The Trouble With Cordless Power Tools

If you grow up around a small engineering business you are likely to gain something of an appreciation for power tools. You’ll see them of all ages, sizes, manufacturers, and technologies. When thinking of the power tools constantly on hand in the workshop of a blacksmith like my dad for instance, I’m instantly seeing a drill and an angle grinder. The drill that most comes to mind is a Makita mains powered hand drill, and given that I remember the day he bought it to replace his clapped-out Wolf in 1976, it has given phenomenal service over four decades and continues to do so.

41 years of hard use, and still going strong.
41 years of hard use, and still going strong…

Of course, the Makita isn’t the only drill in his possession. A variety of others of different sizes and speeds have come and gone over the years, and there is always one at hand for any given task. The other one I’d like to single out is I think the most recent acquisition, a Bosch cordless model he bought several years ago. It’s similar in size and capabilities to the Makita save for its bulky battery pack, and it is a comparably decent quality tool.

So, we have two drills, both of similar size, and both of decent quality. One is from the mid 1970s, the other from the end of the last decade. One is a very useful tool able to drill holes all day, the other is little more than a paperweight. The vintage model from the days of flared trousers is a paperweight, you ask? No, the not-very-old Bosch, because its battery pack has lost its capacity. The inevitable degradation due to aged cell chemistry has left it unable to hold enough charge for more than maybe a minute’s use, and what was once a tool you’d be glad to own is now an ornament.

... Not so many years of light use, can't say the same.
… Not so many years of light use, can’t say the same.

Naturally, this will not be unfamiliar to most Hackaday readers. We’ve all been offered a pile of dead cordless tools over the years, and as writers we’ve covered quite a few inventive hacks using them. They’re a useful source of motors and sometimes even speed controllers, even if you don’t want to use them as tools.

Comparing the Makita and the Bosch as exemplars of the two strands of power tool ownership, I have though to admit an unease over the rise of cordless tools, and a dislike of the marketing that surrounds them. In converting their customers to cordless tools, the manufacturers have found a way to get them to buy the same tool from them every five years or so when there is nothing wrong with their previous tool, simply because its battery pack has reached the end of its lifetime. Battery pack form factors change with each successive generation of tools, so the customer can not merely buy a new battery pack and move on. Great for the manufacturers, awful for the consumers.

Meanwhile of course, the marketing machine is in full swing pushing the convenience of cordless tools. Amazingly this often concentrates on those problematic batteries themselves, for example where this is being written the manufacturer of those lime-green power tools has a commercial promoting a range of tools that all have the same battery. The idea presumably being that after five years you won’t simply have to replace your drill due to a dead battery, you’ll have to replace all your tools!

"You might as well take that lot away with you Kevin, I'll have to replace them all in a few years anyway!". (Ryobi TV)
“You might as well take that lot away with you Kevin, I’ll have to replace them all in a few years anyway!”. (Ryobi TV)

Of course, a full-on rant against power tool built-in obsolescence is of little use though without some kind of solution. If we’re to identify a problem then we should also provide some way out of it, at least a way that works for we hardware hackers and makers if not for the wider public.

The most obvious way to avoid cordless tool obsolescence is to not buy a cordless tool in the first place. Think carefully, how often do you use a power tool away from a mains socket? Really how often, not just hypothetically. The chances are it won’t be that often, if at all, and buying an extension cord with your electric drill will be a lot cheaper than buying a replacement drill in five years time. And then there are the unexpected benefits, you forget just how lightweight a power tool is when it doesn’t have a battery pack strapped to its handle. Buy a tool with a cord, and like my dad with his Makita, you might still be using it in four decades from now.


But let’s say you have a cordless tool, and its battery is failing. Can you fix the battery? Of course you can. You are Hackaday readers, you’ll all be aware that inside almost all cordless tool batteries you’ll find a set of standard off-the-shelf cells wired together, C or D cells in the case of NiCd or NiMh packs, and maybe 18650 cells for LiIon. If you can defeat the efforts of your tool manufacturer to discourage battery pack dismantling, you can have them out on your bench, and replace them.

This is a rather nicely built tab welder we recently featured.
This is a rather nicely built tab welder we recently featured.

Of course, there is a snag to replacing cells in a pack. This isn’t like the spring-loaded battery compartment in your radio, each cell will have spot-welded metal strip conductors linking it to its neighbour, and you’ll have to come up with a way of replicating that. If you’re lucky you’ll find solderable batteries, otherwise you’ll have to consider a battery welder. But if you can overcome that hurdle, you should at least be able to replace your cells without breaking the bank.

You will be unlikely to find a tool with a NiCd battery for sale new these days, but there are still huge numbers of older ones with dead packs to be found often at next-to-no outlay. It’s not the safest of exploits, but it is possible to rejuvenate dead NiCd cells with the application of short bursts of high current. The theory goes that metal crystals grow in the cell and short it out, and the high current blows these metal crystals and brings the cell back to life. There are tales of this being performed with hefty bench power supplies, car batteries, and arc welders, though you may wish to research carefully before you give it a try.

Finally, who needs cells? If you have a suitably powerful low voltage supply, why not run your tool directly from it and forget about the battery pack? Of course, you lose the ability to run it as a cordless tool, but if it came to you at very little cost than that should present very little hardship. Try a modified PC power supply if it’s a 12 V tool, or a lead-acid pack if it isn’t.

So we’ve got past my rant about the iniquity of the built-in obsolescence of cordless power tools, and identified several ways that we as resourceful Hackaday readers can benefit from the cast-offs of others whose batteries have reached the end of their lives. It doesn’t change my personal view that I’d always still buy a tool with a cord by choice, but at least there are ways forward for those stuck with failing cordless tools. Do you share my feelings on this topic?

222 thoughts on “The Trouble With Cordless Power Tools

  1. my battery pack had a thermister that aged, and was also susceptible to corrosion. It was unidentifiable by the time I saw it. If I knew what to replace it with, and had a strong confidence in not burning down my house or drill, I would rebuild it myself.

    1. Temporarily short out the thermister to get the pack working, and put it under constant load from the target use tool. Measure the temperature achieved, add about 15C onto that to select a new thermister value. If it’s in series with the cells (seeing full current), select one capable of at least 15A current, more being better. Option 2, buy a new battery and get the thermistor part # off of it.

  2. I’m not much into power tools, but I see the category is a huge opportunity for vendor lock-in and reduced tool quality (it’s battery-powered, so less sturdy, etc), and clearly some vendors have taken advantage.

    Is the usefulness of battery tools that there is no cord, or that you’re independent of the grid?

    It seems to me a good option would be a separate battery pack with an inverter, from which you could operate several corded tools. Aside from the cord issue, you’d have just one battery to charge rather than many, it would be separate from the tool, so would not affect handling, and could be larger and therefore higher capacity/power. it could be non-proprietary relative to the tools, and you’d be able to use more ‘standard’ corded tools.

    1. “Is the usefulness of battery tools that there is no cord, or that you’re independent of the grid?”

      We built a cabin on our farm land, nearest power source is 1/2 mile down the mountain.
      Same with rebuilding the fence at home. untangle and drag out 100′ of cords for the kids to trip over or grab the cordless and go to work.

      “It seems to me a good option would be a separate battery pack with an inverter, from which you could operate several corded tools”

      You need an inverter that it big enough to handle the load of corded tools as well as put out clean enough power (some modified sine waves don’t play well with motors). Inverters are also lossy so you need a big battery. At this point the cost of the inverter and battery are greater than the cost of the tools.

      1. Modified sine would play very well with the usual series winding connected motors, they are called “universal motors” for a reason. Probably some of the (phase angle) control electronics could work less than optimal.

        But such a device to “operate several corded tools” exist, I saw it in the catalog of a hardware and tools store shortly ago. A big box with a LiFePO4 battery pack with 1,6kWh if I remember correctly and an inverter with 1 or 2kW. But it was horrendously expensive, somewhere in the 1500 to 2000 Euro range. So it is only justifiable if a generator is absolutely no option.

    2. You have more imagination than attention to the facts. Tool quality has gone up generation after generation, with cordless now rivaling corded for the same size and weight tool. If you have some heavy duty continuous use scenario, do pick a corded tool. Both still exist because both are still relevant.

      The usefulness is that you just grab the tool and start using it. Anything that cuts down the time it takes to get started on a project, makes it more likely you’ll get it done instead of putting it off, or be more productive.

      Separate battery pack and inverter would be the worst option off all because you’re still dealing with a cord in use, but having to lug the setup around with it heavier, bulkier, UGH I am sure once you actually tried to do that, you would realize nobody else does for good reason. Plus corded tools are much less efficient, you might be surprised just how big your battery would have to be to get similar runtime.

      Just one battery instead of several is a bad thing. Several means you can keep working by putting a new battery in while the discharged one is rapid charging, or if the battery fails you still have another. The key thing is pick a brand and stick with it so most if not all your cordless tools use the same batteries.

      It is ironic that today cordless tools are great but instead of appreciating that and benefitting from it, you’d make things hard on yourself, for what exactly? Avoiding paying $50 every few years for a battery? if you don’t want to use cordless at all, nobody is forcing you to. I’m in that situation myself when it comes to replacing very high power tools, whether it be circular saws or gasoline powered blowers, mowers, etc. The batteries for some of these cost as much as the entire gasoline engine powered equivalent and even with the expensive batteries, may only run 20 minutes if that.

      Cordless is best for small hand held tools, until we have a new battery tech that is at least triple the power density at less than half the current cost per KWH.

  3. Throwing this in here; it’s probably already been mentioned but the initial comparison is between a professional tool (the Makita corded drill) and a “homeowner” cordless NiCd drill. Fun fact – the actual operating lifespan of drills for the homeowner is in the range of 4 to 5 hours of total use… spread out over a few years. They might stand up to heavier use… as long as the charge-discharge cycles are religiously managed, but the battery packs still won’t last more than a year or two.

    It’s NiCd batteries – they are unhappy with anything other than near perfect charge/discharge cycles, let alone the infrequent charging and use they get in the usual domestic setting.

    1. I have to agree that many people hated their NiCd batteries due to charge and discharge issues, but once chargers became smart (or the owner payed enough to get a decent product) the bigger issue was a user would continue to try to use the tool once the battery pack got low and ended up reverse charging the weakest cells in the pack.

      I always avoided that and never had a battery that only lasted a year or two except for one drill that I used daily in a profession so it had at least a few hundred charge cycles before it became too short lived/low-capacity to suit the runtime requirement.

      Even today, I have an old NiCd drill I keep as a backup and it works fine with a NiCd pack I rebuilt, but like everyone else I don’t want to have to think ahead to recharge it shortly before using it. NiCd self-discharge was my biggest gripe and reason to switch to Li-Ion, but also that current generation, higher performance tools were using Li-Ion.

  4. Apologies everyone that I am late to the party on my own article, I have been away at SHA2017 in the Netherlands.

    Good point about Ryobi tools, I was unaware they had kept the same format. Here in the UK we’re being spammed with their advert all the time, to the extent that it pissed me off enough to write the article.

  5. Hi! I’ve got some cordless tools and the batteries (life of time, compatibility…) was a pain. Now my tip is to open each kind of battery to keep the connector for the tool and replace the cells by another connector (a standardised one like a DEANS or XT60) and a strap to maintain a lipo. I use big lipos for my quadcopters, so now, I have only my big 4 ways lipo charger and some lipos I can use for my tools and my hobbies.

  6. Another try to post – don’t know why it doesn’t show up so far.
    Some addition + correction to the Article and comments.
    – It’s not C and D Cells, that are commonly used. I’ts Sub-C or sometimes the shorter versions of it.
    – Many Packs are available after decades, the shown Makita Pack is probably the oldest design and still available from various manufacturers.
    – There are also companies that sell Cell replacement packs – so you reuse your original Battery Case.
    – You can substitute 3 NiXX Cells by one Li-XX Cell, but you should never use low power Li-Ion Cells like the ones out of laptop Batteries for such high current applications. You need to get the proper high discharge versions.
    – You must be aware, that Li-XX Cells are safe for a max. current which is below of what they can deliver (unlike NiXX which you can draw as much as they can deliver). So if you have a powerful NiCD drill, and build a Li-XX Pack for it, you need to be sure, that it does not exceed the current rating of your selfmade pack.
    – Be sure to not overdischarge Li-XX cells.

    1. All that being said, I’m a huge fan of NiCD to Li-Ion conversions. I run a Metabo Circular saw off a 5s2p 18650 Pack. A Makita 7.2v Angle grinder with another motor on 3s 18650. And a classic Makita Cordless Drill of a 2s2p 18650 Pack.

      Performance on all these tools is much much better than with the original battery.

  7. unless they come up with some magic batteries that last forever, i’m not buying battery powered tools. Just stocking up for a new workshop for a new business, and it’s all corded tools for me, apart from the screwdrivers.

  8. My dad has a corded bosh hammer drill that is about 40years old too, but hasn’t used the last 10-15 years due to a single failed gear. And although replacements do exist, the fact that the label is worn out and the model not visible, makes the search of said gear a fool’s errand. Hence the drill sits in a closet cause both me and him are not willing to throw it away gathering dust and counting years of not use.

  9. I just don’t get this article. Maybe it was true or relevant 10 years ago. I have a lot of new tools, both corded and cordless. Any new Li-Ion tools from Dewalt, Milwaukee, etc use Brushless DC motors and perform like a champ, are small and light, and have excellent battery life. My corded drills never see the light of day anymore. The battery operated circular saws are even pretty good.

    Comparing a corded tool to one using Ni-cad or even Nimh batteries is just stupid in a contemporary article.

    An honest comparison would focus on the cost difference between good cordless tools and comparable corded tools, which is significant. But performance isn’t such a factor anymore unless you’re buying cheap junk.

  10. The interesting thing is one would spend say… a $100 for a three batteries that last say what? Two years with almost daily use and say… five with light use? So after twenty years that’s between $400 to $1000 dumped into batteries alone?

    Conversely, one can buy some really high quality powered tools for $1000 that can last almost a life time?

    I’m not dissing on cordless per se, I just think it’s interesting how people perceive value.

  11. OK, so its not rechargeable drills, but I have replaced 600 mAh NiCd batteries in the rechargable shaver. Getting new NiCd batteries from Home Depot was hard (all batteries are by the cashier except for NiCd and if you phone the kid says ‘we got lotsa batteries’ and the computer says they have 3 until you get there and they have none. But I did replace them with 900 mAh batteries, and it runs better than new. 7 weeks between recharging. I also have an Alkaline battery recharger. The battery says not to, it will explode, and in fairness, unless you use a smart microprocessor controlled charger, they will get hot and leak acid. You need one that puts in 3 mA and sucks 2 mA back out, and will automatically shut off. Batteries stay ice cold. Even Kodak’s camera battery says not to recharge, and in all fairness it did last about 5 years when new, and the recharges only last about a year, but if I get 10 recharges out of it, that’s 15 years. I recharge the alkaline LED flashlight batteries too. I haven’t bought a battery in at least 5 years, even though I use them all the time.

  12. Something about low capacity NiCads, they last forever it seems. Still using the ones I bought back when folks used them in Airsoft and model packs, in 2002! One thing to watch out for is black wire disease ™ which is trivially prevented by sealing cells with Epoxy leaving the vents open for safety.

  13. The purpose of a tool isn’t to last forever, it’s to make the worker more productive. If you place no value on your time, using the 41 year old electric drill will certainly work for installing a metal roof, but you can do it in half the time with a fresh Makita cordless. Yes, the batteries need to be replaced periodically and yes the next generation of Makitas will make the current ones obsolete, but that’s a good thing and it’s what is known as progress.

  14. The idea that battery form factors change on a constant basis is ignorant. Milwaukee M18 has been around since when? I believe the first tools came out in 2008. And they are still expanding the line so I would say the battery form factor should be around at least another 5 years if not longer. As of this summer that battery line will be 9 years old. So no you may not keep the battery drill for 40 years. But 10 years is quite a stretch, and the tools get better every year. I didn’t buy a new Milwaukee impact because mine died I bought a new one because it was that much better than the old generation.

  15. Have to say BTW, he could take a little care about that old drill and not let it rust that much. I mean is it really that hard to clean it a bit for 3 minutes?
    Also the writeup ignores that mechanical parts do age, I mean the bearing are probably gritty as hell and the thing must be plenty noisy. Although you could replace bearings, but looking at that it doesn’t look like that is something the owner would do.

  16. Go to Harbor freight, buy a 18 volt battery pack for their drill take apart your dewalt battery and swap the guts. Been doing it for years. Last time the battery was 10 bucks with a coupon…..

  17. Want something useful to make with your 3D printer? Look up the name of your cordless tool brand on thingiverse. There are many battery adapters people have designed to fit currently available batteries to older tools, and to use various tool batteries for powering other things.

  18. I was looking for a replacement battery for my Ryobi 9.6V… found one on Amazon for… $1,000… umm… going to go buy a drill with a cord. I don’t even have a voltmeter.

  19. i wish they (the manufacturers would standardize battery voltage and batteries. the current jumble of battery voltages and battery configurations is driving me crazy. it was 12 volt, 18 volt, not 20 volt, where will it stop? i have an old 12 volt makita that runs off a 12 volt plug in i made so it will run off my car battery. the charger and battery got run over years ago.

  20. This is the exact reason why I don’t own any battery tools whatsoever. I’m still using a drill I inherited from my father that was – as best as I’ve been able to determine – built in the late 1920s or early 30s. I hate throwing stuff away – and battery operated equipment will always die when you need it the most.

  21. Hi, Jenny List. Fantastic overview, I hope Ryobi sees your post and sends some love your way! I purchased a Ryobi brush-less kit from Amazon after watching your review. I wish other companies would do what Ryobi do with chargers that can charge 6 batteries at once. I have Hitachi tools & only have a single battery charger which is very frustrating.


  22. It sounds great all you have to do is dismantle that lithium ion pack and replace those 18650 cells. But wait the companies don’t stop their efforts to dissuade you at the security torx screws or plastic welded cases some of them go further than that as a safety measure to stop the possibility of charging a battery that has gone so low it changed its polarity and is now a potential bomb because it’s now technically backwards and will short thus causing the pack to turn into a spark show and fireball that burns down your hacienda. They have features that should the board ever lose all power even if it is only momentary they are designed to break and stop functioning. How they do this I don’t know but it is a function and a real problem you basically have to switch the old pack in for the new one while it’s still connected so it always has power something like an Indiana Jones golden statue switch where the big stone ball is replaced with either total silence and a dead board try again, success or a fiery mess that burns down your house. Shorting lithium cells out even briefly has been known to result in a catastrophic failure and fireballs. I’ve seen many youtube fails where people are leaping over desks to get away from exploding battery packs gone awry. It’s no joke and the cells oftentimes aren’t very well marked and because both ends look exactly the same it’s very easy to screw up an arrangement especially when some are in series and some are parallel all within the same pack. One reversed battery can ruin much more than your day. It’s why I don’t mess with them and i hack everything literally everything else i touch. There isnt a single thing I’ve owned since I was a kid that I haven’t taken to pieces and reassembled again except for lithium batteries I’ve taken them apart but I’ve never had the balls to replace a pack with one I made myself. Maybe I’m worried about nothing but something tells me to listen to the youtube videos and I dont listen to much.

  23. Whew. Lotsa comments.

    I’ve lways got good use out of cordless drills. My go-to is the very common little turquoise Bosch 18v drill – usually comes in a kit with 2 Li batteries and a charger. It’s stood up very well, lots of juice and torque, holds a charge.

    I find that NiCd battery packs always give up the ghost in 5 years or less. And they don’t like the service life of an infrequently-used devicel. I won’t ever buy a NiCd battery-powered anything again.

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