Rechargeable
From CPFWiki
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[edit] Rechargeable batteries
Rechargeable batteries are popular with torch applications, because of the oftentimes relatively high current draw, compared to electronic goods such as IPODs. One set of rechargables can be re-used instead of several sets of alkalines. Not only does this save money over the medium to long term, it also results in less environmental waste.
[edit] Cell voltages
A lot of confusion exists about battery voltage. Ordinary alkalines are rated to 1.5v, but typically are down to 1.2v when 50% used, and rapidly fall thereafter. This is why devices using alkalines often become less responsive over time, or dimmer. Rechargeable batteries are rated to 1.2v, but will hold that until right at the end. You tend therefore to get a more consistent performance from rechargeable batteries. This improved consistency of voltage, is a major reason to prefer rechargeables for torch applications.
[edit] Torch circuitry
3 cell torches, including the Maglite range, often work better. This is because most bulbs, especially LEDs, are designed to operate in the 3-4v range. 3 cells * 1.2 = 3.6v. No conversion circuitry is therefore required in 3 cell torches. The bulb can be powered directly off the battery cells.
[edit] Chargers
Most battery chargers are made as cheaply as possible, and ram too much current in too fast. To get best usage out of your batteries, a charger that polls the voltage of each individual cell via a micro controller, and adjusts charge current depending upon readings, gets best result. The best chargers will also discharge batteries as and when required, before they even start, to eliminate the potential for a "memory effect." The Ansmann Energy 8 is an example of an intelligent premium charger that will look after your batteries.
[edit] Battery types
These are the main types of rechargable batteries sold.
[edit] Nickel-Cadmium (Ni-cd) - 1.2V/cell
The was the first truly mass market rechargeable consumer battery. They retain charge well, but concerns have been raised about the toxicity of the cells in recent years. Still widely sold.
[edit] Nickel-Metal Hydride (Ni-mh) - 1.2V/cell
Currently a popular cell type, with fast charging times, high capacity, and much improved recyclability. However, they do loose charge faster than the old Ni-Cd types, so work less well as, for example, a TV remote battery. Probably the best torch battery type presently sold, based upon the blend of characteristics offered.
[edit] Lithium Ion (Li-ion) - 3.7V/cell
These batteries are typical in mobile phones, where they offer higher density of charge storage. In other words, more amps can be stored in less size and weight. They also do not suffer from the "memory effect." However, they cost more, and are not as long established as the older AA, C, D, types typical in torches.
[edit] Lithium-Polymer (Li-Poly) - 3.7V/cell
Offers about a 20% increase in charge density over LI-ion, but again, offset by cost.
[edit] Lithium Iron Phosphate (LiFePo4) - 3.3V/cell
[edit] Sealed Lead-Acid (SLA) - 2.0V/cell
A classic recharable battery. Never much used for mobile application due to poor size / weight characteristics. However, very reliable if kept topped up, cheap, and as such, often still used in cars, if not torches.
