Literally, a "jolt" is a strong, abrupt push. "I was jolted when my car hit a bump in the road." It can be a synonym for "shock." We sometimes refer to electric "shocks," and also as "jolts." Figuratively, a jolt can mean "a burst of energy," "quick energy." For example, "this high-caffeine drink gives you a real jolt." In your passage "emergency" suggests that the battery is almost out of charge, which in an electric car is a serious situation. Here, "jolt" means "a lot of electricity, put into your battery quickly." It means to give your battery a quick burst of charge, rather than a slow, steady flow. "I'm in a hurry, I can't wait an hour for my battery to charge, I need an emergency jolt!"

Emergency jolt em português seria “carga de emergência”, “abastecimento de emergência”.