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Archive for October 10th, 2016

Rewiring a Baofeng Battery Eliminator

An aftermarket “battery eliminator” for Baofeng UV-5R radios costs under seven bucks delivered:

Baofeng Battery Eliminator - overview

Baofeng Battery Eliminator – overview

That label seemed … odd:

Baofeng Battery Eliminator - Li-ion Label

Baofeng Battery Eliminator – Li-ion Label

The OEM battery, tucked inside a case that’s for all intents and purposes identical to this one, sports an 1800 mA·h rating that I regarded as mmmm optimistic; I’d expect maybe 1000 mA·h, tops. From what I can tell, the 3800 mA·h label should go on an extended-capacity “big” battery that wraps around the bottom of the radio. Maybe the factory produced a pallet of mis-labeled small packs that they couldn’t fob off on actual customers with a straight face and couldn’t justify the labor to peel-and-stick the proper labels.

Anyhow, it’s not a battery.

The circuitry inside shows considerably more fit & finish than I expected:

Baofeng Battery Eliminator - interior

Baofeng Battery Eliminator – interior

It’s not clear how effective that heatsink could be, given that it’s trapped inside a compact plastic enclosure snugged against the radio’s metal chassis, but it’s a nice touch. Two layers of foam tape anchor the terminals at the top and hold the heatsink / LM7808-class TO-220 regulator in place.

Although I wanted the DC input to come from the side, rather than the bottom, so the radio could stand up, the pack simply isn’t thick enough to accommodate the jack in that orientation. I drilled out the existing wire hole to fit a coaxial power plug and deployed my own foam tape:

Baofeng Battery Eliminator - rewired interior

Baofeng Battery Eliminator – rewired interior

Replacing the foam tape at the top holds the bent-brass (?) terminals in more-or-less the proper orientation, with Genuine 3M / Scotch Plaid adding a festive touch. A groove in the other half of the shell captures the free ends of those terminals, so they’re not flopping around in mid-air.

The jack fits an old-school 7.5 V transformer wall wart that produces 11 V open-circuit. It’s probably still a bit too high with the UV-5R’s minimal receive-only load, but I refuse to worry.

Now KE4ZNU-10 won’t become a lithium fire in the attic stairwell…

While I had the hood up, I used Chirp to gut the radio’s stored frequencies / channels / memories and set 144.39 in Memory 0 as the only non-zero value. With a bit of luck, that will prevent it from crashing and jamming a randomly chosen frequency outside the amateur bands…

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