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External battery + solar questions

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Offline Danack

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External battery + solar questions
« on: 22 / May / 2010, 08:19:21 »
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Hi,

I'm planning on making an extenal battery + solar power supply for my S90 to be able to take very long timelapse videos and am looking on insight on a couple of points.

1) What is the third terminal on Canon used for? I can see that Timescience's external battery doesn't have a third terminal so presumably it isn't vital. On the Canon recharger the middle terminal T is marked T, the other two being +-.

2) Attached is the circuit extracted from a knock-off NB-6L battery bought from Ebay. I think it is an over-charge protection circuit rather something that moderates the output - can anyone confirm that? The chip on the left has '8205A 0936MC' written on it and the one on the left has '211OCB CH15'.

3) I've got a couple of these solare panels on the way: http://www.dealextreme.com/details.dx/sku.17441 which are claimed to output 5V at 130mA. However I am in Australia where we don't really have that much Ozone coverage and so the sun is unbelievably strong compared to what I used to from the UK. In general do solar panels in extreme sunlight put out a higher voltage OR a higher current OR both if they're being overwhelmed by direct very bright light?

Thanks in advance for any advice.

Dan
Ack



« Last Edit: 22 / May / 2010, 08:20:57 by Danack »
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Offline thepanoguy

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Re: External battery + solar questions
« Reply #1 on: 22 / May / 2010, 09:17:58 »
You don't mention whether your camera uses off the shelf cells or a propriety battery pack.

If it is a propriety battery pack then the third terminal within the battery pack is both a a thermal resetting breaker and a current sensing/charging feedback loop. If you bypass the third terminal your battery pack may overheat. There are instances where the battery packs have exploded because a person has charged the battery pack externally without the feedback device.  

The solar cells are only a trickle charge device. The voltage is dependent on sunlight. The brighter the light the higher the voltage.

Most of the stuff on Ebay are counterfeit electronics, non compliant to the manufacturer's specifications. You may be lucky, it may work ok. The net is full of people who bought counterfeit electronics only to find their equipment turned into a useless brick.

I suggest that you search a professional electronics site for a proven circuit:
http://www.epanorama.net/

Try posting at:
http://www.epanorama.net/phpBB3/index.php

There is a wealth of electronics experience there. You may find someone has already made what you are looking for.

  
« Last Edit: 22 / May / 2010, 09:20:54 by thepanoguy »
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Offline Danack

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Re: External battery + solar questions
« Reply #2 on: 22 / May / 2010, 09:31:49 »
Thanks for the links.

The batteries are going to be NiMH AA cells held outside the camera.

The circuit was from a worthless NB-6L replacement off ebay. I dismantled it to see what was inside it and so that I could re-use the external plastic case of it, rather than having to make one.
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Offline Danack

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Re: External battery + solar questions
« Reply #3 on: 26 / May / 2010, 08:04:18 »
Hi,

Thought I'd drop a record of what I'm planning to do while I wait for the parts to arrive. Attached is the circuit diagram which shows how the solar panel will trickle feed the batteries (when it has enough power) and how the batteries/solar will be converted to 4.7V to go into the S90.

I will need to tweak a few voltages based on how much voltage drop there is across the diodes and transistors but will do that once I have the components to play with.


cheers
Dan

http://www.blip.com.au/item.aspx?itemid=17
http://www.blip.com.au/item.aspx?itemid=36

http://www.vidisonic.com/2008/07/10/current-limiting-circuit/  or
http://home.cogeco.ca/~rpaisley4/xCurrentReg.html
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