The 24-year-old netted twice in the space of five dramatic late first-half minutes, the second from the spot, but missed out on a hat-trick after missing another penalty in the second half.
It could have all been different though as striker Clayton Donaldson missed a spot-kick of his own for Crewe just 66 seconds before Rendell netted his second.
The game sparked into life four minutes before half-time when Rendell's header flew beyond Rhys Taylor after Andy Sandell's free-kick.
But within a minute the visitors were awarded a penalty when Dave Winfield clumsily fouled Shaun Miller - but League Two top-scorer Donaldson was denied by Nikki Bull.
The miss came back to haunt Crewe as Lee Bell tripped Lionel Ainsworth and Rendell made no mistake in beating Taylor for a second time.
He should have had a hat-trick in the 79th minute but Taylor turned away his second spot kick after Adam Dugdale's handball.
Source: PA
Source: PA