FIELD: well drilling; applicable as source of power supply of downhole apparatuses. SUBSTANCE: power supply has chemical cells enclosed in cases and located in common body secured with clearance inside drill pipe string. Chemical cells are made with separately stored components. In this case, main component is located in closed cavity of chemical cell. Closed cavity is communicated with additional cavity containing component activating the chemical cell. Common body accommodates control unit and voltage monitoring unit, both connected with chemical cells. Component activating the chemical cell may be used in form of drilling mud found in clearance between power supply and drill pipe string. Power supply may be made for alternating of chemical cells use. Closed cavity may be communicated with additional cavity through separating device in form of membrane with piston or in form of membrane and explosive charge with electric detonator, or in form of valve with drive. In latter case, filter may be installed in front of valve. Each chemical cell may have mixer ensuring homogeneity of mixture of separately stored components. Mixer may be made in form of two plates with holes. Holes in plates are located at angle to axis of power supply of downhole apparatuses. EFFECT: increased service life of power supply with insignificant circulation of drilling mud and trouble-free supply of downhole apparatuses. 11 cl, 6 dwg
