Tesla Inc.’s former energy chief has secured more than $230 million to expand his battery startup into new markets. It’s the latest sign that the multibillion-dollar US home energy storage market is heating up as strain on the grid increases.California-based Lunar Energy develops software that helps optimize home batteries to charge when electricity is cheap and send stored energy back to the grid when demand is high. It also began deploying its own batteries by working with distributors last ye...