more batteries or less?

hello guys. I'm trying to decide which would be better.
get 8 rolls s293ah batteries or 4 trojan  L16 335ah batteries? for 24 v system. or would i be better if i just use 8 rolls S293 on a 48 v system?
I can only afford 8 s293 or 4 L16.

Comments

  • Raj174Raj174 Posts: 584Solar Expert ✭✭✭✭
    Hi Castillo,
    I would avoid using parallel strings of batteries if possible. Going with a 48 volt system would require twice the PV array to have the proper charging rate. Example: (with MPPT controller) 24 volt 300 AH battery bank with a 750 watt array is about 30 amps charging rate, about 10 percent of your battery bank. 48 volt 300 AH battery bank with a 1500 watt PV array is about a 30 amp charging rate. Usually a 48 volt battery bank is recommended for inverters over 2000 watts. Also, if you think you may be upgrading in the future you may want to go with 48 volt inverter.
    Rick 
    12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 54.4V 207AH HI Power LiFePO4 no BMS, 4000W gen.
  • castillojcastilloj Posts: 208Solar Expert
    which way would give me more energy before my inverter shuts down overnight?
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    castilloj said:
    which way would give me more energy before my inverter shuts down overnight?
    How much energy do you consume in a day?  That will determine the size of your battery bank. 

    At what voltage does your inverter shut down?  If it's too low a voltage and happening too often, it will ruin your batteries.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • castillojcastilloj Posts: 208Solar Expert
    right now my inverter shuts down at 24.2. i run it from 12-8 am. then at 8 am i run my 20k generator till noon,
     then 6-12.
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    castilloj said:
    right now my inverter shuts down at 24.2. i run it from 12-8 am. then at 8 am i run my 20k generator till noon,
     then 6-12.
    You are running a 20k generator for 10 hours per day.  What are your loads?  Do you have any solar?  How did you figure out the size of your battery bank?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • castillojcastilloj Posts: 208Solar Expert
    my loads when the generator is on is about 60 amps. and when the inverter is on i run about 7 amps-running tv,sat box, a couple of box fans, and sometimes a fridge.
  • BB.BB. Posts: 27,352Super Moderators admin
    60 amps at 120 or 240 VAC?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • zonebluezoneblue Posts: 1,218Solar Expert ✭✭✭✭
    edited November 2015 #9
    Beware the dead battery trap. Hammering batteries leads to hammered batteries, which leads to lots of  experience with hammered batteries. Ones perception of normal is no longer normal.
    right now my inverter shuts down at 24.2. i run it from 12-8 am. then at 8 am i run my 20k generator till noon,
     then 6-12.
    my loads when the generator is on is about 60 amps. and when the inverter is on i run about 7 amps-running tv,sat box, a couple of box fans, and sometimes a fridge.
    With 200 posts here you know the drill, right? But a few alarm bells ringing a bit here. Maybe add your system to your sig, so we dont have to guess the rest of the system.

    So is there no solar, you charge using the genset, then run off the inverter to get a rest from the noise,and repeat?

    A quick refresher on the rules:
    - recomended overnite DOD 25% for best value for life on the batteries.
    - In your situation you can push this to 50%, because there is no reserve requirement.
    - NEVER let the system run til inverter shutdown, that will kill batteries quickly.
    - 0.1C charge rate for FLA
    - 100% charge required at LEAST once a week.
    - just big enough inverter
    - just big enough genset.

    If we assume your daily loads are, say: 2kWh/day. Then, the size battery you need is 2kW/d / 0.5 = 4kWh or
    166Ah at 24V. (For the sake of the illustration we'll round that up to 215AH - GC2.)

    To charge this, to get the best fuel economy etc we want to run the genset at the peak charge rate for FLA which is 0.1C: so charge rate is 215Ah*0.1 = 21.5A. So genset only needs to be 24V*21.5A/0.8 (eff) = 645W, and will run for =10h*0.5/0.8= 6.25hrs. Thus a 1kW genset allowance plus whatever else you need to load it up with 3kVA gives you a couple kW for day time loads.

    You can see how in this scenario using a battery with a higher charge rate capability would radically decrease your charge time. If we were to use one of the lithium chemistrys, 0.5C for LFP, or 1C for the lithium nickel maganese  batteries used in EVs. That reduces daily genset run time from 6 hours to sub 1 hour.  Soemthing like a crashed nissan leaf battery is pretty cool. Still not cheap, but you can sell the cells you dont need and come out square. Or else AGM is still going to be help with 0.2C charge rate.

    Either way you dont want to do daily absorbs with a genset, becasue the amps taper and you waste fuel pointlessly. So bring to up to the absorb voltage and stop there for 6 days, and on the 7th day, complete the absorb plus a 2 hours of float, to top off the SG. And for this a small solar addition, even a single panel could be used to do final part of the absorbs. For more tips on this overall use case application check out the marine forums, those guys are masters at this kind of thing at sea.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • castillojcastilloj Posts: 208Solar Expert
    at 120 but thats when i use fridges , Ac, christmas lights.
  • castillojcastilloj Posts: 208Solar Expert
    edited November 2015 #11
    okay so here is what i have,
    I ended up purchasing 8 rolls s-290 batteries. i switched my inverter to a outback FX 48V system from a FX 24 V( I had the 48 system as backup)
    i also have 8 somali 240 watt solar panels hooked up at a morningstar mmpt60.
    Im trying to setup my outback to 48 v settings but i just don't know what the settings should be.
    absorb setpoint-
    absorb time limit-
    float-
    float time period-
    refloat setpoint-
    equalise setpoint-
    equalise time period-

    also what should my battery cutout be Voltage?

    I run the generator from 8 am to noon  then noon to 6 pm i use inverter/solar
    from 6pm to midnight i use the generator
    then from midnight-8 am i run the inverter.



  • BB.BB. Posts: 27,352Super Moderators admin
    • 8 rolls s-290 batteries.
    OK, some some thoughts about the battery. 6 volts @ 220 AH (I think). 8x for 48 volts @ 220 AH battery bank.

    Recommended solar array 5% to 13% rate of charge:
    • 58 volts charging * 220 AH * 1/0.77 panel+controller derating * 0.05 rate of charge = 829 Watt array minimum (weekend/seasonal cabin)
    • 58 volts charging * 220 AH * 1/0.77 panel+controller derating * 0.10 rate of charge = 1,657 Watt array nominal (full time off grid)
    • 58 volts charging * 220 AH * 1/0.77 panel+controller derating * 0.13 rate of charge = 2,154 Watt array maximum "cost effective"
    Your "over night" / daily no sun load, assuming 2 days of storage, 50% maximum discharge:
    • 48 volts * 220 AH * 1/2 days storage * 0.50 max discharge * 0.85 AC inverter eff = 2,244 Watt*Hours per day average load
    And for your power usage:
    • 48 volts * 220 AH * 0.85 inverter eff * C/20 hour discharge rate = 449 Watt average AC load, 5 hours per night x 2 nights
    • 48 volts * 220 AH * 0.85 inverter eff * C/8 hour discharge rate = 1,122 Watt max continous
    • 48 volts * 220 AH * 0.85 inverter eff * C/5 hour discharge rate = 1,795 Watt max minutes to 1 hour loading
    • 48 volts * 220 AH * 0.85 inverter eff * C/2.5 hour discharge rate = 3,590 Watt max surge (seconds)
    More or less, your AC inverter should be in the 1,100 to 1,800 Watt range for that size battery bank.
    • 8 somali 240 watt solar panels
    8x 240 Watt panels = 1,920 Watt array... Or looking at battery bank sizing from the array:
    • 1,920 Watt array * 1/58 volts charging * 0.77 panel+controller derating * 1/0.05 rate of charge = 510 AH @ 48 volts max battery bank
    • 1,920 Watt array * 1/58 volts charging * 0.77 panel+controller derating * 1/0.10 rate of charge = 255 AH @ 48 volts nominal battery bank
    • 1,920 Watt array * 1/58 volts charging * 0.77 panel+controller derating * 1/0.13 rate of charge = 196 AH @ 48 volts min battery bank
    As always, check with the battery manufacture (I am not a battery engineer)--But good starting points would be:

    absorb setpoint- 59.0 volts
    absorb time limit- 2-6 hours (2 hours if lightly using battery bank, 6 hours for heavy usage/winter usage)
    float- 54.4 volts
    float time period- (unlimited)
    refloat setpoint- 50.4 volts (rebulk voltage?)
    equalise setpoint- try 60 volts... But you may need 61 to 62 volts (some industrial batteries need higher voltage)
    equalise time period- Try one hour, then measure SG (minimum equalize time--Only equalize while cell SG is rising, if after 60 minutes, no further rise in SG, then stop EQ).
    • also what should my battery cutout be Voltage?
    Lead Acid batteries do not have a "stable" voltage vs state of charge... 48 volts and light to no load would be ~50% state of discharge. If you have loads, around 46.0 volts would be a good LBCO cut off voltage to try... Some inverters will vary LBCO depending on load.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • castillojcastilloj Posts: 208Solar Expert
    for the solar panels should i wire them 3x3 andx2?
  • BB.BB. Posts: 27,352Super Moderators admin
    What are the Vmp/Imp specifications for your panels? You want the Vmp-array to be around 72 to 100 VDC for that controller (as always, check the specifications). If Vmp is ~30 volts--Then you need three panels in series...

    Here is the MorningStar string calculator website:

    http://string-calculator.morningstarcorp.com/

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • castillojcastilloj Posts: 208Solar Expert
    36.6 vmp
    7.84 imp
    36.6 voc
    8.3 isc
  • BB.BB. Posts: 27,352Super Moderators admin
    Voc and Vmp should not be the same value.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • castillojcastilloj Posts: 208Solar Expert
    30.6 vmp
    7.84 imp
    36.6 voc
    8.3 isc
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    castilloj said:
    i also have 8 somali 240 watt solar panels hooked up at a morningstar mmpt60.
    Im trying to setup my outback to 48 v settings but i just don't know what the settings should be.
    castilloj said:
    30.6 vmp
    BB. said:
     If Vmp is ~30 volts--Then you need three panels in series...
    Castilloj, do you see the problem here?  You need 3, or 6, or 9, or 12 (etc) of those panels in a 48 volt system with that morningstar controller.  You can't use 8 and get a full charge with that controller.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • castillojcastilloj Posts: 208Solar Expert
    oh ok, i hate it that i lost  the 9th to a rock :-(. ill try and purchase a 9th panel.
  • MarkCMarkC Posts: 159Solar Expert ✭✭✭
    zoneblue said:


    Soemthing like a crashed nissan leaf battery is pretty cool. Still not cheap, but you can sell the cells you dont need and come out square. 


    Anyone seriously considered a Leaf for energy storage?  At over 20KWH in a used Leaf for less than $10,000 (used) with engineered battery management - could be a consideration if you need the transportation also.  Don't know much about it, but seems interesting.  Another interesting aspect is the "Fast charge" system - DC charging at a wide variety of input voltages.  Can solar panels be integrated to direct charge thru the CHAdeMO port?  Likely this concept would be for off-grid emergency use only in power failures - not likely to be much use for totally off-grid.  HOWEVER - if panels become much more efficient and cost effective - could you build a whole home energy/EV transportation sized system for totally off-grid economically?

    Bill - do we need to start a new topic on this one?
    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • BB.BB. Posts: 27,352Super Moderators admin
    I would suggest that if somebody wants to discuss Leaf Batteries in detail--That a new thread be started in the New Battery Technologies section.

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