how to back the 100 percentage on my battery

If you are asking how to restore the battery's Maximum Capacity to 100%, you can't – except by paying to have the old battery replaced with a new one. The new battery's Maximum Capacity should start at 100%, but it, too, will go down as you use the phone.

Or, in Apple's terms,

"All rechargeable batteries are consumables and have a limited lifespan — eventually their capacity and performance decline so that they need to be replaced."

I don't know the right point at which to get a battery replaced – though I've seen posters here say that a good time is when the Maximum Capacity estimate drops below 80%.

Batteries - Service and Recycling - Apple

Get your iPhone, iPad, or iPod touch ready for service - Apple Support

An iPhone battery will degrade with use. You can’t get it back to 100%. You can expect a 1 - 2% drop each month. When the battery health gets to 80% or less, get a new battery.

rohitbantawa wrote:

how to back the 100 percentage on mya iphone 7 battery

Get a new battery installed by Apple or an Authorized Apple Service Provider.

You must buy a new battery for this.

You can have 100% when you replace the battery with a new battery.

You need to replace the battery with a new battery.

Replace the battery.

Increase my battery 100%

My battery was 88 % after one day is 55%

I need my to 100 percent

I need my battery to 100 percent

how to back the 100 percentage on mya iphone 7 battery

I want back up my battery percentage