Low-voltage radial electricity cables will have more and more difficulties to carry the increasing load of novel consumption devices (e.g, electric vehicles) and the expected generated input of decentrally-generated power (e.g, from photovoltaic cells). One solution to avoid replacement is to install a battery at the end of a cable which is expected to be overloaded frequently. The intelligent operation of this battery needs to combine the protection of the cable with optimizing its revenue, in order to be economically viable. This paper formulates the offline optimization problem and proposes two robust heuristic online strategies. We show in computer simulations that these heuristics, which make fast just-in-time responses, reliably deliver good results. Our second heuristic, H2, reaches up to 83% of the approximated theoretical optimum.