Windy-nation TrakMax 40 MPPT Solar Charge Controller Bedienungsanleitung PDF herunterladen (Seite 13)

TrakMax 40 User Manual

Revision 1.0

power, than a hot PV array. When PV voltage is sufficiently high for MPPT to operate, a constant power

output is delivered to the battery. Since output power is constant while MPPT is operating, a decrease in

battery voltage produces corresponding increase in charge current. This means that the greatest current

increase occurs with a combination of cool ambient temperature and low battery voltage. The unit delivers

the greatest charge current increase when you need it most, in cold weather with a discharged battery.

Additionally, anything that can be done to lower PV array temperature will also lead to increased charge

current by increasing PV power production. In cool/comfortable temperatures and typical battery states of

charge, most systems see about 10 – 20% increase. Charge current increase can go to zero in hot

temperatures, whereas charge current increase can easily exceed 30% with a discharged battery and

freezing temperatures.

Figure 4.1: Current / Power vs. Voltage Characteristics

4.1.1 How MPPT Works

A PV module is a constant current type device. As shown on a typical PV module voltage vs. current curve,

current remains relatively constant over a wide range of voltage. A typical 75 watt module is specified to

deliver 4.45 amps @ 17 volts @ 25 C cell temperature. Conventional PV controllers essentially connect the

PV array directly to the battery when the battery is discharged. When a 75 watt PV module is connected

directly to a battery charging at 12 volts, the PV module still provides approximately the same current. But,

because output voltage is now at 12 volts rather than 17 volts, the PV module’s power production is

artificially limited and the 75W PV module only delivers 53 watts. This wastes 22 watts of available power.

TrakMax’s MPPT technology operates in a very different fashion. Under these conditions TrakMax calculates

the maximum power voltage (V) at which the PV module delivers maximum power, in this case 17 volts. It

then operates the PV module at 17 volts which extracts maximum available power from the PV module.

TrakMax continually recalculates the maximum power voltage as operating conditions change. Input power

from the maximum power tracking controller, in this case 75 watts, feeds a switching type power converter

which reduces the 17 volt input to battery voltage at the output. The full 75 watts which is now being

delivered at 12 volts would produce a current of 6.25 amps. A charge current increase of 1.8 amps or 40% is

achieved by converting the 22 watts that would have been wasted into useable charge current. Note that this

example assumes 100% efficiency to illustrate the principal of operation. In actual operation, the power boost

will be somewhat less.

4.2 CHARGE MODE

4.2.1 Factory Default Settings

Charge Mode

Three (3) Stage

Absorption Voltage

14.4V

28.8V

Bulk Voltage

14.6V

29.2V

Float Voltage

13.4V

26.8V

Equalize

14V

28V

Page 13 of 20

windynation

03/06/2013

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