I’ve had my KX2 for a while now, but one drawback is having to open it up each time to charge it. The original KX2 charger is a constant current (CC) charger, but it costs around $130.
One possible solution I’m considering is soldering a CC chip between the input and the battery, which would simplify things. However, I’m interested to know if anyone has a better charging solution.
I also wondered about the CS pin on the real-time clock (RTC) module—when enabled in the menu, could it potentially be used to toggle the charger on and off?
Any ideas or suggestions would be greatly appreciated!
Another Idea is to add a MOSFET which connects the outside port with the battery when the radio is turned off…
Really who build a radio with an internal battery and not includes to charging this battery externaly
This charging possibility would cost them nothing more…
There are tons of cheap and tiny 3S charger boards available. I think it was @K6ARK who drilled a hole in the back panel and put in a DC socket wired to a tiny charger board. Problem solved for a few bucks.
I have the internal charger in my KX2 and love it, especially for travel. I fitted a 3.4Ah pack in my KX2 (higher capacity 18650 cells) and it’s good for several activations. Recharges overnight, and ready to go for the next day. If I know I will need more power, I can still take along an external pack and plug it in - the KX2 will run from whichever has the highest voltage. Prior to getting the internal charger I rarely used the internal battery.
Of course I could drill a hole😅 but I don’t want to do that. I thought to make a circuit and when the radio is off it closes the connection with my diy 3s internal battery (3500mAh) and it limits the current with 500-1000mA. And if I turn the radio on the charging process pauses.
Then I have implemented a better charging circuit then the original one.
I activated last time 5 peaks 170 qso in total with 8W and I used only 1400mAh
There’s a simple solution for this, but be careful not to plug in an external battery if you already have an internal one connected, as this could cause excessive current flow. By bridging pins E and B, you can safely charge it externally with a 3S charger
The windcamp side bars (or their copies on AliExpress ) have a hole and port for charging.
Quite a few people use this port to charge the battery and use a barrel jack socket which isolates the radio from battery when this port has a plug in it. In other words it acts as a switch between the charging port and radio if a plug is inserted or not!
There are videos on this on YouTube!
Yes I Know the video, but the windcamp sidepanels are dicker and u need other screws. I have it here
Mounted them, but I didn’t like them. And somehow the isolation between the drain pin of the MOSFET and the GND of the Radio was not isolated.
So I changed it back and it was fine again.
Drill a hole as needed and connect the battery to the circuit.
Bridge Pins E and B
Connect Pins E and B to bridge internal and external connectors.
Bridge Pins E and B with a small switch
Connect Pins E and B to bridge internal and external connectors with a small swtich that will fit in the 3.5mm connector or the LED hole.
Use a 3.5mm Connector for Charging
Utilize a 3.5mm connector similar to the Elecraft KXIO2 Real Time Clock. This will allow you to bridge the pins needed for charging.
OR charge it directly over the 3.5mm connector on the side
Add an Extra Circuit with the Following Features:
Current Limiting: Limit current during charging to around 500-1000 mA for safe operation.
Buck-Boost Converter (Optional): Consider using a buck-boost converter for scenarios where the input voltage is lower than 12.6V. This configuration ensures sufficient input, ideally with +1.6V above the requirement, considering a minimal loss of around 1.2V across the circuit. I’m searching an IC that could do that. And it would also stop charging or slow down the charge process in the end.
Charging Indicator LED: Install an LED in the drilled hole to indicate when charging is active, similar to the official charger.
Automatic Battery Disconnect: When the radio is powered on, it disconnects the battery with the external DC plug. (The P3 and P4 headers provide 12V and GND when the radio is powered on.)
This is a brief summary of the setup, and I plan to proceed with steps 2, 3, 4 or 5.
) have a hole and port for charging.