Very good,
If you worry about the battery backup, then get this and use it, you won't have to worry about the charge anymore.
If you want to use an iPhone according to your liking at a low price, I can say from my experience that this will be the best phone. The only issue is that the home button doesn't work, you have to use the assistive touch button, and since it's an old phone, there is no face ID & fingerprint.