Variable voltage: a lighter alternative

In a previous article, I described how I was feeding 13.8 V portable power to my radios (and other devices) from a cheap lead-acid battery.

Although I am still happy, on occasion, to lug the 25 kg or more of battery, radios, and other guff, I felt that there were times when it would be preferable to travel lighter. Looking at the options, I decided to try a powertraveller powergorilla Lithium Polymer battery, and completed the first field trial yesterday.

If you are unfamiliar with this particular model, the powergorilla has a capacity of 21 amp-hours (Ah) – that is more than twenty times the capacity of the built-in NiMH battery in a Yaesu FT-817 portable transceiver. However it weighs just 700 grams, and is the size of an iPad mini 3, only rather thicker.

Unlike most similar portable power products, the powergorilla can deliver adjustable voltage up to 24 V output at up to 3 A through a wide range of connections, not just USB. Intended mainly to power and charge laptops and similar, it comes with a large collection of plugs and sockets, including a short tail to a 12 V vehicle socket.

Having fully charged the powergorilla, I packed a small rucsac with two radio transceivers, the FT-817 and my SDR, ELAD FDM-DUO, and strolled up the Downs in far greater comfort.

I tried the powergorilla first with the Yaesu, which displays the input voltage when started up from a power supply. With the powergorilla set to deliver 12 V, it was reporting only around 11 V: sufficient for the radio to work fine, but well below its optimal 13.8 V. I therefore switched the powergorilla to deliver 16 V, which reached the radio as 15 V, which is well within its 15% tolerance.

Later I connected the FDM-DUO to the 16 V supply, and it worked beautifully too.

With the two radios, I operated from the top of the Downs for well over an hour, which proved a small fraction of the power in the powergorilla: recharging once I returned home took less than an hour.

The radio session was well worthwhile: I worked one station on each radio, on the 20 metre amateur band, EW1MM Gary in Minsk, Belarus, on the Yaesu, and 4O/IT9RGY in Montenegro on the ELAD. This was using a mere 5 W output to a SuperAntennas vertical whip antenna at around 2.5 metres. I heard – but did not work – N4P in Virginia, a big signal who sadly did not hear me, and 9V1RN in Singapore, who was much more faint (peaking at S7 on the meter) but inevitably had a huge pile-up of full-power stations calling him.

Conclusion: the powergorilla is much more expensive (£160 or less, including VAT) than a lead-acid battery (£40 or so), but set to 16 V output does not need any further conditioning to power 13.8 V + 10% portable transceivers. Although I did not go looking for it, I was not troubled by any stray RF from the powergorilla.

If you want to go lightweight, the powergorilla is the perfect solution.

(Note: the photo above shows my wife and my portable station on the Downs, when I was using a Buddipole antenna rather than the vertical used as described above. The weather and views were even better yesterday.)