To: I. N. Vester who wrote (8057 ) 2/6/1999 7:01:00 PM From: Dennis V. Respond to
I.N.,interesting article, but actually omits certain safety concerns in keeping with the source (company PR). Differences in electrode materials and electrolyte have real effects. However, even where the chemistries are similar to poly, no liquid electrolyte, cannister battery has passed the nail gun test. Often, when pierced by a high speed projectile they explode into flame. Plastic batteries usually endure this test without catastrophic results. There are safety differences between cobalt and manganese(spinel) batteries. VERY careful regulation during charging is mandatory for cobalt batteries(liquid or plastic). In keeping with this, the article addressed the need for regulating circuits, thermal links and current limiters to protect against temp rise, short circuits and overcharge. Overcharging the cobalt battery can cause metallic lithium to be electroplated onto the cathode, causing a fire. The manganese battery is not susceptible to the latter problem, but does, naturally, require charge control. Other safeguards, similar to those listed above may be elected by the manufacturer. The referenced article omitted the safety concerns attendant to the lithium metal electrodes used in the Moltech battery. Charge, discharge cycles cause lithium to "migrate" and form dendrites(icesickles) which can pierce the separators causing internal short circuits and fire. In spite of efforts to suppress dendrite formation, this type of battery can only be safely cycled a couple hundred times vice 500 times for the manganese battery and cobalt battery.
