Battery cycle

HumMichael
HumMichael Registered Users Posts: 26 ✭✭
edited March 2017 in Solar Beginners Corner #1
When a battery manufacturer speaks of battery cycle, what do they mean?
Down to what % capacity to full charge is a cycle?
If I only bring it down to 80% discharge before recharging, is that still a cycle?

Thanks
Sincerely
Michael
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #2
    Good question.

    Have a warranty claim, 90 to 100% state of charge is cycle... :wink:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • HumMichael
    HumMichael Registered Users Posts: 26 ✭✭
    #3
    Bill
    Basically. a techniical jargon. Haha.
    Thanks
    Sincerely
    Michael
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,654 admin
    #4
    Is one reason we try to get people to cycle their system by ~25% per day.

    Shallow cycling is not good. Deep cycling (below 50%) with several day recharging (typical with solar power) is not good either.

    The typical industrial battery has grid power for full recharging in 8 hours or so. Does not fit how solar folks can operate their systems (limitation of sun vs 24 hour per day grid).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #5
    Well, if we're talking *warranty* cycles, that's different ;-) Those cycles are always definied by the failure of the battery, both in number and in depth.

    Seriously though, the idealized life of a lead acid battery will be defined by a curve, where number of cycles declines with increasing depth of discharge. For example, three points on the curve might be 100 cycles at 75% DOD, 500 cycles at 50% DOD or 1000 cycles at 25%.

    In real life, it's more complicated. A battery only very lightly cycled can die of old age before it dies of overwork. A battery left partly discharged will die even with very few cycles. An overcharged battery can dry out and fail. Batteries stored at too high or low temps can fail, etc Then there's the question of defining failure and end of life. Is it 80% of capacity, if so, tested how?

    In other words, a general understanding of a vendor's curve might help, but don't take one as anything but a rough, idealized, likely marketing inspired guide.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited March 2017 #6
    HumMichael said:
    Bill

    Basically. a techniical jargon. Haha.
    Thanks
    Sincerely
    Michael
    Here is some useful information, technical but not jargon.
    Although it is primarily about VRLA, the basic information regarding life vs depth of discharge and effects of temperature  are true to all lead acid batteries. 

    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.  
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