| BATTERY KNOWLEDGE |

Welcome to our battery knowledge page. Here you will find some quick notes on batteries and battery assemblies. This page is designed to help our customers become more familiar with the general principles of battery assemblies. If you have questions or would like us to add more information relevant to your needs, please contact us.

Basic Assembly Process:

• Individual cells are glued together into a configuration:
  
  
  
  
• Resistance spot welding is used to attach nickel strip material between the negative and positive terminals of the cells. This will turn a group of cells into a battery pack that has a voltage which a multiple of the number of cells (for example: a 10 cell assembly of NiCd or NiMH cells (1.2v per cell) is a 12 volt battery pack):
  
  
  
  
• Circuit protective devices such as resettable fuses are added to the assembly. These components usually take the place of the nickel strip mentioned above and will act as the connection between cells:
  
  
• The assembly is often shrink wrapped to insulate the cells and prevent short circuits:
  
  
  
  
• Finally, if the battery pack is to attach externally to a device, the battery may be housed in a plastic housing:
  
  

 

Some Typical Equations and Chemical Reactions:

Ohm's Law: E=I*R (E=Volts, I=Amps, R=ohms)
Power: P=E*I or P=(I*I)*R (P=Watts)
Amp-Hours: expected life (hours)*Average amps=Amp-Hours

Current (Amp)=Volts/Resistance
Resistance (ohms)=Voltage/Current
Voltage=Current*Resistance

NiCD:

At the positive
NiOOH + H20 + e- Ni(OH)2 + OH-

At the negative
Cd + 2OH Cd(OH)2 + 2e-

Overall
2NiOOH + Cd + 2H2O 2Ni(OH)2 + Cd(OH)2

NiMH:

At the positive
NiOOH + H20 + e- Ni(OH)2 + OH-

At the negative
MH + OH- M + H2O + e-

Overall
NiOOH + MH Ni(OH)2 + M
(M: Hydrogen absorbing allowy, MH: Metal Hydride)

Lithium Primary :

At the negative
(Li-Al ) Al + Li+ + e-

At the positive
MnO2 + Li+ + e- MnO2 (Li+)

Overall
MnO2 + (Li-Al) MnO2(Li+) + Al
(Li-Al : lithium alluminum alloy)

Glossary of Common Battery Terms:

• Battery - a device that converts energy, by chemical reaction or physical reaction, into electric current.
• Primary Battery - energy is exhausted when active materials are consumed (carbon-zinc dry cell, lithium battery, silver oxide battery, alkaline battery)
• Secondary Battery - active materials are regenerated by charging (nickel cadmium (NiCd), nickel metal hydride (NiMH), Lithium Ion, Lithium Polymer, Sealed Lead Acid.
• Series Connection - Connection of a group of battery cells by sequentially interconnecting the terminals of opposite polarity thereby increasing the voltage of the battery group but not increasing capacity (i.e. positive to negative connections).
• Parallel Connection - Connection of a group of batter cells by interconnecting all terminals of the same polarity, thereby increasing the capacity of the battery group but not increasing the voltage (i.e. positive to positive and negative to negative).
• Cadmium - Chemical symbol Cd. This metallic element is the chemically active material of a nickel cadmium battery's negative electrode. When the battery is charged, the negative electrode surface consists of cadmium. As the battery discharges, the cadmium progressively changes into cadmium hydroxide (Cd (OH2)).
• Cadmium Hydroxide - Active material used at the negative electrode of the Nickel-Cadmium Cell.
• Metal Hydride - A general name for chemical compounds consisting of metal elements and hydrogen.
• Nickel Hydroxide - The active material in the positive electrode of NiMH and NiCd batteries.
• Nickel Oxyhydroxide - The chemical name of NiOOH. Indicates that oxidation of Ni (OH)2 has progressed, and that the active material of the positive electrode of an NiCd or NiMH battery is charged.
• Capacity - The quantity of electricity that can be obtained from a battery in one cycle from full charge to full discharge when the battery is discharged under conditions of rated current level and ambient temperature within the predetermined range. Generally, capacity is expressed in units of mAh (milliampere-hour).
• Nominal Capacity - The standard capacity designated by a battery manufacturer to identify a particular cell model.
• Nominal Voltage - The standard voltage used to express the capacity of a particular battery model. It is generally equal to its electromotive force or its approximate voltage during normal operation. Typical Values:
  • 1.2 volts per cell for NiCd and NiMH
  • 3.6 or 3.7 volts per cell for Lithium Ion or Lithium Polymer
  • 3 volts per cell for lithium primary
  • 2 volts per cell for sealed lead acid
  • 1.5 volts per cell for alkaline and carbon zinc
    
• Discharge Rate - The discharge rate is the rate at which current is removed from a battery. When a battery is discharged at a current level "i", for a period until the end discharge voltage is '"h", the discharge is referred to as the h-hour rate discharge, while "i" is known as the h-hour rate discharge current. For practical use, nominal capacity is used as standard.
• End-Voltage - The voltage that indicates the end limit of discharge. This voltage is almost equivalent to limitation of practical use. Typical values:
  • 1.0 volt per cell for NiCd and NiMH
  • 1.75 volts per cell for sealed lead acid
  • 2.75 volts per cell for lithium ion and lithium polymer
  • 2.0 volts per cell for primary lithium
  • 0.9 volts per cell for alkaline and carbon zinc
• Open circuit voltage - The voltage between terminals of a battery without any load.
• Operating voltage - The voltage between terminals when a battery is subjected to a load. Usually expressed by the voltage of the battery at 50% discharge point.
• Polarity Reversal - Reversing of polarity of the terminals of a small-capacity cell in a multi-cell battery due to overdischarge.
• Positive Electrode - The electrode which has a positive potential. Electric current from this electrode flows in the external circuit during discharge.
• Negative Electrode - The plate which has an electrical potential lower than that of the other plate during normal cell operation. Electric current from the external circuit flows into the cell at the negative electrode during discharge. Also called minus electrode.
• Self-Discharge - a decrease in battery capacity which occurs without any current flow to an external circuit. Typical values:
  • 1% per day for NiCd
  • 2% per day for NiMH
  • ~0% per day for Lithium Ion and Lithium Polymer
• Short Circuit - Directly connecting the positive electrode (terminal) to the negative electrode (terminal) of the battery.
• Thermistor - A circuit element with a negative temperature coefficient. It is built into batteries and used to detect ambient temperature or battery temperature. A battery charger may use this device to properly charge a battery.