If a battery is on a shelf and you do nothing with it, its voltage will drop gradually, which is called shelf life of that particular battery.
I have recorded daily voltage drop of different rechargeable batteries for more than 10 years. I only put the first two to three year's data on the graph, since the software i'm using will not handle that amount of data.
The batteries which voltages were recorded daily are:
1. Rayovac rechargeable, AAA, NiMH. 1.2 V
2. Energizer AAA, NiMH, 1.2 V, 850 mAh
3. Power Genix rechargeable, NiZn, 1.6 V, 2500 mAh (average of 4 cells)
4. Duracell rechargeable, AA, NiMH, 1.2 V, 2850 mAh (average of 4 cells)
5. Raynovac Hyvrid AA, NiMH, 1.2 V, 2100 mAh (average of 4 cells)
6. 浩霸 haoba, rechageable, NiMH, 9 V, 280 mAh (voltages are devided by 7)
7. Raynovac rechageable, NiMH, 9 V (voltages are devided by 7)
8. Eneloop rechageable, AA, NiMH, 1.2 V, 1900 mAh
9. Digital rechageable, NiMH, 1.25 V, 1800 mAh (average of 4 cells)
10. Rayovac rechargeable, AA, NiMH. 1.2 V, 2000 mAh
11. rechargeabe 9 V, lithium-ion battery. Missing in the picture, it was not mine, I don't own this battery
12. Tenengy rechargeable NiMH, 4/5A, 2000 mAh
Partial raw data recorded on the sheets:
A shelf life chart (rechargeable battery's daily voltage drop):
9 V, lithium-ion battery (for battery number 11):
Conclusion:
Best: Eneloop AA (Battery No. 8), Rayovac hybrid AA (battery No. 5), Rayovac AAA (battery No. 1), lithium-ion battery (9V) (battery No. 11)
Better：浩霸 haoba 9 V (battery No. 6)
Worst:
Battery No. 2. Energizer AAA, NiMH, 1.2 V, 850 mAh
Battery No. 3. Power Genix rechargeable, NiZn, 1.6 V, 2500 mAh (average of 4 cells)
Battery No. 4. Duracell rechargeable, AA, NiMH, 1.2 V, 2850 mAh (average of 4 cells)
Battery No. 7. Raynovac rechageable, NiMH, 9 V (voltages are devided by 7)
Battery No. 9. Digital rechageable, NiMH, 1.25 V, 1800 mAh (average of 4 cells)
Battery No. 10. Rayovac rechargeable, AA, NiMH. 1.2 V, 2000 mAh
Battery No. 12. Tenengy rechargeable, 4/5A, NiMH, 2000 mAh
