In this paper we present the results of an expert elicitation on the prospects for advances in battery technology for electric and hybrid vehicles. We find disagreement among the experts on a wide range of topics, including the need for government funding, the probability of getting batteries with lithium metal anodes to work, and the probability of building safe Lithium-ion batteries. Averaging across experts we find that U.S. government expenditures of $150M/yr lead to a 66% chance of achieving a battery that costs less than $200/kWh, and a 20% chance for a cost of $90/kWh or less. Reducing the cost of batteries from a baseline of $384 to $200 could lead to a savings in the cost of reducing greenhouse gasses of about $100 Billion in 2050.