Re: Battery power for the QDX? #power

Mike Perry, WA4MP

Here is an option some might consider for powering the QDX with its expectation of 9 volts. It’s 8.4 volts, but might do until you have something better.

A little background. I just ordered a QCX mini for 40. Looking for a way to power it from 18650 batteries, I was going to cobble together a three-battery holder, when I came on various 18650 waterproof case outputting USB plus either 8.4 v. or 12 v. from either three or four 18650s. They were only a little bit more and offered waterproofing, so I ordered one. They’re intended for bikers and apparently 8.4 and 12 volts are the standards for high-end bike lighting.

They are cheaply made. I’d already purchased a 12 v/three-battery version whose switch for the USB output didn’t work. This time I ordered a 8.4 v version for a bit under $12. It runs off four 18650 batteries (not included). If it knows how to use them wisely, might mean a bit more battery life. It is also a bit more compact.

The eBay prices are all over the place, even for products that look identical, so I won’t recommend a specific vendor. If you’re interested, search eBay for "8.4V 4x 18650 Waterproof Battery Pack Case Box House Cover For Bicycle”. You’ll get dozens of results, many using the same pictures.

Just keep in mind that I don’t yet have a QRP-Lab products to test them with. They must do something to get 8.4 volts from four 3.7 volt batteries, so that might mean noisy RF. If alll else fails, you can use that USB output to recharge a smartphone for days.

—Mike Perry, WA4MP

On Oct 14, 2021, at 7:48 am, Curt wb8yyy via <> wrote:

Consider how and where one will use this qdx. In the shack the dissipation of an adequate 9 volt linear regulator is just a little more heat, on battery well not so nice. One could install the regulator network in an adapter unit for in shack use, retaining 9v operation for field use. Or an excuse to build some kind of low noise 9v supply.

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