Help/Advice to build a digital camera external battery pack.

Thanks CSM1,

That link is good, but I still need to know about the thermistor and what
its purpose is in the camera (if its needed on my battery pack)..

Cheers


On Tue, 09 Sep 2003 15:47:42 GMT, CSM1 <nomail.DeleteThis@nomail.com> wrote:

 > Check out this page on how to build a battery pack.
<font color=purple> > <a style='text-decoration: underline;' href="http://www.aljacobs.com/universal_battery_packs.htm</font" target="_blank">http://www.aljacobs.com/universal_battery_packs.htm</font</a>>
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Help/Advice to build a digital camera external battery pack. 

It is my understanding that the thermsistor is used in the charging process.

The charger uses the thermsistor to measure the temperature of the battery
and reduces the charging current when the battery gets too hot.

The thermsistor is not used by the camera in any way that I know about.
--
CSM1
<a style='text-decoration: underline;' href="http://www.carlmcmillan.com" target="_blank">http://www.carlmcmillan.com</a>
--
"no_one" <no_one DeleteThis @no_placel.com> wrote in message
news:opru9c27yb3q8bmn@news.dart.net.au...
 > Thanks CSM1,
 >
 > That link is good, but I still need to know about the thermistor and what
 > its purpose is in the camera (if its needed on my battery pack)..
 >
 > Cheers
 >
 >
 > On Tue, 09 Sep 2003 15:47:42 GMT, CSM1 <nomail DeleteThis @nomail.com> wrote:
 >
  > > Check out this page on how to build a battery pack.
<font color=green>  > > <a style='text-decoration: underline;' href="http://www.aljacobs.com/universal_battery_packs.htm</font" target="_blank">http://www.aljacobs.com/universal_battery_packs.htm</font</a>>
  > >
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Help/Advice to build a digital camera external battery pack. 

Thanks again CSM1,

I initially thought this was the case with regard to the thermistor, but
there are a few things which suggest to me that it does play a role in the
camera.

1) There is a spring loaded contact in the camera mattery compartment which
contacts this third terminal.

2) The charger to camera power adapter also has this third terminal (if it
wasn't required then why would it be there? since this can not be charged
or put into the charger).

3) I have read on a couple of forums that a user had an issue with an
PowerShot S10 where he could only get about 10 - 15 shots out of his
battery, but he discovered that by covering this third terminal (with tape)
he could get more like 150 shots. Now, I don't intend on doing this as it
is probably not a good idea, but it does show that it does play a role in
the camera, but what that role is is unknown to me!

One guess I have made is that the camera uses this 10K ohm load as a dummy
load to determine the batteries charge before performing some action like
extending the lens just to find that there is not enough power to retract
it and shut down (?) but this to me is just 1 possibility amongst many.

I just don't feel comfortable attaching my home made battery pack to my
camera until I can determin exactly what this does in the camera.

Thanks again for you thoughts.


On Wed, 10 Sep 2003 14:17:59 GMT, CSM1 <nomail DeleteThis @nomail.com> wrote:

 > It is my understanding that the thermsistor is used in the charging
 > process.
 >
 > The charger uses the thermsistor to measure the temperature of the
 > battery
 > and reduces the charging current when the battery gets too hot.
 >
 > The thermsistor is not used by the camera in any way that I know about.<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Help/Advice to build a digital camera external battery pack. 

The third contact is usually a data line for the electonic device to talk to
the battery. Some batteries have ROMs in them which contains a table
indicating how much current to apply at certain voltages. It also allows the
charger to read the thermister value. If the third contact is not present
the charger will assume that its some default battery type. The reason the
camera has this third contact is because the camera can be used as a
charger. In the case of the devective battery. The ROM was probably
corrupt. By covering up the data contact on the battery, the camera used
different assumptions to charge the battery. I definately would not
recommend doing so because there is no telling what the differences are.
One battery could be a NiCad the other a Lithium Ion and using chaging
parameters for one battery could damage the other.

"no_one" <no_one.TakeThisOut@no_placel.com> wrote in message
news:oprvbd8mvr3q8bmn@news.dart.net.au...
 > Thanks again CSM1,
 >
 > I initially thought this was the case with regard to the thermistor, but
 > there are a few things which suggest to me that it does play a role in the
 > camera.
 >
 > 1) There is a spring loaded contact in the camera mattery compartment
which
 > contacts this third terminal.
 >
 > 2) The charger to camera power adapter also has this third terminal (if it
 > wasn't required then why would it be there? since this can not be charged
 > or put into the charger).
 >
 > 3) I have read on a couple of forums that a user had an issue with an
 > PowerShot S10 where he could only get about 10 - 15 shots out of his
 > battery, but he discovered that by covering this third terminal (with
tape)
 > he could get more like 150 shots. Now, I don't intend on doing this as it
 > is probably not a good idea, but it does show that it does play a role in
 > the camera, but what that role is is unknown to me!
 >
 > One guess I have made is that the camera uses this 10K ohm load as a dummy
 > load to determine the batteries charge before performing some action like
 > extending the lens just to find that there is not enough power to retract
 > it and shut down (?) but this to me is just 1 possibility amongst many.
 >
 > I just don't feel comfortable attaching my home made battery pack to my
 > camera until I can determin exactly what this does in the camera.
 >
 > Thanks again for you thoughts.
 >
 >
 > On Wed, 10 Sep 2003 14:17:59 GMT, CSM1 <nomail.TakeThisOut@nomail.com> wrote:
 >
  > > It is my understanding that the thermsistor is used in the charging
  > > process.
  > >
  > > The charger uses the thermsistor to measure the temperature of the
  > > battery
  > > and reduces the charging current when the battery gets too hot.
  > >
  > > The thermsistor is not used by the camera in any way that I know about.
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Help/Advice to build a digital camera external battery pack. 

I used to own an S20 and did exactly what you want to do, the spring in the
camera is nothing more than that, because the battery contacts are on the
side of the battery there is no presure on the top from where contacts
usualy are to make the battery a snug fit so they put a spring in there
instead, the reason why you get no measurement between the third terminal
and negative in the charger is because it is not connected internally, I
know this for a fact as I'm an electronics engineer by trade and took apart
my charger to remove the stupid socket that canon fit so I could put a
standard 2.1mm centre pin DC socket in and changed the plug on the DC lead
to suit, then (and call me a butcher if you like) I shaved some plastic from
the charger battery compartment so the dummy pack with the wire coming out
would fit in, that way I plug the dummy pack in to my home made pack then
stick the dummy pack into the canon charger to charge my battery packs !!,
the charger is intelligent and so because my pack is almost 4 times the
rating of the canon it takes 4 times longer to charge but it saved me having
to mess about building a charger. I've now got a new camera and passed my
S20 on to my Dad, its still going strong on my home made pack, you get about
300 shots + with the flash and rear screen on using a pack made from 5 x
2100mAh AA batts, what I also did was to make my pack in a small box that
screws onto the bottom of the camera using the tripod fixing. All in all a
great mod, unfortunately my Dad lives quite far away so I can't get hold of
the camera easily to send you any photo's.

Hope the above info helps

Dave.
"no_one" <no_one.DeleteThis@no_placel.com> wrote in message
news:opru8of5dz3q8bmn@news.dart.net.au...
 >
 > Hi, I am interested in building a simple external battery pack for my
Canon
 > Powershot S20.
 >
 > I would like advice on if the concept will work and have a few technical
 > questions for which I can not find answers for.
 >
 > The camera uses a 6v 650mAh Ni-MH battery (NB-5H) .
 >
 > Now, I understand that these battery packs are built using 5 AAA Ni-MH
 > cells, can some one confirm this?
 >
 > I want to construct an external battery pack that will use 5 AA Ni-MH
cells
 > ( perhaps 2200mAh -> much cheaper and better )
 >
 > Is this a feasable idea?
 >
 > Now with my camera came an adapter which plugs into the charger and has an
 > battery pack shaped plug which is put into the camera as if it were the
 > battery.
 >
 > My idea is to use this adapter and plug it into my external battery pack
 > instead of the charger.
 >
 > The unanswered questions I have relate to the third terminal on the
battery
 > packs and adapter.
 >
 > From what I can determin, the third terminal is for a thermistor. If I
 > check my battery packs, this terminal is connected to the negative
terminal
 > of the battery pack with approx 10K ohm resistance.
 >
 > I initially thought this was used for charging only, but there is a spring
 > loaded terminal in the top of the battery compartment of the camera which
 > contacts this third thermistor terminal, so I assume that it plays some
 > role with regard to the camera and is not only for charging.
 >
 > If I check the same terminal on the power charger adapter mentioned above,
 > there is no resistance between the negative terminal and the third
 > terminal.
 >
 > What does this mean? how will this impact my attempt to create an external
 > battery pack? and can I use this adapter without modifying it?
 >
 > Any help/suggestions/ideas would be great.
 >
 > Cheers<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: Help/Advice to build a digital camera external battery pack.