Lithium mower battery seated in a garage charger

Can a Lithium Mower Battery Stay on the Charger?

ByKen

As an Amazon Associate we earn from qualifying purchases.

If you are asking can lithium batteries be left on charger, the short answer is that the manufacturer pages we opened do not agree. Black and Decker says a cordless mower battery kept in storage above 40 degrees Fahrenheit should stay connected to the charger with the charger plugged in. Husqvarna’s UK guide says to take the battery off the charger once it is fully charged, and to unplug the charger once charging is complete. This guide sets out what each page states and what it leaves open.

Quick answer

  • Below 40 degrees Fahrenheit, Black and Decker says to charge the battery fully and disconnect it from the charger until the next mowing season.
  • Above 40 degrees Fahrenheit, Black and Decker says to keep the battery connected to the charger with the charger plugged in. Husqvarna UK gives a different rule for its BLi-X 36V battery: remove it once it is fully charged.
  • The sources give no time limit for leaving a lithium pack on a charger, so check the manual for your model before you leave one connected for weeks.

What the storage temperature changes

Black and Decker ties its charger rule to the storage temperature. For storage below the line, its guide says: “When storing the mower in an environment that will be consistently below 40 degrees Fahrenheit (but not below -40 degrees F), the battery should be fully charged and disconnected from the charger until the next mowing season.” For the warmer case, it says: “If the mower and battery will be stored in a location where the temperature will be consistently above 40 degrees Fahrenheit, the battery should be stored connected to the charger with the charger plugged in.”

The same page covers a battery left in the cold. It says the battery “can remain in the cold temperature, but will have to be charged before first usage in the next season.” It also gives a third option: “Alternatively, the battery can be brought inside to a warm environment with the battery connected to an active charger.” That option keeps the battery on the charger, but in a warm room rather than in a cold garage or shed.

What each manufacturer says about maintenance charging

The table lists each page and the rule it gives for a battery that is on, or near, its charger. A cell marked not stated means the page does not address that point.

Source Product type Battery on the charger Maintenance charging
Black and Decker support (US) Cordless mower battery Connected above 40 F; fully charged and disconnected below 40 F Charge before first use after cold storage
Husqvarna BLi-X 36V guide (UK) 36V battery and charger Remove once fully charged; unplug the charger when charging is complete not stated
Ryobi dual-platform charger (US) 18V ONE+ and 40V batteries Indicator lights show when batteries are charged and maintained Duration not stated
Husqvarna Automower winter guide (US) Robotic mower battery Fully charged before power-off Most models need no charging in storage; older models every three months
Husqvarna winter storage, petrol mowers (US) Lithium battery, petrol-mower page not stated Follow the battery maker’s recommendation

The table shows that the sources disagree in direction, not just in detail. Black and Decker’s warm-storage rule keeps the battery connected, while the Husqvarna UK rule removes it once full. The Husqvarna robotic-mower page asks for a full charge before power-off and does not ask for a connected charger, but it covers a different machine. It does not settle the question for a cordless push-mower pack.

The Ryobi listing is the only charger page in this group that describes a maintenance state. Its indicator lights show when batteries are charged and maintained, which tells you the dual-platform charger has a maintenance indication. The page does not say whether a battery in that state can stay on the charger for weeks, and it does not give the rate at which maintenance charging happens.

Why the storage charge level changes the answer

The Husqvarna UK guide also gives a storage charge for long periods. It says “Charge to 30-50% before long-term storage,” and it adds that “For extended storage, ensure that the battery has a partial charge to avoid deep discharge.” A battery held at full charge on its charger is not at the partial level that page gives for extended storage. That makes the UK guide’s charger advice and its storage advice point the same way: take the pack off the charger once it is full, and keep long-term storage at a partial charge.

Black and Decker’s cold-storage rule points the other way for a cordless mower battery. It asks for a full charge and disconnection below 40 degrees Fahrenheit, and it does not ask for a partial charge. Two manufacturers therefore give different advice for the same storage question, and the difference is in the charge level as well as the connection.

Robotic mowers are a separate case

The Husqvarna US robotic-mower page handles power differently. Its winter checklist says: “Power supply: Disconnect and store in a dry, frost-free location.” That line covers the power supply for the robotic mower’s charging station, not a cordless push-mower pack, so it does not answer the question for a pack on a charger. It does show that the same manufacturer’s winter guidance for a robotic mower disconnects power during storage.

Steps for a battery on the charger

Use these steps when you decide whether a pack stays on its charger. Each step names the page it comes from.

  1. Find out which side of 40 degrees Fahrenheit your storage spot is on. Black and Decker’s guide splits its advice at that line, so check the storage temperature before you decide anything about the charger.
  2. Keep the battery connected only if your brand’s rule says so. Black and Decker says a battery stored above 40 degrees Fahrenheit should stay connected with the charger plugged in. Husqvarna UK takes a different line, so do not apply the Black and Decker rule to a Husqvarna pack without checking its guidance.
  3. Remove the battery when it is full, if your brand says so. Husqvarna UK says: “Once fully charged, remove the battery from the charger to avoid overcharging or unnecessary wear on the charger.”
  4. Unplug the charger when charging ends. Husqvarna UK says: “Once charging is complete, disconnect both the battery and the power plug.” The same page adds that “Leaving the charger powered continuously can reduce its lifespan.”
  5. Follow the operator’s manual for a robotic mower. Husqvarna’s US robotic-mower page says: “Check your operator’s manual for specific requirements.” This step applies only to robotic mowers.

If a pack will not charge at all, read the related guide on a lawn mower battery that is not charging before you change the charger routine. For 12-volt and 6-volt battery types, see 12-volt and 6-volt mower battery types. For a trimmer’s battery and charger, the related guide on Black and Decker hedge trimmer batteries and chargers covers that case.

Safety when a battery sits on a charger

Keep the battery and charger away from heat, and stop using a charger with a damaged cord. Three non-retail pages support the heat point. The EPA advises against “Avoid long periods of extreme cold or hot temperatures (e.g., dashboard of car in direct sunlight).” Husqvarna UK says never to store the battery in a hot car, in direct sunlight, or in unconditioned spaces such as outdoor sheds and garages. Husqvarna’s US petrol-mower page warns that high temperature sources, such as fire, can damage the battery, so keep a charging battery well clear of heat sources.

For the cord, Husqvarna UK says to check the power cord for damage, and to unplug it immediately and stop using it if the cord is compromised. The same guide tells you to disconnect the battery and the power plug once charging is complete, which is the same habit as the charger-removal step above.

How we chose

We opened six pages on 2026-10-22, and each returned HTTP 200. Five are manufacturer pages: Black and Decker, two Husqvarna pages for a robotic mower and a petrol mower, the Husqvarna UK BLi-X guide, and the Ryobi charger page. The sixth is an EPA page, used for the heat point only. The criteria were that a page had to address a battery on a charger, or give a storage rule that touches the charger.

The Husqvarna UK page is a non-US locale. We could not open a US page for the BLi-X battery guide, so the UK page is used and labelled as such. The Ryobi page is included for its maintenance-status wording, and it does not say how long a pack can stay on the charger. We did not use retail listings, forum answers or blog posts. Forum threads on leaving batteries on chargers came up in searches, and we did not quote them.

What we could not verify

  • A US manufacturer rule for leaving a cordless lithium pack on its charger for weeks. The Black and Decker page covers cordless mower batteries but gives no time limit.
  • The owner’s manuals for the packs. The manuals are PDF files, and the tool used for this post cannot open PDFs.
  • Whether a connected charger shortens the life of a particular pack. The Husqvarna UK page says the charger’s life can be reduced, and it does not say the same for the battery.
  • How your charger behaves once a pack is full. The Ryobi page describes indicator lights and does not describe a shut-off or trickle behavior.
  • Whether the robotic-mower rule of charging every three months applies to every model. The page says to check the operator’s manual, and it does not list the models.

What the sources do not say

None of the pages we opened gives a time limit for a lithium pack on a charger. The Ryobi page says its lights show when batteries are “charged and maintained,” but it does not say whether that state can last. Black and Decker’s warm-storage rule gives no number of weeks or months. The Husqvarna robotic-mower page says that older models may need charging every three months, but it does not state the charge level to hold during that time. The Husqvarna UK page does not say what happens to a pack that stays on its charger after it is full for long periods, and it gives only the removal advice.

FAQ

Can lithium batteries be left on charger over the winter?

It depends on the brand and on the storage temperature. Black and Decker says a battery stored above 40 degrees Fahrenheit can stay connected to the charger with the charger plugged in. Below that temperature, the same guide says to charge the battery fully and disconnect it. Husqvarna UK says to remove the battery once it is fully charged.

Is it safe to leave a battery on the charger?

The sources treat the charger and the cord as the main points. Husqvarna UK says to check the power cord for damage and to unplug it immediately if the cord is compromised. The EPA says to avoid long periods of extreme heat or cold, and Husqvarna’s petrol-mower page warns that high temperatures or fire can damage the battery.

Does a Ryobi charger keep a battery topped up?

The Ryobi dual-platform charger page says its indicator lights show when batteries are charged and maintained. The page does not say how the maintenance works or how long a pack can stay on the charger, so check the Ryobi manual for your charger model.

Should I unplug the charger after charging?

Husqvarna UK says to disconnect both the battery and the power plug once charging is complete. It adds that leaving the charger powered continuously can reduce its lifespan. That advice is for the BLi-X 36V battery and charger.

What does a robotic mower manual say about charging in storage?

Husqvarna’s US robotic-mower page says most models need no charging during storage if they were fully charged before power-off. Older models may need charging every three months. The operator’s manual sets the requirement for each model.

What if my manual says something different?

Follow the manual for your model. The pages in this post cover specific brands and models, and they disagree with one another, so the manual for your own pack settles the question. If the manual is a PDF, download it from the maker’s site and read the storage and charging sections.

Bottom line

Before you leave a lithium pack on its charger, check the manual for your model, and treat the pages in this post as a map of where the brands disagree rather than as a rule for your battery.

Sources

Similar Posts