The Powerhouse Capacity: 28,000mAh Unpacked The Energizer HardCase P28K defines high-capacity portable power with its staggering 28,000mAh (100Wh) lithium-polymer battery. This immense energy reserve translates directly into unparalleled real-world endurance. Forget daily top-ups; the P28K is engineered for marathon usage. For the average modern smartphone (assuming a 4,500mAh battery), it delivers approximately 6 full charges.