NICKEL METAL HYDRIDE HANDBOOK, PAGE 3 AUGUST 2005

PRECAUTIONS FOR DESIGNING DEVICES WITH NI-MH BATTERIES

Underlined sections indicate information
that is especially important
In order to take full advantage of the properties of Ni-
MH batteries and also to prevent problems due to
improper use, please note the following points
during the use and design of battery operated
products.
1. Charging
1.1 Charging temperature
Charge batteries within an ambient temperature
range of 0C to 40C.
Ambient temperature during charging affects
charging efficiency. Since charging efficiency is
best within a temperature range of 10C to
30C, whenever possible, place the charger
(battery pack) in a location that is within this
temperature range.
At temperatures below 0C the gas absorption
reaction is not adequate, causing gas pressure
inside the battery to rise, which can activate the
safety vent and lead to leakage of alkaline gas
and deterioration in battery performance.
Charging efficiency drops at temperatures
above 40C. This can disrupt full charging and
lead to deterioration in performance and battery
leakage.
1.2 Parallel charging of batteries
Sufficient care must be taken during the design
of the charger when charging batteries
connected in parallel.
Consult Panasonic when parallel charging is
required.
1.3 Reverse charging
Never attempt reverse charging.
Charging with polarity reversed can cause a
reversal in battery polarity causing gas pressure
inside the battery to rise, which can activate the
safety vent, lead to alkaline electrolyte leakage,
rapid deterioration in battery performance, battery
swelling or battery rupture.
1.4 Overcharging
Avoid overcharging. Repeated overcharging can
lead to deterioration in battery performance.
(Overcharging means charging a battery when it
is already fully charged.)
1.5 Rapid charging
To charge batteries rapidly, use the specified
charger (or charging method recommended by
Panasonic) and follow the correct procedures.
1.6 Trickle charging (continuous charging)
Trickle charging cannot be used with Ni-MH batter-
ies. However, after applying a refresh charge using
a rapid charge, use a trickle charge of 0.033 CmA
to 0.05 CmA.
Also, to avoid overcharging with trickle charge,
which could damage the cell characteristics, a
timer measuring the total charge time should be
used.
Note : CmA
During charging and discharging, CmA is a value
indicating current and expressed as a multiple of
nominal capacity. Substitute C with the batterys
nominal capacity when calculating. For example,
for a 1500mAh battery of 0.033CmA, this value is
equal to 1/30 1500, or roughly 50mA.
NICKEL METAL HYDRIDE HANDBOOK, PAGE 4 AUGUST 2005
2. Discharging
2.1 Discharge temperature
Discharge batteries within an ambient tempera-
ture range of -10C to +45C.
Discharge current level (i. e. the current at which
a battery is discharged) affects discharging
efficiency. Discharging efficiency is good within a
current range of 0.1 CmA to 2 CmA.
Discharge capacity drops at temperatures below
-10C or above +45C. Such decreases in
discharge capacity can lead to deterioration in
battery performance.
2.2 Overdischarge (deep discharge)
Since overdischarging (deep discharge) damages
the battery characteristics, do not forget to turn off
the switch when discharging, and do not leave the
battery connected to the equipment for long
periods of time. Also, avoid shipping the battery
installed in the equipment.
2.3 High-current discharging
As high-current discharging can lead to heat
generation and decreased discharging effi-
ciency, consult Panasonic before attempting
continuous discharging or pulse discharging at
currents larger than 2 CmA.
3. Storage
3.1 Storage temperature and humidity (short-term)
Store batteries in a dry location with low humidity,
no corrosive gases, and at a temperature range
of -20C to +45C.
Storing batteries in a location where humidity is
extremely high or where temperatures fall below -
20C or rise above +45C can lead to the rusting
of metallic parts and battery leakage due to
expansion or contraction in parts composed of
organic materials.
3.2 Long-term storage (1 year, -20C to +35C)
Because long-term storage can accelerate
battery self-discharge and lead to the deactivation
of reactants, locations where the temperature
ranges between +10C and +30C are suitable
for long-term storage.
When charging for the first time after long-term
storage, deactivation of reactants may lead to
increased battery voltage and decreased battery
capacity. Restore such batteries to original
performance by repeating several cycles of
charging and discharging.
When storing batteries for more than 1 year,
charge at least once a year to prevent leakage
and deterioration in performance due to self-
discharging.
4. Service Life of Batteries
4.1 Cycle life
Batteries used under proper conditions of charg-
ing and discharging can be used 500 cycles or
more.
Significantly reduced service time in spite of
proper charging means that the life of the battery
has been exceeded.
Also, at the end of service life, an increase in
internal resistance, or an internal short-circuit
failure may occur. Chargers and charging circuits
should therefore be designed to ensure safety in
the event of heat generated upon battery failure at
the end of service life.
4.2 Service life with long-term use
Because batteries are chemical products involv-
ing internal chemical reactions, performance
deteriorates not only with use but also during
prolonged storage.
Normally, a battery will last 2 years (or 500
cycles) if used under proper conditions and not
overcharged or overdischarged. However, failure
to satisfy conditions concerning charging, dis-
charging, temperature and other factors during
actual use can lead to shortened life (or cycle
life) damage to products and deterioration in
performance due to leakage and shortened
service life.
PRECAUTIONS FOR DESIGNING DEVICES WITH NI-MH BATTERIES- CONTINUED
NICKEL METAL HYDRIDE HANDBOOK, PAGE 5 AUGUST 2005
5. Design of Products Which Use Batteries
5.1 Connecting batteries and products
Never solder a lead wire and other connecting
materials directly to the battery, as doing so will
damage the batterys internal safety vent, separa-
tor, and other parts made of organic materials.
To connect a battery to a product, spot-weld a tab
made of nickel or nickel-plated steel to the
batterys terminal strip, then solder a lead wire to
the tab.
Perform soldering in as short a time as possible.
Use caution in applying pressure to the terminals
in cases where the battery pack can be sepa-
rated from the equipment.
5.2 Material for terminals in products using the
batteries
Because small amounts of alkaline electrolyte
can leak from the battery seal during extended
use or when the safety vent is activated during
improper use, a highly alkaline-resistant material
should be used for a products contact terminals
in order to avoid problems due to corrosion.
(Note that stainless steel generally results in higher contact resistance.)
5.3 Temperature related the position of batteries in
products
Excessively high temperatures (i.e. higher than
45C) can cause alkaline electrolyte to leak from
the battery, thus damaging the product and
shorten battery life by causing deterioration in the
separator or other battery parts. Install batteries
far from heat-generating parts of the product.
The best battery position is in a battery compart-
ment that is composed of an alkaline-resistant
material which isolates the batteries from the
products circuitry. This prevents damage that
may be caused by a slight leakage of alkaline
electrolyte from the battery.
5.4 Discharge end voltage
The discharge end voltage is determined by the
formula given below. Please set the end voltage
of each battery at 1.1 volts or less.
5.5 Overdischarge (deep discharge) prevention
Overdischarging (deep discharging) or reverse
charging damages the battery characteristics. In
order to prevent damage associated with forget-
ting to turn off the switch or leaving the battery in
the equipment for extended periods, preventative
options should be incorporated in the equipment.
At the same time, it is recommended that leak-
age current is minimized. Also, the battery should
not be shipped inside the equipment.
PRECAUTIONS FOR DESIGNING DEVICES WITH NI-MH BATTERIES- CONTINUED
High Alkaline-resistant Metals
Nickel, stainless steel, nickel-
plated steel, etc.
Tin, aluminum, zinc, copper, brass,
etc.
Low Alkaline-resistant Metals
Number of Batteries Arranged Serially
1 to 6
7 to 12
(Number of batteries x 1.0) V
((Number of batteries - 1) x 1.2) V
NICKEL METAL HYDRIDE HANDBOOK, PAGE 6 AUGUST 2005
6. Prohibited Items Regarding the Battery
Handling
Panasonic assumes no responsibility for prob-
lems resulting from batteries handled in the
following manner.
6.1 Disassembly
Never disassemble a battery, as the electrolyte
inside is strong alkaline and can damage skin and
clothes.
6.2 Short-circuiting
Never attempt to short-circuit a battery. Doing so
can damage the product and generate heat that
can cause burns.
6.3 Throwing batteries into a fire or water
Disposing of a battery in fire can cause the
battery to rupture. Also avoid placing batteries in
water, as this causes batteries to cease to
function.
6.4 Soldering
Never solder anything directly to a battery. This
can destroy the safety features of the battery by
damaging the safety vent inside the cap.
6.5 Inserting the batteries with their polarities re-
versed
Never insert a battery with the positive and nega-
tive poles reversed. as this can cause the battery
to swell or rupture.
6.6 Overcharging at high currents and reverse
charging
Never reverse charge or overcharge with high
currents (i.e. higher than rated). Doing so causes
rapid gas generation and increased gas pressure,
thus causing batteries to swell or rupture.
Charging with an unspecified charger or specified
charger that has been modified can cause batter-
ies to swell or rupture. Be sure to indicate this
safety warning clearly in all operating instructions
as a handling restriction for ensuring safety.
PRECAUTIONS FOR DESIGNING DEVICES WITH NI-MH BATTERIES- CONTINUED
6.7 Installation in equipment (with an airtight battery
compartment)
Always avoid designing airtight battery compart-
ments. In some cases, gases (oxygen, hydro-
gen) may be given off, and there is a danger of
the batteries bursting or rupturing in the presence
of a source of ignition_(sparks generated by a
motor switch, etc.).
6.8 Use of batteries for other purposes
Do not use a battery in an appliance or purpose
for which it was not intended. Differences in
specifications can damage the battery or appli-
ance.
6.9 Short-circuiting of battery packs
Special caution is required to prevent short-
circuits.
Care must be taken during the design of the
battery pack shape to ensure batteries cannot be
inserted in reverse. Also, caution must be given
to certain structures or product terminal shapes
which can make short-circuiting more likely.
6.10 Using old and new batteries together
Avoid using old and new batteries together. Also
avoid using these batteries with ordinary dry-cell
batteries, Ni-Cd batteries or with another
manufacturers batteries.
Differences in various characteristic values, etc.,
can cause damage to batteries or the product.
7. Other Precautions
Batteries should always be charged prior to use.
Be sure to charge correctly.
8. Final Point to Bear in Mind
In order to ensure safe battery use and to prolong
the battery performance, please consult
Panasonic regarding charge and discharge
conditions for use and product design prior to the
release of a battery-operated product.