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Old Mar 06, 2006, 07:29 AM
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meteor's Avatar
Ontario, Canada
Joined Nov 2002
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Zener diode as rudimentary Li-Ion protection?

Just wondering if a Zener diode would work as a rudimentary Li-Ion "under-volt" protection device?


I have an older Kodak Pro digital camera for which I've cobbled together a few 2S Li-Ion packs. (stock pack is 6-cell 4/5A NiMh or NICd, and FYI, I've flown with Li-Ion and Li-Po for about 4 years now, and know the drill...)

The problem is that the camera will slowly drain a pack down to zero, even if it's turned off! I think it's to do with having a CF card in the slot...

With NiMh's this is not too big a deal (my first "re-pack" used KAN 950's!), but with Li-Ion this will kill the cells!


Can a Zener diode be used as a low-voltage "cut-off", or will there always be some residual drain? (anything over a few millamps is bad...)



Thanks.
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Old Mar 06, 2006, 09:25 AM
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Milton Keynes UK
Joined May 2003
384 Posts
Can't you just unplug the battery when you are finished?

The only way I can think to do it with zero current after cutoff is to use a relay, but this will increase current drain during the ON time.

Maybe others with more electronic knowledge can think of a better way.

Stuart
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Old Mar 06, 2006, 12:20 PM
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Slovakia
Joined Apr 2005
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Problem is more complex... voltage drop and so on. Look at this page, it is very nice design, resulting in microampere pack load and acceptable current passed by, hysteresis.. However, it looks quite complex on first touch? It is not in english, but circuit scheme and dps is international.
http://www.zajic.cz/odpojovac/odpojovac.htm
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Old Mar 06, 2006, 01:59 PM
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United Kingdom, Oxford
Joined Feb 2003
3,654 Posts
Meteor,

Look at...

http://pdfserv.maxim-ic.com/en/ds/MAX1665S-MAX1665X.pdf

This is the simplest LI-ion/poly protector device available, you could try scrounging some samples from Maxim if you can look like a bona-fide electronics business.

Andy.
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Old Mar 09, 2006, 09:32 PM
I'm a builder, not a flighter.
Coon Rapids, Minnesota, USA
Joined Mar 2006
46 Posts
Look at the Smart BEC product and see if you could put your cam on the output of this device.

http://www.dimensionengineering.com/SmartBEC.htm
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