As lithium-ion batteries age, the state-of-health (SOH) of the batteries reduces, which implies that the capacity that can be stored reduces, and simultaneously, the internal resistance increases. Before such batteries are discarded for recycling or used for a second life, the estimation of the SOH becomes very important. In this work, we investigated the applicability of thermal and entropy measurements for SOH determination. Lithium-ion cylindrical cells of three different chemistries, NMC/Graphite, NCA/Graphite and NCA/Graphite with doped silicon, were wrapped in a Styrofoam with about 10cm thickness to provide good thermal insulation, and the temperature sensor was placed between the cells and the Styrofoam. The cells were aged using 1C charge and 1C discharge cycles, while at intervals, the cells were charged and discharged at a C rate of 0.2C, and temperature variation with respect to the voltage was observed. Result shows that the differential temperature, with respect to the voltage during charging within a specific voltage range of 3.8 V to 4.2 V, where there is usually a drop-in temperature due to the entropic heat, shows some good correlation with the SOH. In the same experimental setup, the galvanostatic intermittent titration technique (GITT) was carried out, in which the cell was discharged using a pulse discharge current of 0.2C for 2.4 min and the rest of 6 min till low voltage cut-off. The differential temperature in the GITT measurements also shows a similar but worse correlation to the SOH due to the impact of the rest time. This proves that differential temperature at low C-rates is an effective method for estimating the SOH without carrying out the time-consuming full-capacity checks. The approach can also be incorporated into the BMS system for the online SOH estimation or to guide current-limiting circuits to operate the cell within safe limits as it ages.