Lifejacket Quick Charge Battery (4000mAh) Black. Call it what you like – A battery, A power bank, A quick chargeWe like to think of it as a lifejacket – something you hope to never use but are so grateful to have when you need it.This lithium-polymer battery has 4,000mAh of storage capacity – more than enough to rescue you or a friend in your hour of need. And who doesn’t love a great rescue story?