Duracell's Warning: Mixing Different Age Batteries Can Lead to Leakage

Duracell has warned users that mixing old and new batteries in the same device can potentially lead to leakage, and this warning is backed by sound technical reasoning. In this article, we will delve into the reasons behind this warning and how it affects the performance and safety of your devices.

The Problem With Mismatched Batteries

When two batteries of different ages or charge levels are used in the same device, there are several issues that can arise:

Voltage Differences

A new battery typically has a higher voltage than a partially discharged battery. When these batteries are used together, the new battery tends to be overworked, leading to excessive heat and pressure buildup inside the battery. This can cause the battery to function improperly and eventually lead to leakage.

Chemical Imbalance

When batteries of different charge levels are used together, the chemical reactions inside the batteries may become imbalanced. This imbalance can lead to faster deterioration of the older battery, which increases the risk of leakage.

Leakage Risk

Over time, the stress from these conditions can lead to leakage, which can not only damage the device but also pose safety risks. Mixing different age batteries is not recommended to avoid such issues.

Why Mixing Batteries Can Be Problematic

Consider the scenario where you have one new and one used AA battery. Suppose you use a flashlight with a capacity of 2 Ah (2000 mAh), where both batteries start at 1.5 or 1.6 V and drop to about 1.0 V when they are nearly dead. When both batteries start with the same charge level, they discharge together, and after delivering 2 Ah of energy, both will end at a low voltage but still retain a positive voltage.

Now, let's consider the scenario where one battery is partially drained, leaving it with only 1 Ah of capacity, while the other is new. When you use these two batteries in a flashlight, the flashlight will work initially. However, after 1 Ah of energy has been delivered, the used battery will be nearly dead and its output voltage will drop below 1 V. The new battery, on the other hand, will still have half its original capacity and an output voltage of around 1.3 V.

Since the batteries are wired in series, the current will continue to flow, and the remaining voltage in the stronger battery will reverse-charge the weaker battery. This reverse-charging is not designed for the weaker battery and can cause damage to its internal structure, leading to electrolyte leakage.

Conclusion

To avoid these issues, it is recommended to use batteries that are all new or as close to the same age and charge level as possible. This ensures optimal performance and safety, and the device will stop working while all cells still have a positive voltage, extending the overall lifespan of your devices.

It is crucial to follow Duracell's advice to enhance the longevity and safety of your battery-operated devices.