What happened

Shares of electric vehicle leader Tesla (TSLA -1.92%) zoomed higher on Wednesday morning, and were up by 5% through 11:58 a.m. ET.

You can give some credit to Cathie Wood for that.

Man in suit holding a cell phone while driving is amazed at acceleration.

Image source: Getty Images.

So what

Over the past two days, as Tesla stock trended lower, famed (and lately, famously embattled) growth investor Wood scooped up nearly 42,000 shares -- 15,858 shares on Monday, and another 26,081 shares Tuesday -- according to data provided by the website of her investment management firm, ARK Invest. These were Wood's first purchases of Tesla stock in at least the last two months -- and they followed a two-month-long selling streak during which her ARK exchange traded funds (ETFs) sold off more than 490,000 shares.  

Wood, it appears, had been waiting patiently for Tesla stock to top $1,000, and she's been steadily unloading the EV maker's shares ever since, but after they sank below $700 on Friday, she resumed buying.

Now what

What prompted Wood's sudden shift? A stock price that's now 30% cheaper than it was when she started selling was likely one catalyst. But there was also some more substantive news out regarding Tesla on Wednesday. As U.K. newspaper The Independent reported, Tesla's Advanced Battery Research division has announced it has developed a nickel-based rechargeable car battery that has the potential to last 100 years -- or at least 1 million miles -- before it must be recycled. (For the technically curious, the key material's chemical formula is Li[Ni0.5Mn0.3Co0.2]O2.)  

Granted, Tesla's current LiFePO4 batteries are already estimated to have a service life of more than 20 years before they lose 20% of their maximum charge capacity -- longer than the lifespan of most cars. But even so, increasing that lifespan by a factor of five implies the batteries might effectively never lose any significant charging capacity within a car owner's time of ownership. That would give Tesla's vehicles another strong competitive advantage in an electric car market that's getting more crowded by the day.

Even more than Cathie Wood's stamp of approval, this battery news is a good reason for Tesla stock to be rising.