Which hardware to choose considering no AC-plug is near?

[ham5urg]

Frequently I do hiking tours, lately beyond the reach of cellular towers and any AC-plug.

While hiking I depend on a usb-powerbank/solarpanel combination. I tested a pair of Baofeng UV-5R+ and am happy with it. I ordered the 3800mah battery which can be charged with a Baofeng-USB-to-barrel cable

But now I stumbled onto OpenGD77 and would like to use it. The only question for me is the USB-charging-ability while on the move.

The neccessities are

• OpenGD77 compatibility

• attaching a USB-charging-cable directly to the radio

My first look was at the GD77 but I did not found such battery/cable, only a dock to put the radio into it.

The second look was for the Baofeng RD-5R, quite simillar to UV-5R+ and it looks like both radios are 'accessories-compatibile'. Am I right? If so, I would order a pair of RD-5R if

• it is well supported by OpenGD77

• the extra size BaoFeng BL-5 battery is compatible with RD-5R

What are your thoughts?

Regards

[nr0d]

If you look at the thread regarding the RD-5R firmware version, I think it'll become pretty clear pretty quickly that the hardware is vastly inferior to the GD-77. You'll have to decide if that's overridden by your power needs - they're cheap, after all.

There are plans for battery eliminators online that would let you run a GD-77 from an external battery that's more easily charged by solar, but the lack of an external 12V port on this radio is a definite downside. Do you really need DMR support when you're out away from civilization? If not, there are many better alternatives for that use case.

Edit: I just remembered, the charging base apparently has a voltage regulator in it and will accept any voltage between 11 and 16 volts - so just plug it into a 12V battery to charge the radio and you should be good. USB is too low of a voltage, though, so that's right out. It would have to be a 12V battery - for hiking, look into LiFePo4 as they're light and take quite a few charge cycles.

[ham5urg]

Hello, USB-C may help.

USB-C power delivery with profile

• 2 supports 12v/1.5a

• 3 supports 12v/3a

• 4 supports 12v/1.5a

• 5 supports 12v/5a

and should be pretty easy to implement with a tiny IC.

As I took a look here, maybe I could do it. But first I must find an IC which will do the job. Maybe something simillar like this

What is the maximum amperage the battery is capable to take in? I guess the IC will take care of not to deliver more ampere as it is allowed to, but to be on the safe site, I would search for an IC which can deliver more ampere.

What are your thoughts?

Regards

[ham5urg]

I just found here that the battery is taking 8.4v in. That is a hard task. USB-C can't provide 8.4v.

Will the battery be good with 9v charging? Because this little thing can provide 9v and maybe it can be stored inside the battery-case.

[ham5urg]

There are USB to 8.4v cables but havn't found any ICs yet. Nevertheless, with such cable and a simple barrel-plug it should be possible.

[ham5urg]

I guess a combination of this and this will do it.

But will this fit into the battery case? I could remove the entire battery and let it run via usb-powerbank.

[Zl1XE]

Don't forget that a diode drops 0.6V (normal silicon) or 0.2V (Shottky) so you can drop the voltage reliably if your diode(s) can carry the current required. Cheap too.

[ham5urg]

I ordered 4 pieces each of this and this.

I will play around with it and see if the to-be-charger will work correct on normal 18650s. If so, I'm gonna try to 3d print a new enclosure for the GD77 battery.

[ham5urg]

Don't forget that a diode drops 0.6V (normal silicon) or 0.2V (Shottky) so you can drop the voltage reliably if your diode(s) can carry the current required. Cheap too.

Thanks for this hint, I will try and see if the 0.7V drop is stable while temperature and ampere changes over time.