Converting mains battery charger for 12v operation

  • Thread starter Daniel Kelly (AKA Jack)
  • Start date
D

Daniel Kelly (AKA Jack)

Guest
Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is the
charger that comes with the camera as default). I'd like to convert the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an 8.45volt DC
source across the smoothing capacitor after the transformer and rectifier
diodes. Does this sound sensible? I figure that all I need to do is build
a regulator circuit that will produce 8.45v from 12v and pump this into the
charger over the capacitor (C22)..

However, I'm not very experienced at these things and I'd be enormously
thankful if you geniuses (or genii?) could have a look at the PCB. I've
scanned it...

The large images are LARGE (400 kbytes). I've flipped the top side so it
matches up with the track side

LARGE images
http://www.ucl.ac.uk/~ucgadak/charger_tracks_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_merged_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_components_large.jpg


SMALLER images (for those with slow internet connections)
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

Many many thanks,
Jack
 
On Sat, 24 Jul 2004 17:25:44 +0100, "Daniel Kelly \(AKA Jack\)"
<d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is the
charger that comes with the camera as default). I'd like to convert the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an 8.45volt DC
source across the smoothing capacitor after the transformer and rectifier
diodes. Does this sound sensible? I figure that all I need to do is build
a regulator circuit that will produce 8.45v from 12v and pump this into the
charger over the capacitor (C22)..
Click to expand...
---
Unless your charger has some smarts in it which will keep it apprised
of the battery's condition (state of charge, temp, etc...) or your
camera does it and talks to the charger, there's probably no reason
why you couldn't just connect the output from your 8.45V regulator
(the one you're going to build) directly to the camera.

Having said that, though, and as far as connecting 8.45V to the
charger goes, I think you're courting disaster (not to mention voiding
any warranties which may exist for the camera _and_ the charger,
unless you know _exactly_ what the circuitry in there looks like.

For $165, a CB-910 or CB-920 sounds to me like a better way to go.

--
John Fields
 
Hi John,

Many thanks for your reply. Unfortunately, I can't connect my regulator
directly to the camera to charge the battery because the charger connects to
the camera using a 'battery-shaped' plug! In other words, the ONLY way to
charge the battery is using the battery charger, which only accepts 240v.

I think you're courting disaster (not to mention voiding
any warranties which may exist for the camera _and_ the charger,
unless you know _exactly_ what the circuitry in there looks like.
Click to expand...
Yes, you're probably right! I thought I'd look into it though.

For $165, a CB-910 or CB-920 sounds to me like a better way to go
Click to expand...
Yeah... but for that price I might as well buy myself a 12v to 240v inverter
(not as efficient, I know - but I'd like to be able to plug other mains
devices into my car, so a 12-240v inverter would be useful).

Thanks,
Jack

"John Fields" <jfields@austininstruments.com> wrote in message
news:6185g0945bef9iiuaub2p4nb64bgkqg84a@4ax.com...
On Sat, 24 Jul 2004 17:25:44 +0100, "Daniel Kelly \(AKA Jack\)"
d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is the
charger that comes with the camera as default). I'd like to convert the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an 8.45volt
DC
source across the smoothing capacitor after the transformer and rectifier
diodes. Does this sound sensible? I figure that all I need to do is
build
a regulator circuit that will produce 8.45v from 12v and pump this into
the
charger over the capacitor (C22)..

---
Unless your charger has some smarts in it which will keep it apprised
of the battery's condition (state of charge, temp, etc...) or your
camera does it and talks to the charger, there's probably no reason
why you couldn't just connect the output from your 8.45V regulator
(the one you're going to build) directly to the camera.

Having said that, though, and as far as connecting 8.45V to the
charger goes, I think you're courting disaster (not to mention voiding
any warranties which may exist for the camera _and_ the charger,
unless you know _exactly_ what the circuitry in there looks like.

For $165, a CB-910 or CB-920 sounds to me like a better way to go.

--
John Fields
Click to expand...
 
On Sat, 24 Jul 2004 19:16:26 +0100, "Daniel Kelly \(AKA Jack\)"
<d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi John,

Many thanks for your reply. Unfortunately, I can't connect my regulator
directly to the camera to charge the battery because the charger connects to
the camera using a 'battery-shaped' plug! In other words, the ONLY way to
charge the battery is using the battery charger, which only accepts 240v.
Click to expand...
---
An easy way around that problem (if you want to take the risk :) is
to cut the cord and affix mating connectors to the cut ends so that
you can plug them in and out. Then, you'll have the end which plugs
into your camera, and you could plug the other end into either the
mains charger or the output of your regulator, to which you've also
connected a connector identical to the one on the charger. Make the
connectors on the charger and your regulator female, and the one on
the charger cable male. RCA plugs and jacks work fine, or if you
wanted to you could use some nice little locking circulars.

--
John Fields
 
Thanks for your second really helpful reply on this topic!

Yes, you're right - I should do that. However, this solution wont actually
charge the battery - which is really what I want to achieve.

Thanks,
Jack


"John Fields" <jfields@austininstruments.com> wrote in message
news:cqb5g0dpjtvhn6e2v0ga0vgecbhk4ttqq5@4ax.com...
On Sat, 24 Jul 2004 19:16:26 +0100, "Daniel Kelly \(AKA Jack\)"
d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi John,

Many thanks for your reply. Unfortunately, I can't connect my regulator
directly to the camera to charge the battery because the charger connects
to
the camera using a 'battery-shaped' plug! In other words, the ONLY way
to
charge the battery is using the battery charger, which only accepts 240v.

---
An easy way around that problem (if you want to take the risk :) is
to cut the cord and affix mating connectors to the cut ends so that
you can plug them in and out. Then, you'll have the end which plugs
into your camera, and you could plug the other end into either the
mains charger or the output of your regulator, to which you've also
connected a connector identical to the one on the charger. Make the
connectors on the charger and your regulator female, and the one on
the charger cable male. RCA plugs and jacks work fine, or if you
wanted to you could use some nice little locking circulars.

--
John Fields
Click to expand...
 
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message
news:cdu2ca$23qu$1@uns-a.ucl.ac.uk...
Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is the
charger that comes with the camera as default). I'd like to convert the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an 8.45volt DC
source across the smoothing capacitor after the transformer and rectifier
diodes. Does this sound sensible? I figure that all I need to do is build
a regulator circuit that will produce 8.45v from 12v and pump this into the
charger over the capacitor (C22)..

However, I'm not very experienced at these things and I'd be enormously
thankful if you geniuses (or genii?) could have a look at the PCB. I've
scanned it...

The large images are LARGE (400 kbytes). I've flipped the top side so it
matches up with the track side

LARGE images
http://www.ucl.ac.uk/~ucgadak/charger_tracks_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_merged_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_components_large.jpg


SMALLER images (for those with slow internet connections)
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

Many many thanks,
Jack
Click to expand...
I'm probably missing something here, but why don't you get a power inverter
which coverts 12V DC to AC. (And which can also be useful for other things.)

Bill
 
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message
news:cdu8rt$316s$1@uns-a.ucl.ac.uk...

Yeah... but for that price I might as well buy myself a 12v to 240v
inverter
(not as efficient, I know - but I'd like to be able to plug other mains
devices into my car, so a 12-240v inverter would be useful).
Click to expand...
I would go with the inverter.

It's not a good idea to connect a voltage regulator (a voltage source) to a
battery (another voltage source). What would limit the current when you hook
it up with a flat battery?

The charger will be designed to include a current limit if not an actual
constant current source.
 
In article <cdu2ca$23qu$1@uns-a.ucl.ac.uk>, d.kellyNOSPAM@NOSPAM.ucl.ac.uk
says...
Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is the
charger that comes with the camera as default). I'd like to convert the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an 8.45volt DC
source across the smoothing capacitor after the transformer and rectifier
diodes. Does this sound sensible? I figure that all I need to do is build
a regulator circuit that will produce 8.45v from 12v and pump this into the
charger over the capacitor (C22)..
Click to expand...
Why don't you just buy a cheap, low power inverter for $20 to $30 and use
this to power your existing charger?? These things are made by all sorts of
companies and plug right into a car's cigarete lighter.

The topology of a mains charger is TOTALLY different than the topology needed
for a charger operating off 12V. You aren't going to be successful in trying to
"convert" a mains charger to 12 V input operation.

Bob.
 
Dear Collin,

Thanks loads for your reply.

Sure, I wouldn't dream of connecting a battery directly to my voltage
regulator. What I'm proposing to do is to connect my 12v battery to the
battery charger, just downstream of the 240v to 8.4v transformer and
upstream of the charge controll circuitry. In other words, I hope my
battery charger will think it's connected to the mains, even though it's
connected to my car. So the charger will look after all the current
limiting etc.

Thanks,
Jack


"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:Z3TMc.194615$1e4.9639011@phobos.telenet-ops.be...
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message
news:cdu8rt$316s$1@uns-a.ucl.ac.uk...

Yeah... but for that price I might as well buy myself a 12v to 240v
inverter
(not as efficient, I know - but I'd like to be able to plug other mains
devices into my car, so a 12-240v inverter would be useful).

I would go with the inverter.

It's not a good idea to connect a voltage regulator (a voltage source) to
a
battery (another voltage source). What would limit the current when you
hook
it up with a flat battery?

The charger will be designed to include a current limit if not an actual
constant current source.
Click to expand...
 
Yes, I think you're right - I will go for the inverter.

Thanks,
Jack

"Bill" <xxx@yy.zz> wrote in message
news:rECMc.432$uC7.288@newssvr19.news.prodigy.com...
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message
news:cdu2ca$23qu$1@uns-a.ucl.ac.uk...
Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is the
charger that comes with the camera as default). I'd like to convert the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an 8.45volt
DC
source across the smoothing capacitor after the transformer and
rectifier
diodes. Does this sound sensible? I figure that all I need to do is
build
a regulator circuit that will produce 8.45v from 12v and pump this into
the
charger over the capacitor (C22)..

However, I'm not very experienced at these things and I'd be enormously
thankful if you geniuses (or genii?) could have a look at the PCB. I've
scanned it...

The large images are LARGE (400 kbytes). I've flipped the top side so
it
matches up with the track side

LARGE images
http://www.ucl.ac.uk/~ucgadak/charger_tracks_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_merged_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_components_large.jpg


SMALLER images (for those with slow internet connections)
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

Many many thanks,
Jack



I'm probably missing something here, but why don't you get a power
inverter
which coverts 12V DC to AC. (And which can also be useful for other
things.)

Bill
Click to expand...
 
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message
news:ce2mga$2bj0$1@uns-a.ucl.ac.uk...
Yes, I think you're right - I will go for the inverter.

Thanks,
Jack
Click to expand...
Jack,
Don't they make a car charger for it? As for modifying the charger, you
would have to open the unit up and see what the raw DC is off the rectifier.
My guess would be around 12V for an 8V battery.

Tam
"Bill" <xxx@yy.zz> wrote in message
news:rECMc.432$uC7.288@newssvr19.news.prodigy.com...

"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message
news:cdu2ca$23qu$1@uns-a.ucl.ac.uk...
Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is
the
charger that comes with the camera as default). I'd like to convert
the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an
8.45volt
DC
source across the smoothing capacitor after the transformer and
rectifier
diodes. Does this sound sensible? I figure that all I need to do is
build
a regulator circuit that will produce 8.45v from 12v and pump this
into
the
charger over the capacitor (C22)..

However, I'm not very experienced at these things and I'd be
enormously
thankful if you geniuses (or genii?) could have a look at the PCB.
I've
scanned it...

The large images are LARGE (400 kbytes). I've flipped the top side so
it
matches up with the track side

LARGE images
http://www.ucl.ac.uk/~ucgadak/charger_tracks_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_merged_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_components_large.jpg


SMALLER images (for those with slow internet connections)
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

Many many thanks,
Jack



I'm probably missing something here, but why don't you get a power
inverter
which coverts 12V DC to AC. (And which can also be useful for other
things.)

Bill
Click to expand...
 
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



"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:sKadnSQvtYMwPZjcRVn-gw@comcast.com...
"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message
news:ce2mga$2bj0$1@uns-a.ucl.ac.uk...
Yes, I think you're right - I will go for the inverter.

Thanks,
Jack

Jack,
Don't they make a car charger for it? As for modifying the charger, you
would have to open the unit up and see what the raw DC is off the
rectifier.
My guess would be around 12V for an 8V battery.

Tam

"Bill" <xxx@yy.zz> wrote in message
news:rECMc.432$uC7.288@newssvr19.news.prodigy.com...

"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message
news:cdu2ca$23qu$1@uns-a.ucl.ac.uk...
Hi,

I have a Canon XL1-S camcorder with a CA-910B mains charger (this is
the
charger that comes with the camera as default). I'd like to convert
the
charger so I can power it from car battery.

I've taken the lid off the charger. I think I can connect an
8.45volt
DC
source across the smoothing capacitor after the transformer and
rectifier
diodes. Does this sound sensible? I figure that all I need to do
is
build
a regulator circuit that will produce 8.45v from 12v and pump this
into
the
charger over the capacitor (C22)..

However, I'm not very experienced at these things and I'd be
enormously
thankful if you geniuses (or genii?) could have a look at the PCB.
I've
scanned it...

The large images are LARGE (400 kbytes). I've flipped the top side
so
it
matches up with the track side

LARGE images
http://www.ucl.ac.uk/~ucgadak/charger_tracks_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_merged_large.jpg
http://www.ucl.ac.uk/~ucgadak/charger_components_large.jpg


SMALLER images (for those with slow internet connections)
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

Many many thanks,
Jack



I'm probably missing something here, but why don't you get a power
inverter
which coverts 12V DC to AC. (And which can also be useful for other
things.)

Bill
Click to expand...
 
"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
Click to expand...
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
 
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
Click to expand...
 
Hi Tam,

Thanks loads for your reply.

I guess this is
what you proposed originally.
Click to expand...
Yup, exactly! I didn't explain it very well - but you've figured it out.

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?
Click to expand...
The Brick has a battery mount on it. To charge the battery you have to take
the battery out the camera and plug it into The Brick. The camera has no
charge circuitry. All the charge circuitry is in the brick. So I want to
pump 9V into The Brick onto the smoothing capacitor (which is downstream of
the transformer and rectifier diodes).

Thanks, Jack.



"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
Click to expand...
 
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
Click to expand...
 
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
Click to expand...
 
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
Click to expand...
 
On Tue, 27 Jul 2004 10:29:25 -0400, "Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote:

"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
Click to expand...
Just a few thoughts, I have been watching the posts but haven't had time to
absorb all of the detail.

The Li-Ion battery will have its own regulating circuitry in the battery, and
most batteries take a raw DC feed from whatever is charging them. They monitor
overvoltage and undervoltage and charge current. We have done very large
series/parallel Li-Ion battery chargers at 110V 50A X 4 outputs for a subsea
application and also a more conventional multi-way version for a
series/parallelled cells, but generally the battery defines what it needs.

Re the high DC voltage on the charger, it sounds like a conventional switchmode
step-down and isolating circuit, probably to keep the volume and weight down.
It's cheaper to buy a volume switcher in from thr far east that make a
conventional transformer/rectifier capacitor DC supply over here, and it has the
advantage of being universal input, 90 - 260V at almost any frequency.

My 2c worth.

Peter
--
Peter & Rita Forbes
diesel@easynet.co.uk
Engine pages for preservation info:
http://www.oldengine.org/members/diesel
 
On Tue, 27 Jul 2004 18:46:42 +0100, "Daniel Kelly \(AKA Jack\)"
<d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

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.
Click to expand...
Whoa!!! 8v45 sounds VERY much like the CV charge potential across two Li-Ion
cells in series. If that's the case, it sounds also VERY much like a "type B"
system.
 
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