Why is my iPhone 7plus charging so slow

Hey there!

So I understand your iPhone is taking longer to charge than what you're expecting. This article may help you: If your iPhone, iPad, or iPod touch won't charge - Apple Support

For general information about the battery in your iPhone a strongly recommend this article iPhone Battery and Performance - Apple Support. It is full of super helpful info!

I do have a few questions for you.

How long is it taking to charge your iPhone? How long are you expecting it to take to charge?

When did you notice this issue?

Are you using an Apple charging cable and adapter or a 3rd party?

How are you charging your iPhone? There are many ways to charge, for instance, connecting to a computer, using a car charger, or connecting to a wall out. If you're connecting to a wall outlet is directly through an adapter or are you using a hub, or power strip of some sort?

Is there any sign of damage with what you're using to charge? This article may help identify if there is an issue: Using Apple power adapters, cables, and duckheads with Apple products - Apple Support

Check your port for any debris. This article discusses how to clean your iPhone. Cleaning your iPhone - Apple Support

Let me know if you have any questions. If after this you still have an issue, you can consider contacting Apple Support at: Contact Apple Support.