I just wanted to mention that the Hankzor store on Aliexpress has the JK BMS with a screen option. It also has a power button on the screen to easily turn the BMS on and off. This means no more messing about with 9V batteries or power supplies to turn on the BMS. It seem that Hankzor is the only store right now with this option. I've ordered two of them and I'll report the results here once I have them.