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1. Charge as often as possible. It's the healthiest thing to do for those batteries.

2. Don't try to deplete the iPhone battery. The iPhone has a limited amount of charge cycles. A charge cycle is fully drained and fully charged again. However, if you use 50% of the battery and charge it back to 100%, you only used half of a charge cycle. So charging more often will make your battery live longer.

Sorry but this doesn't make sense.. Wouldn't the net time spent charging the battery always be the same thus making the "amount" of the spent charge cycles the same as well?

Say I start in the morning and follow your advice and after half a day when I've gone from 100 to 50% I re-charge the phone to 100% again. Then at night I've gone from 100 to 50 so I recharge again. Total amount of charge cycle spent = 50%+50%=100% = 1 full charge cycle.

Or I can just let it go from 100 to 0/10 throughout the day and then at night I recharge to 100%. Total amount of charge cycle spent = 100% = 1 full charge cycle.
 
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