The iPhone 11 Pro Max has one of the best batteries on an iPhone. The battery boasts approximately 10-15 hours. Of course it depends what you’re doing on your iPhone but the battery on the Pro Max will give you a decent amount of juice. If you tend to use your phone more for audio playback and phone calls than internet browsing you can expect more time out of the battery. The iPhone 11 Pro Max has a 3969 mAh which not only beats out the XS Max battery but also is the best of the iPhone gen 11 phones. It will charge faster and last longer.
It’s important to note that when you purchase a refurbished iPhone, the battery has likely been slightly depleted but at Frank we guarantee our batteries retain a minimum of 80% of their original capacity (which Apple has declared sufficient for efficient battery performance).
Apple's lithium-ion batteries are designed to hold at least 80% of their original capacity for a high number of charge cycles, this will vary depending on the product.