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From: "Phil Allison"
References: <0001HW.B9D43FDF0325BBB11662EAD0@news.covad.net> <0001HW.B9D4EE870344BA681662EAD0@news.covad.net> <3DB01FBB.EAF744F9@usa.net> <0001HW.B9D572FB034E39101662EAD0@news.covad.net> <3DB02E27.firstname.lastname@example.org> <3DB42BB1.EC27E431@bellatlantic.net> <3DB4C57E.B06B96D5@bellatlantic.net> <3DB61379.5EFB8B5C@bellatlantic.net> <3DB6D61C.483F9D22@bellatlantic.net>
Subject: Re: Difference between AC adapter and charger?
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Thu, 24 Oct 2002 09:28:33 +1000
NNTP-Posting-Date: Thu, 24 Oct 2002 09:19:52 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
wrote in message
> Phil Allison wrote:
> > If the supply has
> > a current limit circuit and is connected to a pack of Ni-Cds then it is
> > ipso facto a constant current charger since the pack will draw current
> > that limit. The voltage on the pack will vary with the state of charge -
> > in God's name can that be called "constant voltage".
** No right. A power supply is not a "charger" and "connecting" means
The pack will not "draw current at that limit".
** Yes it will.
> in the example I posted, the current limit established by connecting
> the 7.2 V battery pack to the supply through a 150 ohm resistor,
> using a supply regulated at 13.8 volts, is 92 ma. But when the
> pack is fully charged, it will draw 36 ma. - well below the 92
> ma limit. Both the current through the cells and the voltage
> across them will vary as they charge.
** Then it is NOT constant voltage charging - is it ??
> > So you are arguing with something
> > > I not only never said, but specifically and strongly denounced.
> > ** Rubbish - you posts were full of ambiguity and still are.
> I'm beginning to see the light. You wish to argue for the sake
> of argument. I don't. I apologize if my posts are not clear
> to you.
** Your post are full of lies and obfuscations.
> > > >
> > > > >
> > > > > You may have missed the part of the post that mentions current
> > > > > limiting. The fact that a supply is voltage regulated does not
> > > > > preclude a current limiting resistance between the supply and
> > > > > the load. Ohms law. :-)
> > > >
> > > > ** What? 0.27 ohms worth - gimme a break.
> > >
> > > What are you talking about? Where did you come up with .27
> > > ohms resistance?
> > ** Read the whole thread mate - w toms gave that figure.
> What w_tom posted is his affair - I did not use that figure, and
> your response was to me, not him. If you disagree with what I
> said, then use what I said as the basis for your disagreement -
> not what someone else said.
** Read the whole threa - so you will know what is being claimed.
> If you take exception to what w_tom posted, take it up with him.
> Don't assume that because a figure was mentioned once in a thread
> that another poster uses that figure.
** Get real.
> > Try 150 ohms between a 7.2 volt pack consisting
> > > of 6 1600 mah cells and a 13.8 volt regulated supply. Worst
> > > case - 92 ma. With the cells fully charged, 36 ma. It makes
> > > a real nice trickle charger.
> > ** That is what is known in the trade as constant current
> So you understand that a constant voltage supply through a current
> limiting resistor (assuming values are properly chosen) does not pose
> no problem. We agree!
** No - you have repeatedly used the terms "constant voltage" or
"voltage regulated" charging incorrectly, and so have others, massivly
confusing a simple topic for any readers.
> Now, the next step is to graduate to constant voltage chargers.
> Build a voltage regulator that provides a constant 8 volts
> output. Connect it to your 7.2 volt battery pack. Put the
> current limiting on the input side of the supply, such that
> the supply is protected. You'll charge the cells to
> somewhat less than full capacity - but wou won't harm them,
> until a cell within the pack develops a short.
** With an 8 volt limit the 7.2 volt pack will not charge
Then you may
> over charge the remaining cells, which is what I indicated
> in my first post.
** Such a charger is useless, as I explaind and you snipped the lot.
> FYI, "constant voltage" (as I believe tom_w had in mind) chargers
> for NiCds exist in plenty.
** There you go again (to steal a phrase) - there is no such thing.
You mentioned wall wart style chargers -
> most of them are of that type.
** No, I mentioned "wall warts" - ie DC power supplies.
They don't include much more than a
> transformer & diode. They work fine.
** The not "much more" is the crucial bit. Maybe a resistor ??
I would prefer a different
> meaning to "constant voltage" than what I believe tom_w had in mind,
> and I would also prefer a different meaning for "constant current"
> that what you call it
> "That is what is known in the trade as constant current charging."
> referring to a constant voltage through a current limiting
** Misquotes. Charging with the use of a series current limiting
resistor is known as "constant current". It is not literally true ( ie
invariant) since as the pack voltage rises the current falls. Constant
voltgae uses a hard voltage source and the current tapers as the battery
acquires charge - used with lead acid and SLA only.
> > BTW Why did you snip my detailed explanation ??
> I did not respond to it - so there was no need to include
> it and waste bandwidth.
> We have, as I see it, no technical disagreement. You
> have explained what you meant by "dangerous" and using
> your description of that term I no longer have a hard
> time seeing how a simple voltage regulated charger is
** So you see the risk of explosions, fire etc - bloody marvellous.
. . . .. . ............ Phil
> > . . . . . . . . . . ..................... Phil
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