Batteries, Accumulators

Storing electrical energy. (Page just started. I have much more material available on file.)

The right temperature

Most usual chemistries work best at a moderate temperature, like 20 to 35 celsius.

Endurance, my experience

A NiCd from 1960 years inside a Flash device used for Camera had seen infrequent use only, storage at 20 to 25 celsius. It worked very well 1980, 1990, 2000, and will probably do its job even after 2011.

LiIon 3.6V 750 mAh, size of 2 AA (R6) cells, for Casio A-20 handheld. Frequently used and charged, I did not count cycles, but it got more than 500 from 1999 to 2011. Nevertheless it still works. I have not measured the real capacity left, my feeling is 50%, but it is impressive considering notebook accus use to fail after 2 years. I believe the primary reason is coolness. This WinCE 2.0 / SH3 CPU based device stays just cool. Second reason may be full cycling. I operated the A-20G always on B, and only after Low warning connected to Mains adapter, or echanged for a short time to some primary AA cells.

Sanyo AA / R6 NiCd 500 mAh purchased 1980 still do their infrequent job to power a model radio control (transmitter, receiver) and e-motor power in 2011, without any leaking.

LiIon Battery of SONY SR-11K small notebook failed completely (rapid loss of capacity to less 10%) after 2 years, although not that much mobile use, not that much real use charge / discharge cycles, but kept installed all the time as a replacement for a stationary UPS. Although at the rear end of SR-11K, it felt very warm.

Common errors in computer design

A lot of notebook or laptop computers show at least one of the following major design faults regarding their main Battery.

Hot place

The Battery is placed in a hot location. The new common error is to cover the whole bottom of the device by a conformant Battery.

Although it may look ugly, and may be bad for other reasons, a Battery sticking out is a thermally good solution, keeping Battery close to environmental temperature.

Always 100% charging

It makes little sense not to charge a Battery to 100%, because you could use a lower capacity B instead, if you only intend to use let's say 80% of it.

It makes definitely sense not to start a charge cycle every time a B has been discharged a little. If there is e.g. still 95% inside, do not charge it (unless you really need full capacity next), but at 90% start to charge, and charge to full 100%. Give the user a choice what level he wants the charge to start at.

I have seen devices which start a charge cycle on every connection of Mains adapter. After some minutes they detect the Battery is full (it has been full already before!). This is worst stress for B.

NiMH: Nickel Metall Hydride

Their start in the 1990 years was very disappointing: Higher capacity than NiCd, but self discharge to less than 50% within less than 2 weeks. Higher internal resistance, making high current use impossible or at least inefficient. You had to take them out of the charger at the morning when you wanted full capacity for the day. No way to leave them unattended in a box for some weeks and pull out for usage, as I did with NiCd.

I stayed with NiCd for many years. Gave NiMH another try after AA / R6 top capacities reached 2800 mAh, may have been 2003? Found self discharge to be at NiCd levels now (6 months).

With introduction of Sanyo eneloop, self discharge is much less than conventional NiCd, some years before 2011. But eneloop internal resistance is higher than other NiMH, and of course higher than the famous NiCd sinter cells.

Capacity of NiCd has increased, too, but not reached NiMH.

Around 2008, NiMH started slowly to enter into the last wide-spread exclusive business of NiCd: High temperature + long endurance + high reliability. I refer to contiguous operating temperatures of 60 celsius and above, connected with service life of more than 5 years. Very few LiIon cells intruded that business before NiMH. (I know there are other chemistries and much more extreme conditions, but they are rare, like drill holes into earth.)

NiCd, NiMH as Alkaline replacement, NiXX SPECIAL prop

Basically, every well designed device using standard Alkaline cells shall work with NiCd and NiMH as well (as long as they give power).

NiCd and NiMH usually have 1.2 V, directly after charge up to 1.5 V for a short time, and discharge is complete at 1.1 or 1.0 V. This is compatible to Alkaline. Ugly is the voltage collapses completely within fractions of a second when cell is empty. Every device not prepared for this can get into serious trouble, e.g. loosing memory.

Fresh from shelf, quite fresh from Maker, Alkaline have up to 1.75 V or even a little more. I have seen it. Nominal voltage is 1.5 V, but due to quite high internal resistance (even for Duracell and comparables) under significant load they give less, e.g. 1.2 V. Discharge complete is at 0.9 V.

Of course I have seen devices, in this case radio controlled digital clocks with LCD, which do not operate on NiCd or NiMH, but use only a fraction of a Alkaline cell, because they stop working as soon as voltage drops below approx. 1.4 V (worst cases where 1.5 V), very far from Alkaline being empty.

Unexpectedly well

AA / R6 Alkaline from large Discounters

In Germany, large (food) Discounters like Aldi, Lidl, Plus offer their own brands of primary cells. Performance is a below the top performers, comparable to average cells of known brands, reliable, have a much better performance / price ratio than e.g. well known Duracell.

Cheap shit

AA / R6 Alkaline from unknown brands

They leak within a few month and may damage the device they are installed in.

NiCd AA / R6

Already 1990, I learned that there are a lot of bad NiCd (AA / R6) cells on the market, usually having a high self discharge rate (empty after few weeks). Usually from unknown companies, sold as "Turbo" and with other attractive key words.

Coin cells in multi packs

Do not buy the low price multi packs, even if they bear historically well known brand names (of radio+TV) like Grundig. Often you can see just by intense look at a cell it loses electrolyte (leaks) already the time you buy it. If it does not, good chance it starts to leak 1 or 2 years after purchase - my personal experience.

You do not have to pay the premium price for no value some large stores demand. Buy from a really qualified electronics (component) or battery dealer.



As of 2009, this seems to be top class, and still in 2011. Low internal resistance, efficient hat high discharge currents, fast and superfast charging, good characteristics -40 to well above 60 celsius.

Lithium primary AA and AAA

Appeared first as "Energizer ULTIMATE LITHIUM" (pay attention to LITHIUM printed on package) in 2009 or earlier, later clones(?), too. Exceptionally long shelf life of of more than 13 years, lowest self discharge, large operating range, far surpassing Alkali cells, for temperatures below 10 celsius better than NiMH / NiCd. Price comparable to Duracell Alkaline, or even lower, got a lot in 2009-05 for below 1.50 EUR/piece AA in 4-packs while on sale at regular Superstore, AAA for 1.00 EUR.

May consider it serious waste of Lithium.

Author: Harun Scheutzow
Last change: 2011-07-04