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BATTERY ELECTRICAL CHARACTERISTICS WATER CONSUMPTION & VENTILATION

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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  1. BATTERYELECTRICALCHARACTERISTICSWATERCONSUMPTION& VENTILATION

  2. 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

  3. 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.

  4. Water consumption S/PBE

  5. 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

  6. 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.

  7. 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

  8. 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]

  9. 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

  10. 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

  11. 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

  12. Ventilation

  13. Ventilation

  14. Ventilation

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