I’m not that firm with charging and battery knowledge.
They are writing “50% charge in 30min with minimum 20W charger”
So is it harmful for the device to charge with an Plug of 30W?
(Like their own one: Dual-port 30W Charger (EU) - Accessory | Fairphone )
As they promote it for the FP4 and say “minimum” I would say no.
But I loaded my tabled once with my super-charge- Huawei Mate 9 charger and that wasn’t good at all for the tablet.
I already asked Rae (currently on a brief holiday) if the USB-A to USB-C cable is fit for the FP4 in any way. It would be good to know if it allows at least slow charging.
Although the specs mention output, that is what it is capable of not what it does.
In it’s use with the FP4 there is a protocol and algorithm which the phone and charger communicate by following procedures collectively termed QC4.1
Any supply or charger that does not conform the QC4.1 will not be able to use the fast charge rate which may charge the phone in 1 to 1.5 hours.
The 4Ah battery of the FP4 will require 4 hours at 1A for example and maybe more. I have a 5V 2.4A supply but it take 5hours to charge a 3Ah battery. 4Ah > 3905mAh