The ratio method is a recent observable that has been proposed for the study of halo nuclei \cite{PhysLettB705_112}. It consists of the ratio of breakup angular distribution and the summed angular distribution (which includes elastic, inelastic and breakup) and removes the reaction model dependence. Originally, this method was developed for high and intermediate energies and studies of the reactions of $^{11}$Be halo nucleus on $^{12}$C and $^{208}$Pb targets at 70 MeV/u have shown this observable to provide precise information about the halo structure \cite{PhysRevC88_044602}. Given the potential interest in applying this method at lower energy, we explore its validity at beam energies of 20 MeV/u in this work. We use the Continuum Discretized Coupled Channel method and the Coulomb-corrected Dynamical Eikonal Approximation for the study of the reactions of $^{11}$Be on $^{12}$C, $^{40}$Ca and $^{208}$Pb at 20MeV/u. We compare the various theoretical descriptions and explore the dependence of our results on the core-target interaction. Our study demonstrates that the ratio method is still valid at these lower beam energies \cite{PhysRevC93_054621}. This opens up the way to its experimental use in ISOL-type laboratories.

\begin{thebibliography}{99}
\bibitem{PhysLettB705_112} P. Capel, R. C. Johnson, and F. M. Nunes, Phys. Lett. B705, 112 (2011).
\bibitem{PhysRevC88_044602} P. Capel, R. C. Johnson, and F. M. Nunes, Phys. Rev. C 88, 044602 (2013).
\bibitem{PhysRevC93_054621} F. Colomer, P. Capel, F. M. Nunes, and R. C. Johnson, Phys. Rev. C 93, 054621 (2016).
\end{thebibliography}