can you use a 40v battery in a 20v tool

Can You Use a 40v Battery in a 20v Tool?

In Building Materials by Jamie

If you’ve amassed a collection of battery-operated yard equipment, then you’ll likely come upon a situation where using the 40v battery of one tool to power another tool that uses a 20v battery will save you a lot of time. In this specific situation, it’s best to think twice before mismatching different-sized battery packs.

In short, you should NOT use a 40v battery in a 20v tool. The voltage overload will destroy the battery and the tool. The same goes for charging equipment: it is NOT safe to charge a 40v battery with a 20v charger and vice versa.

To ensure proper usage and optimum performance of your power tools and yard equipment, it’s important to stay informed about their different battery sizes. Below you’ll find some handy pointers regarding 40v and 20v battery packs.

What is the Difference Between a 20v and 40v Battery?

Battery packs used for battery-operated tools such as trimmers and leaf blowers are commonly 40v or 20v. The “voltage” is the measurement of the battery’s power capacity. With a higher power capacity (a higher voltage), a power tool has greater strength, speed and usage time—all qualities that one typically wants from a power tool.

While it may seem that a 40v battery is always better than a 20v, there are reasons that tools running on a 20v battery are the better choice. The motors are smaller and lighter, thus easier to handle. And the time it takes to recharge a 20v battery is much shorter. If you have a small yard requiring lightweight maintenance, a 20v tool will do just fine.

Differences Between:

20v vs 40v Trimmer?

The main reason to opt for a 40v trimmer is if you have a considerably large area to cut. The 40v will limit the chance that you’ll run out of battery before the job is complete. However, a 20v trimmer is smaller and more maneuverable, making it useful in crowded or tight spaces (which is the purpose of a trimmer in the first place). Also, since trimmers are used mostly for grass and weeds, there’s no need for the added strength of a motor running on a 40v battery.

20v vs 40v Leaf Blower?

The chief consideration with cordless leaf blowers is the wind strength. A 40v will produce a hefty wind. With a 20v, the wind strength is much weaker. And if the wind is too weak to quickly clear away a thick layer of fallen leaves, the task will take longer, which is a problem for a 20v due to the limited time use before the next recharge. However, if all you need is to knock dead leaves out of your rose bushes, a 40v might blow too hard, damaging the plants and knocking over your garden decorations.

20v vs 40v Chainsaw?

The differences between a 20v chainsaw and a 40v chainsaw are certainly significant enough to determine your user experience. Since power and speed are crucial to a chainsaw’s purpose, these are the qualities to pay most attention to. A 40v chainsaw has a high-speed motor that provides smoother cutting and prevents those annoying jerks and bumps. And greater strength means quicker cuts.

The main drawback to a 40v chainsaw is its weight. A heavier chainsaw is especially problematic as most jobs require holding the tool out in front of you or even over your head, causing your arms to wear out quickly—and, for obvious safety reasons, the last thing you want is to lose control of a chainsaw due to tired arms.

So, what’s nice about a 20v chainsaw is the reduced weight. Also, a 20v chainsaw has less motor vibration, making it easier to handle and control. However, as with all cordless power tools, the 20v chainsaw has a limited runtime, making full-day projects problematic.

20v vs 40v Lawn Mower?

Unlike most other lawncare tools and appliances, the weight of a lawnmower isn’t too much of an issue, especially with self-propelled mowers. So, batteries with higher voltage (thus greater weight), aren’t going to be too much of a problem.

Since lawn mowers require such a large amount of power to do their thing, a single 20v battery just won’t do. However, if you’re interested in a battery-powered lawn mower that you can recharge quickly, consider a model that runs on a 2X 20v battery system. With these, two 20v batteries provide power simultaneously, giving the mower motor sufficient voltage.

That said, for larger yards or commercial work, you’ll likely want your cordless lawnmower to run on a heftier battery.

20v vs 40v FAQs

Can you charge a 40v battery with a 20v charger?

A 20v charger won’t have the strength to charge a 40v battery. Also, the connectors are most likely different in size. In fact, for batteries of all sizes, it’s best to only use the charging equipment that came specifically with the tool unless it’s specified otherwise.

Is there ever a time where 20v and 40v batteries are interchangeable?

The only way to safely use a 40v battery on a 20v tool is if you alter the battery circuitry to reduce its output to 20v, but this would be more of a hassle than simply recharging the battery. Otherwise, don’t do it.

Final Thoughts

The key takeaway here is that mixing 40v with 20v is a no-go. For this reason, when buying your next power tool, it’s important to know what you need before heading to the store. Making the best choice takes a bit of careful consideration, and each tool has a different set of criteria to think about. Things to keep in mind: weight of the tool, usage time needed, battery recharge time, motor strength, lawn size, and, also, price (40v tools, and their replacement parts, tend to be more expensive). It might sound complicated, but the extra effort is with worth it!

About the Author


Jamie is the Founder of My Home Dwelling. He is a homeowner and enjoys sharing his homeowner tips with others. He has real estate experience working as a new home construction Realtor. Jamie has worked on numerous residential construction sites helping with interior and exterior renovations. He loves refinishing furniture, DIY home projects, and sharing his knowledge online.