What is considered a "charge cycle"

pabloesguapopabloesguapo Solar Expert Posts: 116 ✭✭
My battery bank is a little small this time around (630Ah),
but it's what we could afford.  On an average overnight, 
the battery bank drains down to about 55%, SOC, without 
any "intervention" by the generator.  I have the Mate 3s AGS voltage
start set at aca 55%.  One of these days, I'll be able to afford a
Flexnet DC and be able to set a voltage stop point too.  Currently, I'm 
setting a "quiet time" stop point, so the generator doesn't  
charge the batteries too much, and we waste all that free sunshine
the next day.  I'd rather not burn all that propane if I don't have 
To.

My questions are:

-is this an advisable course of action in the first place?

-is it better for the batteries to partially charge them like this,  to prevent their SOC
from going too low, or am I inadvertantly adding charge cycles to 
these batteries, thereby shortening their overall lifespan?

-is a generator assisted partial charge, set to end just before dawn,
considered a charge cycle, or the beginning or end of one?

Thoughts?  Suggestions?


27 Kyocera panels, 6,500w
24 CG2 6v batteries, 48v, 630Ah
Midnite Classic 150 & Classic 150 Lite in "follow me" mode
(2) Outback fx3648 inverters
Generac ecogen 6kw backup generator
Mate3s

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,015 admin
    In theory, a cycle is "any charge" then "discharge"... Charge by 5% and discharge  by 5% is a "cycle". You can find charts that have cycle depth vs cycle life... A first approximation is that a 25% discharge battery will last 2x longer vs a 50% discharge cycle battery (a 25% cycle battery bank may last 6 years, and a 50% discharge battery bank may last 3 years--made up numbers). For example:

    https://www.solar-electric.com/learning-center/deep-cycle-battery-faq.html/

    Typical deep cycle lead acid Cycle life vs depth of discharge... 25% = 2,000 cycle life; 50% = 1,000 cycle life


    More or less--For lead acid batteries, they take "time" to recharge. A 50% cycled battery can take roughly 10% rate of charge is 5 hours to "charge" and another 6 hours to "absorb" (battery bank takes less current as battery is >~80% State of Charge to 100% state of charge... So you are looking at almost 11 hours of charging (very rough estimate) when 50% cycled--Longer than the sun is up and charging for most people.

    A 25% cycled battery only need around 2.5 hours (10% rate of charge) + 2 hours of Absorb for ~4.5 hours of charging--Fully charged by early afternoon.

    More or less, FLA batteries are very efficient charging (close to 100%) as they charge from 0% to 80% State of charge (bulk). From 80% to 100% SoC, they become less efficient (absorb charging phase).

    So--If you can load your propane genset >~50% of rated output (propane and gasoline gensets are generally most fuel efficient >=50% loading). And charge battery bank up to ~80% SoC (say genset very early charging in the morning for 3 hours @ 10% rate of charge) then stop the genset, and for >80% SoC, let the solar charging finish charging from 80% to 100%...

    So, basically run the genset just enough so you can get your battery bank finished charged with the solar array.

    Just to give some numbers to above (note using 10% here--13% or a bit more is OK too):
    • 630 AH * 10% rate of charge = 63 Amps
    • 63 amps * 59 volts charging = 3,717 Watts
    • 3,717 Watt charging / 0.80 charger efficiency = 4,646 VA (sort of Watts) estimated Genset loading
    • 6,000 VA genset * 0.80 suggested max continuous loading = 4,800 VA max loading (suggested)
    So--That seems doable (depending on what you are using for your AC charger).

    Note that a larger battery bank would need a larger solar array/genset to keep 10% rate of charge (usual minimum suggested by FLA battery manufacturers).

    People the cycle their FLA battery banks a lot... There is a school of thought that you can cycle (for example) 50% to 75% every day, and only need to charge to >90% once a week (one vendor said once in 30 days)... And the FLA batteries will not sulfate while actively cycling (battery setting below ~75% SoC for hours/days/weeks sulfate and eventually fail--Sulfation is not reversible--Desulfators are out there but have a "mixed" bag of results. Better not to let the batteries sulfate in the first place).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,015 admin
    Reviewing your energy usage before going even larger--Always a good idea. Usually cheaper to conserve energy than to generate it.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pabloesguapopabloesguapo Solar Expert Posts: 116 ✭✭
    Thanks.  That all pretty much falls in libewith what I'm doing.  
    27 Kyocera panels, 6,500w
    24 CG2 6v batteries, 48v, 630Ah
    Midnite Classic 150 & Classic 150 Lite in "follow me" mode
    (2) Outback fx3648 inverters
    Generac ecogen 6kw backup generator
    Mate3s
  • mike95490mike95490 Solar Expert Posts: 9,362 ✭✭✭✭✭
    You need to monitor your battery charging .  If you are reaching a full charge daily, you don't need generator

    If you find you need to run generator, run it in the morning, so your charger most efficient to recharge low batteries. Let the solar finish the charge off and save your  fuel.
    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 ,

  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    mike95490 said:
    If you find you need to run generator, run it in the morning, so your charger most efficient to recharge low batteries. Let the solar finish the charge off and save your  fuel.
    Assuming lead acid this statement is true, with Lithium it would be better to wait until the end of the day as there is no absorption, just maximum current until charged enough to get through the night, being that partial state of charge is not an issue.

    During my lead acid days I found using the generator in the morning was almost a gaurentee the overcast sky would clear.
    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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