Comment on the following is welcomed. The following are (stated said to be by the source) statements by the actual manufacturers of each of the NimH brands involved. Avoiding high temperature storage is a major requirement of successful longer term storage. Not having any load applied is also very important. Note general advice re loss of charge with time and a need to recharge several times on first use before full capacity is reached. General advice on new NimH is that they do not attain full capacity for "several" cycles. With manufacturer-new cells my experience has been that they are largely at full capacity by the 2nd cycle. YMMV. With stored cells this could take more cycles, as suggested below. My personal experience with older well used NimH cells is that charging them on a regular basis is liabl;e to keep them in good condition longer. As always, YMMV. Russell __________________ *From: http://www.powerstream.com/Storage.htm * NiMH (Nickel Metal Hydride) Battery Storage Duracell NiMH Battery Storage Ni-MH batteries can give years of safe and reliable service if they are used in accordance with recommended procedures and are not abused. Batteries should be kept clean and dry both during use and storage. They can be stored for many months in a charged or discharged state without any detrimental effects as long as they are not exposed to extreme temperatures for any long period of time. After periods during which the battery has not been used, the battery should be charged before being placed in service. Extended overcharging or overheating of the battery should always be avoided. Varta NiMH: Battery storage in any state of charge is possible. Storage temperatures between -20 and +35 are recommended, relative humidity approximately 50%. In case of long term storage cells must be recharged once a year. *Sanyo NiMH*: Under the recommended storage conditions (-20 C to +35 C) the Twicel can be stored indefinitely in either a charged or uncharged state. Recovery may take several cycles. If a battery is stored for a prolonged time connected to a load, electrolyte fluid will leak, the battery will begin to deteriorate, and capacity will be impaired after storage. During long time storage battery deactivation may tend to occur, and for this reason charging may stop early during recharging after storage. This problem can be solved by charging and discharging the battery several times= .. *Sanyo NiMh Battery Storage*: Generally speaking, a loss of voltage and capacity of batteries due to self-discharge during storage is unavoidable. The factors inducing this self-discharge of Nickel-Metal Hydride batteries is listed below: 1. The inside of the cell is a hydrogen atmosphere at low pressure, which gradually reduces the active materials at the positive electrode, resulting in a drop of cell capacity. Accompanied by this, the negative electrode which is thermodynamically unstable in its charged state gradually gives off hydrogen gas, thus reducing cell capacity. 2. The active materials at the positive electrode in its charged state self-decompose, causing the cell capacity to decrease. 3. Impurities within the cell, especially nitric ions, are reduced at the negative electrode and diffuse to the positive electrode where they = are oxidized. This results in a lowered cell capacity. The factors (2) and (3) also apply to Nickel-Cadmium Batteries. As discussed above, the self-discharge of Nickel-Metal-Hydride Batteries during battery storage causes a loss in stored energy. However, once recharged, this lost portion of the capacity will be almost completely restored. The self-discharge characteristics of Nickel Metal Hydride batteries is affected by storage temperature. . . If the battery is stored at high temperatures, the self-discharge will be accelerated. Also, the longer the storage period, the more the cell capacity decreases. As mentioned above, since the capacity of Nickel Metal Hydride batteries lost by self-discharge can be restored by recharging, there are virtually no noticeable adverse effects of battery storage. However, prolonged storage at high temperatures may deteriorate or deform the gasket or the separator, and should be avoided. Either fully charged or discharged, Nickel Metal Hydride ( NiMH ) batteries may be stored indefinitely. . . In either cased (charged or discharged) the capacity is recovered within two or three charge / discharge cycles. Panasonic NiMH Battery Storage Because long term storage can accelerate battery self-discharge, and lead to the deactivation of reactants, locations where the temperature ranges between +10=B0C and +30=B0C are suitable for long term storage. When charging for the first time after long term storage, the deactivation of reactants may lead to increased battery voltage, and decreased battery capacity. Restore such batteries to orginal performance by repeating several cycles of charging and discharging. When storing batteries for more than one year, charge at least once a year to prevent leakage and deterioration of performancedue to self-discharging. __________________ Some advice here. Sounds good. Quality unknown: http://www.camlight.com/techinfo/techtips.html --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .