Re: Converting mains battery charger for 12v operation
From: Tam/WB2TT (t-tammaru_at_c0mca$t.net)
Date: 07/27/04
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Date: Tue, 27 Jul 2004 16:12:05 -0400
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: Peter A Forbes: "Re: Converting mains battery charger for 12v operation"
- Previous message: Karl: "FA: Vintage 1970 Chips - 8080, 8080A, 1702, 2708, 2114 - PROM, RAM, Microprocessors, etc."
- In reply to: Daniel Kelly \(AKA Jack\): "Re: Converting mains battery charger for 12v operation"
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