Another battery Queestion

petertearaipetertearai Solar Expert Posts: 471 ✭✭✭✭
Another question. Is running the vacume 65 amps at nominal 12 volts have the same or similar effect as an eqilize in that it willl mix the electrolite ? Also is 65 amps for 10 min or so ok on my 900 ah batts. Assuming a soc of approx 90%
Thanks for your replys I am finding this forum very informative.
Regards Peter
2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 


  • BB.BB. Super Moderators, Administrators Posts: 32,994 admin
    Re: Another battery Queestion


    It is the formation of Hydrogen and Oxygen gas on the plates while charging that "stirs" the electrolyte--Not just any heavy current flow (discharging in your case with the loads does not generate gas at the plate/electrolyte boundaries).

    A good starting Rule of Thumb for Flooded Cell Lead Acid Batteries. Note Battery Amp*Hour Capacity is spec'ed here at the 20 Hour Rate:
    • C/20 (5%) minimum rate of charge--planned long term discharge rate (efficient)
    • C/10 (10%) about the optimum maximum rate of charging (recommended for tall "L16" type batteries) and discharging.
    • C/8 (12.5-13%) Generally the maximum continuous charge/discharge rate for flooded cell batteries. Run risk of overheating batteries with higher rates of continuous current flow.
    • C/2.5 (40%) maximum short term recommended surge current (starting loads for pumps, minimum battery bank capacity for Hybrid Inverter systems). Current in excess of C/2.5 for flooded cell may take the battery bank outside of 10.5-15.5 volt range (12 volt bank reference).
    The above is my recommendations on posts I have read over the last few years here (and other Mfg. recommendations).

    For your 900 AH battery bank (assuming 20 Hour Specification):
    • 900 AH * 1/20 = 45 Amps minimum recommended charging current / optimum long term discharge current
    • 900 AH * 1/10 = 90 Amps Optimum maximum current
    • 900 AH * 1/8 = 112.5 Amps maximum continuous current
    • 900 AH * 1/2.5 = 360 Amps maximum short term current (well pump starting surge, etc.)
    Feel free to discuss offer other suggestions. Just one guy's opinion.

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