Datasheet

Rechargeable Button Cells
4.7 MULTICELL BATTERIES
BATTERY ASSEMBLY RECOMMENDATION
1. Connection between Cells
When NiMH cells are connected, spotwelding methods
are to be used. This is to avoid excessive temperature
rise of the cell which would occur if soldered on to them.
Tags used for cell connections should be nickel plated.
They should have a 0.1–0.2 mm thickness and be
3–6 mm wide.
The temperature of NiMH cells or batteries rises when
the charge gets close to completion. Temperature rise is
larger for a battery pack than for a single cell because
of different heat dissipation; the temperature rise is even
greater when the cells are enclosed in a plastic case.
In the final stage of the charging period the temperature
of cells enclosed in a plastic case becomes about +10°C
higher than in the case of cells with wide spacing. The
charge efficiency also decreases with an increase in
temperature.
Therefore, when a NiMH battery is being designed, it
is important to make provisions for a temperature rise
during charge as low as possible by means of facilitating
good heat dissipation. This is achieveable with appro-
priate design of the plastic case surface.
Air ventilation should be provided in the plastic cases of
batteries to allow for egress of any gasses which may
result from activation of the PRV of cells after abuse.
Deflection space should be considered in the battery
compartment to assure proper function of PRV.
2. Thermal Protection for Battery Packs
Battery packs exceeding 3 cells intended for fast charg-
ing methods (HR and HRT-Family) need to have a ther-
mal protection device. A thermistor (NTC) which allows
the charger sensing the temperature inside the pack is
to be implemented. An accuracy of 1% of such device is
recommended.