Can You Mix Rechargeable Batteries and Regular Batteries?

Rechargeable batteries, like these high-quality Eneloop ones from Amazon, offer several important benefits to our electronically-enhanced lifestyles. One is to our pocketbook; as the need to buy disposable batteries reduces, we save money. Another is to our environment, as fewer of those toxin-containing disposables head to the landfill. Since there is easy access to both kinds, is it smart to mix and match them?

It would be best if you did not combine rechargeable and disposable batteries in the same device. While batteries of the same size look very similar, disposable and rechargeable batteries are made of different materials with different electrical characteristics. The mismatched voltage can damage the batteries and the equipment they’re used in.

If your need for juice is immediate and short-term, mixing the two different types won’t present a problem right away. The electronic receiving device should normally work without incurring any damage. Just be sure to remove the unsuitable batteries and replace them with fresh batteries of a matching type as soon as you can. You can do this in a pinch, but don’t do it for days or weeks at a time.

How Rechargeable Batteries Work

All batteries work because of an electrochemical relationship between two different materials. One material, called the anode, has a quantity of “free” electrons that it wants to get rid of. The second material, the cathode, desires electrons. If a wire or an electrical circuit connects these two materials, the electrons flow, creating electricity.

Like the common Energizer brand (on Amazon), traditional disposable batteries have a fixed quantity of free electrons. When all of these electrons find their way from the anode to the cathode, the battery ceases to have any electrochemical potential, and the battery is pronounced “dead.” Disposable batteries are typically combinations of carbon and zinc, lithium, potassium hydroxide, and manganese dioxide.

Why you Shouldn’t Mix Rechargeable and Non-Rechargeable Batteries

Rechargeable batteries have a fixed quantity of free electrons, but these electrons can be returned to the anode with a little push from the appropriate battery recharger. This key difference is due to the different chemical material makeup of the two kinds of batteries. Nickel, cadmium, lithium-ion composites, and metal-hydrides are common rechargeable materials.

When a battery is “dead” and has no more available free electrons, it is called its terminal voltage. Nearly all disposables have a higher terminal voltage than their rechargeable counterparts. This is why rechargeable batteries tend to die sooner. Electrochemically, dead batteries have moved all of their once free electrons to the cathode.

When rechargeable and disposable batteries are placed together on the same circuit, the disposable battery will have a higher terminal voltage. As they create the flow of electricity, the rechargeable battery will run out of free electrons first. When this happens, the disposable battery will electrically demand that the rechargeable battery give up electrons that it does not have.

In this case, the rechargeable battery will enter a state called “over-discharged.” If this condition goes on for long enough and at a sufficient electrical intensity, the rechargeable battery will begin to heat up and, over time, can physically degrade. Under the right conditions, this can result in the battery leaking material, which can destroy the battery and possibly damage the device.

Other kinds of batteries can become over-discharged as well. This is often caused by mixing different types or ages of disposable batteries. When alkaline batteries are over-discharged, acidic and hazardous material can leak out of the battery. Some over-discharged rechargeable batteries will sometimes leave a fine, easily cleaned, white powder behind.

Why You Shouldn’t Worry If You Do Mix Rechargeable And Non-Chargeable Batteries

Damage by mismatched batteries can lead to problems, but it usually takes time for this to happen. If the device you need to power requires batteries, but you only have a mismatched set to choose from, using this collection for a short amount of time will likely not damage the device or the batteries.

This is large because the main negative effect on over-discharged batteries is excess heat. The heat takes a length of time to build up due to the structure of the battery and the relatively low power draw from its less terminal neighbors. In turn, it takes a decent amount of heat to deform and damage the device those batteries are in ultimately. But, you don’t get to choose when this problem occurs…it will happen sometime after the hybrid batteries start being used together, but it’s hard, even foolish, to try to predict when and time it “just right.”

How to Prevent Damage to Rechargeable Batteries

Changing the batteries as soon as possible when using mismatched batteries will also ensure that the rechargeable batteries mixed in with the lot will not incur damage. That same tendency to build up the heat while being over-discharged will be strongest with the rechargeables, and over time this can reduce and eliminate the capacity of the batteries to hold a charge.

When replacing the batteries, it’s also best to use all the same brand, chemical type, and age. This will ensure that all of the batteries used in a device will have nearly identical terminal voltages. It will be extremely unlikely to cause any of them to become over-discharged. Keeping your rechargeable batteries at a 40% or higher level of charge will help as well since the mismatched voltage becomes more of a problem when rechargeable batteries are low on charge.

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