Could Activ Energy rechargeable batteries be Eneloop killers?

All of my rechargeable nickel-metal hydride AA cells are Eneloops. I was surprised to find that Activ Energy cells from ALDI give similar performance at half the price.

Active Energy NiMH rechargeable AA cell.

Active Energy NiMH rechargeable AA cell.

Product description

The Activ Energy AA cells tested were 2400 mAh capacity, low self-discharge and “extra long life”. Here is a comparison with Eneloop specifications:

Cell Origin Date Min. cap. (mAh) Max. cycles Diam. (mm) Length (mm) Mass (g)
Activ Energy MSN 5004 9143 China Jan. 2015 2400 14.4 50.4 27
Sanyo Eneloop HR-3UTGA (2nd Gen.) Japan 1900 1500 14.3 50.4 27
Panasonic Eneloop BK-3MCCE (4th Gen.) China 1900 2100 14.3 50.2 26
Panasonic Eneloop Pro BK-3HCC Japan Feb. 2014 2450 500 14.4 50.3 30
Activ Energy AA cells compared to Eneloops. Minimum rated capacity reported. The standard eneloops I own and measured. The Panasonic Eneloop Pro dimensions and mass are from lygte-info.dk

The mass of the Activ Energy AA cell is about the same as for 1900 mAh Eneloops and lower than 2450 mAh Eneloop Pros. The capacity of the Activ Energy cells appears over rated in this comparison.

Maximum cycles was not specified for the Activ Energy AA cells. I assume maximum cycles is about 500, like Chinese Eneloops

Self-discharge performance was not specified for the Activ Energy AA cells. I assume 85% capacity retention in one year, like the Eneloop Pros and 2nd generation Eneloops.

The Activ Energy packaging included an LGA tested quality mark. It was not explained what product features were tested.

Capacity

I don’t have a battery tester. I discharged the cells using a 2.4 ohm resistor and recorded voltage and current at regular intervals. Discharge current was about 400 mA and discharge duration was about 5 hours. I stopped the discharge when voltage decreased below 0.9 V under load. Estimates of capacity are imprecise because of low sampling frequency and variable end-points.

I charged the cells with an Olympus Ni-MH Battery Charger BU-100 (around 2002 or 2003 vintage) at 490 mA per cell.

The Activ Energy cells were tested in the following sequence:

  1. Initial charge (top-up).
  2. Discharge 1.
  3. Recharge.
  4. Discharge 2.
  5. Recharge and one week rest.
  6. Discharge 3.

For comparison, I also tested one new Panasonic Eneloop and one well-used Sanyo Eneloop:

Capacity (mAh)
Cell Test Mean Low High
Activ Energy 1 1830 1743 1899
Activ Energ 2 1950 1880 2120
Activ Energ 3 1897 1849 1944
Panasonic Eneloop (new) 1 1755
Sanyo Eneloop (used) 1 1708
Discharge capacities. Four Active Energy cells were discharged three times. One Sanyo Eneloop and one Panasonic Eneloop were tested one time.

Average discharge capacity for Activ Energy cells was similar to Eneloops. Other tests of Activ Energy cells have reported mean capacities of 2045 mAh after a few break-in cycles (previous generation, 2300 mAh cells) and 2220 mA. Altogether, these tests show 200 to 500 mA less than rated capacity.

Voltage

The Activ Energy cells had flat discharge curves and mid-discharge voltage was close to nominal 1.20 V for NiMH cells.

Discharge curves for Active Energy Cell 1. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 1. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 1. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 2. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 3. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 3. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 4. Discharge test 3 had the highest voltage.

Discharge curves for Active Energy Cell 4. Discharge test 3 had the highest voltage.

Self discharge

Activ Energy cell voltages initially were 1.29 V at 12 months after manufacture. This was not far below freshly charged 1.42 V and well above nominal 1.20 V. Although I did not measure initial capacities, these voltage measurements strongly indicate that the Activ Energy cells are low self-discharge cells.

Referring to the previous section, discharge capacity after one week of rest was 3% lower than the preceding test. Another test of Activ Energy cells reported 3% capacity loss in 5 days and 8% capacity loss in one month. The self-discharge rate declines over time and maybe these Activ Energy cells can retain 80% of their capacity after one year.

Cost comparison

In four-cell packs, Activ Energy AA cells (AUD 1.75 per cell) cost less than the Australian retail price of Chinese Eneloop AA cells (about AUD 5.00 per cell). However, I am not confident about cycle life for either of these products. I would choose Activ Energy cells if I urgently needed to buy NiMH cells. I would choose Activ Energy cells over Chinese Eneloops if cycle life was similar. The best choice remains quality Japanese Eneloops.

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