Help increasing the solar system

criscris Registered Users, Users Awaiting Email Confirmation Posts: 4
My weekend cabin system has 2 100 Amphr 12 V batteries (US AGM 31), 10 PV panels 12V (I think 80 Watt judging by size, there is nothing written on it), a Cotek 1000 W inverter, and a controller.  I use this system for 6 lights (110 V 13 Watts) and charging a computer. I need to increase my system to power a dometic refrigerator.  This refrigerator is 110 V electric/propane.  I use it on propane but the pilot keeps blowing off.
By my calculations, my battery bank is too small.  To increase it, I have a few options.  I already have 17 batteries 40 Amphr (sealed lead acid) that were given to me (new) and the connectors.  I could replace the 2 100 amp hr battery bank with this one (680 Amphr, 12 V).  Or I could buy more of the old battery but I understand I shouldn't mix old and new batteries.  I wanted to know your thoughts before I replace the battery bank with the 40Amphr batteries as moving these batteries up the hill on a trail won't be an easy task.  

Comments

  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Welcome 
    Firstly forget the idea of using 17 batteries in parallel, it would be impossible to keep ballance across so many, adding new to old in parallel is possible but not desirable. As far as a refrigerator is concerned you would more than likely need a larger inverter  to handle inrush, a larger capacity battery to support the refrigerator and the inverter self consumption, which in turn would mean a larger PV array, possibly exceeding the charge controllers rated capacity....in short you are looking at a new system, a refrigerator is not a small load, in fact off grid it is usually the largest single load, 2-3Kw per day . Being this is a weekend cabin you may want to seriously consider sticking with the propane unit and work on draft prevention. Sorry to be the bearer of bad news.

    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.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,628 ✭✭✭✭
    Why is the pilot light blowing out?  I could light my Dometic RV refer and pull my 5th wheel at 70 MPH and never has the pilot light blown out. Do you need to clean the orifice? Do you need a shroud around the pilot light area? Those RV refers aren't anywhere near as efficient as a modern full size refer so running it on solar really isn't a good idea.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 540 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    You also need to tell us how the refrigerator runs on 120vac.

    A typical propane+electric refrigerator is about ammonia absorption cycle. It uses the heat of the propane flame to run three cooling cycle.

    Many for 12/120 volt operation simply use an electric heater to replace the propane flame. While the are reasonably cost efficient with propane, They tend to use a lot of electricy fit their size and cooling load.

    Generally, to run an electric fridge with reasonable amount of power, they use a mechanical refrigeration compressor of some sort.

    You can get a kill a watt power meter and see how much electricy it would use.

    A very efficient refrigerator will run on 250 to 1,500 Watt×hour per day (larger fridge, ice maker, frost free, etc. use more energy).

    If your uses on the low side of consumption, then you could use it on solar reasonably.

    - Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Based on practical experience, using a very small refrigerator, a converted freezer and an 11 cubic foot with drawer freezer 3 cf, with  inverter compressor, I've never seen anything as low as 250Wh, not even 500Wh per day. Tropical temperatures play a large part in the overall consumption figures being higer, we don't get below 24°C very often.
    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.
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    Spiders like to get into propane orifaces. Cleaning it may be the best solution.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • criscris Registered Users, Users Awaiting Email Confirmation Posts: 4
    Thank you!  These responses have been very helpful.  The huge chain of batteries is a pain to connect so I am glad to learn this isn't the best idea.  
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