OpenGD77

Modification of the Radioditty charger with a $2 "TP5100" lithium-ion battery charger module.

I recovered the 12V socket and the input choke of the original charger.

I glued the plug with cyanoacrilate glue, added some DC and RF filtering components. The output voltage is 8.42V
and the leds of the card are visible through the box, as at the origin.
The central tab has been removed, fixed upside down to strengthen the support of the 12V socket
On the 5100 board you have to set up the shunt (2 cell mode) and remove one of the two 0.1ohm resistors to reduce the charging current.

The charger box remains cold, after several hours of operation with a GD77 plugged on, in hotspot mode (on TG91 )
With Hotspot @ 250mW, no reaction from the new charger with the GD77 placed on it during transmission.

(Tests with rod antenna plugged)
Edit : Allways ok @500mW
I added aluminum foil covered with foam to insulate and maintain, in the bottom, U-shaped case to make a screen
Edit : Allways ok @750mW
Edit : A few blinking of the LEDs @ 1W

First test :

.
.
Final :

.

.

........

Hi Thierry,

F1CXG wrote: ↑

Wed Jan 29, 2020 2:33 pm

Modification of the Radioditty charger with a $2 "TP5100" lithium-ion battery charger module.

I recovered the 12V socket and the input choke of the original charger.

I glued the plug with cyanoacrilate glue, added some DC and RF filtering components. The output voltage is 8.42V
and the leds of the card are visible through the box, as at the origin.
The central tab has been removed, fixed upside down to strengthen the support of the 12V socket
On the 5100 board you have to set up the shunt (2 cell mode) and remove one of the two 0.1ohm resistors to reduce the charging current.

With Hotspot @ 250mW, no reaction from the new charger with the GD77 placed on it during transmission.



.
........

Nice. I just ordered few TP5100 modules.

Is it me or the leds colors are red and blue ?

Cheers.
---
Daniel

Yes Red during charge and blue at end of charge or open...

F1CXG wrote: ↑

Wed Jan 29, 2020 3:05 pm

Yes Red during charge and blue at end of charge or open...

Great, I will stop asking people around me about the current color

hi, can you be a bit more specific about the location of the diode please

or maybe, if it's not too much trouble, a circuit diagram

i had done the basic mod but haven't added the ancillary components and it would be great to add the extra bits

thank you

Here is a diagram handmade quickly to clarify
the position of the added elements
.
.

that's great, thank you very much

Looks good..

But why did you put a diode across the output?

Hi Roger,
Just seen on another assembly, useful questionable, but not expensive and easier to weld in parallel a small capacitor with short lead (10nF)

This small charger module works much better than the original card, faster charging, more resistant to HF from the GD77 transmitting on the charging base and does not heat up...and a very low price

Yeah, maybe you found it on my compact hotspot. And yes, I am an idiot! My drawing is wrong. The picture of the TP5100 board is the wrong way around. So the diode has to go on the input, not the output. I will fix it right away.

The diode protects the TP5100 from sudden death in case you switch off the power and the inductor produces a uncontrolled reverse polarity. I killed quite a few boards until I realized this.

73s,
Jens