Research Topic: Which Battery Will Do?
An example of trying to get blood out of a stone is the Energizer Helpdesk page in the Humour section of this web site. All I wanted to know was the most basic of information about what batteries suited what kind of devices.
Energizer has continued to generate bad feelings with their 2500 mAh NiMH cells, widely regarded as the worst high capacity cell available, and that hasn't changed with the latest version, available in 2450 mAh and 2500 mAh. Tests are hard to come by because almost no one in their right mind wants to buy the pathetic things, but one three week self discharge test does investigate the claim they last up to six months. It seems very unlikely - they lost 13% in three weeks, more than twice the other high capacity cell tested.
For more information on rechargeable batteries have a look at this battery article at Extreme Tech or for single use D cells I quite like this battery test by a couple of home-school students (you'll have to scroll about two thirds of the way down to find it).
Imaging Resource has a very good test/review of AA rechargeable batteries, covering a huge range of NiMH battery brands and models. It's unfortunately somewhat out of date (stopping at 2300mAh) but it does include three brands of alkaline batteries for comparison - and they do not compare well when run at 1 amp in the test.
Robert's Photography Blog has a Battery Round-up that lists a few brands of AA and AAA NiMH cells and notes how much capacity they actually have as measured by the La Crosse AlphaPower BC-900 - a nifty charger that can cycle NiCd and NiMH cells and measures their capacity as it discharges them. I don't know how accurate it is, but it's interesting to note how poorly a couple of brands of the AAA cells performed, having only around 78% of their claimed capacity. One of those brands, Moden, is commonly available in New Zealand. Robert found that the supposedly 1,000mAh AAA cells he tested actually failed to reach even 800mAh. It's particularly bad because the BC-900 discharges straight after charging, without resting the cells at all, which leads to unrealistically high results as far as real world usage goes, where cells are not normally used hot off the charger. One of the footnotes is also interesting:
Imaging Resource has a Great Battery Shootout by Dave Etchells. Although somewhat dated now, it lists a large number of NiMH cells, some of which are available in New Zealand. Very interesting is his inclusion of three leading brands of alkaline battery, which don't compare well to the NiMH cells at the 1 amp test current.
Eneloops and Imedions are compared in a camera flash cycle-time test by Calvin Foo. He writes: Eneloop completed at 1564 shoots and Imedion completed at 1660, approximately 100 shots more than Eneloop, which is pretty much expected as it is a 2100mAh vs 2000mAh, with approximately 5% extra power. ... On cycle performance point of view, Eneloop out performed Imedion from 4rpm to 14rpm with an amazing everage of 6rpm on a consistant performance. In this experiment, it is concluded that the Sanyo Eneloop is a better performer than PowerEx Imedion, at least on a [S]peedlight point of view.
Note that all these tests are not directly comparable with each other because of the different test methods used, but each individually gives useful results. Also note that batteries' claimed capacities are based on a low current test method very similar to the MH-C9000 Break In mode.
Zinc Matrix Power in the Unites States has created the Silver Polymer™ battery (available in several models). They love to point out how the gravimetric storage density is about the same as lithium ion batteries but the volumetric energy density is much greater because the materials are far denser than those in lithium batteries. Their standard cells can be recharged only about 100 times, which doesn't sound all that wonderful at all, but supposedly compares well with lead acid. A 12V 15Ah battery made from 8 silver polymer cells would weigh 1.4kg - supposedly a quarter of what a similar spec lead acid battery weighs. However, the Silver Polymer battery has "only" 80 amps peak, probably costs several tens as times as much, and has very fussy recharging requirements.
Update August 2008: Now known as ZPower Battery, they are pushing the technology as silver-zinc batteries, which "are inherently safe", for mobile electronics. They say they will provide laptops with 40% longer than lithium ion batteries, and expect them to be available in 2009.
NEC Corporation in Japan has shown off the world's first proton-polymer battery - using protons (hydrogen ions) instead of lithium ions. They say the battery takes just five minutes to recharge - nice! Storage density is a bit low for my liking (just 10-15 Wh/kg, or half that of lead acid). However, specific power is quite good (1 kW/kg), so fast discharging goes hand-in-hand with its fast charging. These properties mean that it may have important uses in electric and hybrid vehicles, where very high pulse currents are often needed and batteries need to be able to take sudden rapid charging to reclaim energy from braking. (These fast charge/discharge characteristics mean they have some features more like super capacitors than normal batteries.)
Power Paper has figured out a way of printing batteries onto just about anything, making a 1mm thick flexible battery. They claim 2.5 mAh/cm2, which is about a third of what lithium ion polymer cellphone batteries have for the same volume. So they're not likely to be used for normal cellphones but the flexibility and thinness could find uses in other areas.
Yuasa Delta Technology (Taiwan), a subsidiary of motor battery giant YUASA, is first company in the world to develop nickel-hydrogen AA batteries which can be charged in just 15 minutes. Yuasa has started mass production of two types of battery: AA (2,000 mAh capacity) and AAA (850 mAh capacity). Sanyo Electric, the world's largest manufacturer of nickel-hydrogen batteries, has released a 30 minute chargeable product and was expected to launch a 15-minute charger version in (northern) spring 2004.
Carbon Air batteries look quite promising also. As explained in a May 2009 article (broken link), the STAIR cell (for St Andrews Air cell) uses a block of porous carbon and draws in oxygen from the air, a bit like a zinc air battery as used in a hearing aid. By having one reactant outside the cell, more energy can be produced from the same size cell. The porous carbon is also cheaper than the lithium cobalt oxide used in present batteries. Sadly someone has stuffed up the units in the 3rd to last paragraph.
Envia Systems has created (Feb 2012) a lithium ion battery they claim achieves an energy density of 400 Wh/kg - roughly twice as good as present li-ion batteries - and is half the cost of present batteries. This has been done by adding manganese to the cathode and carbon nano-tubes to the anode. It appears to be good; they say it is at 400 cycles and still going strong. Their next step is several years of testing by electric car makers.