The Energizer L91 Lithium AA cell is a fantastic power source. For high-drain applications, it offers great advantages over ordinary alkaline cell and rechargeable NiMH cell. However, it is also very expensive as a disposable battery. So it is important to recognize the strength of L91, and use it only in applications that give you the best results. Otherwise you'll be wasting your money.
According to data sheet published by Energizer, the capacity of the Lithium AA cell (L91) is 3000mAh. This number remains nearly constant with load current. In comparison, the ordinary Alkaline battery (such as the Energizer E91 AA) is rated as 2800mAh, but only at a very light load of 25mA. At a heavy load of 1000mA (typical for a digital camera or flash unit), its capacity drops to below 1000mAh. This number gets even worse at low temperature. At zero degree C and 1000mA load, the L91 can provide about seven times more energy compared to the E91. This is where the marketing claim of "Last up to 7 times longer" comes from.
When used in a digital camera at room temperature of 25 degree C, the L91 is more likely to last 3-4 times longer than alkaline. This is enough to justify its price, which is also around 3-4 times higher than alkaline. However, in low-drain applications (such as smoke detector, wireless mouse or remote control) alkaline cells will last just as long at a fraction of the cost.
The L91 also contains much higher energy when compared to an ordinary rechargeable NiMH cell such as the Energizer NH15-2500. This is partially due to its higher terminal voltage of 1.5V, which is 20% higher than that for NiMH.
Energy stored in NH15-2500 : 2.5Ah * 1.25V = 3.125Wh,
Energy stored in L91 : 3Ah * 1.5V = 4.5Wh (44% higher).
Higher terminal voltage for L91 is especially advantageous in digital camera applications, because your camera flash will recharge up to 20% faster. An added benefit is that the L91 weighs only 14.5 grams (0.5 oz) each, compared to 30 grams (1 oz) for NiMH. So your camera becomes much lighter.
The NH15-2500, like all ordinary NiMH cells, suffers from rapid self-discharge problem. If you charge up a set of those cells and leave them in your camera for a few weeks, you're likely to be greeted by 'Low Battery' sign when you try to take a photo. The new generation of 'ready-to-use' NiMH cells such as SANYO eneloop and Rayovac Hybrid solved this problem by having very low self discharge rate. But they have lower capacity of only 2000-2100mAh.
Bottom line: If you need AA batteries for a long hiking trip, then L91 is obviously your best choice. For most other situations, I recommend using low self-discharge NiMH cells for lower operating cost. Energizer Ultimate L91BP-4 Lithium AA Battery 4 Pack
[Updated on June 8, 2011]
Note: Amazon has moved two of my previous reviews (one for Energizer Lithium AA 4-pack, one for 8-pack) under one page. Therefore I have to update my review to add some new information - or else I look like a fool who says the same thing twice.
=== New information follows ===
There seems to be some confusion about those Energizer Lithium AA batteries. Several people have bought those batteries under the assumption that they are rechargeable, only to be disappointed later.
Despite the name 'Lithium', those Energizer Lithium AA batteries are very different from the commonly known 'Lithium-ion' rechargeable batteries. Namely:
- They are single-use batteries (NOT rechargeable like Li-ion)
- The terminal voltage for each cell is around 1.65V (compared to around 3.7V for each Li-ion rechargeable cell)
The two types of batteries are not compatible. If your camera accepts AA cells, then you should use those Lithium AA cells and not Li-ion rechargeable battery. Alternatively, you may explore other rechargeable battery options, namely:
1. Low-self-discharge NiMH AA cells, such as Sanyo Eneloop or Sony Cycle Pre-Charged. Those have a operating voltage of 1.25V per cell, so some cameras (especially those that use only two cells) may not operate correctly on those.
2. Nickel-Zinc rechargeable such as PowerGenix AA. Those have higher terminal voltage of 1.65V, same as that of Lithium AA cells. The down-side is that the higher voltage may cause some older cameras to burn out, and the NiZn cells themselves have very poor lifespan.
No matter which rechargeable option you pick, remember that they each need their own special charger. Choosing a good charger is the key to longer lifespan for rechargeable batteries.
I recommend most people to try eneloop cells first. They are the most reliable among NiMH batteries. If it doesn't work well for your camera, you can still use those celll in other appliances such as flashlights or Wii remotes.
Finally, it is a good idea to keep a set of those Lithium AA cells as backup, or in case or emergency. They can be kept in storage for ~10 years!
The Energizer L92 Lithium AAA cell is a fantastic power source. For high-drain applications, it offers great advantages over ordinary alkaline cell and rechargeable NiMH cell. However, it is also very expensive as a disposable battery. So it is important to recognize the strength of L92, and use it only in applications that give you the best results. Otherwise you'll be wasting your money.
According to data sheet published by Energizer, the capacity of this Lithium AAA cell (L92) is 1200mAh. This number remains nearly constant with load current. In comparison, the ordinary Alkaline battery (such as the Energizer E92) is also rated as 1200mAh, but only at a very light load of 25mA. At a heavy load of 500mA (typical for a P&S digital camera), its capacity is reduced to about one-third. The difference gets even greater at low temperature. At zero degree C and 500mA load, the L92 can provide about seven times more energy compared to the E92. This is where the marketing claim of "Last up to 7 times longer" comes from.
When used in a digital camera at room temperature of 25 degree C, the L92 is more likely to last 3-4 times longer than alkaline. This is enough to justify its price, which is also around 3-4 times higher than alkaline. However, in low-drain applications (such as smoke detector, wireless mouse or remote control) alkaline cells will last just as long at a fraction of the cost.
The L92 also contains much higher energy when compared to rechargeable NiMH cell such as the Sanyo Eneloop AAA. This is partially due to its higher terminal voltage of 1.5V, which is 20% higher than that for NiMH.
Energy stored in eneloop AAA: 0.8Ah * 1.25V = 1.0Wh,
Energy stored in L92 : 1.2Ah * 1.5V = 1.8Wh (80% higher).
Higher terminal voltage for L92 is especially advantageous in digital camera applications, because your camera flash will recharge up to 20% faster. On the other hand, it may create problems with some applications such as unregulated LED flash light. Higher than expected voltage will make the lamp burn brighter, but the excessive heat may also cause the lamp to burn out quickly.
Bottom line: If you need AAA batteries for a long hiking trip or for emergency standby, then L92 is obviously your best choice. For most other situations, I recommend using low self-discharge NiMH cells for lower operating cost. - Energizer - Energizer Lithium Aa Batteries - Battery - Aa'
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