We describe a new setup for in-situ study of solar cell degradation that accumulates the damage of several subsequent doses of radiation on the same cell. The system has been designed for measurements under in-air proton and electron irradiations. For fluence measurements, the present setup employs a versatile permanent magnet-suppressed Faraday cup, which was calibrated for 10 MeV proton, and 2.65 MeV electron beams. We have used this setup to compare the equivalent proton dose between the JPL method and a new one, proposed by Alurralde for estimation of damage in solar cells due to protons in low altitude orbits.