Battery electrical characteristics water consumption ventilation
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BATTERY ELECTRICAL CHARACTERISTICS WATER CONSUMPTION & VENTILATION PowerPoint PPT Presentation


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BATTERY ELECTRICAL CHARACTERISTICS WATER CONSUMPTION & VENTILATION. Water consumption. Water loss is associated with the current used for overcharging.

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BATTERY ELECTRICAL CHARACTERISTICS WATER CONSUMPTION & VENTILATION

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Battery electrical characteristics water consumption ventilation

BATTERYELECTRICALCHARACTERISTICSWATERCONSUMPTION& VENTILATION


Water consumption

Water consumption

  • Water loss is associated with the current used for overcharging.

  • A battery which is constantly cycled, (i.e. is charged and discharged on a regular basis), will consume more water than a battery on standby operation.

    • Example :

      • Decomposition of 1 cm³ (1g) H2O requires - 3 Ah


Battery electrical characteristics water consumption ventilation

Water consumption

  • The overcharge current is a function of both voltage and temperature, so both have an influence on the consumption of water.

  • Example : An SBM 161 is floating at 1.43 V/cell

    • The electrolyte reserve for this cell is 500 cm3

    • M type cell at 1.43 V/cell will use 0.27 cm3/month for one Ah of capacity

    • 0.27 x 161 = 43.5 cm3 per month and the electrolyte reserve will be used 500 / 43,5 = 11.5 months.


Water consumption1

Water consumption

S/PBE


Ventilation

Ventilation

  • Gas generation

  • Charging (float, boost) gas generation

    • 1 Ah overcharge decomposes H2O into :

      • 0.42 l H2 + 0.21 l 02

    • Decomposition of 1 cm³ (1g) H2O requires :

      • 3 Ah

    • Safety limit from gas explosion

      • < 4% vol hydrogen concentration


Ventilation1

Ventilation

  • Ventilation requirements :

    • The purpose of ventilating a battery location is to maintain the hydrogen concentration below 4% (US 2%) vol hydrogen threshold.

    • Check the local regulations regarding battery installation and ventilation.


Ventilation2

Ventilation

  • Ventilation air flow (Q) calculation formula is :

  • Q = 0.05 x n x Igas x Crt x 10¯³ [m³ / h]

Current producing gas in mA

per Ah rated capacity

Number of cells

Capacity C5 for NiCd cells


Battery electrical characteristics water consumption ventilation

Ventilation

  • The current producing gas is determined by the formulas :

    Igas = Ifloat x fg x fs [mA / Ah]

    Igas = Iboost x fg x fs [mA / Ah]


Ventilation3

The consequence of any increase in the temperature up to a max. 40°C has been accommodated in the values in the table.

Ventilation

  • Electrical protection against charger malfunction must be provided. If not the ventilation should be calculated to correspond with the maximum current available from the charger


Ventilation4

Ventilation

  • Calculation method :

    • 0,42 liter hydrogen per overcharged Ah per cell are max. produced during overcharge

    • 24 Dilution factor to avoid a 4% hydrogen concentration in the air. ((100% - 4%) / 4%)

    • 5 General safety factor.

    • Current (Igas) during overcharge (Including safety factors)

      • 5 mA/Ah during floating at 1,40 V to 1,43 V at 20°C

      • 50 mA/Ah during boost at 1,50 V to 1,55 V at 20°C

    • resulting in a required ventilation of :

      • 50 liter (or 0,05 m3) air ventilated per overcharged Ah for each cell


Battery electrical characteristics water consumption ventilation

Ventilation (only for US)

  • Calculation method :

    • 0,42 liter hydrogen per overcharged Ah per cell are max. produced during overcharge

    • 49 Dilution factor to avoid a 2% hydrogen concentration in the air. ((100% - 2%) / 2%)

    • 5 General safety factor.

    • Current (Igas) during overcharge (Including safety factors)

      • 5 mA/Ah during floating at 1,40 V to 1,43 V at 20°C

      • 50 mA/Ah during boost at 1,50 V to 1,55 V at 20°C

    • resulting in a required ventilation of :

      • 100 liter (or 0,1 m3) air ventilated per overcharged Ah for each cell


Ventilation5

Ventilation


Ventilation6

Ventilation


Ventilation7

Ventilation


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