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Best Practices for Reliable Electronic Deployment
#41
(03-29-2013, 09:23 PM)Ken Kressler link Wrote: Hey JD and the rest of you, I got one question for ya, why can't we use lithium pack instead of 9v batteries or heavy nickel metal batteries?? No wonder you guys buy a lot of 9v batteries and JD pointed out the calculations of the decay time of batteries' life.  Am I correct on this, huh?? :-[

You can use lithium but you need to be careful and check with the altimeter manufacturer about voltage ratings. 2-cell lithium has a nominal voltage of 7.8 volts which may not be enough for some altimeters.  3-cell lithium has a nominal voltage of 11.1v which may be too much for some altimeters.  Also lithium power packs usually come with overcurrent protection circuits of unknown function and quality, just another thing that can fail.

Occam's Razor applies.  The simplest solution is almost always the best one.

Its just my opinion (based on some engineering knowledge) that a 9v NiMH rechargeable is pretty darn close to the perfect choice for rocketry electronics. 
John Derimiggio
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#42
Do you have an idea photo of 9v NiMH would look like? I just want to get an idea of it, please guys don't get me wrong, sometimes it can be deceiving in sizes.
I have a rechargeable transistor 9v battery in which I bought it from Radio Shack. Is that the one are you referring to??  ???
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#43
(03-31-2013, 12:34 PM)Ken Kressler link Wrote: Do you have an idea photo of 9v NiMH would look like? I just want to get an idea of it, please guys don't get me wrong, sometimes it can be deceiving in sizes.
I have a rechargeable transistor 9v battery in which I bought it from Radio Shack. Is that the one are you referring to??  ???

Sure. See this post
http://www.marsclub.org/forum/index.php?...77#msg4077

The battery construction itself is important. Duracell and the above battery have internally welded tabs that connect the cells.  Most common 9v batteries just use assembly pressure to provide the electrical contact.  Not good for a rocket.  I wouldn't recommend any other 9v battery other than the one pictured above (only because I have not dissambled others to see how they are made).  You will also need the specific charger because this battery is a 9.6v instead of the more common 8.4v rechargeable "9V" batteries.
John Derimiggio
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#44
I have not had good luck with rechargeable 9V batteries. I buy disposables and they work fine. To check power I stick my tongue to the poles. If I get a good charge, the battery is fine.
Evan Brown
NAR# 92851
Level 2
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#45
Never depend on luck.
John Derimiggio
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#46
(03-31-2013, 09:47 PM)ebrown link Wrote: I have not had good luck with rechargeable 9V batteries. I buy disposables and they work fine. To check power I stick my tongue to the poles. If I get a good charge, the battery is fine.

Of course, if you get a really good charge, you may have just discharged it!  Wink ;D ;D
Greg Young - L3
NAR #42065
TRA #00234
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#47
Hey Evan,
Tasting the 9v gives you some jolting feelings, doesn't?? He,he he, pretty soon you won't feel a thing until you get yourself 12v wakey jolt!! ;D  Wink
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