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More introduction :
Batteries are perishable and will eventually fail despite all efforts to prevent them from doing so; The Battery Nurse is a proactive weapon designed to minimize the effects of battery aging.
Battery care and conditioning is somewhat of a dark art and most conventional approaches still rely on the time-tested methodology of battery conditioning through cycling and discharge, even while batteries have changed significantly.
It is important to understand that all batteries exhibit a certain amount of self-discharge; the tendency is most pronounced, how-ever, in nickel-based batteries. NiMh batteries tend to self-discharge at 3-4% of capacity per day, NiCd batteries self-discharge at a rate of about 1% per day. The self-discharge rate is highest for the first 24 hours after being charged and continues at a rate of about 10-15% in the following week, dropping to 10-15% per month thereafter.
Just what defines a loss of battery performance can be described in several ways, physical failure, loss of capacity, and loss of power. The Battery Nurse works by addressing each of these failure mechanisms.
Physical component failure in NiCd and NiMh batteries typically involves the separator between the conductive plates. Separator failure can happen in a number of ways, the principal causes are dry-out due to loss of water in the cell and by crystal growth. Abusive overcharge and over-discharge conditions can contribute to water loss in the cell and cause the separator to dry out; these conditions can be inflicted during the matching process before thebattery even reaches the end-user and cannot be remedied. Con-versely, crystal growth occurs over time and can be rectified. As a cell self-discharges it becomes more susceptible to high-resistance shorts, a phenomenon in which crystal growth is so extensive that the separa-tor is bridged by conductive material. The Battery Nurse monitors the State of Charge (SOC) and attends to the cells to help minimize the formation of crystals. Any high-resistance short that attempts to de-velop is summarily zapped; blown like a fuse.
Loss of capacity and loss of power both occur for the same reasons, to some extent the cause is again the failure of the separator but a sec-ondary cause has been found to be the degradation of active material on the electrodes. Degradation occurs in the form of corrosion, and research indicates that corrosion formation is intensified through the charge and discharge cycle. The Battery Nurse uses the VCS system to prevent unwanted discharge, i.e. self-discharge, and in doing so eliminates the formation of corrosion that is not a direct result of active use of the battery. Just as significantly, the Battery Nurse VCS also avoids any unnecessary charging, which can also contribute to corro-sion formation. Batteries that are stored on the Battery Nurse between uses will not require any potentially damaging cycling, which was pre-viously necessary to achieve peak performance levels. This should be noticeable immediately in newer packs; they can be taken directly from the Battery Nurse, discharged, peaked on a charger, and will still de-liver good punch.
Simply put, the Battery Nurse helps delay the inevitable, it keeps good batteries good longer, helps keep batteries that want to go bad from going bad as quickly, and does absolutely nothing for bad batteries that are already bad (if only it could…).