NS（国半）的充电电池基础知识！

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NS（国半）的充电电池基础知识！
17p

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BATTERY CHARGING
Introduction
The circuitry to recharge the batteries in a portable product is an important part of any
power supply design.  The complexity (and cost) of the charging system is primarily
dependent on the type of battery and the recharge time.
This chapter will present charging methods, end-of-charge-detection techniques, and
charger circuits for use with Nickel-Cadmium (Ni-Cd), Nickel Metal-Hydride (Ni-MH),
and Lithium-Ion (Li-Ion) batteries.
Because the Ni-Cd and Ni-MH cells are similar in their charging characteristics, they will
be presented in a combined format, and the Li-Ion information will follow.

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NI-CD/NI-MH CHARGING INFORMATION
In the realm of battery charging, charging methods are usually separated into two gen-
eral categories:  Fast charge is typically a system that can recharge a battery in about
one or two hours, while slow charge usually refers to an overnight recharge (or longer).
Slow Charge
Slow charge is usually defined as a charging current that can be applied to the battery
indefinitely without damaging the cell (this method is sometimes referred to as a trickle
charging).
The maximum rate of trickle charging which is safe for a given cell type is dependent on
both the battery chemistry and cell construction.  When the cell is fully charged, contin-
ued charging causes gas to form within the cell.  All of the gas formed must be able to
recombine internally, or pressure will build up within the cell eventually leading to gas
release through opening of the internal vent (which reduces the life of the cell).
This means that the maximum safe trickle charge rate is dependent on battery chemis-
try, but also on the construction of the internal electrodes.  This has been improved in
newer cells, allowing higher rates of trickle charging.
The big advantage of slow charging is that (by definition) it is the charge rate that
requires no end-of-charge detection circuitry, since it can not damage the battery
regardless of how long it is used.  This means the charger is simple (and very cheap).
The big disadvantage of slow charge is that it takes a long time to recharge the battery,
which is a negative marketing feature for a consumer product.

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