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I've had a corded electric lawn mower for 5 years and I am very pleased with its performance and value. However I am not pleased with the "chain" of the cord. I do not live in the suburbs, I live in the city and do not have a large lawn, so its only annoying for about thirty minutes worth of lawn which I just live with. I am considering a new electric with batteries but herein lies my question.

I live in the north east and I only need to mow the lawn maybe three months our of the year. The rest of the year the mower and its batteries will sit idle in an unheated garage. Will the lithium-ion batteries go flat and not recharge after sitting idle though the cold winter? Will I have to constantly keep them charged wasting money?

I realize I will want to get at least 2 batteries and I'm fine with that investment if its going to worth it. I don't want to have to replace them each year.

I wanted to ask other people who live in similar climates what their experience was before cutting-the-cord, as it were.

Update: Thanks to all the responders for your expert responses. I maybe posted on the wrong forum tho, because I was looking for people who've actually lived it and done it and not so much theory as to how it "should" work or lessons about batteries. Thx.

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    Batteries are small enough it should be no problem keeping them inside during the winter, if manufacturer recommendations are to avoid freezing temperatures. May 23, 2021 at 14:13
  • Why would you need "at least two" batteries? Do you plan to get an edger or line trimmer that would use the same battery as the mower? May 23, 2021 at 16:06
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    Do you have hard numbers on the money cost of leaving batteries on sustainer charger 24x7 all year? At a buck a watt a year, I would exepect it to be under $2. May 23, 2021 at 18:50
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    Most of the answers have good points, but one point appears overlooked. Storage should not be done at full charge. Discharge the battery to 30-50 percent through use, before making the batteries sit idle.
    – fred_dot_u
    May 23, 2021 at 19:56
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    Aside - I bought a battery mower and regret it intensely. Persevere with your corded one, or even go back to petrol.
    – Criggie
    May 24, 2021 at 2:55

4 Answers 4

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Lithium batteries are not lead-acid. They don't have all those "bad habits" like decaying when left in storage.

Tiny palm-sized packs such as for power tools do tend to age like normal power-tool packs and only give you 3-5 years life... but I understand lawnmower packs are bigger.

This assumes you buy quality and not some cheapo piece o' junk off Amazon Marketplace.

However, I gather you have apprehension about large lithium packs. Lithiums do have certain rules.

  • Do not discharge them literally to zero. Now, any competent lithium battery will have a Battery Management System (BMS) to protect the battery from a variety of things (including overcharge)... and it will disconnect the battery and shut down your appliance to protect it from too-deep discharge. That does nothing about self-discharge from long storage, and I'd suggest putting them on charger every couple of months to keep them from reaching zero.
  • Do not recharge them if temp is below freezing. In fact, if you try to recharge a Tesla whose battery has deep-frozen, it will first heat and circulate battery coolant, before it attempts to charge.
  • Never, ever, feed them after midnight. Just kidding!

As far as buying 2 battery packs, if the supplied battery pack lacks the range to cut the whole lawn, just put the battery back on charger and cut the rest of it later.

Lithiums are happiest working in their midrange: 20-80%. Charging is fastest and it does not need to be tapered/limited, like it must for 0-20% and 80-100%. That's the trick about crossing the country in an EV: you can DC fast-charge within that 20-80% range very quickly.

So if it doesn't have range for the full lawn, stop at halfway and recharge... that way you'll be recharging from 20-50% SOC and it will charge pretty fast up to 80%.... then finish.

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Usually manufacturers give instructions for storage of batteries in the instructions - did you check what they suggest?

I have batteries that are used both for my mower and my cordless drill - bought the same make specifically, so I have not had an issue yet.

And I store my stuff above freezing fwiw.

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Li-Ion batteries should be stored chareged. They usually have no self discharge so they should survive the winter when charged after last use. However, for longevity you may want to store them chaged only to 40%. Charging them fully weres them out quicker. Also better if the temperature in the garage was above freezing.

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    Lithium batteries should not be stored fully charged. The batteries do have a self discharge, although much lower current than other chemistries.
    – fred_dot_u
    May 23, 2021 at 19:57
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    @fred_dot_u: it's not the best written answer, but they said "40%", which is great and pertinent advice.
    – dandavis
    May 23, 2021 at 22:34
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I have an Ego mower and trimmer, and until this year I used them in Duluth Minnesota. The batteries are fine come spring. You're overthinking it.

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  • The question is a good one. This would be the most informative answer so far without the "overthinking" comment.
    – jay613
    May 24, 2021 at 11:58

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