Tesla is updating its utility-scale Megapack batteries as it seeks to stem the decline of its lucrative energy storage business.The new battery product known as Megapack 3, which Tesla revealed late Monday, are a bid to lure utilities and data center developers that are desperate for power. Megapack 3 stores around 1 megawatt-hour more electricity than Tesla’s largest existing offering and promises a longer lifespan. Tesla also introduced Megablock, a grouping of four Megapack 3 units that can store 20 meg ...