Your iPad will automatically limit charging to ~80% is some circumstances to protect the battery - this often occurring when the ambient or device temperature is relatively high.
As described, your iPad’s thermal management may be influencing the charging rate of your iPad. Quoting directly from Apple… If your iPhone, iPad, or iPod touch gets too hot or too cold - Apple Support
“If your device gets too warm
iOS and iPadOS devices have built-in protections to prevent overheating. If the interior temperature of your device exceeds the normal operating range, your device will protect its internal components by attempting to regulate its temperature. Here are some of the higher ambient-temperature conditions and activities to avoid, because they might cause your device to change performance and behavior:
- Avoid leaving your device in a car on a hot day.
- Avoid leaving your device in direct sunlight for an extended period of time.
- Avoid using certain features in hot conditions or direct sunlight for an extended period of time, such as GPS tracking or navigation in a car, playing a graphics-intensive game, or using augmented-reality apps.
If the interior temperature of your device exceeds the normal operating range, you might notice these changes:
- Charging, including wireless charging, slows or stops.
- The display dims or goes black.
- Cellular radios enter a low-power state. The signal might weaken during this time.
- The camera flash is temporarily disabled.
- Performance slows with graphics-intensive or augmented-reality apps or features.”
If your iPad is inside a fitted case, try removing the iPad from its case while charging - as this will improve cooling.
If your iPad is being charged in cool environment - and/or you see thermal management and high temperature warnings - your iPad or its Power Adapter may have a fault that will require investigation. In such circumstances you would be best advised to visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad, Power Adapter and charging cable:
Genius Bar Reservation and Apple Support Options - Apple
Otherwise, these support pages should help with troubleshooting general battery and charging issues:
Charge and monitor the iPad battery - Apple Support
If your iPad won't charge – Apple Support
Troubleshooting generally requires substitution of the Power Adapter and cable for another known-good item. Most models of iPad require a Power Adapter rated at 12W (i.e., 2.4A @5V) or greater to reliably charge. 5W Power Adapters (1.0A @5V) intended for older models of iPhone are inadequate to charge an iPad; if the iPad charges at all, charging will be very slow. Recent models of iPad are supplied with a 20W USB-C Power Adapter.
Some third-party USB-C power adapters (and portable PowerBanks) may not support USB PD (Power Delivery). Power Delivery mutually negotiates the charging voltage; the source, load and cable are all elements involved in the negotiation protocol. Unless the Power Adapter explicitly supports USB PD, it will almost certainly fail to charge the iPad; proprietary charging standards, such as QC (Quick Charge), are not supported.
Many computer USB ports also cannot source sufficient power to charge an iPad. Unless explicitly designed for charging connected devices, computer USB ports are typically limited to 0.5-1A @5V (i.e., 2.5-5.0W).
If you continue to experience difficulties when using an appropriate Power Adapter of 12W or greater, you might be best advised to seek assistance directly from from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad, Power Adapter and cable(s):
Genius Bar Reservation and Apple Support Options - Apple
