The converter is delivered with two plastic faces to protect the mainboard and the display, together with the fixing accessories (screws and spacers). But, a dedicated enclosed box is highly recommended for more safety, especially if you will use it in portable or mobile activities.le activities it will not be so easy to carry them.
A better solution is to use high capacity Li-Ion batteries, designed to charge laptops, having at least 20 Ah and capable to provides minimum 4 Amps as discharging current. These batteries are lightweight and easy to carry, but in order to benefit from a higher discharge current, you must set the battery's output voltage at 16 or 19 Volts, which are to higher than the standard voltage usually designed for transceivers, at 13.8 Volts.
This issue can be fixed with the following DC-DC convertor, which accepts a very large voltage range input (from 6 to 30 Volts) and provides an adjustable and stabilized output voltage, with up to 5 Amps of loading current.
First of all, there are two important things to keep in mind:
When you power on for the first time, the output voltage is near the input value, so do not use it directly if the source voltage is higher then the nominal voltage of your radio equipment. Find a consumer which can be supplied at the voltage provided by your power supply and adjust the output voltage at the right value (e.g. 13.8 V), using the first (right sided) multi-turn potentiometer.
This converter provides, also, an USB connector, but the output voltage is the same with the main output connector. Do not use the USB if the output voltage was not prior adjusted at 5 Volts ! My highly recommendation is to completely block the access to this connector, in order to prevent any tentative to use it for charging of a mobile device.
Now, what this little gadget can do for you ? Bellow display, there are two multi-turn potentiometers: the right-side potentiometer is used to adjust the output voltage, while the next one is used to set the maximum limit of the output current.
To supply a FT-817 transceiver for maximum RF power, at least 2.5 Amps must be provided. Assuming that you already set the output voltage at 13.8 V, you need to select the CW mode, to keep down the Morse key and to read the output's current value, simultaneously with the status of small LED in the left side of the display. If this LED is red, the supplied current is limited at the displayed value. Use the right-sided potentiometer to increase the current value, till the red LED turns off. For a proper antenna tuning (and low SWR value), the consumed current, in CW mode with the keyer pressed, is somewhere between 2.4 and 2.6 A and could exceed 2.8 A in some conditions (like in the picture below, where the antenna tuning was not a proper one).
Going further, in the right side of the display, there are two small red push buttons. Using the upper one, you can select what voltage you will see on the display: F0 - Input voltage, F1 - Output voltage, F2 - alternate between input and output voltages. There is a forth option, for USB, but as I warning earlier, don't count on it, just block it.
The next red button, in normal operation mode, power-on or power-off the display's light or interrupts the selection menu (F0 to F2), showing the output's current value.
Both red buttons are used, also, for calibrating the power supply. Connect the output to a lab multi-meter and, with the supply powered-off, keep pushed the upper red button and apply the input voltage. When the display starts to blink, release the push button. If the displayed output voltage is not the same with the lab equipment value, calibrate the device by pressing upper button for increasing or lower button for decreasing the measured voltage.
Same procedure must be followed to calibrate the measured current, with the only difference that you have to keep pushed the lower red button before start the converter. Also, release it as soon the display starts to blink.
The maximum supported output current of this DC-DC converter is around 5 Amps, but you can safely reach this limit only with the help of a 5V small fan, like those used to cooling down the Raspberry Pi type 3 computers. But, because the converter does not have a dedicated 5V output, you will need a 7805 IC connected to the input, in order to obtain the necessary voltage for this fan. And, don't forget to use the 7805 together with a radiator...
Anyway, for up to 3 A output current, you can use the convertor as it is, without fan. But, for heavy (full) duty modes, like JT65 or SSTV, where a transmission session can takes a long time, remember to check more often how warm become the final stabilizer.
The converter is delivered with two plastic faces to protect the mainboard and the display, togheter with the fixing accessories (screws and spacers). But, a dedicated enclosed box is highly recommended for more safety, especially if you will use it in portable or mobile activities.
Even is not visible, I've included also a fan, together with a 7805 stabilizer, which provides, despite the applied input voltage, the 5V requested by the fan to cool down, if necessary.