Celebrating the independent kiwi spirit of invention.

Research Topic: Which Battery Will Do?

Last updated:	Overview & Terms 31 May 2007		Single Use 8 November 2007		Rechargeable 29 May 2009		Suitable Uses 24 August 2008		More Info & Links 24 August 2009
Original article by Ian Mander, 22 July 2002.			Single Use Test 6 November 2007		Rechargeable Test 13 April 2008
			Battery Analyser 12 April 2008

On this page: Battery Testing | Conclusions | AA NiMH Cells | AAA NiMH Cells | Testing Procedure

Rechargeable (Secondary) Battery Testing

AA and AAA NiMH cells are the most common type of rechargeable battery, so I've started testing some that are available in New Zealand.

This testing raises the question do these NiMH cells break fair trade laws? Many of the used cells do not have the claimed capacity, some falling short by a wide margin. There is also doubt that they last anywhere near as long as the 1,000 cycles often claimed for NiMH cells.

At a later date I may accept NiMH cells for testing, especially if they are a brand or capacity not yet listed, but unless in sealed packaging they will be included in the results as used. However, at present (and while I fine-tune my procedures) I have enough cells yet to test.

Conclusions

Eneloop AA 2000. Testing has shown these to be great cells (at least when new - long term testing will show). Capacity of 71.3% is a little disappointing for only 8 months on the shelf (since manufacture), since Sanyo claims 70% capacity after two years. I have since found out that Sanyo has said they only charge Eneloop cells to about 75% before they leave the factory (a bit strange for "ready to use" batteries, though) so 71.3% is pretty good.

Eneloop AAA 800. Again, initial testing shows a great cell. Like all new Eneloops, they appear to have had a ³/₄ charge after manufacture.

AA NiMH & NiCd Cells

DSE 2000mAh. Used. Cell labeling includes "210AAHC".

Eneloop 2000mAh. New. "Typ. 2000mAh (Min. 1900mAh)". Low self-discharge/long shelf life NiMH, with a claimed 85% charge after one year - an untested claim. Also untested is the claim of a higher voltage during discharge than other NiMH cells (and therefore greater power).

GP 1800mAh. Used. Each cell has the claim "min. 1750mAh" printed on it, along with "Standard Charge 16Hrs at 180mA". Also has "180AAHC".

Yuasa 450mAh NiCd. Used. Very used. Don't know if the charger can charge slowly enough - might skip this one. I'm told some still hold volts, though.

Used cells are listed in italics.

Notes/Detailed Results

Unless otherwise mentioned, all capacity results are in ascending order, not in slot order. The ranking order between particular tests may vary.

Eneloop 2000 - bought from Thomas Distributing (8 cells), manufacture date May 2006; bought from Online Shop Singapore (4 cells), manufacture date November 2006. Packaging for Online Shop cells labelled RWPrince,... Singapore, although the cells shipped from Hong Kong. As delivered they were partly charged, with an average cell voltage 1.308V (from TD), while the newer cells (from OSS) were all 1.310V.

Off shelf disch at 500mA (0.25C): 1420, 1420, 1423, 1441 - average 1426.
Off shelf disch at 400mA (0.2C): 1413, 1431, 1452, 1455 - average 1437.75.

1st break in (400mA, 0.2C): 1991, 1996, 1999, 2005, 2010, 2012, 2018, 2036 - average 2008.375.
2nd break in (400mA, 0.2C): 1977, 2000, 2002, 2005, 2007, 2017, 2020, 2032 - average 2007.5.
1 amp (0.5C) disch: 1980, 1983, 1987, 1992, 1992, 2000, 2016, 2025 - average 1996.875.

Testing the charger's effectiveness at fast charging these cells, I also ran some other tests on the 8 TD cells.

1 amp (0.5C) disch after 1A (0.5C) fast charge: 1923, 1930, 1933, 1934, 1936, 1939, 1962, 1962 - average 1939.875.
1 amp (0.5C) disch after 1A (0.5C) fast charge and leave overnight: 1934, 1937, 1973, 1974 - average 1954.5 (first set of four only).
1 amp (0.5C) disch after 2A (1C) fast charge: 1889, 1910, 1912, 1930 - average 1910.25 (first set of four only).

The first break in capacities seemed pretty good but to see if they would all go over 2000mAh I restarted the break in cycle after the discharge rest, and sure enough, the 1999mAh cell was up to 2005mAh. The second break in with the second set of 4 left just one cell below 2000mAh, at just 1977mAh, but strangely the same cell gave 1987mAh at a 1 amp discharge (both in outside slots on the charger). With the best two cells from the second set, the best cell was always the one positioned in slot 2 or 3, while the other was in slot 1 or 4.

Update 20 June 2007: I've just put one set of Eneloops through another break in and was pleasantly surprised to see the results, both for their high capacity and for their consistency, within 1.1% of each other. In slot order, in mAh: 2092, 2115, 2100, 2116.

Another six Eneloops have been tested.
Off the shelf voltage: 1.320 V average.
Off the shelf capacities: 1341, 1348, 1374, 1396, 1387, 1392 mAh.
Break in: 2061, 2072, 2067, 2059, 2086, 2067 mAh. (Same order.)
1 amp (0.5C) discharge: 2045, 2050, 2069, 2066, 2100, 2078 mAh. (Same order - some have gone up!)

April 2008: Another four Eneloops are being tested, with the datestamp June 2006. These results have not been included in the results shown in the table because they were made using an analyser from a different batch.
Off the shelf voltage: 1.295 V average.
Off the shelf capacities: 1316, 1305, 1338, 1318 mAh (in slot order).
Break in 1: 1946, 1936, 1940, 1930 mAh.
Break in 2: 1943, 1934, 1939, 1929 mAh.
Break in 3: 1944, 1933, 1935, 1928 mAh.
1 amp (0.5C) discharge: 1929, 1928, 1930, 1919 mAh.

GP 1800 - sold by Dick Smith Electronics as a set of four with a fast charger, and have been observed to have a low self discharge rate. One of the cells died a few months after purchase, leaving only three in that set. The GP battery charger rejected it as defective so it hadn't been used since, but for reasons best understood by squirrels it was kept. It showed 2.4 ohms and 0 volts before the successful (?) attempt was made to resurrect it. That the 500mA test capacity was larger than the 0.2C rate (360mA) indicates that the cell still needs a bit of cycling.

Break in (360mA, 0.2C): 1648, 1745, 1764.

Yuasa 450 - hasn't been sold for years, if not decades. These cells are perhaps 25 years old. They've had a hard life and a long one, and will be shortly retired. (Well, when new NiMH cells are available with six times the capacity... yeah.) Testing them will be difficult since the positive lug/nipple isn't big enough to contact the MH-C9000. (Might need some magnets.)

AAA NiMH Cells

Eneloop 800mAh. New. "Model HR-4UTG 1.2V   Typ.800mAh, Min.750mAh".

Powertech 800mAh. Used. "Standard Charge: 80mA for 15hrs". This is the Jaycar house brand, and not to be confused with Maha PowerEx.

Used cells are listed in italics.

Notes

Eneloop 800 - premium brand low self discharge AAA made by Sanyo.

First set of 4, manufacture date April 2006, so they're one year old.
Voltage straight off shelf 1.30 V, average shelf capacity 568 mAh.
Average break-in capacity 844 mAh.

8 more, manufacture date October 2006, tested September 2007 (about 11 months old).
Straight off the shelf, average voltage 1.301 V.
Capacities straight from packet: 589, 600, 590, 602, 589, 590, 598, 607 mAh, average 596 mAh.
Break-in: 836, 835, 844, 856, 842, 849, 839, 849 mAh, average 844 mAh.

8 more, manufacture code 06-07 00 (July 2006), tested January 2008, so 18 months old at time of testing.
Straight off the shelf, average voltage 1.294 V - the lowest for Eneloops I've seen yet.
Capacities straight from packet: ?, ?, ?, ?, 555, 564, 570, 570 mAh, average 564.75 mAh.
Break-in: 845, 855, 858, 860 (first set), and 853, 860, 839, 857 (second set, slot order) mAh, average 853 mAh.
Capacities @ 0.5C: ?, ?, 841, 853, 831, 850 mAh.

Powertech 800 - sold by Jaycar Electronics. Used regularly, seems to have quite a high self discharge. Many also have high impedance - to the point that the MH-C9000 refuses to charge 4 of the 12, and had issues with several more before eventually deciding they were OK. They haven't had several hundred charges, so at this point I cannot recommend these cells.

Break in, 0.2C (160mA) discharge: 603, 615, 616, 619, 651, 687 - average 631.833.
0.5C (400mA) discharge from 16 hour charge: 563, 575, 587, 594 - average 579.75. Also 615, 619 - they've gone up! Time for some cycling perhaps? These will be retested before being include in overall results.

Other testing, to see how well charger works with these cells:

0.5C discharge from 0.5C charge: 512, 518, 528, 544 - average 525.5.
0.5C discharge from 1C charge: 424, 483, 497, 513 - average 479.25.
0.5C discharge from 1C charge, left overnight: 489, 535, 541, 561 - average 531.5.
Same again after a bit of cycling: 515, 581, 608, 613 - average 579.25.

Powertech 900 solder tag - sold by Jaycar Electronics. These were installed in the battery of a cellphone in May 2005, and were basically abandoned in February 2007 as being too unreliable to power the phone. They were recharged every 2-3 days on average so probably had only about 250-300 cycles, and probably far fewer than 200 cycles before their capacity noticeably decreased. Not good. The two previous sets of cells each lasted over three years (a respectable 500+ cycles for each set), and while the earlier cells had a lower claimed capacity (eg, 650mAh for the initial set), the life of the phone with the latest set of cells did not seem appropriately longer. So it seems as though the quality of the Powertech cells is decreasing, and once again, I cannot recommend them.

Testing Procedure

Proposed testing procedure is as follows, designed to produce reasonably relevant results for real-world uses such as digital cameras.

1. New cells only: Discharge at 0.2C to determine maximum off-the-shelf capacity (for Eneloop cells) and prepare all cells for breaking in. The 0.2C rate is used here because it will provide a direct comparison with the 0.2C discharge used in the break in (step 3).
    
2. Used cells only: Fast charge (0.5C rounded up to nearest 100mA), then discharge at 0.2C to determine initial condition.
    
3. Both new and used cells are broken in (or "formed"), using the claimed capacity entered into the MH-C9000 for it to determine charge and discharge rates. As per the MH-C9000 regime (from an IEC specification, apparently), cells are charged at 0.1C for 16 hours, rested for one hour, discharged at 0.2C, rested for one hour, charged at 0.1C for another 16 hours.
    
4. Rest then discharge AA cells at 1 amp, AAA cells at 400mA.
    
5. Fast charge (0.5C rounded up to nearest 100mA), rest, then discharge at 1 amp (AA) or 400mA (AAA).
    
6. For Eneloop AA cells: Charge at 2 amp for 1.1 hour, rest, discharge at 1 amp.
   For Eneloop AAA cells: Charge at 800mA for 1.1 hour, rest, discharge at 400mA.

All charge and discharge rates are nominal; the MH-C9000 integrates the total mAh based on the actual current. It terminates discharge at 0.90V, avoiding a possibly damaging deep discharge. 500mA is the analyser's default discharge rate but at present sounds like too much work to include it in the test regime, and it's the same as the 0.2C test for 2500mAh cells anyway. 1 amp is a very common discharge test, since digital cameras often use about that much current.

Resting the cells after charging gives more realistic capacities than using them "hot off the charger".

All testing done at room temperature. All results listed in order of capacity.

Break-in Start/Finish Completion Times Chart

The whole break in process takes at least 39 hours - more than a day and a half. See the table below for start and finish times.

Light grey for the day after commencing, darker grey for the day after that.

A few battery shoot-outs are mentioned on the More Info & Links page, or get information on the charger/analyser I use.

Read on for suitable uses for particular battery types.

Last updated:	Overview & Terms 31 May 2007		Single Use 8 November 2007		Rechargeable 29 May 2009		Suitable Uses 24 August 2008		More Info & Links 24 August 2009
Original article by Ian Mander, 22 July 2002.			Single Use Test 6 November 2007		Rechargeable Test 13 April 2008
			Battery Analyser 12 April 2008

Celebrating the independent kiwi spirit of invention.

Contact:
Return to ianman HOME | Back to Aqualab Home | Return to TOP
Inventions: Super Soaker Backpack | Air Cannon | LED Torch