Solar panels to battery charge.

cptmikercptmiker Registered Users Posts: 4
edited December 2018 in Solar Beginners Corner #1
Hello all New here just looking for a bit of help for my dad this question centers around solar panel to battery

how many watts of solar panels are needed to support 1800 amp hr of battery's

Setup=
16 TROJAN T-105 wired to make a 12volts system as a note I cant go to 24 volts at this time.

3000 watt inverter 12v to 120v

16 100 watt solar panels output in strings of 2 to combiner with 6 breakers in each box.
Maximum Power: 100W Maximum System Voltage: 600V DC (UL)
Optimum Operating Voltage (Vmp): 18.9V Open-Circuit Voltage (Voc): 22.5V
Optimum Operating Current (Imp): 5.29A Short-Circuit Current (Isc): 5.75A
Weight: 16.5lbs Dimensions: 47.3 X 21.3 X 1.4 In

Max amps on a perfect day 84

1 tristar ts60
1 tristar ts45

There are ancillary parts combiners breakers cutoffs surge and lightning arrestor
auto switch over for generator power.

Basic question is. is there enuff solar panels to maintain the battery assuming 50% or less discharge per day assuming good sun. or am i under powered with panels.

Thanks

As an fyi I do have two new outback flexmax FM80 mounted but not hooked up yet need to program them

Also on a side note what would be the best battery charger to use when I dont get enuff power to charge the batterys. He is useing and standard 40amp automotive roll around charger i think its not good to use that.

Comments

  • mcgivormcgivor Solar Expert Posts: 2,834 ✭✭✭✭✭
    edited December 2018 #2
    With just looking at the total capacity of the batteries along with the PV numbers, a discharge to 50% would take more than 10 hours of full output, not taking into account inherent losses, to recharge.  To do an accurate calculation geographic location is needed, but this system has some severe deficiencies in the charging ability. There are other issues such as having 8 parallel strings bof batteries and as you are aware the 40A automotive charger will not be capable of recharging, unless left on for 24 hours perhaps.  

    Based on battery capacity, this system should be configured for a higher nominal voltage, 12V  should only be used to about 1Kw to avoid high current and the need for heavy gauge conductors, Ideally a charging current of around 200A, if cycled daily, would be a better figure both PV and backup charger, for a 12V nominal system.

    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.
  • mike95490mike95490 Solar Expert Posts: 8,250 ✭✭✭✭✭
    That's 8 parallel strings of batteries.   They will not be happy, and you will be replacing failed battery banks often.   I think a 24V or 48V inverter is going to be a less expensive option.
    Those same 16 batteries, wired into a 48v configuration will still provide the SAME watt hours, but at reduced current density, meaning you need 1/4 of the charge controllers, much smaller wires 

    1600W of panels gives you (after derating) 1280 w of expected harvest.   At  15V, that's 85A.  At 60V (a 48v bank) that's only 22A and just 1 charge controller.

    As to what the batteries need, they need to be charged at about 10% of total capacity.   
    12 v   ;1800ah needs  180A for a good charging
      configured into 
    48 v ;450ah needs 45A for good charging  (still just 1 controller)
       note that both require about 2,430 harvested watts, or about a 3,000 w PV array

    You may find that 300W panels cost you less per watt than the little 100w panels, and 1/3 less mounting hardware
    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 ,

  • cptmikercptmiker Registered Users Posts: 4
    Thanks for your comments The location is in Seligman AZ the last two battery banks lasted about 4years, then went down hill to last about 4.5 years in total. So 2K every 4.5 years, before giving up the ghost. I could rearrange the system to 24v 4 strings of 6v battery's but the cost to add a good inverter and reconfigure the solar array to 24v would be costly. The mounting is minimal as they are on a wood rack base's on the roof. conversion cost would run in the 1500 to 2k range. but would lower the amperage output from the panels, so i would need to add more panels. I will be converting the the new Outback controllers when i can. Converting to 48v is not feasible and. On average the only thing sin use is two 32 inch tvs, two Satellite DVRs, 1 dvd recorder a laptop. and minimal led lighting. Once in a while a 700 watt microwave. and a 12v water pump for house water from the storage tank no water leaks so the pump only runs when demand is needed.  everything else is propane washer and dryer are only used when the generator is on and bypassing the solar. any recomendation on a conversion to 24volts would be helpfull. number of more panels needed inverter selection. and maybe some added battery capacity. 
  • mike95490mike95490 Solar Expert Posts: 8,250 ✭✭✭✭✭
    You need to understand how a MPPT controller works.   12V or 48V, it's the same wattage ,   
    Currently, you are under paneled for the amount of batteries you  have.  However, you must not be loading them down too much, if you are getting 4.5 years out of a bank of T-105s

    Re-arranging the panels to be a series string instead of parallel might cost you a couple hours and a few cables, I don't understand how it could be a higher expense than that.  A 2Kw inverter for 24v or 48v should be about the same cost.  More than a 12V, but you can find some higher efficiency units than you can get with 12V
    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 ,

  • cptmikercptmiker Registered Users Posts: 4
    battery bank 16 t105 at 225amp hour each configure to 12v =1800amp hours
    Battery
    8 strings
    225x8 = 1800x12 = 21,600 watt hours

    total usage per day estimated at 2,766 watt hr per day

    if Satellite box are left on 24/7 then usage would be 5,626 watt hr per day.

    Solar panels are a total of 1,600 watt hr at 88.96amps x4hr per day average 6400 watt hr per day at 355.84 amps per 4 hour charge time

    ( note ) Seligman AZ is an average of 6hr per day good sun. so if I calculated by 6hr it would be 9600 watt hours at 533.76 amps for a 6 hour day. backup generator to run on low output days. and to run other high useage appliances like wash and dryer etc. they are never used without the generator. 

    ""Assumes perfect condition and max output"" 

    guessing loss of 20 % efficiency on average leaves
    5120 watt hr per day harvest at 71.168 amp per hour at 4 hr per day

    So I am not sure why going to 24 or 48v would be that much better aside from efficiency gains and significant cost of hardware. If money was no object I would gladly upgrade solar panels higher capacity battery's to reduce the strings. I'm not knocking anyone or anything and very much appreciate the feed back. But money is an issue to make conversion and I am trying to work with what I have. is this realy that bad. Is 4 to 4.5 years a reasonable time for battery's? 

    On a side note what would you recomend for a battery charger to run off the generator on bad days?
  • cptmikercptmiker Registered Users Posts: 4
    mike95490 I am aware how Mppt's work I can present it with 12/24/36/48v of PV input and it will convert as need to match output charging I would like to keep them under 70 input utilization to be safe and not over work them that is why I go two of them. Keep in mind that they are installed but not connected yet. I am still useing the tristars, and there is a lot of wasted energy useing the PWMTristars. When I switch over the the MPPTs I should gane better harvesting from the solar panels in any voltage configuration. I was getting 4 to 5 years out of costco 6v battires. This is the first time I am going with the T105's so I was hope/expecting to get a few more years out of them since they should be a better battery like 6 or 7 years.

  • EstragonEstragon Registered Users Posts: 3,614 ✭✭✭✭✭
    I find the Iota chargers sold by our hosts adequate for bulk charging.  They lack some features (notably fully adjustable voltages etc) found in more expensive chargers, but do the job of occasional bulk charge, with solar finishing to the extent sun is available.

    The main advantages to higher bank voltage is fewer parallel strings to keep balanced, and lower operating currents for a given charge/discharge wattage.  3kw inverter at 12v is 250a, with surge capability of maybe 2x that, needing heavy wiring to handle safely.

    Generally speaking, mppt won't really be a "game changer" vs properly designed pwm.  The difference will be mainly seen in cool/cold and breezy climates where the higher Vmp of panels can be utilized by mppt.  In hot climates, mppt could actually be worse, as they need some voltage headroom (often ~20%)  to buck down to charging voltage.

    6-7yrs for T105s cycled daily in an 8 parallel string setup sounds optimistic to me, but if you're getting 4-5yrs now, who knows?
    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
  • mike95490mike95490 Solar Expert Posts: 8,250 ✭✭✭✭✭
    Systems over 600w, generally benefit from MPPT because you can run higher PV string voltage, and use smaller wire.  If you have a long run, that can save a lot of expensive fat copper wire.  
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 29,045 admin
    One big issue--If you have a longer wire/cable run from the solar array to the solar charge controller/battery shed, MPPT controllers can run the Vpanel input at much higher voltages (upwards of 80-100 VDC for many higher end controllers, and even a few at 200-400+ Volts--At a much higher cost for the controller).

    The second reason for MPPT is that, in general, the larger format >150 Watt solar panels (panels for Grid Tied Solar) are about 1/2 the cost or less for smaller format panels. Because the larger format panels generally are not PWM voltage friendly (i.e., Vmp~18 volts for a 12 volt battery bank on PWM controller, etc.), the "cheaper" large format solar panels need the more expensive MPPT controller... Very roughly, over ~800 Watt solar arrays usually works best with MPPT controllers (price/functions) and systems less than 400 Watts array work more cheaply with PWM charge controllers and 150 Watt or smaller solar panels (cheap PWM controller and more expensive per watt solar panels).

    There are other secondary issues where MPPT controllers are "better" than PWM... One is if your array is in a hot area (desert), Vmp falls and the array+PWM controller may not be able to equalize the battery as effectively (Vmp-panel falls as the solar panels get hot).

    And if you like to connect your solar charge controller to the Internet, have aux output contacts for alarms/vent fans/electric water heater dump loads, etc., generally you find the fancy stuff more available with MPPT controllers.

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