The present invention concerns a process for the recovery of metals and of heat from spent rechargeable batteries, in particular from spent Li-ion batteries containing relatively low amounts of cobalt. It has in particular been found that such cobalt-depleted Li-ion batteries can be processed on a copper smelter by: feeding a useful charge and slag formers to the smelter; adding heating and reducing agents; whereby at least part of the heating and/or reducing agents is replaced by Li-ion batteries containing one or more of metallic Fe, metallic Al, and carbon. Using spent LFP or LMO batteries as a feed on the Cu smelter, the production rate of Cu blister is increased, while the energy consumption from fossil sources is decreased.