UV-5R with 3800 battery... usb 5v to 7.4-8v charger

Question

I have a Baofeng UV-5R with an extended 3800 battery. The usb cable I bought only works for the dock that comes with the baofeng but I would like to only carry a cable and charge the baofeng via anker solar or usb 20K battery. I want to run everything off 5v and to be able to keep it running while i go camping. Everything else i have has been converted to usb power (flashlights and headlamps, cellphones obviously, usb to charge AA and AAA amazon batteries, and thats all I really need.

I tried looking into 2x 18560 batteries used in powering rc cars and other small toys because the can add up to 7.4v. Worst case scenario, I can use a separate charger to charge the 18560 from the usb battery, but I'm not sure if it's the correct voltage needed to charge the baofeng (7.4v to 8.?v range), or if there is something that can do directly from my anker usb setup to the 3800 extended battery.

I have also seen a tyt charging cable that everyone recommends but I'm not sure if there is smarts in the device and if I can get from 12v back down to 5v (usb). It seems like a lot just to charge a 7.4-8v battery.

Can the radio accept 9v? I've seen usb to 9v or 12v (switching) charging cables , but is that too high. I know enough about electricity and electronics to be dangerous, hence asking rather than blowing up a perfectly good radio.

Any help would be appreciated.

Answer 1

The UV-5R has a nominal battery voltage of 7.4V and the supplied charger provides 8.4V with 600mA current limit. I believe this means the battery max charging voltage is 8.4 volts.

Directly applying 9 volts would be risky. Certainly make sure the current stays limited to a sane amount and certainly make sure the battery never gets charged above 8.4 volts.

It is easy enough to make a buck or boost circuit to transform 5 or 9 or 12 volts to 8.4. This seems like a route you might want to go. Google "DIY Baofeng Charger" for more ideas and check with EE Stack Exchange for safety information related to charging lithium batteries such as here: https://electronics.stackexchange.com/questions/230155/why-is-there-so-much-fear-surrounding-lipo-batteries/230164#230164

Answer 2

The two extended batteries I have (for a BF-F8HP, but as far as I know, this model uses the same batteries as the UV-5R) have direct charging input socket on the battery, separate from the contacts for the charging cradle. The chargers made to plug into this socket (that I've seen advertised) are direct USB, suggesting that either the charge cable itself includes boost converter, or the battery does (the battery has much more room for this).

It might be worth contacting BTech's support address to verify this, but I suspect this is the solution to your need to run off plain 5V -- just get one of those USB charge cables that plugs into the battery's socket.