method of using battery voltage to tract and determine system perform is low tech if not completely incorrect but all I have currently available.

So I'm looking for recommendations on following:

  1. what inexpensive meter can I install to better track battery state of charge/usage
  2. from the video results, would adding 200w of PV be a significant improvement
  3. or lastly my 24v system has 4 155ah AGM's for a total of 360ah which have been online about 15 months, can I add two new batteries to the bank or would that be a waste

Test Video: https://youtu.be/kiaQGQvypYY

Thanks.

TriStar MPPT, 8 x 100w PV, MNPV6 Combiner, 4 x 12v 155ah VMAXTanks AGMs and GoPower 2000w PSW Inverter.

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 4,880 ✭✭✭✭

    Best way to get a realistic handle on the State of Charge would be with a shunt based meter like the Trimetric

    https://www.solar-electric.com/bogart-engineering-tm-2030-rv-battery-monitor.html

    ...or Victron...

    Photo of the 'smart version which allows Bluetooth connectivity, the original is similar to the Trimetric and cheaper but NAWS doesn't sell it any longer;

    https://shop.pkys.com/Victron-Energy-BMV-700-Precision-Battery-Monitor_p_2810.html

    These type of meters use the current passing into and out of the meter and the variables you set to accurately measure the current SOC. So things like your battery capacity, type and voltage should be correct. 4 - 155 amps 12 volt batteries in a 24 volt configurations would be 2x155 or 310 amp hour 24 volt battery bank.

    It's almost always better to have more solar...lol. Panels produce about 75% of their panels rating, and most AGM can handle 13% of capacity at charging voltage, So a 1000 watt array could produce 750 watts ÷ 29 volts = 26 amps or about 8.3% of 310 amphour 24 volt battery bank.

    I personally don't like adding new batteries to batteries even 6 months old. So that would be a personal choice.

    Since the camper should be enclosed, I'd try running the dehumidifier for maybe an hour in the morning and 2 hours in the late afternoon. Should keep the humidity under control, I actually have lived in Florida and I understand what a 'Dragon' humidity is there.

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • mcgivormcgivor Solar Expert Posts: 2,841 ✭✭✭✭✭

    The dehumidifier is 5A at 120VAC is 25A at 24VDC, so every hour on it consumes 25 Ah, not including inherent losses, the 800W array will produce less than that, 800 × 75% =600, 600÷28= 21.4A excluding losses. So basically the dehumidifier will kill the system if not used sparingly, very sparingly.

    For full time useage the PV is insufficient for the battery capacity, the very least should be 10%, approximately double the existing would be close to what's needed as a minimum. Adding battery capacity to support the dehumidifier will mean increasing the array capacity as well.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • mcgivormcgivor Solar Expert Posts: 2,841 ✭✭✭✭✭

    For what it's worth AC is also a dehumidifier, difference is it dumps the heat and moisture outside rather than inside, the dehumidifier you have uses more than my mini split 8500 BTU 26 SEER unit.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • NANOcontrolNANOcontrol Registered Users Posts: 123 ✭✭✭

    I have a chest fridge system that operates off monitoring battery voltage and it is quite effective. Your dehumidifier does not need to run all the time. I run my fridge with only a car battery and it needs to keep the battery at nearly full charge. I don't start the fridge till the battery is at least 13.4V indicting panels are seeing light. I run for 6 minutes and check the battery again. If it is not at least 12.6V I shut down. Higher I keep running for another 4 minutes, check again and shut down after 15 minutes regardless. This guarantees the inverter does not lock up from a possible low voltage condition. Restart has a 6 minute time out. This process has been running for years.

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