The galvanostatic intermittent titration technique is a well-known technique for estimating various transport properties of an electrochemical cell. Because of usage of a highly resistive potentiostat, however, no smooth data can be obtained. In the present paper, the spontaneous intermittent titration technique without usage of a potentiostat is proposed and is applied to the commercially available lithium-ion and nickel-metal hydride batteries. It is found that the simple relation V-oc = i(R-i + R-r) holds during the whole process of discharge, with the internal resistance of a battery (R-i) remaining more or less intact. Here, V-oc is the open-circuit voltage of a battery, i is the discharge current, and R-r is the external reference resistance. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3082376] All rights reserved.