so I can buy a GMC screwdriver for $100 (roughly 3.5 times the cost of
a B&D VersaPak) and trust that the capacitor will never go bad?
vs $29 B&D
(Amazon.com product link shortened)
I'll skip both and stick with a screwdriver that has a 'real' lifetime
guarantee (including the battery)
(Amazon.com product link shortened)
Do your "lifetime guarantee" tools charge in less than a minute?
I went to the GMC website and found their so called specifications to be nothing
than an advertisement for the product. Example: "High Shelf Life - Fully
it's own, the Flashcell will remain charged almost indefinitely". The phrase
indefinitely" is pure marketing speak. In your review you mentioned the relative
self discharge rates for L-ion and NiCd but not a word about the GMC.
Fast charging is great but how long does a charge last? How many screws will it
Chemical batteries have a shallow voltage discharge curve until the charge is
depleted then it falls rapidly. A capacitors voltage immediately, and linearly,
falls as charge is pulled out of it. At half charge there is half the initial
voltage which will have a devastating effect on the torque produced by the
There is not a word about this on the GMC website. If the user has to recharge
only using 10% of the charge this would be a big negative.
Uh, what do you expect? The specifications for any product are an
advertisement for the product.
What matters is how many fasteners it can drive on a charge, not what
percentage of discharge is achieved before it can no longer drive a
fastener with acceptable performance.
It's sold in the US under the "Coleman" brand and you can find another
According to them it can screw in 22 fasteners under the same
conditions that a Skil IXO can screw in 37.
The thing that fascinates me about this particular tool is that
capacitor technology has developed to the point that such a tool _can_
I remember from electronics school, way back when the big cathode ray tube
(TV's) was a field of study. And how we had to isolate them with special
transformers and ground it before working. Otherwise, it would kill you.
Because it was a massive capaciter that stored enough charge to zap your
heart into the great beyond. And there were folks who killed themselves
this way on a regular basis.
I think this technology is great though. I am just wondering when the
charge gets big enough to become dangerous. And if it is enough power to do
many of the jobs now done by portable tools using current battery
technology. The nearly instant charge thing is really interesting. That
feature is definitely different. It could easily change some work habits if
it proves to work well.
I have this image in my mind of a capaciter driven car. Can you imagine the
charge that thing would take? And how many people would be electrocuted if
the thing got into a wreck? One bright thought on that idea is that you
could easily incorporate a deadly thief deterrent into its design.
The instant charge thing is really not too new. Older cars with mechanical
distributors had a capacitor that signaled the coil to discharge and would
charge and discharge 8 times per revolution of the distributor rotor on a
V8. At an idle, 600 RPM, that capcitor would charge and discharge 2400
times per minute or 40 times per second. That sorta backs up the theory
that the battery in the GMC driver can go through 500,000 cycles.
That may be a feasible thought, I was thinking about that last night. The
electric cars use a Lithium style battery that came on strong about the same
time the Lith ion batteries became widely available for tools. Voltage
should not be any more of a problem with the capacitor type battery, the
current battery driven car batteries deliver in excess of 400 volts and they
like tool batteries are being recharged in as little as 15 minutes. I would
think that the capacitor type battery would charge even faster.
The stored energy in a capacitor is 1/2C*V^2, so the higher the
voltage the more the charge stored. As has been pointed out here
before, the voltage will go down linearly as the capacitor
discharges. The power into a load (resistor) will go down by the
square of the charge pulled out. It *might* be able to be charged
faster, but all that energy still has to make into the "cell". High
currents aren't friendly either. Whatever you do, you're storing
significant energy and it will turn to fire if let loose.
In short, ;-) count me skeptical.
I suspect that these super capacitors at least in tools are low
voltage, High current ( charge = number of extra electrons on one side
of the capacitor). Other than arcing they should not be dangerous.
Think of them like a car battery.
The capacitors in TV
s are high voltage.
Well........, when you are working with high voltage and/or current, you
have to be careful. And the message was pounded home by instructors, many
of them ex-military, who had some gory stories to tell.
We had an expression in that school. If somebody got a shock, we said they
got "bit". And often when this "biting" took place, there was some yelling
and screaming. At that point all classes came to a stop for a moment. The
instructor would point in the general direction of the scream and say
something to the effect that another person just got bit.
I made it all the way through a year of that school without getting bit.
But two days before I graduated, while working on a peice of test equipment
I picked up at a garage sale, I got bit. I got bit big time. I still have a
dead spot on my right index finger from that. Rumors were that that scream
was heard down the block.
That impresses me as well. If this is like most new things, it starts
off slow and progresses into a battery killer. The sooner the better I say.
My favorite drill is "almost" a B&D versa drill. It fits my hand
perfectly, and is perfectly balanced and super light weight. It seems
B&D quit making them. The problem is the two versa batteries suck and
they don't seem to last worth diddly. I've gone through about 4 sets
and have about given up on it, but still, the drill is the nicest
battery powered drill I have, except for the battery problem. If they
made lithium-ion replacement batteries for it I would by them. Better
would be the same drill with capacitor technology, but it would have to
be a little more powerful than the GM thing. Hopefully thats in our future.
I have a couple of capacitor flashlights you shake to charge up and I
They always work unlike the damed battery lights that never work when
you need them...
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