Re: Converting mains battery charger for 12v operation
From: Tam/WB2TT (t-tammaru_at_c0mca$t.net)
Date: 07/28/04
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Date: Wed, 28 Jul 2004 09:49:24 -0400
Jack,
I took a look at your pictures. Hard to tell what is there, but a lot of
stuff. In line with what some others have been saying, the 8.45V may be the
actual battery charging voltage. Can you measure the voltage coming off the
charger at the two spring loaded(?) contacts that connect to the battery to
see if it is 8.45V. I would still look at the Canon web site if they make
some kind of car adapter.
Tam
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message
news:ce89k6$fbe$1@uns-a.ucl.ac.uk...
> Hi,
>
> The measured battery voltage (no load) is 7.65v. The battery claims to be
a
> 7.2v 3Ah LiIon pack. I guess it is a 2S Li-Ion pack.
>
> Thanks,
> Jack
>
>
> "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
> news:jtadnXe2gJmXKpvcRVn-ig@comcast.com...
> > Jack,
> > What is the nominal battery voltage? I will take a look later, but the
> > 320VDC sounds bad. The 8.45V sounds about right for a charging voltage
> for
> > a nominal 7.5V or so battery. Unregulated 8.45V would be on the low
side
> > for a charger input that charges a 6V or higher battery.
> >
> > The charger for my Motorola GSM phone appears to use a switching
regulator
> > type of charger. The blob that plugs into the wall is not big or heavy
> > enough to contain a 50/60 Hertz transformer.
> >
> > Tam
> > "Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
> message
> > news:ce64eq$2ldg$1@uns-a.ucl.ac.uk...
> > > Hmmm... having looked again at the PCB, I'm not so sure!
> > >
> > > Take a look:
> > >
> > > http://www.ucl.ac.uk/~ucgadak/charger_components.jpg
> > > http://www.ucl.ac.uk/~ucgadak/charger_merged.jpg
> > > http://www.ucl.ac.uk/~ucgadak/charger_tracks.jpg
> > >
> > > I want to put 8.45v onto C22 (it's marked on the last 2 JPGs). There
> are
> > a
> > > total of 3 transformers. 2 of which have 240v on both sides (i.e.
their
> > > coils are symetric). And there's definitely circuitry to produce 320v
> DC
> > > (D1 is a high voltage rectifier).
> > >
> > > Urg. I dunno anymore. Any thoughts?
> > >
> > > Thanks,
> > > Jack
> > >
> > >
> > > "Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
> > message
> > > news:ce647t$1qe8$1@uns-a.ucl.ac.uk...
> > > > Hiya,
> > > >
> > > > I'm 99.999% sure my charger works in way "A".
> > > >
> > > > All the control circuitry for the LiIon charging is on a little
> daughter
> > > > board, which is definitely downstream of the 8.45v I measured across
> the
> > > > smoothing cap.
> > > >
> > > > Thanks,
> > > > Jack
> > > >
> > > >
> > > >
> > > >
> > > > "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
> > > > news:zb-dnTGSQPl56JvcRVn-ug@comcast.com...
> > > > > Jack,
> > > > >
> > > > > I want to point out that there are basically two ways the charger
> can
> > > > work:
> > > > >
> > > > > A. The AC line is stepped down to a low voltage, rectified, and
fed
> to
> > > the
> > > > > charger. The 8.45V is the input to the charger. This is what I am
> > > > assuming.
> > > > >
> > > > > B. The AC is rectified to give 160 -340 VDC, which then goes to a
> > > > switching
> > > > > regulator. The 8.45V is what goes to the battery. If this is the
> case,
> > > > > forget it.
> > > > >
> > > > > Tam
> > > > > "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
> > > > > news:0Y-dne4Ly4wn-5vcRVn-qg@comcast.com...
> > > > > >
> > > > > > "Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote
> in
> > > > > message
> > > > > > news:ce5d6i$1oeu$1@uns-a.ucl.ac.uk...
> > > > > > > Hi Tam,
> > > > > > >
> > > > > > > Yes, I've taken the lid off the battery charger. It turns out
> the
> > > > > voltage
> > > > > > > across the smoothing capacitor (downstream of the step-down
> > > > transformer
> > > > > > and
> > > > > > > diode rectifier) is 8.45v.
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Jack
> > > > > >
> > > > > > This is the unregulated voltage, right? I can't come up with a
> > reason
> > > > why
> > > > > it
> > > > > > should not work if you run 8 - 9 V from a 3 terminal regulator
to
> > this
> > > > > > point. Your rectifier diodes will prevent the transformer from
> > > shorting
> > > > > out
> > > > > > the DC. I assume the actual battery voltage is 6V nominal. I
guess
> > > this
> > > > is
> > > > > > what you proposed originally. The thing to watch for is if the
> thing
> > > > uses
> > > > > > positive ground. Could cause fireworks if any grounded metal on
> the
> > > > > > camcorder touched grounded metal on the car. Of course, the
> > camcorder
> > > > > > probably has no exposed metal. At any rate I would be sure to
> > include
> > > a
> > > > > > fuse. Measure the DC current when running off AC.
> > > > > >
> > > > > > I think some of us are confused as to what the topology is. Is
the
> > > > actual
> > > > > > charger in the camera, in the brick, or do you remove the
battery
> > from
> > > > the
> > > > > > camera and connect it to the charger? Any power jack on the
camera
> > > > should
> > > > > be
> > > > > > labeled as to what the voltage range is. Either on the camera,
or
> in
> > > the
> > > > > > instruction book. My Ricoh Hi8, for instance, uses a 6V battery.
> The
> > > > > camera
> > > > > > has a label that states 6 - 7.5VDC. You remove the battery for
> > > charging.
> > > > > >
> > > > > > Let us know how things work out
> > > > > >
> > > > > > Tam
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
>
>
- Next message: Kevin G. Rhoads: "Re: History of decoupling capacitors"
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- In reply to: Daniel Kelly \(AKA Jack\): "Re: Converting mains battery charger for 12v operation"
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