h a l f b a k e r yCeci n'est pas une idée.
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While a supercap doesn't contain as much energy per volume as a battery, it can be charged, with close to 100% efficiency, as fast as you can pour the power into it.
So rather than leave the screwdriver in the charging cradle plugged into the wall, just to ensure that the tool has some juice when
you want to rehang that picture frame 'one of these days', the Supercap Cordless is stored in an uncharged state.
When it's needed, plug it into the wall for a few seconds and it's good to go. When you're finished, just put it back in your toolbox; any energy left in the cap will self-discharge in a couple days.
And it means that after a couple measly decades the battery won't be shot requiring you to get a new one which they don't make any more so you either have to buy an entirely new tool complete with accessories you already have or spend a few days/weeks trying to figure out if a newer chemistry battery set will work 'cuz when you go to the website all it says is "discontinued" cheap bastids.
Super_20capacitor_2..._20for_20cellphones
[spidermother, Jun 03 2011]
Ultracapacitors
http://www.rell.com...px?productId=937403
Use (4) 3000F caps in series [csea, Jun 03 2011]
Coleman Flashcell
http://www.google.c...0l0l0l0l176l176l0.1
baked, but rather crappily. One of the key points (of the post) is that you just plug it into the wall... not into a charging cradle... yeesh. [FlyingToaster, Jun 11 2011, last modified Aug 12 2015]
[link]
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Also, because of their minimal ESR, they can deliver very high currents, thus high torque is easier to deliver without elaborate gearing.
[+] |
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I thought you were going to take advantage of the fast discharge rates and blast the screws in place in a blink of an eye. |
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A powerful idea. Could crack a few tough-nuts loose, if
utilized within a hammer drill. |
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You poor, poor, people, whose radiusses and ulnas have fused from underuse. |
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The supercapacitor idea could equally be applied to most cordless power tools. It is very rare that a single operation of any such tool consumes the whole capacity of the battery, or anywhere near it. |
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Typical cordless battery pack is 12V, 1300mAh, or
15.6W-h, or 56kJ of storage. |
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Are there suitable caps available with this energy
storage? E=1/2cV^2, so at 12 V, need 780Farads. |
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I found [link] some 2.7V 3000F caps [link] that
could be used in series to give 750F at 10.8V. A
bit pricey at $105 each! |
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But it passes the reasonability test, so + . |
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There's still a limit to how fast you can charge a single cell, and therefore a battery, even in parallel. |
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I was thinking the same about the voltage, but there's some fancy electronics available that can deliver a well regulated output, from a wide range of supply voltages, at decent efficiency. It adds to the cost and complexity, of course. |
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I wouldn't be surprised if supercapacitor battery replacements started appearing in the next few years - complete with electronic regulators. |
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The idea here is "replace x's battery with a supercapacitor", with the same objections in the annos to the 1st linked idea. I agree with the rant, though. Batteries are a bit crap, and non-standard, unsupported batteries are practically evil. Why can't a cordless screwdriver just use C or AA cells? |
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Because when the batteries failed, you would simply replace them with cheap, off the shelf items from a generic source, rather than buying another new, expensive tool from the manufacturer, despite the fact that the mechanical parts of the one you have are still perfectly functional. |
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It's called "the free market", apparently. |
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Does that answer your question ? |
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[eighth] Yes it does. My question was rhetorical, but thanks anyway. |
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//could be applied to most cordless power tools// Not really: s/c's have like a tenth of a decent battery's energy density at best. This idea is for a light use tool which has minimal energy requirements, for a home handyman. Enough to take the TV apart and put it back together, maybe put those bookshelves together, though mind that you only need plug it in again for a few seconds to recharge. |
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//15.6Wh// I'm thinking more like 1-2Wh : enough for 5 minutes or so of constant use (actual figure forthcoming eventually) |
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// same objections in the annos as linked idea (supercapacitor cell phone)// The objection (that I had) is that a cellphone has to stay operational for quite a while: for that application you need all the energy that's in the existing battery, so a supercap equipped cellphone need be larger to accomodate the larger power source. |
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// just use C or AA cells ?// I actually saw one in the hardware megastore the other day that used non-rechargeable batteries: quite (relatively) inexpensive. I'm thinking of picking one up and using rechargeable batteries in it :) § x1 |
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//Capacitor voltage drops linearly with energy
used// |
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But DC:DC voltage regulators are cheap. Not an
issue. |
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//Capacitor voltage drops linearly with energy used// |
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With a series wound electric motor, the voltage doesn't really matter all that much. |
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Coleman licensed technology from Demain (an Australian firm) and came out with a "Flashcell Cordless Screwdriver" a few years ago <link>. Sadly, discontinued: Coleman's Canadian rep had to be hit with a 2x4 (figuratively) to admit they existed and couldn't even tell me the model number. |
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However if anybody wants one they're apparently still available online from US retailers for $30 (originally $100). |
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Gotta admit I like my overall design better though: I mean if you have a screwdriver that you don't need to leave plugged into a base for a day or so, then why have a base at all? just plug it into the wall and toss it back into the toolbox. |
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Best thing would be that if you did have a job that fully dicharged it, a fresh charge is only a short time away. |
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The supercaps might not have the torque/stamina of my
beloved 36v DeWalt Cordless tools, but could they be
employed to recharge the batteries, sort of a 'cordless
charger' system? That way, I only have to hang around near
the wall socket for a minute or two, and half an hour later
when my power packs are charged up, they're right there
where I'm working instead of down on the ground floor or
wherever. |
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I went to Lowes last month and to my dismay they no longer make corded power tools. So now every time I want to work on a DIY project I have to let my Dremel charge for 3.5 hours to get a whopping 10 minutes of use out of it. [+] |
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[Ao] Have you checked our lineup of Jobsite Powerbox/Radios ? I'm not sure if Engineering's worked out all the kinks yet on the Supercap Edition, but they haven't requisitioned new walls or personnel in a couple weeks so they could be on the right track. |
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[DIYM] I feel ya bud. This'd be a decent fit for a Dremel/multitool as well, and of course can be operated in corded mode. |
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The HB edition is a Steampunk mini-raygun look with an optional high-powered laser attachment and a push-button extensible bit-holder... as well as the more mundane, yet almost as useful, functions of a ratcheting mechanism and a built-in spirit-level. |
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I think solution is using standardized rechargeable batteries rather than customized ones. This way you can always have a few spare ones charged and kept in the shelf. These battery can then be used for any appliance, not just screw drivers. |
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[VJW] I haven't tried this (yet), but if the batteries are the same chemistry then they should be able to be mixed and matched easily. Of course that requires taking the pack apart and popping out/desoldering the individual batteries... do they (the batteries, not the packs) come in the standard sizes ? |
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