The outter List layer of your data was giving FindFit some heartburn. I had to remove that with First. The result of FindFit is replacement rules of the form {R1 -> val1, R2 -> val2, R3 -> val3, ...}. These rules will directly replace the matching paramaters in your model formula md1. This result I call solution numbe one, sol1. To visualize the performance of the solution, Show the data and the Plot of the fitted curve together.
sol1 = mdl /. FindFit[First@datav, mdl, RC, var]
Show[ListPlot[datav, PlotRange -> All], Plot[sol1, {t, 0, 2}, PlotStyle -> Red]]
