Everything You Need To Know About Batteries

How long do batteries last?

When it comes to how long batteries last, (not in terms of runtime on a single charge, but in terms of years or age), this is impacted a lot by how the battery is used and treated. Let’s look at some of the various factors and best practices that should be followed.

How is lifespan measured?

Generally speaking, we measure the lifespan of non-rechargeable batteries in terms of their fully-charged max storage time, and rechargeable batteries in terms of this max storage time, and also “cycle life.”

What is the max storage time?

Again, speaking generally, most alkaline batteries can last up to 5 years. Some will advertise, but in many cases rarely make it to 10 years or more. The chance of leakage with alkaline batteries increases greatly as time goes on, and after 5 years, increases dramatically.

For rechargeable lithium batteries, this lifespan can be much longer than 5 years, but only if the product doesn’t drain the battery faster.

What causes batteries to drain when not in the product or not in use?

This is due to what is called “self-discharge” or the battery’s own internal chemistry. Due to chemical reactions internal to the battery, it cannot maintain full power for forever, and does slowly lose charge over time.

Why do batteries drain or discharge in a product when not in use?

Many products will have what is known as a “sleep” or “idle” current, even when off or inactive. Some products do not, but these tend to be simpler products with a mechanical on/off switch that interrupts all current flow from the battery. In order to achieve some functions, like memory or a faster start-up sequence, microprocessors are used to monitor input buttons or other activity while remaining in a low-power “sleep” or “idle” state. This drains little power, but still some, and can cause a battery to discharge faster than it would if it were removed from the product.

In general, all our products are designed with a 5 year shelf life from date of manufacture, to allow the product plenty of time from production to store shelves and then on to the customer to use. Due to time on the shelf or in this process, the actual shelf life once the consumer receives the product will be somewhat less than this. Due to various regulatory and freight/air carrier restrictions, our rechargeable products are not shipped at full charge, though we still design these with this shelf life in mind.

What is cycle life for rechargeable batteries?

Rechargeable battery life can also be expressed in terms of cycles of use, or cycle life. This number of cycles doesn’t mean the number of cycles until the cell stops working, rather, this is an indicator of what is considered a noticeable decrease in capacity. As Lithium batteries are cycled, they lose some capacity. Think of it as a gas can that gets slightly dented every time it is used. It still can be used, but with every dent a little of the capacity is lost. This is usually expressed as an “80%” value. To determine cycle life, the cell is discharged at least 80% (from say at least a 90% charge to a less than 10% charge), and this is done until the product can no longer charge to more than 80% of it’s original full capacity. So at the “end” of it’s cycle life, a 1000mAh capacity cell may only be capable of 800mAh capacity. It’s still useful and works, but has lost some capacity that you may notice as reduced run time of the product.

What is mAh? What is Wh? What do these represent?

mAh (milli-Amp-hours) and Wh (Watt-hours) are different measures of battery capacity. These may also be expressed as Ah (mAh / 1000) or mWh (Wh x 1000). When mAh or Ah are used, voltage must also be specified, and the mAh or Ah alone cannot be used to compare battery sizes. For this reason Wh or mWh is the preferred measure of true battery capacity. The larger the number, the more capacity the battery has, and typically the longer runtimes the product will have (all other things being equal). Ah and Wh are not the same, and can’t be compared directly without also including voltage. Wh can be calculated as Ah x V, so a 1000mAh x 3.7V battery is 3700mWh, or 3.7Wh.

What temperature can I use or store my product or batteries at?

For virtually all battery types, including all of ours, the closer the battery can be kept to room temperature, the better. Storage, even when the product is not used, at very hot or very cold temperatures for long periods, or repeated cycling between hot/cold can reduce the lifespan of the battery. It is recommended, when possible, to keep the battery as close to room temperature as possible. We do rate all our products and batteries to their max/min temperatures for storage and use (generally -40C to +80C for storage, and -20C to +60C, unless otherwise noted in the manual or on the product or battery). Use at the extremes can reduce the life of the battery, but generally not by more than about 20%, unless this is the majority of usage or storage. You should always avoid leaving batteries in direct sunlight on a very hot day or inside of a vehicle where direct sunlight can cause the product to heat beyond ambient temperatures.

How long can I store my product or battery without charging it?

Generally speaking, we design our products to last a year or more without being charged, assuming they are stored fully charged. Many different factors such as the age of the product, the number of times a rechargeable battery has been cycled, temperature, and environment can reduce this. We recommend that all products be checked each year to make sure they work and are recharged, or if using alkaline batteries, replace these at least every 3 to 5 years to reduce the chance of leakage.

What causes alkaline batteries to leak?

Typically, alkaline batteries leak when they are over-discharged, or stored very low or “dead” for a long time. You should only ever store an alkaline product for an extended period with fresh or relatively fresh batteries. You should also never mix the cell chemistry/type or new or old cells; this is perhaps the most common cause of leakage we see. There primary reason for this is the new cells trying to “charge” old or even weaker or dissimilar brand or type of cells. When this happens the lesser cell may leak and cause product damage or even injury. When it comes time to replace batteries, always replace them all, at the same time, using the same brand. Not doing so will usually result in leakage and product damage. You should also use the recommended type; using one that’s not recommended will at the least provide less-than-stated performance.

What causes batteries to swell, become swollen, or bloat?

Batteries can become swollen due to several reasons, primarily external damage, exposure to moisture or air after seals are damaged, over-discharging, or internal defects. If this happens, batteries of this size do not present any risk of injury to consumers. When electrolytes are contained and no fumes or chemicals are vented or leaked outside of the product, a swollen battery is considered to be a safe failure mode. In this case, or if the battery has leaked or gives off a strong odor, it should be disposed of. Batteries that are swollen, leaking, or giving off odor should NEVER be recharged. Doing so may cause the battery to become dangerous.

Is it OK to use a battery that is old but still works?

There is no reason to not use a battery that is not dead or very weak if it still works, regardless of age, unless it was subjected to some physical damage, extreme heat or cold, or moisture. If the battery has been damaged or exposed to these conditions in any way, they should be replaced.

How do I safely dispose of a battery?

Non-rechargeable batteries can generally be thrown in the trash, but check with your local regulations. It is always preferred to recycle them if possible. For rechargeable batteries, these should always be recycled. Most cities or counties will have a hazardous waste program that will allow for dropoff of batteries for proper disposal or recycling. You may also find that local electronics stores may also have similar recycling or disposal programs. It’s highly recommended to tape the terminals of batteries until you can dispose of them to keep them from shorting against metallic items (or other batteries).