Apple had been planning for a June launch for the AirPower - it's wireless charger - but “a series of technical hurdles” and “supply-chain challenges” mean that it now won’t launch until September - at the earliest.
The Bloomberg report claims that the engineering team has encountered a number of challenges including ensuring the charger doesn’t overheat.
Another issue is likely to be related to the placement of sensors on the pad. The AirPower will be the first wireless charger to charge three devices at a time - the iPhone, watch and AirPods. It’s thought that it is because Apple wants users to be able to place the three devices anywhere on the pad that the design is proving difficult. This means that the mat requires multiple charging sensors - and not just multiple versions of the same sensor. Each type of device requires different sized charging components, suggests Bloomberg’s source (from an Apple partner that manufacturers third-party wireless chargers.)
Other possible reasons for the AirPower delay that aren’t mentioned in the Bloomberg report include problems with the design of the Apple Watch Series.
Because the Watch has a convex back it doesn’t sit on flat chargers - this is why it’s incompatible with some non-Apple chargers. This convex back may also stop that Watch from being charged on the flat AirPower mat.
The Bloomberg report also claims that AirPower will include a custom Apple chip running iOS that will conduct on-device power management and pairing with devices. It’s suggested that Apple has been battling issues with the firmware onboard.