Portable electronic devices like remotes and battery-operated appliances play a ubiquitous role in our lives. One thing they all have in common is a need for reliable electricity. Even as the number of battery options for consumers continues to grow, battery hygiene exists, and there are rules of thumb regarding how to work with traditional batteries that will help keep you and your portable electronic devices happy.
You can mix different battery brands together, but it’s not recommended. While it’s usually not hazardous, mismatched batteries can lead to unexpected device and battery failure due to mismatched voltages between batteries of different chemistries.
Even though two of the same size batteries may look nearly identical, there are key differences between them that can be less obvious. Age and chemical makeup are the primary factors, and both directly affect the amount of energy a battery has at its disposal. Potential hazards come into play over time when two connected batteries discharge their energy at different rates.
What Can Happen if you Mix Battery Brands
Batteries, like the rechargeable Eneloops from Panasonic (on Amazon), create electricity by combining two different materials, each with opposing electrochemical potentials, and placing them next to one another separated by an electrolyte barrier. The material making up the anode releases electrons, and the cathode material receives those electrons. The materials used determine the power characteristics of the battery.
4 Types of Battery Types on the Market
For consumer electronics, there are essentially four types of batteries available on the market today. These are: alkaline, zinc-carbon dry cell, rechargeable nickel-cadmium (NiCad) or nickel-metal hydride (NiMh), and lithium-ion. Each battery type is capable of the same electrical output for its size, but even different brands of the same material are not identical.
Discharge Rates Are the Reason Why It’s Not Wise to Mix Battery Brands
Although each can type can be purchased in the same sizes, and all have essentially identical electrical output, different types “die” at different times on average. This rate of battery “death” is called the discharge rate. Electrochemically, it’s the point when either the anode has released all of its available electrons, or when the cathode has taken on its maximum.
When different brands, types, or ages of batteries are used together, those batteries may have significantly differing discharge rates. When connected to the same circuit, batteries with faster discharge rates, the ones that “die” more quickly, can become over-discharged. If a battery is over-discharged for too long, it heats up, can become a fire hazard, and may leak material.
When It’s OK to Mix Battery Brands
Generally, different battery brands are fine to use together, as long as they are the same type, and again, not for extended periods of time. Even batteries constructed of the same materials can consist of different qualities and quantities of their anodic and cathodic material. This creates a terminal voltage different from other brands even when the batteries themselves appear to be the same size (both AA or AAA, for instance).
All batteries start with essentially the same electrical output, depending on the size. So for a short time, mixing together different types and/or brands of batteries in a device is not problematic (more on this in our guide), provided all have some charge. The powered device will likely work fine, provided there is sufficient charge in the batteries, and the batteries themselves should not degrade.
How Battery Leakage Damages Devices
The main culprit, when considering damage from mismatched batteries becoming overcharged, is heat. With alkaline batteries, over discharging could result in material leakage which could degrade the device and indicate a spent battery. With rechargeables, over discharging rarely results in degrading leakage, but can create significant heat within and outside the battery. In both of these cases – leakage of battery acid or excessive heat, the device with the batteries in it can also be damaged.
Even in a device that is rarely turned on, the batteries it holds are still releasing energy. Over time, batteries that are mismatched in brand, type, or age will force their weaker neighbors to become over-discharged. So even in a device that is rarely used or needed, the potential for damage to the batteries or the device itself still exists. Incidentally, this means devices that use batteries should have those batteries removed for long-term storage, when not in use. This is true regardless of the batteries being used, whether they match or not.
Alkaline disposable batteries were once the most common type of batteries. When they become over-discharged, the excess demand on the battery can cause it to create a gas, and develop a leak. This leak could release some potassium hydroxide, which is a highly basic (like highly acidic, but on the other end of the spectrum) material used in the battery. It can be caustic and damage the surrounding casing, and it’s especially good at damaging the metal battery electrodes, rendering the device itself useless.
NiMh and NiCad batteries can also leak material, but the likelihood of this happening varies by manufacturer. In addition, the material leaked from over discharged NiMh or NiCad batteries is not caustic and presents as a fine, white powdery substance. In any case, this power is not harmful to human skin or to plastic, so cleanup is a relatively straightforward task.
What to Do if you Think your Batteries are Leaking
When a battery leaks material, promptly but carefully remove the batteries from the device and dispose of them properly. The best method of disposing of used or damaged batteries is to recycle them, as opposed to simply placing them in the trash. This might mean throwing them in a ziplock bag and storing them in a drawer until your next trip to the hardware store, which will typically have a battery recycle drop box near the main entrance.
If you suspect the leaky material is potassium hydroxide, you can simply use a cotton swab and a dilute mixture of lemon juice or vinegar to neutralize and remove the leaked material. If the leaked material is white and powdery, after removing the batteries use a swab that is dry or with a small amount of rubbing alcohol, and remove the material. If you’ve caught the problem quickly enough, you can save the battery terminals in the device, keeping it useful for whenever you can pop in some (matching!) replacement batteries.