An electrical storage device which can come in numerous shapes, sizes, voltages and capacities.

How batteries work?

construction of battery

 

Chemical means of storing electricity

 battery chemicals

Oxygen generated at the positive plate „migrates” through the separator or gel and recombines with spongy lead on the negative plate to form lead sulphate and water.

O2 at +ve plate + 2Pb at –ve plate => 2PbO

PbO + H2SO4 => PbSO4 + H2O

 

 

 

 

 

 

Basic chemistry - Lead Acid

For secondary cells, e.g. Wet Lead acid,
the process is reversible.

If the correct voltage (battery charger) is connected across the electrode terminals, electron (current) flow is reversed. 

Electrical energy is converted into
chemical energy: the battery recharges.

Hydrogen is generated which combines with the sulphate on the +ve and –ve plates. The oxygen combines with the lead on the +ve plate to give lead dioxide and thus we return from  PbSO4 + H2O to PbO + H2SO4 + Pb. 

In wet (vented) lead acid batteries, hydrogen will be given off into the atmosphere!  

Danger!
4% mixture in atmosphere is explosive

 

VRLA BATTERIES

Oxygen generated at the positive plate “migrates” through the separator or gel and recombines with spongy lead on the negative plate to form lead sulphate and water.

O at +ve plate + Pb at -ve plate = PbO

PbO + H2SO4 = PbSO4 & H2O

 

Batteries don’t last forever

  • Physical structure of a lead acid battery
  • Old age
    • Positive grid corrosion & growth
    • Drying out
    • Active material degradation
  • Abuse
    • Over charge
    • Under charge
    • Cycling (LV)
  • Poor Maintenance
    • Reverse polarity
    • Dead short
  • Sulphation
    • Inherent losses (1mA/Ahr)
    • No charge
    • Storage

 

Battery types

Classic

  • Vented (Maintenance)
  • Liquid electrolyte
  • Traditional technology
  • Large application range

AGM

  • VRLA 
  • Low maintenance 
  • Starved electrolyte / Glass Mat
  • Cost effective technology
  • High rate and power performance

GEL

  • VRLA 
  • Gel electrolyte
  • Reliability and Robustness 
  • Good cyclic performance

Ni-Cd

  • VRLA 
  • Very high
  • discharge rate
  • Rugged
  • Expensive
  • Low maintenance