iPad not charging using external battery

Ron-Jon wrote:

The same cable and battery pack charge my phone just fine. The iPad is the only thing that won’t charge.

They can still be particular. I have specific power supply/cable combinations that sometimes don't work well.

No.

mAh (Milliamp/hours) is a measure of energy storage. Power transfer/delivery is measured in Watts (W). These specifications and units of measurement are entirely independent of each-other.

By example, your car battery has huge energy storage - but the wiring connected to it will only be able to sustain a small current flow - this being determined by the size (i.e., cross-sectional area) of the wire conductors and any associated electronics.

Your PowerBank should have two specifications - the 20,000mAh specification (energy storage of the battery) being only one of them.

Phones and Tablets have a protection which is interrupting the charging if it is not safe for the device.

Did you try to charge your iPhone with the battery? If your iPhone doesn’t charging as well, then the problem is with your battery. If your iPhone charging, then the problem is with your iPad.

Many PowerBanks intended to charge a mobile phone may have insufficient output to successfully charge an iPad.

Regardless of the PowerBank capacity, as most iPads require at least 12W to reliably charge, the PowerBank must be able to supply 12W (i.e., 2.4A @5V) or greater to the connected iPad.

Ron-Jon wrote:

The bank says it carries 20,000mah, isn’t that 70 watts?

No. That's typically a measure of raw energy capacity. In that case it means that it can "soak up" input power into the battery equivalent to 1000 mA for 20 hours. The amount of energy depends on the voltage, and in this case means the voltage of the battery, which is a nominal 3.7V with most lithium-ion batteries, although it varies over time since battery input/output voltage changes over time. These things are a lot more complicated than the numbers that they provide to the user.

The output power is different. Most USB power packs use some sort of charge pump or other electronics to step up the voltage to 5/9/12V. It might be possible to use two lithium-ion cells and step down the voltage, but that's not as common. I've got a mophie 20,000 mAh power bank. It outputs 5V at 2.4A (12W), 9V at 2A (18W), or 12V at 1.5A (18W). But it has to work harder to provide this output as the battery is drawn down. The battery gets weaker with lower voltage and lower peak current capability as it's drawn down. At a certain point a lot of these power banks will refuse to provide power and give a hint that they need to be recharged (usually a flashing light that then turns off).

Have you perhaps tried a different cable? Sometimes particular power/cable combinations don't work for whatever reason, especially if the cable has internal damage.

Im having the same issue. The powerbank and wire can even charge my table fan just fine, but not my iPad. Try using another wire.