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I'm looking to buy a new drill, but all of them seem to be corded or cordless. Are there drills that can either run cordless, or off the mains, depending on whether it's plugged in? It seems that would give the best of both worlds.

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closed as primarily opinion-based by The Evil Greebo, Tester101 Oct 11 '13 at 10:55

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.If this question can be reworded to fit the rules in the help center, please edit the question.

    
Far too subjective. Does not ask a "how to" question, and any answer given will be purely opinion. –  The Evil Greebo Oct 8 '13 at 17:01
    
Not really; there must be an objective set of reasons as to why people don't make these hybrid drills. Extra complexity increases price perhaps? –  Jez Oct 8 '13 at 17:06
    
I don't agree that there must be an objective set of reasons - but if there are, only the manufacturers could provide them. Answers found here will still be speculative. –  The Evil Greebo Oct 8 '13 at 17:14
    
Not necessarily. Maybe someone here has worked in the industry or has expert knowledge of it. –  Jez Oct 8 '13 at 17:23
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You will basically have to make it yourself as I've not come across a cordless manufacturer that's ever considered it. You lose all the advantages of cordless and gain all the disadvantages of corded without any power/torque increase which is the real reason you choose to buy a corded drill motor. Search for "cordless drill power adapter" and you'll find various DIY power adapter schemes. Just don't fry yourself for no good reason. –  Fiasco Labs Oct 8 '13 at 18:31
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2 Answers 2

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The main reason there is not a hybrid is the motor voltage. Corded drill use motors that run on 120 volts AC, (supplied by the grid). Cordless drills use motors that run on a lower voltage, usually between 12 and 18 volts DC (supplied by the batteries). A standard motor cannot run on both high voltage and low voltage. It also cannot run on both AC and DC.

To have a convertible or hybrid unit, it would have to run using a low voltage motor. There are three basic approaches to this that come to mind:

  1. The unit could run on its batteries all the time. When the cord was attached, it would merely be charging the battery. The problem with this is that the discharge rate is much higher than a safe charge rate, so all this gains you is a little longer runtime until the battery runs out. You would also get no increased torque.

  2. The unit could run on the 120 volt AC voltage when plugged in, which would have to be both reduced to the lower voltage of the motor and would have to be converted to DC. This would require a serious transformer and circuitry that would add significant weight and bulk to the unit (that is what is in most of the brick type power supplies and battery chargers). The transformer would still be there when you went cordless.

  3. It might be possible to build the transformer into a unit that plugs in like a battery and has a cord out the back end. But this would make the drill significantly heavier and bulkier than a conventional corded drill, a step backward in the evolution of tools.

The disadvantages to these approaches make it impractical. There also may be limitations that have to do with torque, speed, etc. for low voltage motors, but that is beyond my knowledge.

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I think the AC/DC difference is probably more significant than the voltage. AC power is well-suited to motors, but batteries are DC. –  Henry Jackson Oct 8 '13 at 23:45
    
@Henry: Universal Motors are fairly common and are used in at least some hand-held drills - so the need for a step-down transformer (or equivalent) may be the more compelling reason. –  RedGrittyBrick Oct 9 '13 at 15:23
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A very subjective question, but I'll attempt an answer anyway.

Probably because there isn't enough sustained demand for something like this, for manufacturers to sit up and take notice.

Probably because this just might show up as the worst of both worlds. For it to be truly cordless, you need a beefy battery (and that adds weight). For it to be truly corded, you need a long-enough cord (and that's cumbersome). Add both, and the results may not match up with everybody's expectations.

I would really like such a tool, but don't know if a target market of two would make manufacturers scramble for our business.

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