Fujitsu mini PC not booting

I had a couple of Fujitsu mini PCs purchased cheaply, used from amazon - but neither of them would boot up now, a couple of years after I had used them last. Suspected the BIOS battery - used these videos to help with opening them up - similar, ours was Q920 without the DVD drive - 

Tearing down a Mini PC | Fujitsu Esprimo Q910

Mini PC Teardown - Fujitsu Espromo Q910

Got the CR2032 lithium cell bios batteries also from Amazon, put in new batteries, and they booted up fine.