I'm trying to plot some data to see how a battery loses its charge over several days. It is two separate batteries connected to two separate testers started at the same time and running in parallel, but generating separate files. The source data is just two worksheets each consisting of timestamps in the left column and voltage measurements in the right column. The timestamps within each worksheet are not identical, but are during the same time period, since both tests were running simultaneously.

Why is Excel only plotting everything across the left half of the space, leaving the right half completely blank?

See the generated plot:

plot.PNG