Juniper Systems Allegro CX Manual - Manual (Page 36)

36 Allegro CX Owner’s Manual
How NiMH Battery Gauging Works
As batteries discharge, the power available from the battery follows
a voltage discharge curve. This means that if you plotted out the
power of a battery on a graph there is a discharge curve as batteries
lose power.
The voltage discharge curve of NiMH batteries differs from the
discharge curve of other batteries. When the battery is fully charged,
the battery charge registers at 100%. As the battery drains, the
voltage drops off a little and levels out from 90% to 20% of the
battery’s charge.
As the charge on the battery falls to 10%, the voltage drops rapidly.
Therefore, the charge percent cannot be read directly from the
voltage as with other battery types, like alkaline batteries.
This is why it is important to set the battery charge capacity when
the battery is fi rst installed and then charge the battery pack to 100%
capacity. The battery status icon automatically changes to 100 when
the battery registers to the Allegro that it is fully charged.
If the gauging circuitry is not properly synchronized with the
actual charge on the NiMH battery, the battery status icon shows an
incorrect battery charge. If this happens, your Allegro battery charge
level can actually be lower than the gauge indicates. You can go into
the fi eld to collect data without the awareness of the actual battery
charge.
To better assist you in understanding the battery functions of your
Allegro, we highly recommend reading the section on battery
gauging so you understand the proper setup, functionality, and
limitations of battery gauging. Setting the battery charge percent and
capacity are both described earlier in this chapter in the New Battery
Detected options section.
The battery gauging is an estimate. It works well in applications
where the Allegro is used heavily and charged every day. When it is
not used much and goes several days between charges, the gauging
may not be as accurate in refl ecting the true charge of the battery
pack.
Keep the Allegro attached to the AC charging adapter or in the
USB/Power Dock when you are not using the Allegro. This practice
prevents the battery pack from self-discharging. The battery stays
fully charged and the battery gauging refl ects the correct status of
the battery pack.
▲