Proper winter storage of lawnmower batteries is essential for maintaining their performance and extending their lifespan through cold months when this equipment sits unused.
The key factors to consider include maintaining appropriate charge levels, storing in climate-controlled environments, and following specific protocols based on whether you have lead-acid or lithium-ion batteries.
Understanding Battery Chemistry and Cold Weather Impact
The fundamental chemistry of lawnmower batteries determines how they respond to cold temperatures and storage conditions.
Lead Acid Batteries
For example, let’s start with a common choice for lawnmowers: the lead-acid battery, which are often found in riding mowers and older equipment. This popular choice experiences significant capacity reduction when facing cold weather, dropping to 50-60% of their normal capacity at 32°F.
This dramatic performance decrease occurs because the chemical reactions within the battery slow down substantially as temperatures drop, making it harder for the battery to deliver power when needed.
Lithium-Ion Batteries
Next, let’s talk about another increasingly popular power source for mowers: the impressive lithium-ion battery.
These have become the go-to choice for owners of modern electric mowers, but not just because they can be recharged. They also demonstrate superior cold weather performance compared to their lead-acid counterparts (speaking of which, we’ve talked at length about lithium batteries and cold weather here if you’re interested).
These advanced batteries maintain an absolutely incredible 95-98% of their capacity even in cold conditions, which makes them more reliable for equipment that might be used during cooler months.
Typically, this would not be a lawnmower, but most people store their mowers in their garages where temps still drop for much of the year.
Despite their impressive capabilities, lithium-ion batteries have their own specific storage requirements that differ significantly from lead-acid batteries, particularly regarding optimal charge levels during extended storage periods.
The electrolyte in lead-acid batteries can actually freeze if the battery becomes sufficiently discharged, causing permanent damage to the internal plates and structure.
But a fully charged lead-acid battery has a much lower freezing point than a discharged one, which is why maintaining proper charge levels becomes critical for winter storage.
Conversely, lithium-ion batteries face different challenges, as storing them at full charge for extended periods can actually cause stress and reduce their overall lifespan (if you’re curious, here’s how long mower batteries last).
The Best Storage Temperatures and Environmental Conditions for Your Lawnmower Batteries
Temperature control represents the most critical factor in successful battery storage during winter months.
We recommend storing batteries indoors during the winter where temperatures remain between 40°F and 80°F, minimizing temperature fluctuations that can stress battery components.
The ideal storage temperature probably hovers around 60°F, which represents the sweet spot for most battery chemistries.
Unheated garages, sheds, and outdoor storage areas should be avoided entirely, as these spaces subject batteries to the same temperature extremes that can damage equipment left outside.
Even insulated garages are often a bad choice as they can experience significant temperature swings that can accelerate battery degradation and reduce storage life.
Climate-controlled basements, utility rooms, or heated workshops provide the stable environment batteries need to maintain their condition through winter months.
Humidity control also plays an important role in battery storage success. The optimal relative humidity for battery storage sits around 50%, preventing both excessive moisture that can cause corrosion and overly dry conditions that might affect certain battery components.
Storage areas should be well-ventilated but protected from direct exposure to weather elements, ensuring consistent environmental conditions throughout the storage period.
Charge Level Management for Different Battery Types
The appropriate charge level for winter storage depends entirely on the type of battery in your lawnmower. Once again, lead-acid and lithium-ion batteries require completely different approaches.
Lead-acid batteries should be stored at full charge, ideally reading 12.6 volts or higher when measured with a voltmeter.
This full charge prevents sulfation, a process where lead sulfate crystals form on the battery plates during discharge, potentially causing permanent capacity loss.
So, before storing lead-acid batteries (check out this blog on battery storage for more info), charge them completely using an appropriate charger, then verify the voltage reading to ensure they've reached full capacity.
During extended storage periods (i.e., the months of winter), these batteries will actually self-discharge, so checking them monthly and providing supplemental charging when voltage drops below 12.4 volts will help to maintain their condition. Battery maintainers or trickle chargers can automate this process, providing just enough current to offset self-discharge without overcharging.
Lithium-ion batteries require a fundamentally different storage approach, with optimal storage charge levels between 30-60% of full capacity.
Storing lithium-ion batteries at full charge creates stress on the battery chemistry that can reduce overall lifespan, while storing them too low risks deep discharge damage. Many battery manufacturers recommend targeting around 40-50% charge for long-term storage, which provides the best balance between preventing deep discharge and minimizing storage stress.
Battery Removal and Preparation Process
Removing the battery from your lawnmower before winter storage provides several important benefits beyond just temperature control.
Batteries left in equipment remain connected to various electrical systems that can create parasitic drain, slowly discharging the battery even when the equipment isn't being used. This gradual discharge can lead to deep discharge conditions that damage battery chemistry and reduce overall lifespan.
The removal process begins with ensuring the mower is completely shut off and all electrical systems are disconnected (for obvious reasons)
Remove the negative terminal first, followed by the positive terminal, to prevent accidental short circuits during the disconnection process. Clean the battery terminals and cable connections with a wire brush or terminal cleaner to remove any corrosion or buildup that might interfere with proper electrical contact when reinstalling the battery in spring.
Inspect the battery case for any signs of damage, swelling, or leakage before storage. Damaged batteries should not be stored and require proper disposal through appropriate recycling channels. For flooded lead-acid batteries, check the electrolyte levels in each cell and add distilled water if necessary to cover the plates, but avoid overfilling as this can cause problems during charging.
Storage Location Selection and Setup
The physical storage location significantly impacts battery condition during winter months, making proper selection crucial for successful long-term storage.
Indoor storage locations with stable temperatures provide the best environment, with basements, utility rooms, and climate-controlled workshops offering ideal conditions. The storage area should remain dry, well-ventilated, and protected from temperature extremes that could stress battery components.
Batteries should be stored upright in their normal operating position to prevent electrolyte leakage and maintain proper internal component alignment.
Try to place your battery on wooden shelves, plastic surfaces, or rubber mats rather than directly on concrete floors, as concrete can conduct small amounts of current that contribute to self-discharge. If its original packaging is available, storing batteries in their factory containers provides additional protection and helps maintain proper positioning.
Organize storage areas to prevent accidental contact between battery terminals and metal objects that could cause short circuits. Keep batteries separated from other stored items, particularly anything containing metal or conductive materials. Label batteries with storage dates and charge levels to track their condition and ensure proper rotation if you have multiple batteries in storage.
Maintenance During Storage Period
Regular monitoring during the storage period helps ensure batteries remain in good condition and ready for spring use.
Fortunately, “regularly” here just means checking your stored batteries every month, measuring voltage levels and looking for any signs of physical deterioration or damage.
Lead-acid batteries that drop below 12.4 volts need recharging to prevent sulfation and maintain their condition throughout the storage period.
Although lithium-ion batteries require less frequent monitoring, they should still be checked every few months to ensure they haven't self-discharged below safe levels. If lithium-ion batteries drop below 20% charge during storage, they risk entering deep discharge conditions that can permanently damage the battery chemistry. Most quality lithium-ion batteries have built-in protection circuits that prevent deep discharge, but monitoring provides an additional safety margin.
Temperature monitoring in storage areas helps identify potential problems before they affect battery condition. Sudden temperature changes or extended periods outside the recommended range indicate the need for storage location adjustments or additional climate control measures. Keep detailed records of battery condition checks, including voltage readings and any observations about physical condition or performance changes.
Prepare Early for Storing Your Mower Battery This Winter
The time to start preparing for storing your mower battery is now (unless, of course, you’re reading this in the dead of winter; in that case, it was months ago).
Really, all you need to do is find a dry, warm area indoors where you can keep your mower battery during the cold winter months and then put reminders on your calendar to check it every month.
Any questions about how to do it?
Contact us to talk with one of our experts.
