Guldmann GH1 F, Service Manual

Page: 88 / 168

© Guldmann
GB/US
-09/2016 •
#550376_3
90
SERVICE AND
REP
AIR
Battery storage NiMH
Battery Maintenance
Periodic visual inspection of the battery is recommended .
If the battery is stored for over six months, it is recom-
mended to charge and discharge the battery several times
to resume the battery capacity, failure to do so may result
in a loss of capacity and shorter battery life .
Bear in mind that self-discharge has to be taken into con-
sideration when storing a charged battery . The remaining
battery capacity should be at least 50% after a month of
storage at room temperature for a dully charged battery .
High storage temperatures will accelerate the self-dis-
charge, and reduce the remaining capacity .
Storage Characteristics
Essentially all rechargeable battery cells gradually dis-
charge over time whether they are used or not . This capac-
ity loss is typically due to slow parasitic reactions occurring
within the cell . As such, the loss rate (self-discharge rate)
is a function of the cell chemistry and the temperature
environment experienced by the cell . Due to the tempera-
ture sensitivity of the self-discharge reaction, relatively small
differences in storage temperature may result in large dis-
charge that is difficult or impossible to reverse .
Cell and battery storage issues of concern to most appli-
cation designers relate either to the speed with which the
cells lose their capacity after being charged or the ability of
the cells to charge and discharge “normally” after storage
for some period of time . In both situations, general guide-
lines developed for nickel-cadmium cells work acceptably
for nickel-metal hydride cells .
Storage temperature
As already mentioned, the self-discharge reaction rate
increases with higher temperatures . Prolonged storage of
the battery material deteriorating faster; leakage perfor-
mance will also deteriorate, resulting in a reduced battery
lifetime . It is recommended that, for long storage, batteries
should be kept at room temperature or below (0-30°C) .
Storage time
As the battery loses energy during storage, the voltage
also drops . In general, the battery capacity loss due to self-
discharge during storage can be recovered by recharging .
If the battery is stored for over six months, it is advisable
to cycle the battery several times to resume the battery
capacity . Use good inventory practices (first in, first out) to
reduce time cells spend in storage .
Storage humidity
Leakage and rusting of metal parts are accelerated in high
humidity environments, especially those with correspond-
ingly high temperatures . The recommended humidity level
for battery storage is a maximum of 60% RH .
Capacity Recovery after Storage
In normal practice, stored cells will provide full capacity on
the first discharge after removal from storage and charging
with standard methods . Cells stored for and extended peri-
od or at elevated temperatures may require more than one
cycle to attain pre-storage capacities . Consultation with the
manufacturer is recommended if prolonged storage and
rapid restoration of capacity is requested .
Discharge: 1.0C (E.V. 0.9V)
Temperature: 25°C
Storage time (days)
0 5 10 15 20 25 30 35 40 45 50
40°C
20°C
0°C
0
10
20
30
40
50
60
70
80
90
100
110
Storage Characteristics
Retained capacity (%)