Anker 25k mAh power bank charging iPad slowly

hello everyone, I bought an anker 25k mah power bank but When I plug my ipad it only gives 15-20 watts and it is charging really slow, I used both the built in cable and the inbox ipad cable and still the same , any help or advice would be really appreciated

[Re-Titled by Moderator]

Original Title: Powerbank -ipad compatibility