iPad Pro battery takes a long time to charge

The time required to charge you iPad is influenced by many factors - such as how much the battery has been depleted prior to charging, the power output of the Power Adapter (Watts), the maximum charging rate supported by the iPad - and, if using the iPad whilst charging, the CPU load and screen brightness (greater CPU and higher screen brightness slows the charging process).

Factors that do not directly impact the charging time are your available storage and the installed version of iOS.

Be aware that with only a few exceptions, iPad requires a Power Adapter of at least 10-12W to reliably charge. When charging is attempted with an iPhone Power Adapter (typically rated at only 5W), charging will be very slow - of the iPad charges at all.

Many of the more recent models of iPad support USB-PD (Power Delivery) Fast Charging. These models, when charged with a suitable Power Adapter (typically rated at 18W, 20W or greater) can very rapidly charge a compatible iPad battery to 80% of its maximum charge - after which the charging rate is reduced to protect the battery.

Depends.

A little hard to help/advise you when you provide NO information about your iPad.

Can you, please, confirm what year and model iPad do you have/own?

The “A” model number can be found on the aluminium back of your iPad, in very small print, right under the larger bold print “iPad” on the back of the iPad.

What iOS/iPadOS version is this iPad, currently, running?

What is the rated, internal data storage space/capacity of your iPad model and how much of this free, internal data storage capacity is left inside of your iPad model?

All of that additional info can be found in the Settings app, General settings panel, About.

Please try to attempt to answer all questions asked.

Thank You.

Okay.

You own a 2017, 2nd gen iPad Pro.

Without a faster power/charging adapter block, If using the supplied 12W adapter, it will take approx between 5-6 hours for tbat iPad to charge when the iPad is NOT in use.

It will take longer IF using the iPad while trying to charge it at the same time.

If you purchase the Apple 20W USB-C power/charging adapter block with Appe's Lightning to USB-C cable, charging time will take about 2-1/2 to 3 hours.

Best of Luck to You!