During the May Day holiday, I had some free time and assembled a new set of batteries. Initially, I was planning to use 33140 cylindrical iron lithium batteries with a capacity of 15Ah and 4 cells, which cost less than 100 yuan. However, one of the 15Ah batteries seemed to exceed the standard capacity, and I was concerned that it might not be suitable for traveling by train. Also, the power output of the radio itself is relatively low, so I thought it would be better to travel light. Ultimately, for safety reasons, I chose a set of 32700 cylindrical iron lithium batteries with a capacity of 6Ah, which are designed for use in G90N vehicles.
The handwritten labels are very detailed, so I'll explain the process here without mentioning the brand. The packaging is well-done, and they default to using SF Express. The price is 40 RMB or more.
The actual test of 4 batteries showed excellent voltage consistency, which was very consistent with the specifications provided by the seller.
I chose the 32650 battery holder, which is compatible with both 32650 and 32700 batteries. I installed four cells, and the tightness is just right.
The iron lithium battery used is specifically for protection boards. This time, I chose the one with a metal casing, which is more organized. The schematic is still BYD BM3451, with passive equalization. The detection line is made of silicone, which is very soft, so it took a long time to plan and lay out the position and routing of the protection board. To achieve the shortest distance, I directly used a soldering iron and nickel sheet for welding. The稞纸 insulation was used, and I chose 14AWG silicone wire for the power lines. I manually opened an outlet hole for both power lines, which provides a fixed point and ensures that they are oriented upwards, making heat shrink easier later.
This version also adds a power display function, which provides a rough estimate of the battery status. The actual voltage accuracy is also very high. When turned on, the screen current is about 10mA, and when off, it's less than 200uA, which is acceptable. Compared to common LED displays with several levels or percentage-based power display, this allows you to directly see the battery voltage, making the power estimation more accurate. I also considered using a coulomb meter, but they are expensive, have low capacity, and consume a lot of power themselves, so I decided against it.
Using稞纸 and polyimide tape to insulate the battery electrodes and wires, and then using heat shrink film to complete the heat shrinking process. The red LED power display can pass through the heat shrink film, which is effective. You can see the power level by pressing the button, and you can also set it to turn off the button or automatically turn off after a few seconds, which is very convenient. It allows you to see the voltage at the battery end, and you can also estimate the line loss during discharge and charging. The final effect is good.
The battery was completed just in time for the annual Chinese Amateur Radio Festival. After fully charging, I used the radio with FT8 mode and a 5W transmit power, and it lasted for about 6 hours without needing to be recharged. The new battery is good; although the capacity of 6Ah is not large, its size is similar to that of a mobile phone, which feels just right in terms of续航 (battery life), volume, and weight. I also completed another round of modifications on accessories around the radio.
The power supply section of the radio is now functioning as expected and has been put into use. I'm currently working on some other projects, but haven't decided on specifics yet. If you have any ideas or are interested in collaborating, please let me know! 73!
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