Ask LH: Can I Keep My Cordless Tools Charged Up All The Time?

Ask LH: Can I Keep My Cordless Tools Charged Up All The Time?

Dear Lifehacker, Like many other Lifehacker readers, I have the usual collection of cordless power tools that don’t get used quite as often as they should or I’d like. I’ve read that keeping the battery pack constantly charging is no good for the battery. Can you recommend a strategy for ensuring the cordless power tools have the power when you need them but maintaining the battery life? Thanks, Cordless and Powerless

Picture by Douglas Muth

Dear C&P,

There’s no denying the convenience of cordless tools — but there’s also no denying that if you don’t use them regularly, chances are they’ll be entirely out of power when you want to use them. I often find myself thinking “OK, now I need the drill” and then having to hold off while the battery charges up.

If you regularly plan to use your cordless tools, the obvious solution is to leave the batteries plugged into the charger all the time. Assuming you have the space in your garage and shed, this means they’ll always be available for use. But is it a good idea? Many of us vaguely recall the warnings over battery memory that applied to notebooks and mobile phones, and worry that taking this approach will actually reduce the life of the devices.

As we’ve pointed out before in the context of PCs, with modern lithium ion batteries, it’s not true that constantly charging them will reduce battery life. And this is also true for newer power tools, which are designed to charge the battery more intelligently. Here’s what it says in the manual for a Bosch PSR 18 cordless drill which I’m currently testing:

Due to the intelligent charging method, the charging condition of the battery is automatically detected and the battery is charged with the optimum charging current, depending on battery temperature and voltage. This gives longer life to the battery and always leaves it fully charged when kept in the charger for storage.

This won’t necessarily apply if your cordless tools are older, or you have purchased them from a brand-name supplier. But if you have new modern tools, keeping the batteries in their chargers plugged in and ready to go will make it easier to engage in a spot of DIY when the mood takes you.

Cheers Lifehacker

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  • The above is fine if you already have a new drill/tool that “intelligently” charges, but going out and buying such hardware kind of defeats the purpose. If you’re going to do that, you may as well leave your batteries plugged in permanently (albeit at a shorter service life) then go and buy a new tool when your existing one carks it.

    As a cheap stop-gap method of preventing constant charging, whilst still keeping the battery relatively fully charged – duck into Bunnings (or any hardware store) and buy yourself a 24-hour mains timer. People often use them for lamps or heaters, and you can get a cheap HPM branded one from upwards of $5. Run a power board off the timer, and plug in your various tool chargers from there. Depending on the frequency of use of your tools, you can set your batteries to receive a daily charge anywhere upwards from 15mins per day, in 15 minute increments. As a bonus, if you have a smart meter in your meter box, set your batteries to charge in the middle of the night so you can take advantage of the off-peak tariff. If plugging your depleted battery in after use, most timers also have an over-ride switch to keep the power permanently on until you manually disable it.

    Obviously this probably isn’t as great as using an intelligent charger, but at least you’re minimising constant charge, and allowing up to 23-hours-and-45-minutes downtime for your batteries to naturally discharge throughout the day before it receives another top up.

    • Like Dale mentioned, you get what you pay for. Ryobi are in the bottom imo.

      Im a carpenter aswell and i see so many people mistreating tools.
      To save juice, adjust your cordless drill settings. Read the manual and learn the settings. I think alot of the ones these days have 3 speed, screw/hammer/drill features.

      I found the new lithium makita batteries charge up very quick.
      Quality seems to be down on makita tools aswell. Made in china, not made in japan anymore.

    • Tom, I have never had a Riobi battery last over a year and usually about 9 months. And this is when using Sam’s 24 hour charger procedure. I have been doing this for years. I have quit using Ryobi for this battery life issue. Whether the battery is kept charged or not, it just does not last. The problem with Ryobi is not your charging method, it is the low grade batteries.

  • As a carpenter, cordless power tools are something i deal with every day, i have a total of 11 cordless power tools in my van at all times and quite often im using 3 or 4 of them at a time. I was taught from a very early age in my apprenticeship to not skimp on tools, infact my boss told me “if you pay for a $4 haircut you are going to get a $4 haircut”. over the many years i have seen power tools come and go but the Lithium Ion batteries have changed the way i work for the better. Battery memory used to be the biggest pain in the ass to deal with.

    Another tip, if your thinking of investing in some cordless power tools, buy all your tools THE SAME BRAND, more specifically the same model line and voltage if you can. This ensures that you can swap batteries between all of your different tools. For your drill invest in some quality bits and make sure they stay sharp, there is no need to put excessive strain on your power tool because the bit is blunt. Its unsafe and it decreases battery charge a fair bit. And the last point, KEEP YOUR TOOLS CLEAN. i cant stress this enough to apprentices, those shiny new power tools are bloody expensive and you want to make sure you get the best out of them, stray bits of dirt and wood chips can reek havoc on a power tool, keep dirt and sand and other small particles away from the vent slots, more than often a few of those vent slots are for air intake and you can be damn sure that a few small grains of sand will completely fuck the motor in your new tool, also dont cover the vents while using the tool, motors, need air too.

  • It depends mainly on the chemistry of the batteries.

    If they’re NiCd types, then leaving them charged will shorten their life considerably, and they should be left as close to fully discharged as possible and only charged up when you’re about to use them. (Yes, that can be a hassle, but they usually charge to a usable level pretty quickly for small jobs.)

    Lithium batteries (of whatever type) are best kept charged, and Sam’s timer idea sounds like a good one if the charger’s not specifically marketed as being an intelligent one.
    If they’re not used often, then a short re-charge once a week is probably enough, given that Lithium cells don’t self-discharge much.

    NiMHs are like lithium except that they typically self-discharge more quickly, so might need a more frequent top-up.

  • Buy lithium batteries, or get your nicad/nimh converted by a battery shop.

    One hour of charging gets you four hours of use (compared to 4 hours of charging to get you one hour of use with nimh), and the charge will last 6 months without recharging.

    Problem solved.

  • I have been searching the internet for sam’s idea and ended up here. I had the same idea based on the tickle feature of my AA charger. Has anyone tried this idea? Would 15 minutes a day be enough to keep the batteries charged?

  • Hmm! Good information.

    I now have Ryobi 18v drills, small circular saw, reciprocating saw, leaf blower, weed whacker, light, etc.
    I run all of them on Lithium batteries, Yes, they are lightweight tools, they do not weigh much which I like and as I now only do small household jobs they are more then adequate.

    What I do is plug a Belkin timer switch which plug into a surge strip and the Belkin is set for 6 hours flip it on and it turns itself off, so I can walk away and not have a vampire load running. 6 hours is long enough to charge all of the different batteries that I have plugged in. The lithium batteries in the smart chargers really do work well and take a short time to charge and long to self discharge.
    They cost more yet it is a very good deal for me. I have a small yard and do small projects.

    The most surprising for me was how well the little circular saw works and how long it runs on a charge. It is especially nice when you have to cut over head. It does cut a 2×4 @ 90 degrees and whips through 1/2 – 3/4 plywood very well. I do use good Freud blades which I keep clean and oil them with WD 40 between uses. Also I very much enjoy the little leaf blower, very light weight and enough wind to blow the leaves out of my garage and driveway. Not what I would use when I had a large yard, yet perfect for a postage stamp size and the 2 car driveway.

    I have professionals come by for the bigger jobs and they often borrow the Ryobi’s and comment how well they work and then later I see they have the small circular saw or another Ryobi tool for the small jobs or when weight is an issue.

    Ryobi is not a professional grade tool yet for the cost of a professional tool I can buy a whole set of Ryobi tools with 2 Lithium batteries and a smart charger.

    The Belkin Conserve Socket F7C009q Energy-Saving Outlet for $10 on and it can be set for 1/2, 3 or 6 hours. You set it for the time you and then flip the switch and walk away.

  • I hear and read big praises for the new Li-on batteries but beware! The new highly touted Li-on batteries commonly supplied with less than super expensive professional grade tools are VERY small in size and equally small in watt-hour capacity. (I don’t know if this observation also applies to the super expensive professional tools because I have never yet paid $300 for a 1/4″ drill) The Li-on batteries that came with my Skil power tool set lasted only a few minutes from full charge to discharge. When the drill stops, do not attempt to restart it because you will kill the brand new super expensive battery battery is just a few additional seconds after the initial stop. Ask me how I know this! I am a Ni-Cad fan for life.

  • Have two excellent Makita Drills that use nicad batteries and need replacement. Why are the replacements so expensive-almost$85.00-to $90.00 each ? Does anyone make lithium replacement batteries and is it worth it.? It is a shame to just throw out these drills. Any advise /comments welcomed..

  • I recently inherited two cordless drills (DeWalt and Porter Cable). They both have 2 batteries each, but the batteries will not accept a charge. They go through the “charging process,” but do not get enough of a charge to actually work.
    My question is this: Is it worthwhile for me to purchase new batteries for them and follow the timer steps outlined in Sam Cook’s June 10th 2011 idea? Or, is it time to invest in a new cordless drill?

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