It all depends, the app learns your habits on how you use your phone. For example in my case once my phone reaches 61% the extra juice kicks in until it charges my phone to 100%. At the bottom of the case there are 10 LED light indicators of how much juice you have left on the extended battery, after that first charge I usually have about 4-5 LED Lights left (each LED light represents roughly a good 10% charge so 4= additional 40% more or less) and then again once my phone reaches 61% and it goes up to 90% or so almost a full charge. Now have in mind I keep brightness to the max, location services on all day, and check my phone constantly. But again the smart app iON technology will charge accordingly but roughly speaking if your phone was at 1% Im sure the case would give it a complete charge to 100% and still have one LED Light left. Hope this helps!