Low self-discharge NiMH battery

From Wikipedia, the free encyclopedia

Jump to: navigation, search
Question book-new.svg
 This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (March 2010)
This article contains weasel words, vague phrasing that often accompanies biased or unverifiable information. Such statements should be clarified or removed. (July 2009)


The low self-discharge nickel-metal hydride battery (LSD NiMH) was introduced in November 2005. These batteries were developed by Sanyo[1], who called them "Eneloop". Subsequently other manufacturers also offer LSD NiMH.

This kind of battery reduces self-discharge and, therefore, lengthens shelf life compared to normal NiMH batteries. By using improved separator and improved positive electrode, manufacturers claim the batteries retain 70 to 85% of their capacity after one year when stored at 20 °C (68 °F), while standard NiMH batteries may lose half their charge in this time period. Low self-discharge cells are marketed as "ready-to-use" or "pre-charged" rechargeables.

Low self-discharge NiMH batteries are good for photography and other high energy requirement applications. Due to the low self-discharge, they are also suitable for long-term intermittent or low-current uses; they might last a year or longer between charges, much better than ordinary NiMH batteries. They can therefore also be used for electrical clocks, remote controls, etc.

Aside from their longer shelf life, and moderately higher prices, they are otherwise similar to normal NiMH batteries of equivalent capacity and can be charged with normal NiMH chargers. However they are generally available at lower capacities than the highest capacity of normal NiMH batteries, being rated at 2 to 2.2 Ahrs compared to up to 2.8 Ahrs for normal NiMH. In 2009 LSD-NiMH batteries rated at 2.3 to 2.5 Ahrs, actually reaching a capacity of 2.3 Ahrs[2][3], were introduced by Varta[4], Ansmann[5] and Rayovac[6]. Besides, in many devices, run-times for LSD NiMH batteries are as good or better than normal cells that have higher rated capacity, because of slightly higher operating voltage not tripping under-voltage shut off circuits in devices like digital cameras. Some LSD NiMH brands also claim over 1000 charge cycles compared to 500 for normal cells.

Brand names for LSD NiMH batteries include:

Most manufacturers produce only size AAA and AA batteries and the vast majority of low self discharge batteries are sold in these sizes.

Several manufacturers also offer 9v (PP3) LSD NiMH batteries (Varta, Accupower, Gold Peak, Vapex, Uniross, Ansmann, NexCell), rated between 150mAh and 250mAh.

However, many battery companies also market "low capacity" C- and D-size battery by inserting an AA battery into a larger case. Re-wrapped Cs typically have a capacity of just 2 to 2.2 Ah. Re-wrapped Ds typically have a capacity of just 2 to 2.2 Ah when constructed of one AA, or 4 to 4.4 Ah when constructed of two AAs. Although re-wraps offer very limited storage capacity, they are typically priced the same as full capacity C and D batteries. In late 2008, Sanyo announced full capacity (not re-wrapped) C and D cells in Japan, but at that time said they had no plans to bring them to the U.S., whereas other manufacturers (Ansmann, NexCell, AccuPower) do offer full capacity C (rated at 4.5 Ah) and D-size LSD-NiMH-cells (rated from 8-10 Ah) in the U.S. Unlike Sanyo's C and D cells, these cells, however, do not contain a Positive Temperature Coefficient (PTC) device to protect them against overheating. Their capacity, on the other hand, is superior to Sanyo's cells, since Sanyo's C size LSD-NiMH-batteries are rated at 3 Ah and Sanyo's D size LSD-NiMH batteries are rated at 5.7 Ah[7].

Full capacity low self discharge batteries are noticeably heavy. However, one should always read the specifications when shopping for low self discharge batteries. Because re-wrapping and repackaging is a problem in the battery business, one may also wish to avoid low self discharge batteries that do not have the specifications clearly printed on the actual battery.

[edit] Other benefits

Low self-discharge NiMH batteries typically have a significantly lower internal resistance than traditional NiMH batteries. This has a number of desirable effects especially for high-drain applications:

  • Voltage is more stable (less load- and capacity-dependent). This can have a beneficial effect on runtime in electronic devices, which typically have a cut-off voltage per battery that is not much lower than NiMH's nominal voltage. (However, this can also cause some devices with battery status indicators to overestimate the remaining capacity of a nearly drained cell.)
  • Reduced heat buildup when the battery is quickly charged or discharged
  • Higher efficiency
  • Higher instantaneous current discharge capability

[edit] Developments in 2009

Whereas Varta, Ansmann and Rayovac increased their LSD-NiMH batteries' capacity to roughly 2.3 Ah, Sanyo introduced a new version of their Eneloop batteries with improved durability. Sanyo claims that the new Eneloops retain 75% of their charge after 3 years and can be recharged up to 1500 times[8].

[edit] External links

[edit] References

  1. ^ http://www.eneloop.info/home/general-description.html
  2. ^ http://www.candlepowerforums.com/vb/showthread.php?t=257311&page=2
  3. ^ http://www.candlepowerforums.com/vb/showthread.php?t=243283
  4. ^ http://www.candlepowerforums.com/vb/showthread.php?t=243283
  5. ^ http://www.candlepowerforums.com/vb/showthread.php?t=257311&page=1
  6. ^ http://www.candlepowerforums.com/vb/showthread.php?t=234007
  7. ^ http://www.eneloop.info/fileadmin/EDITORS/Portal/PRESS_RELEASES/080911_cd_eneloop_release_FINAL_German
  8. ^ http://sanyo.com/news/2009/10/06-1.html


v • d • e
Galvanic cells
Non-rechargeable:
primary cells		 Galvanic cell
Rechargeable:
secondary cells
Kinds of cells
Parts of cells
Retrieved from "http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery"