Technical Evaluation of Nickel Cadmium Batteries and VRLA Batteries

In Present scenario where energy storage is increasing rapidly, we should aware of Battery Technology. Presently lots of batteries are in the market but Industrial preferences are Nickel Cadmium and VRLA Battery due to its reliability and cost.

Comparison between Ni-Ca Vs VRLA batteries

Reliability :

Nickel Cadmium :

  • Very High
  • Extremely good reliability. No components are affected by the electrochemical reactions or by the electrolytic ageing, proven since many decades.
  • Reliable performance also after storage overcharging and even reversal of polarity.

VRLA :

  • Moderate
  • Electrolyte involved in the chemical reaction all the time. This leads to varying corrosion, resistance and growth behavior of the electrodes. Over a period of time battery may have sudden death.
  • After an idle period, sulphation may take place and the battery performance.

Performance at High and Low Temperatures :

Nickel Cadmium :

  • Recommended max. Temp. for continuous operation is 45 deg C. Occasional operation at 60 deg C lowers the capacity temporarily by 5-10% but no permanent effect.
  • Long time storage at 60-80 deg C will not deform the battery containers and will little affect the capacity.
  • Can be used down to –50 deg C with stronger Electrolyte. Freezing doesn’t harm the battery.

VRLA :

  • Recommended operating temperature is 27 deg C Operation at higher temp. curtails the life expectancy considerably.
  • Storage at 60-80 deg C will rapidly discharge (self-discharge) the battery.
  • Discharged battery may freeze at –10 deg C. Freezing harmful to the battery.

Charging Properties :

Nickel Cadmium :

  • Can be charged by any standard method in the temperature range of -5 deg  to +45 deg C.
  • Is not affected by high charging rates.
  • Is not affected by partial charging.

VRLA :

  • Great care must be taken during charging. Low Charging currents are necessary to avoid excessive formation of sludge from the positive plate and densification of the negative plate, which will lead to decreased capacity and shorter life. High charge rates also result in risks for short-circuiting. High temperatures during charging increases the risks for short circuiting owing to attack of acid on separators and plates.
  • Over charging, even at low charge current, is detrimental resulting in decreased capacity and shorter life.
  • Partial Charging results in sulphation of plates. This in turn may lead to buckling of plates.

Expected Life :

Nickel Cadmium :

  • 15 – 20 years
  • Due to Nickel fiber structure no swelling of the electrode.
  • No loss of contact between active material and fiber matrix.
  • No corrosion of the conducting fiber matrix due to pure active materials.

VRLA :

  • 8 – 10 years
  • Tendency of electrodes to swell and shedding of active mass. Over a period of time, reduces the life.

Storage:

Nickel Cadmium :

  • Upto 9 months for filled & charged battery without giving freshening charge.
  • Upto 10 years for dry & discharged batteries

VRLA :

  • Upto 6 months without freshening charge.

Resistance to abuse :

Nickel Cadmium :

  • Mechanically very rugged due to the strength of steel components and the carefully welded and bolted design of the cells. Can stand very severe shocks and vibrations.
  • Excellent resistance to electrical abuse. Can be overcharged, deep discharged, polarity reversed and short-circuited without permanent damage.

VRLA :

  • Mechanically strong; however, lead components are weaker than steel.
  • Sensitive to overcharging, deep discharging, polarity reversal and short-circuiting which will damage the battery. 

Voltage Recovery:

Nickel Cadmium :

  • Very Fast

VRLA :

  • Several Hours

Discharge Performance :

Nickel Cadmium :

  • Very Good

VRLA :

  • Moderate

Float voltage :

Nickel Cadmium :

  • Ranges between 1.38 to 1.42 volt per cell

VRLA :

  • Constant voltage: 2.25 volt per cell

Internal Resistance :

Nickel Cadmium :

  • Lowest – Less heat loss.

VRLA :

  • Moderate – More heat loss.

Operating Temperature :

Nickel Cadmium :

  • – 50 deg C to 55 deg C

VRLA :

  • – 10 deg C to 55 deg C

Above comparison is only for information only. To get exact data please refer vendor product datasheet.

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