FIELD: equipment providing for well drilling; applicable in power supply of downhole devices. SUBSTANCE: power source has body installed in interval between string drill pipes. Secured to body are thermoelements interconnected with one another and with downhole devices by wires. Thermoelements are installed in recesses made over circumference on body external surface. Recesses may be arranged in several rows. Thermoelements may be filled in recesses with composite material or rubber mixture. Electric wires may be introduced inside body and insulated. Each thermoelement consists of series circuit of different conductors forming points of electric contacts. Thermoelements may be connected in parallel, or series, or series-parallel. EFFECT: increased power and reliability of power source. 6 cl, 2 dwg
