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Subject: Re: Difference between AC adapter and charger?
Date: Mon, 21 Oct 2002 10:22:46 -0400
Organization: Posted via Supernews, http://www.supernews.com
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References: <0001HW.B9D43FDF0325BBB11662EAD0@news.covad.net> <0001HW.B9D4EE870344BA681662EAD0@news.covad.net> <3DB01FBB.EAF744F9@usa.net> <0001HW.B9D572FB034E39101662EAD0@news.covad.net> <3DB02E27.email@example.com>
Many rechargeable appliances such as 'snap on the wall'
flashlights and dust busters apply a constant DC voltage to
charge and maintain NiCds. Same can be installed in any
portable radio or other appliance with an adaptor of proper
voltage. Always ignore those who must insult others and then
claim manufacturers say something else. Phil Allison must
insult when he cannot logically prove his point.
NiCds can be charged by a constant voltage as manufacturer's
voltage vs time curves demonstrate. As Phil notes, NiCds get
warm when they are being overcharged. Heat is how some fast
NiCd chargers determine when to stop applying excessive
voltage created by a high current mode power supply. But the
recharge circuit used so universally for generations never
applies overvoltage to put a NiCd into that 'warm' region on
the voltage curve. Same to recharge a NiCd inside the
appliance. Slow NiCd chargers simply use a constant voltage -
If recharge voltage is excessive, then NiCds simply no
longer hold a charge. No danger. Just damaged batteries. If
the recharge voltage is OK, then, like that 20 year old
rechargeable flashlight, three NiCds still work just fine,
whenever needed, for about 4+ years now. Previous batteries
worked just fine, for over ten years, with application of a
constant voltage to maintain charge.
This is a VersaPak portable electric drill. It also uses a
simple constant voltage to recharge the NiCds - circuit so
standard even in 1960 NiCd battery chargers. This recharger
is a constant voltage through a .27 ohm resistor that can
apply up to 150 ma to a discharged Versapak 7.5 volt NiCd.
Phil also makes wild assumptions that all wall warts are
unregulated DC power supplies. Appliance typically are
powered by a regulated supply wall wart which is cheaper than
installing power supply circuits inside the appliance.
Regulated supply wall warts are also less expensive since the
current limiting circuit is easier inside the wall wart. All
wall warts, contrary to Phil, must have current limiting
circuits to obtain a UL rating. But then Phil make wild
assumptions to justify his insults.
NiCds were always recharged by a constant voltage power
supply using a wall wart such as this VersaPak NiCd recharger
model number VP130. Phil Allison's insults contradict what is
inside so many NiCd chargers.
Phil Allison wrote:
> ** Please ignore the above- it was written by a demeted person.
> All Ni-Cd makers warn against attempting to use constant voltage
> charging with their cells - it is dangerous and it does not work. Ni-Cds
> and lead acid cells are very different.
> If you apply a fixed voltage equal to the final charged voltage to a
> discharged Ni-Cd pack then a very large current will flow - this will burn
> out the charger. Current limiting is essential and the average wall wart has
> no such thing.
> As Ni-Cds charge with a constant current their voltage rises and
> eventually goes through a peak and then falls as they get warm - this is
> how you know they are fully charged.
> A fixed voltage, with the addition of a safe current limit to protect
> the charger, of less value than the previously established peak could be
> applied and the cell/s would be partly charged - but only partly and that is
> the problem.
> If the applied fixed voltage ( still with a safe current limit ) were
> equal to the peak voltage then the cells will be overcharged and likely
> Recommending a standard DC wall wart (unregulated?) with added diode
> as a Ni-Cd charger is Gung Ho at best.
> . ... . . . . . . . . ............. Phil
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