Handy Tech
Elektronik GmbH
Easy Braille
Battery
Management
Page 31
Charging of fully discharged batteries takes about 1.5 hours. The electronic circuit
detects and evaluates the end-of-charging voltage and the maximum-discharge
voltage, which means that the batteries cannot be excessively discharged or
overcharged. You can thus leave the external power supply unit connected to the
Easy Braille for long periods.
6.3 Battery Capacity Display
The state of charge of the batteries is monitored in all operating states of the Easy
Braille. It is thus possible to display the state of charge at any time, either as the
battery voltage or as the remaining battery capacity.
The battery voltage is an indirect indication of the state of charge. The voltage when
the batteries are fully discharged is about 4.2V. If the battery voltage drops to this
value, the Braille display is switched off and can be switched on again only after the
external power supply has been connected in order to charge the batteries. With fully
charged batteries, the voltage may be up to 5.6V. During charging, the voltage may
rise to above 6V.
If you wish to know more about the state of the batteries, you can display all
important values in the configuration menu (see Section 3.5).
The remaining capacity is displayed as a percentage. A fully charged battery has a
capacity of at least 99%. The remaining capacity is determined in a complicated
operation during which the device observes the state of charge of the batteries over a
long period and collects the data needed for the calculation. The capacity can be
displayed correctly only after the batteries have been fully charged and then fully
discharged. If this has not been done (which is normally the case in newly delivered
devices), a question mark is displayed after the capacity display to indicate that the
value may be incorrect. This also means that the battery capacity must be calculated
again each time you remove the batteries and insert them (or new ones) again.
6.4 Automatic Undervoltage Detection
Your Easy Braille has a two-stage battery voltage detection circuit. The first stage
activates a signal tone which sounds at intervals of about 18 seconds when the
battery voltage drops to 4.6V. This indicates that the batteries are almost exhausted
and should be recharged. This signal tone can be switched on or off in configuration
mode.
If the battery voltage drops to its lower limit of about 4.2V, your Easy Braille switches
itself off. However, it still draws a small current even in this state, and you should
therefore not leave your Easy Braille in this state for longer than one day. It is best to
recharge the batteries immediately. If this is not possible, you should at least switch
off your Easy Braille with the main switch.
If you do not intend to use your Easy Braille for several weeks, you should either fully
charge the batteries first or remove the batteries and store them outside the device.
