I dropped in to Lindy UK today and bought a couple of their cables, one of their 20cm USB A to Micro B for connecting the controller to the phone, a 50cm USB 3.1 C to C with Power (rated at 100W Power Delivery) and one of Lindy's USB C Power/Voltage monitors.(DC<24V/6A)
I used battery 1 (of 3) today down to RTH level. Plugged it in to the Imuto mains charger C port with the Lindy cable.
The monitor indicated 4.94V charging at 1.75A. This took 3 hours to charge the pack fully.
I don't think the Imuto charger is up to the job.
Lets hope the new chargers arrive soon.