How does Low Power Mode affect iPhone Battery Health?

Hello,

No it's fine this will make your battery last longer. Your iPhone uses charge cycles. The more cycles you use the lower the capacity is. Here's more info:

It makes charging easier.

Charge your Apple lithium-ion battery whenever you want. There’s no need to let it discharge 100% before recharging. Apple lithium-ion batteries work in charge cycles. You complete one charge cycle when you’ve used (discharged) an amount that equals 100% of your battery’s capacity — but not necessarily all from one charge. For instance, you might use 75% of your battery’s capacity one day, then recharge it fully overnight. If you use 25% the next day, you will have discharged a total of 100%, and the two days will add up to one charge cycle. It could take several days to complete a cycle. The capacity of any type of battery will diminish after a certain amount of recharging. With lithium-ion batteries, the capacity diminishes slightly with each complete charge cycle. Apple lithium-ion batteries are designed to hold at least 80% of their original capacity for a high number of charge cycles, which varies depending on the product.

It is absolutely safe, although remember that Low Power Mode will turn off automatically if battery level reaches 80% while charging. Also, don't forget that LPM temporarily disables some of the phone's features and services.

You can learn more about the iPhone Low Power Mode from this article.

About iPhone Low Power Mode on your iPhone - Apple Support

There is absolutely no hardeare problem with turning low power mode at any battery percentage. It just uses less resources to lower battery consumption.

You can use Low Power mode at any percentage. The point is to extend your remaining battery life, so you'll see a greater benefit if you turn it on earlier. You can't extend the time you've already used your phone...

I only charge my phone when it reaches 30% or less, but yeah. Charge it whenever you want.