Aqualab: Research: Which Kind of Battery?

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Research Topic: Which Battery Will Do?

Last updated:

Overview & Terms
8 March 2012

Single Use
7 January 2016

Rechargeable
10 November 2019

Battery Analyser
23 April 2021

Battery/Charger Shopping
24 April 2021

Original article by Ian Mander, 22 July 2002

Single Use Test
6 November 2007

Rechargeable Test
21 September 2023

Test Procedure
4 June 2011

Button and Coin Cell Shopping
31 July 2021

More Info & Links
29 February 2012

LSD Shootout
7 January 2016

When Battery Testing
Goes Bad –
Consumer Magazine
20 June 2023

Battery Holder Shopping
28 July 2022

On this page: Contenders | Results | Conclusions

Low Self Discharge NiMH Shootout

Testing and report originally posted 8-12 June 2011 by Ian Mander.

Low self discharge (LSD) NiMH cells are very quickly becoming one of the most popular rechargeable battery types. How well do they perform after they've been used a bit?

Please note that this test is in no way "fair". The cells are different ages and have been used a different amount. However, the results do give an indication of how the cells will perform when their newness has worn off.

Contenders

In June 2011 the following cells were tested.

Camelion AlwaysReady AA LSD NiMH

Claimed 2100 mAh. Two cells, said to have about a dozen cycles. "NH-AA2100AR typ.2100mAh 1.2V AA HR6".

Apparently no longer available on TradeMe, having been replaced by a 2300 mAh cell.

Sanyo Eneloop AA LSD NiMH

Claimed 2000 mAh. Two cells, bought four and a quarter to four and a half years previous to time of testing, said to have "a fair few" cycles. "HR-3UTG 1.2V Typ.2,000mAh Min.1,900mAh". One has the manufacture date code "06-10SC", the other "06-11HN", which means October and November 2006, so that places them at a little over four and a half years old.

These Eneloops are of the first generation which claimed 1000 cycles. They have been replaced in most shops by the second generation claiming 1500 cycles, or the third generation claiming 1800 cycles; available from PB Tech.

Both contenders were put through the same testing scheme:

A Break In using the MH-C9000. This supposedly helps condition the cells and should give an optimum value for the capacity. (It's based on the IEC test for cell capacity, which should be how manufacturers arrive at their claimed capacity. Some manufacturers exaggerate.)
A 48 hour pause. (Well, they are LSD cells – I figure they're not likely to always be charged immediately before using, but don't want to hang around for ages before testing them.)
A 500 mA discharge taking note of the voltage as it discharged. Having the voltage figures means that the amount of energy each cell had can be calculated.
Another 0.1C charge (interrupting the Break In after the first charge).
A 48 hour pause.
A 1 amp discharge, taking note of the voltage under load.

Results

For each battery type, results are the average of the two cells, and the percentage difference between the two cells.

Test		Camelion AlwaysReady	AlwaysReady cell variation	Sanyo Eneloop	Eneloop cell variaton
Break In capacity		1900 mAh	4.8%	1726 mAh	2.5%
% of claimed		90.5%		86.3%
500 mA	Capacity	1815 mAh	5.0%	1594 mAh	2.9%
	% of claimed	86.4%		79.7%
	Rest voltage before test	1.414 V	0.14%	1.415 V	0.07%
	Discharge voltage after 30 seconds	1.230 V	5%	1.295 V	0.8%
	Voltage at half capacity	1.115 V (ie, 4.46 V for 4 cells)	0.90%	1.178 V (ie, 4.71 V for 4 cells)	0.43%
	Energy	2218 mWh	2.8%	2070 mWh	3.5%
1000 mA	Capacity	1812 mAh	3.1%	1600 mAh	3.6%
	% of claimed	86.3%		80%
	Rest voltage before test	1.420 V	0%	1.421 V	0%
	Discharge voltage after 30 seconds	1.215 V	5.9%	1.290 V	0%
	Voltage at half capacity	1.115 V (ie, 4.46 V for 4 cells)	2.7%	1.175 V (ie, 4.70 V for 4 cells)	0.85%
	Energy	2215 mWh	0%	2075 mWh	3.9%

The AlwaysReady cell with the lower voltage during the 500 mA discharge managed a higher capacity, thus reducing the difference in energy between the two cells; in the 1000 mA discharge the energy just happened to end up the same.

The MH-C9000 uses a 90% duty cycle, so the times in the first graph are longer than would otherwise be expected for the discharge rates used.

Conclusions

For each brand, capacity and energy was not much different between the two tests (500 mA and 1 A). Both brands were able to cope with the higher discharge rate without losing capacity.

The Eneloop cells held their voltage quite well until near the end of their capacity then died more quickly (and sooner of course) than the AlwaysReady cells. In other words, the Eneloop's rolloff was faster.

The capacity of the Eneloop cells was higher for the 1 A test than for the 500 mA test. Perhaps a bit of cycling would increase their capacity some more.

Test	Camelion AlwaysReady	Sanyo Eneloop	Notes
Capacity			The AlwaysReady cells had higher capacity and energy in both tests. They will last longer in devices that are not fussy about their battery voltage.
Energy
Voltage under load			The Eneloop cells had slightly higher voltage under load. They will work better in devices that are somewhat (or very) fussy about their battery voltage.
Capacity with voltage-fussy devices
Cell consistency			The Eneloop cells generally had lower cell variation (higher consistency). Implies they are better manufactured, and being better matched as a set means less chance of reverse charging when the first cell in a battery goes flat. Both factors mean they should last for more cycles.

Which one is better? It depends on how you're going to be using them and what you're going to be using them in.

How likely will the Eneloop's extra voltage be noticeable in the real-world? It's not a lot – just 0.25 V for a 4 cell battery in the middle of its discharge. That might slightly reduce the cycle time of a camera flash, or an incandescent light bulb would be slightly brighter. But it won't be by much, and you may not even notice. In most devices you could get by with either. However, in some electronic devices that are particularly fussy like digital cameras, GPS units, or LED drivers that drop out of regulation suddenly, it might make all the difference. If a device wants 1.15 V per cell to function at an acceptable level then the Eneloop has 1200 mAh while the AlwaysReady has just 200 mAh.

How many cycles will either type of battery last and keep a usable capacity and voltage under load? That remains to be seen.

In summary, long term reliability and a little bit extra voltage is nice, but it comes at the cost of capacity and energy. Both brands of used LSD cells tested are OK, but neither is ideal.

A few battery shootouts 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.