Lawn mower battery lifetime if diligently unplugged after charging?
July 12, 2022 1:42 PM Subscribe
We're interested in buying a battery-powered lawn mower, and the thing that gives us pause is that the batteries are too expensive to have to replace often. Lots of reviews say the batteries go bad quickly, but we've read this is because people don't know that they can't leave them plugged in once they're fully charged. If we're good about doing that, will the batteries last many years?
Have you had a battery-powered lawn mower for years, and been diligent about unplugging it whenever you're done charging it? Have the batteries lasted a lot of years that way, or have they still gone bad more quickly than the lawn mower has?
The one we're thinking of is a Greenworks mower.
Have you had a battery-powered lawn mower for years, and been diligent about unplugging it whenever you're done charging it? Have the batteries lasted a lot of years that way, or have they still gone bad more quickly than the lawn mower has?
The one we're thinking of is a Greenworks mower.
Charge behavior is almost exclusively a function of battery chemistry. Older electric mowers (especially ryobi) were lead-acid which is sub optimal for the way most people want to use something like a mower.
Edit: missed the part about greenworks.
posted by Dr. Twist at 1:46 PM on July 12, 2022
Edit: missed the part about greenworks.
posted by Dr. Twist at 1:46 PM on July 12, 2022
I have had a Greenworks battery lawnmower for a little over a year. I always unplug the batteries soon after charging and have not had any problems. This is the best lawnmower I've ever had.
posted by a humble nudibranch at 1:48 PM on July 12, 2022
posted by a humble nudibranch at 1:48 PM on July 12, 2022
I've had an Ego mower for, something like four years maybe? I only charge the battery immediately prior to use (so I remove it from the charger as soon as it's done, so that I can go use it), and I'm still on the original battery.
posted by aramaic at 1:54 PM on July 12, 2022
posted by aramaic at 1:54 PM on July 12, 2022
We have a makita 18" that uses two 18v batteries. The charger is smart enough to not overcharge or do any other potentially damaging action even when batteries are left on after getting fully charged. Great mower, on sale now with four 5.0Ah batteries. smart charger, mower for $400. Batteries are able to be used in Makita's other 18v tools, most of which are good to excellent.
posted by bullatony at 2:05 PM on July 12, 2022
posted by bullatony at 2:05 PM on July 12, 2022
Best answer: We have an 21" 40 volt kobalt lawnmower that is almost 8 years old. It came with 2 batteries but I accidentally dropped one in water 7 years ago. The one working battery has lasted 7 years. I do not leave the battery in the charger once it is fully charged if I can help it.
posted by Stynxno at 2:14 PM on July 12, 2022
posted by Stynxno at 2:14 PM on July 12, 2022
We bought a Flymo battery mower in 2017 and we've been somewhat but not totally diligent about unplugging when the battery is fully charged. It's still going strong. My spouse (lawnmower in chief) predicts that if it continues performing as it has done so far, it'll easily outlive the lifespan of the petrol motor machines he grew up using (especially here in a climate where the grass doesn't need mowing during winter, which is a tougher use pattern for getting reliable performance out of a combustion engine mower compared to an electric battery model).
posted by terretu at 2:44 PM on July 12, 2022
posted by terretu at 2:44 PM on July 12, 2022
I have a Ryobi Mower, weed whacker and snowblower, all use the same format battery, and they're interchangeable. 3 yrs+ on the oldest battery and no issues. Snowblower was shockingly effective.
posted by OHenryPacey at 2:57 PM on July 12, 2022
posted by OHenryPacey at 2:57 PM on July 12, 2022
I bought a Ryobi today actually. The batteries are pretty cheap compared to some others, and that was a factor in the purchase. One brand charges $400 for a new battery, and that’s a lot more than I’d like to pay.
posted by Slinga at 3:22 PM on July 12, 2022
posted by Slinga at 3:22 PM on July 12, 2022
I've had an Ego mower for, something like four years maybe? I only charge the battery immediately prior to use (so I remove it from the charger as soon as it's done, so that I can go use it), and I'm still on the original battery.
I have multiple Ego devices, typically leave batteries sitting on the charger for weeks or months at a time, and have no noticeable battery degradation.
posted by NotMyselfRightNow at 3:34 PM on July 12, 2022 [2 favorites]
I have multiple Ego devices, typically leave batteries sitting on the charger for weeks or months at a time, and have no noticeable battery degradation.
posted by NotMyselfRightNow at 3:34 PM on July 12, 2022 [2 favorites]
Best answer: Practically no one doing trade work does anything but plunk their batteries on the charger when drained until they need them next and modern lithium ion batteries with associated smart chargers last for years when treated this way (at a much higher duty cycle than a lawn mower). This doesn't necessarily apply to the greenworks mower (IDK one way or the other) but would to the makita, royobi one+, or milwaukee mowers which all use their standard batteries (though a huge one in the milwaukee's case). You should also be able to buy the batteries for years as the interface shifts have settled down and changing now would lose customers.
posted by Mitheral at 4:47 PM on July 12, 2022 [4 favorites]
posted by Mitheral at 4:47 PM on July 12, 2022 [4 favorites]
Best answer: I have had multiple well cared for Greenworks batteries go completely bad. I've got enough sunk cost in the tools that I buy a new one every few years but eventually I'll probably escape, but I can't say that I'd recommend getting into their ecosystem.
Another thing to keep in mind is the size of the yard. The larger 20 volt battery lasts long enough to do maybe 2/3 of my pretty typically sized front lawn so unless you have a small lawn or are willing to mow parts on different days, probably plan on getting a second battery.
posted by Candleman at 9:02 PM on July 12, 2022
Another thing to keep in mind is the size of the yard. The larger 20 volt battery lasts long enough to do maybe 2/3 of my pretty typically sized front lawn so unless you have a small lawn or are willing to mow parts on different days, probably plan on getting a second battery.
posted by Candleman at 9:02 PM on July 12, 2022
Best answer: This is an explanation of the "generic" Lithium battery that almost everything is powered by nowadays.
These battery's work life is affected by 3 things: a) heat b) rate of discharge, and c) How far it goes above or below its "optimum capacity"
a) and b) are related. Rapid discharge and fast recharge create a lot of heat, and heat kills batteries. You've seen the "bloating" batteries. Basically heat caused gas to form inside the battery, bulging the casing.
But what we'll really talk about is c) how a battery really prefers to stay within its optimum capacity, which is between 20%-80%. (some people use 25-75) And the battery will even accept charging faster in this band.
Which is why on a lot of devices they will tell you you can recharge it to 75% in a MUCH shorter time than to 100%. (often 1/3 the time). In fact, fully charging the battery causes more heat buildup
The batteries also really really hates to be drained completely. In fact, there were cases where a "fully" drained battery is declared dead and had to be replaced.
Most batteries are rated to keep most of its capacity over approximately 300-500 drain/recharge cycles.
However, if you want to keep the batteries longer, consider ONLY charging it enough to to run your task, and NO MORE. Basically the "less" depth of discharge, the more life you can get out of the battery.
In other words, using the device 20% twice, causes less wear on the battery than using the device 40% once.
According to BatteryUniversity, Lithium Ion batteries should NEVER be charged to full (which is 4.2V, in most setups, per cell) as this can significantly reduce its life. According to them, if the battery is rated to ratain capacity for 300-500 cycles at 4.2V< if you charge it to only 4.1V you can almost DOUBLE the battery life, and if you are willing to go even lower, you can quadruple, or more the battery life.
So the folks to keep the lawnmower charged all the time are basically killing their batteries.
posted by kschang at 12:38 AM on July 13, 2022 [1 favorite]
These battery's work life is affected by 3 things: a) heat b) rate of discharge, and c) How far it goes above or below its "optimum capacity"
a) and b) are related. Rapid discharge and fast recharge create a lot of heat, and heat kills batteries. You've seen the "bloating" batteries. Basically heat caused gas to form inside the battery, bulging the casing.
But what we'll really talk about is c) how a battery really prefers to stay within its optimum capacity, which is between 20%-80%. (some people use 25-75) And the battery will even accept charging faster in this band.
Which is why on a lot of devices they will tell you you can recharge it to 75% in a MUCH shorter time than to 100%. (often 1/3 the time). In fact, fully charging the battery causes more heat buildup
The batteries also really really hates to be drained completely. In fact, there were cases where a "fully" drained battery is declared dead and had to be replaced.
Most batteries are rated to keep most of its capacity over approximately 300-500 drain/recharge cycles.
However, if you want to keep the batteries longer, consider ONLY charging it enough to to run your task, and NO MORE. Basically the "less" depth of discharge, the more life you can get out of the battery.
In other words, using the device 20% twice, causes less wear on the battery than using the device 40% once.
According to BatteryUniversity, Lithium Ion batteries should NEVER be charged to full (which is 4.2V, in most setups, per cell) as this can significantly reduce its life. According to them, if the battery is rated to ratain capacity for 300-500 cycles at 4.2V< if you charge it to only 4.1V you can almost DOUBLE the battery life, and if you are willing to go even lower, you can quadruple, or more the battery life.
So the folks to keep the lawnmower charged all the time are basically killing their batteries.
posted by kschang at 12:38 AM on July 13, 2022 [1 favorite]
Ego batteries auto discharge themselves to about 30% if you leave them fully charged for a couple of weeks. That seems to preserve them ok; mine have run my lawnmower and snowblower for 4 years now.
posted by rhamphorhynchus at 5:50 AM on July 13, 2022
posted by rhamphorhynchus at 5:50 AM on July 13, 2022
Best answer: I can only speak to my experience with Makita, but I've charged 5 Ah batteries hundreds of times on the fast charger and am not seeing decline in power or length of charge, even though they are often left on the charger after the green light comes on. Of course, many tool companies are aware of the implications of fully charging on battery life and set up their charging stations to take those factors into account, stopping short of fully charging. In addition, the tools themselves stop performing while there is still charge remaining on the battery, to avoid complete draining. While I imagine that there are tool systems that don't operate in this way, I would avoid those, since there's a clear preference being expressed for creating a product that is primed for failure.
posted by bullatony at 7:59 AM on July 13, 2022 [1 favorite]
posted by bullatony at 7:59 AM on July 13, 2022 [1 favorite]
Best answer: Yeah, the safest way is probably to just use the device (bringing the battery's charge level down to between 20-80%), then let the battery rest on the counter until the next use, then put it in the charger the night before you intend on using it so it spends as little time as possible at a full state of charge.
On the other hand, some of the cycle counts the battery university is reporting are... _fine_? for outdoor power tools? I mean, up here in the frozen north, if I mow my lawn more than 20 times per season, even the low end 300 cycle count would be 15 years of life. I think the pitfall to avoid would be getting a battery that only just barely manages to perform the job - if you're using it at 95% in the first year, any degradation will mean you have to take a charge break.
But, as bullatony says, it all depends on how smart the manufacturer makes their charger and battery management system, whether it holds the batteries at 4.2v or 4v, if it allows the cells to rest if they've been in the charger for weeks during the off season, whether they have a low voltage cutout, etc. I haven't seen any discussion along those lines, unfortunately.
posted by Kyol at 8:19 AM on July 13, 2022
On the other hand, some of the cycle counts the battery university is reporting are... _fine_? for outdoor power tools? I mean, up here in the frozen north, if I mow my lawn more than 20 times per season, even the low end 300 cycle count would be 15 years of life. I think the pitfall to avoid would be getting a battery that only just barely manages to perform the job - if you're using it at 95% in the first year, any degradation will mean you have to take a charge break.
But, as bullatony says, it all depends on how smart the manufacturer makes their charger and battery management system, whether it holds the batteries at 4.2v or 4v, if it allows the cells to rest if they've been in the charger for weeks during the off season, whether they have a low voltage cutout, etc. I haven't seen any discussion along those lines, unfortunately.
posted by Kyol at 8:19 AM on July 13, 2022
However, if you want to keep the batteries longer, consider ONLY charging it enough to to run your task, and NO MORE.
That's not really calculable reliably with the tools available to the buyer of an electric mower, but I do have a strategy that does work. Say it takes a full charge to mow your entire yard. Thus, mowing about 20% of the yard uses 20% of the battery capacity. (If you could mow your whole lawn twice on a battery, then this would be 40% of your lawn; of it takes two full charges, it's 10% of the lawn). So the procedure is:
1 Put your battery on the charger about an hour before you mow. It should charge to full.
2 Mow all but 20% of the lawn (adjust as mentioned above).
3 Put the battery on the charger, charging to full.
4 Mow the remainder.
Your battery will be at 80%, where it will sit until you use it again. As stated, this is optimal for longevity.
posted by flimflam at 8:22 AM on July 13, 2022
That's not really calculable reliably with the tools available to the buyer of an electric mower, but I do have a strategy that does work. Say it takes a full charge to mow your entire yard. Thus, mowing about 20% of the yard uses 20% of the battery capacity. (If you could mow your whole lawn twice on a battery, then this would be 40% of your lawn; of it takes two full charges, it's 10% of the lawn). So the procedure is:
1 Put your battery on the charger about an hour before you mow. It should charge to full.
2 Mow all but 20% of the lawn (adjust as mentioned above).
3 Put the battery on the charger, charging to full.
4 Mow the remainder.
Your battery will be at 80%, where it will sit until you use it again. As stated, this is optimal for longevity.
posted by flimflam at 8:22 AM on July 13, 2022
Best answer: Don't charge it when you're done using it. Let it cool down for several hours. Use a slow charger if you have one available, rather than a fast charger. Not charging while hot and limiting the C rate of charge are the best way to prolong lithium battery lifetimes, that don't involve changing how you use the battery.
The Greenworks 80v fast charger slams power in quite fast (600 watts slowly tapering if I remember correctly) and uses a fan to compensate. I don't think they have a slow charger. So I don't think their charger is good for the battery, but letting it cool down before charging is at least some help.
In general tool manufacturers have perverse incentives to make chargers that are not good for battery life.
posted by joeyh at 9:53 AM on July 13, 2022
The Greenworks 80v fast charger slams power in quite fast (600 watts slowly tapering if I remember correctly) and uses a fan to compensate. I don't think they have a slow charger. So I don't think their charger is good for the battery, but letting it cool down before charging is at least some help.
In general tool manufacturers have perverse incentives to make chargers that are not good for battery life.
posted by joeyh at 9:53 AM on July 13, 2022
I've had a Ryobi mower for four years and don't take special care of the battery (I often drain it completely, set it to charging right away, and leave it on the charger until I need it again) and the battery is still fine. It doesn't have quite the capacity as it used to but probably 75%?
posted by metasarah at 11:36 AM on July 13, 2022
posted by metasarah at 11:36 AM on July 13, 2022
I'm not certain you can necessarily correlate a charger having a fan with necessarily attempting to keep the battery cool during charging - the power conversion circuitry usually needs active cooling. I mean, all of my RC chargers have fans, and the battery is nowhere near them during charge.
(And that RC history has certainly given me unusual lithium charging expectations - we regularly charge at 2-3x capacity for 20-30 minute charge cycles. On the other hand those batteries are only like $40 and tend to die from physical issues before chemistry changes can get around to killing them.)
That said, Greenworks themselves specifically says to remove the battery and unplug the charger after use, but it sounds like they're arguing more from a product liability standpoint than a battery longevity standpoint:
"CAN I LEAVE MY BATTERY IN THE CHARGER AFTER CHARGING IT?
Though you certainly can, we advise customers to remove the battery from the charger after it has been fully charged and to also unplug the charger from the outlet. The battery chargers do have auto cut offs to prevent it from overcharging but it's still best to follow good electrical safety practices. Doing so will also help prevent false defects readings and will allow the charger to reset itself each time it’s used to charge a battery."
For what it's worth the battery comes out of my 80v greenworks mower at ambient temperature. But my lawn is sparse and small, so the hardest it ever had to work was after No Mow May.
posted by Kyol at 12:28 PM on July 13, 2022
(And that RC history has certainly given me unusual lithium charging expectations - we regularly charge at 2-3x capacity for 20-30 minute charge cycles. On the other hand those batteries are only like $40 and tend to die from physical issues before chemistry changes can get around to killing them.)
That said, Greenworks themselves specifically says to remove the battery and unplug the charger after use, but it sounds like they're arguing more from a product liability standpoint than a battery longevity standpoint:
"CAN I LEAVE MY BATTERY IN THE CHARGER AFTER CHARGING IT?
Though you certainly can, we advise customers to remove the battery from the charger after it has been fully charged and to also unplug the charger from the outlet. The battery chargers do have auto cut offs to prevent it from overcharging but it's still best to follow good electrical safety practices. Doing so will also help prevent false defects readings and will allow the charger to reset itself each time it’s used to charge a battery."
For what it's worth the battery comes out of my 80v greenworks mower at ambient temperature. But my lawn is sparse and small, so the hardest it ever had to work was after No Mow May.
posted by Kyol at 12:28 PM on July 13, 2022
Response by poster: Thank you! We're going to try it, and follow the advice here as much as possible. Here's hoping!
posted by daisyace at 2:44 PM on July 14, 2022 [2 favorites]
posted by daisyace at 2:44 PM on July 14, 2022 [2 favorites]
This thread is closed to new comments.
posted by daisyace at 1:43 PM on July 12, 2022 [1 favorite]