How long can a lithium-ion battery last?

Battery-powered tools have come a long way in the past decade. Small handheld power tools have switched from the old nickel-cadmium batteries to lithium-ion batteries as the energy storage medium. Improved power and runtime, combined with a significant weight reduction, proves to be a great shift. For larger tools such as zero-turn lawn mowers and small vehicles, the transition involves moving from gasoline or lead-acid batteries to lithium-ion batteries. No matter what type of battery-powered tool you use, lithium-ion battery life is a top concern for readers.

We spoke to product managers and executives from Bosch, DeWalt, Metabo HPT, Makita, Milwaukee, and Ridgid to get some answers directly from the manufacturers. While the answers vary, there is general agreement on the main points.

How many charge cycles do you expect to get?

When we talk about the life of a Li-ion battery, we're ultimately talking about how many charge cycles it has. However, the number of charge cycles depends on how you charge the battery and what you consider a charge cycle. Do you recharge your batteries at the end of the day? Do you replace them as soon as you're done using the tool, or pop them out at lunch so they're topped up when you get back to work? Finally, battery configuration and capacity also play a role, as does ambient storage temperature.

Unfortunately, most manufacturers define a charge cycle as any time you put the battery in the charger and let it do its job. While one of the advantages of Li-ion batteries is the lack of battery memory, you can still use up the battery's (and battery pack's) maximum life by charging it more often than necessary.

Currently, most power tool manufacturers claim that you should expect to get over 1,000 charge cycles from any given battery. If you charge the battery pack once a day, that's 2.7 years; if you work 5 days a week, that's 3.8 years. Some manufacturers claim 2,000 recharges, in which case you can double those numbers.

How Charge Cycles Affect Li-Ion Battery Capacity

While manufacturers may define a charge cycle differently, all batteries degrade in maximum capacity over time. No matter what battery you use, every time you cycle/charge the battery, it loses a little bit of maximum storage capacity. While we don't think this will actually affect your performance or uptime, it does.

In fact, several studies have shown that battery capacity can drop by 40% or more after 1,000 cycles. Some companies, such as Makita, use a "smart" system to solve this problem. Their chargers and batteries use a communication system that identifies the battery's current charge level and temperature. The charger then regulates the optimum current, voltage and temperature to charge the battery. This process helps extend the life of the battery. It also extends the charge cycles the battery can go through. This is just one of the reasons you might want to stick with the original battery and charger.

How long Li-ion batteries last is one thing, but what about storing them? After all, this might affect whether you want to pick up a "used" battery at a flea market.

Many factors can affect the lifespan of a battery pack on the shelf. Let's start with some best practices. If you don't plan to use the battery again for a week or so, it's best to keep the battery at about 50 percent charge. Some manufacturers may vary slightly on this, but in general, 50% ensures that you don't degrade your battery's storage capacity.

You'll also want to check the battery packs from time to time, as they may be slightly drained. Keep the pack at around 50% or whatever level the manufacturer recommends to ensure the pack is not completely depleted. In doing so, your batteries can be stored for up to 3-5 years.

Heat kills lithium-ion battery packs

You also want to store batteries in a cool, dry place. The worst thing you can do (besides throwing your battery in the pool) is to top it off on a hot summer day. Planning to store batteries in a hot shed? No. Move them to your garage or somewhere you can temper the heat a bit and lower the battery pack temperature.

High temperatures can kill Li-ion batteries. To cut the number of cycles in half, store the pack in a hot environment with a full charge.

If the battery pack falls below a specific charge capacity, the battery pack may not be able to charge. This is due to the charger not registering the battery pack as accepting a charge. A battery below the minimum level indicates the end of its life (although some dead batteries can be "resurrected").

Editor's note: Check out these lithium-ion battery charging tips for our recommendations for maximizing battery life and runtime.

How long does a lithium-ion battery last compared to a nickel-cadmium battery?

We know that NiCad batteries have been dead for so long that many don't even remember. Still, it's a kind of benchmark in some people's minds. A similar nickel-cadmium battery would be larger and heavier due to the higher energy density of lithium-ion. From a functional standpoint, Li-ion batteries also do not experience a voltage drop when depleted. What about the shelf life?

Both batteries self-discharge during storage. However, NiCad self-discharges at a rate of about 1-3% per day. So it's not uncommon for an unused NiCd battery to need charging every few weeks or so — even if you never use it!

Lithium-ion batteries self-discharge much more slowly. In fact, almost imperceptibly. How quickly this discharge occurs depends largely on the quality of the battery pack design.

There are also many more working technologies for lithium-ion batteries than for nickel-cadmium batteries. Really, the comparison seems a bit unfair and dated. Many manufacturers employ overload, over-discharge, and over-temperature protection for their Li-ion batteries. All of these technologies protect the battery. They also extend the expected life cycle. NiCad and NiMH batteries generally do not have these protections.

So while some may claim that NiCad batteries are also expected to last 1000 charge cycles, you'll have to recharge these battery packs several times during use. You also have to deal with the dreaded "battery memory effect". Okay, this is the last time we talk about old technology – we promise!

Editor's note: Check out these lithium-ion battery maintenance tips to keep your battery healthy for the long term.

Beyond Lithium-Ion Lifetime Issues

Answering the question of how long a Li-ion battery lasts often involves replacement and ongoing costs. After all, lithium-ion batteries cost more than lead-acid or nickel-cadmium batteries. They sure cost more than a can of gasoline!

So while moving to wireless convenience requires a significant upfront investment, eventual replacement also needs to be considered. Before moving to a line of cordless tools, the discerning professional needs to understand the long-term implications of this investment.

Related questions include:

• How much can you expect to pay for a replacement battery pack?
• For larger equipment, how much do you save in fuel and maintenance compared to replacing the battery pack?

After answering the question of how long lithium-ion batteries last, we need to answer these related complex questions to get the whole picture.

let's summarize

So, how long can a lithium-ion battery last? All in all, most manufacturers require a minimum of about 3 years or 1,000 charge cycles for their batteries. Having said that, we say "put your warranty where your mouth is". Bosch, DeWalt, Metabo HPT, Makita, Milwaukee Tool, EGO, and Ridgid all offer 2-3 year warranties on their lithium-ion batteries.

This is a good indicator of their minimum expectations for these packages. Go to a company like Greenworks 60V and you can get a 4 year battery warranty. As technology and reliability improve, we expect to see more companies extend these warranties.

If you take care of your batteries, there's no reason you shouldn't expect them to last at least that long, or longer.