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World Voltage Guide
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World Voltage Guide
Frequently Asked Questions
Parameters          Battery Storage          NiMH Battery Charging

1-Parameters for Battery Performance
Voltage: Normal voltage during discharge, maximum and minimum permissible voltages, discharge curve profile

Duty cycle: Conditions the battery experiences during use. Type of discharge and current drain, e.g., continuous, intermittent, continuous with pulses, etc.

Temperature: In storage and in use. Temperatures that are too high or too low can greatly reduce battery capacity.

Shelf life: How rapidly the cell loses potential while unused.

Service life: Defined either in calendar time or, for secondary cells, possible number of discharge/charge cycles, depending on the battery application. Service life depends on battery design and operational conditions, i.e., the stress put on a battery. For stationary and motive power application, the end of service life is defined as the point at which a battery's capacity drops to 80% of its original capacity. Exceptions would include car batteries where the service life ends when the capacity falls below 60%.

Physical restrictions: These include dimensions, weight, terminals, etc.

Maintenance and resupply: Ease of battery acquisition, replacement, charging facilities, disposal.

Safety and reliability: Failure rates, freedom from outgassing or leakage; use of toxic components; operation under hazardous conditions; environmentally safe

Cost: Initial cost, operating cost, use of expensive materials

Internal resistance: Batteries capable of a high-rate discharge must have a low internal resistance.

Specific energy: As discussed in the definition section, this is a measurement of possible stored energy per kilogram of mass. This number is purely theoretical as it does not take into account the mass of inactive materials, nor the variation in chemical reactions.

Specific power: Also defined in the definitions section, a P=E/t, so the specific power is discussed at a specific discharge rate. It is possible for batteries with a high specific energy to have a low power density if they experience large voltage drops at high discharge rates.

Unusual requirements: Very long-term or extreme-temperature storage; very low failure rate; no voltage delay, etc.

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