Tesla, the famed electric carmaker founded by Elon Musk, is not universally loved on Wall Street at the current share price. Ahead of a much-trailed strategy update on battery technology on 22 September, one longtime fan of the stock had a warning for investors.

“If you have a 10-year time horizon, you can make the case the stock is a buy”, said Ben Kallo, an analyst at Baird Equity Research, who has had an “outperform” rating on it for most of the past decade.