Electronics International VA-1A - Manual (Page 8)

Another common electrical problem is a discharging condition. If this condition goes unnoticed (which it
normally does) you will end up with a dead battery in flight rendering all of your electrical equipment
useless. To help you avoid this situation the VA-1A has a “Discharge” Warning Light which acts as an early
warning, alerting you as soon as the battery goes into a discharging condition. The amount of discharging
current can be displayed in the “Amps” position. Discharging current will be displayed as a minus number.
If this situation occurs, turn off any unnecessary electrical equipment. The lower you can get the discharging
current, the longer the battery will last.
The VA-1A will display trend information when your battery is in a discharging condition. As you watch the
battery discharging .1 volts at a time, it becomes relatively easy to judge the remaining time you have before
the battery reaches a seriously low condition. As the battery voltage approaches 11 volts (22 volts for a 24
volt system), the aircraft’s electrical equipment will start to malfunction. The exact voltage at which each
piece of equipment will start to malfunction depends on the design of that equipment. The VA-1A will work
accurately from 40 to 7 volts--far below where most electrical equipment starts to fail.
V VV VVA-1A Installed in the Alternator Lead A-1A Installed in the Alternator Lead A-1A Installed in the Alternator Lead A-1A Installed in the Alternator Lead A-1A Installed in the Alternator Lead
Two common methods of installing the VA-1A or VA-1A-XX in the electrical system of your aircraft are in the
battery lead and in the alternator lead. Following are the operating characteristics of the VA-1A installed in the
alternator lead.
1. Master On, Engine Off: 1. Master On, Engine Off: 1. Master On, Engine Off: 1. Master On, Engine Off: 1. Master On, Engine Off:
The following describes the operating characteristics of the VA-1A installed in the alternator lead with the
master switch on and the engine off.
With the Mode Switch in the “Amps” position the VA-1A will display 000 (+/- a few counts). Since the
battery is supplying all of the electrical load and the alternator is off (not turning), there is no current being
supplied from the alternator and the “Discharge” warning light will be on.
With the mode select switch in the “Volts” position, the VA-1A will display the bus voltage to .1 volts. With
all electrical equipment off and a fully charged battery the bus voltage will be around 12.1 to 12.5 volts
(double these levels for a 24-volt system). Each battery has its own operating voltage when charged. As the
battery gets near the end of its life, this voltage will start to drop. A discharged battery will also run at a
lower voltage. Don’t confuse a good discharged battery with an old battery.
2. Master On, Engine On: 2. Master On, Engine On: 2. Master On, Engine On: 2. Master On, Engine On: 2. Master On, Engine On:
The following describes the operating characteristics of the VA-1A installed in the alternator lead with the
master switch on and the engine on.
Operating Instructions Operating Instructions Operating Instructions Operating Instructions Operating Instructions VA-1A Installed in the Battery Lead VA-1A Installed in the Battery Lead VA-1A Installed in the Battery Lead VA-1A Installed in the Battery Lead VA-1A Installed in the Battery Lead
6