Bimetallic borohydride borate LiCa3(BH4)(BO3)(2) forms during decomposition of LiBH4-Ca(BH4)(2)-carbon composite studied for hydrogen storage. We present LiCa3(BH4)(BO3)(2) as a material suitable for solid state electrolytes. The compound was studied by in situ Synchrotron Radiation X-ray Powder Diffraction, Electrical Impedance Spectroscopy and Cyclic Voltammetry. The conduction pathways in the crystal were estimated via Topology Analysis. Room temperature Li+ ionic conductivity reaches the value of 2.5 x 10(-6) S/cm with an activation energy of E-a = 0.25(5) eV. We have investigated the effect of doping on cation sites on the ionic conductivity in the temperature range 293-383 K, and showed that the heterovalent doping with Na+ increase RT sigma(Li+) up to 1 x 10(-5) S/cm with a saturation at 5 at.% of the dopant. Doping with Sr2+ of the Lithium excess containing samples enhances the Li+ conductivity by one order of magnitude in the same temperature range, and with the same saturation limit. In both cases the activation energy increases into the range of 0.47-0.63 eV which is also the case of self-doping with excess Lithium. The Li+ ions are mobile in the borohydride borate on a particular pathway composed exclusively from borate anions where Li+ was found in a previous work using ab initio calculations in an octahedral coordination. The pathways create a conduction framework, which is stabilized by the second substructure containing calcium borohydride. The compound is a first example of double anion bimetallic ionic conductor combining borate based substructure favourable for light cation mobility with a stabilizing effect of heavier cation borohydride.