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8 Components Description and Features
8.1 Topology
The Power Pak is built according to the following topology.
▪ Inverter: full bridge topology.
▪ AC Charger: isolate boost topology
By using high efficiency Mosfets, a 16bit, 4.9MHz microprocessor and heavy transformers, it outputs pure sine
wave AC with an average Total Harmonic Distortion (THD) of 10% (min 5%, max 15%) depending on load
connected and battery voltage.
The peak overall efficiency of the Power Pak is 80% - 85%, while the efficiency of the inverter is 95%.
8.2 Charging
The Power Pak is equipped with two chargers: a DC charge controller for charging the batteries from solar
panels, and an AC charger for charging the batteries from the electrical grid or a generator.
The AC charger is an active PFC (Power Factor Corrected) multistage battery charger. The PFC feature is used
to control the amount of power used to charge the batteries in order to obtain a power factor as close as
possible to 1. Unlike other inverters whose max charging current decreases according to the input AC voltage,
this charger is able to output max current as long as the input AC voltage is in the range of 95-127VAC or 164-
243VAC and AC frequency is in the range of 58-64Hz or 48-54Hz.
There are 4 stages of charging, described below. The charger will automatically switch to the next stage
without any input from the user.
1. Fast Charging: This is the initial stage of charging. While Fast Charging, the charger supplies the
battery with controlled constant current and the battery voltage will gradually increase. The charger
will remain in Fast Charge mode until the Fast Charge Voltage (determined by the battery type
selection) is achieved. This stage is where most of the energy is added to the battery. Once the Fast
Charge Voltage is reached, the battery can no longer be charged as quickly without reaching a
dangerously high voltage, and charging progresses to the Absorb Charge stage.
During this stage, the LED labelled Fast CHG will be lit.
A software timer will measure the time from when Fast Charging starts until the battery charger
reaches 0.3V below the Fast Charge Voltage, then take this time as T
0
. T
0
× 2 = T
1
.
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