Hello. Today will tell you how I did a DIY charger for radio Baofeng UV5R.
It all started with the fact that friends asked me to make a charger for radio Baofeng UV5R. The problem of regular in charger because it is very bulky, often fails IC of charger, usually you carry a radio in pocket and charging doc often stays somewere at start point and therefore owners often simply lose.
I’ve searched internet and found original charger on LM317 it is designed for one lithium battery voltage of 4.2V and current of 650mA. Very good development thanks to the author.
Everything is good but Baofeng Batteries in series 2, it sets the full charge voltage 8,4V as original charging current is designed to 350mA, this inputs parametrs.
Plus Baofeng is that accumulators are already have a balancing cirquit inside
We will connect to the external contacts of a battery.
From left to the right: “+8,4”, “T. Sensor”,”-8,4″.
The scheme is a copy of the original above but with some changes:
- Group R3, R4, R6 voltage devider calculated for 8,4V.
- Resistor R9 calculated I = 250mV/R9. for resilt current 350mA.
The principle of operation is as follows: string U1, R3, R4, R6 8,4V voltage stabiliser, but the charging cycle should take place with a current stabilized, to control it here is a pair Q2, R7 that depends of the voltage of the shunt R9 and puts appropriate voltage on the leg ADJ chip LM317 so the voltage on the accumulator rises slowly, and the current is stable. Link R1, D2, R2, Q1, R8, D4 is responsible for process indication while charging the glowing “red” LED D4 – charging continues, extinguished – accumulator charged. Glowing “green” LED D3 indicates the presence of external power.
PCB was designed in Altium . You can also do it on one layer PCB but you must add three jumpers marked gray.
I usually show in this section 3D with Altium but today we have a new trick sketchfab.com
And so attention now will be the slides))):
PCB in 3D
Then started to develop the case. I decided to make it a two-layer PCB 1.5 mm, I developed in Rhinoceros 3D.
Case in 3D
Soldered it together:
As the experiments shown the cirquit is stable, charging ends at 8,35V.
That’s all thank you for your attention.
Files of project Altium, Rhinoceros 3d, Proteus.