This paper discusses battery temperature limits as a challenge to be answered when using valve-regulated lead-acid (VRLA) batteries in motor vehicles, and then describes the results obtained in road tests on VRLA batteries used in an idling-stop (stop and go) vehicle. In general, using lead-acid batteries at high-temperature increases grid corrosion and water loss, and accelerates deterioration. VRLA batteries are more susceptible to the effects of temperature than flooded batteries, but that is largely due to their structure. Water loss is fatal to VRLA batteries because water replenishment is impossible. At high temperature not only does the electrochemical decomposition of water increase considerably, but a substantial amount of water also evaporates due to the increased vapor pressure. This requires control to keep batteries from exceeding their maximum temperature. The low-temperature limit of lead-acid batteries is at least -50 to -60 degrees C, and that temperature is higher at a low SOC. This is dependent on change in the solidification point of the sulfuric acid electrolyte. From an environmental perspective there are expectations that idling-stop systems will find wide use as simple systems to improve fuel economy. We studied the performance of a conventional flooded battery, a conventional VRLA battery, and an improved VRLA battery in road tests with an idling-stop vehicle, and found that the improved VRLA battery is suited to idling-stop applications because it had a smaller capacity loss than the conventional flooded battery. (c) 2005 Elsevier B.V. All rights reserved.