Some reports of excess heat have described abrupt changes in cell temperature which appear sporadically, often after a change in operating conditions (e.g. current density), and last for an indefinite period. These frequently occur only in a single run or with a single specimen. In most cases, the heat bursts represent fluctuations in heat power balance on the order of 1.527 V x I or less [ORI, APP, KAI, BEL]. These "small" bursts are subject to the same experimental problems discussed in Appendix 2.C and can be evaluated according to considerations set forth there. Therefore, they will not be considered further here. There have also been reports of "large" heat bursts of claimed integrated energy magnitudes amounting to megajoules. The temperature changes are so distinct (tens of degrees, even to boiling of the electrolyte) that they seem far out of the range of reasonable calibration errors.
In our Interim Report, the Panel indicated its intention to offer a fuller analysis here of these events. To date, we have been informed of them only through oral presentations, press reports, or private communications. No description has been made in writing, therefore we still have no adequate documentation from which to analyze the significance, and we can provide no references. In fact, the Panel has learned of very few, if any, fresh reports of large bursts since the time when our Interim Report was prepared in July. One laboratory that had previously reported large bursts in open cells has seen no further events since switching to closed cells and better instrumentation. Given the very limited and unpredictable appearance of these large heat bursts, they remain mysterious and perplexing.