<br><font size=2 face="sans-serif">Thanks Bob. Your advice appears sound to me. I'm printing this one.</font>
<br><font size=2 face="sans-serif">--Lance</font>
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<td><font size=1 face="sans-serif"><b>WHIP23@aol.com</b></font>
<br><font size=1 face="sans-serif">Sent by: discussion-request@nsrca.org</font>
<p><font size=1 face="sans-serif">03/28/2003 05:00 PM</font>
<br><font size=1 face="sans-serif">Please respond to discussion</font>
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<br><font size=1 face="sans-serif"> To: discussion@nsrca.org</font>
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<br><font size=1 face="sans-serif"> Subject: Re two batteries, was Miracle switch failures</font></table>
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Ok third try, I must be e-mail challenged!!<br>
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Hi Guys<br>
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<br><font size=2 face="Arial">All the "battery backup systems" I have seen put something of unknown reliability/untested in the critical path. The best setup is two batteries diode orred (sp?) together (diode in each path from switch to receiver) through two switches (must be 5 cell to allow for the diode drop) fully redundant, you would have to have a failure in both paths at the same time to loose control due to battery. Assuming you check things every flight the odds of a failure in both paths is too remote to consider. There is little weight penalty, run two batteries 1/2 the size you would normally run. Being a worrier I also make a point of never running either pack down too far (if I happen to be running on one pack I want enough charge in that one pack to last a long flight). The diodes must be in the path from the switch to the receiver (if you put them between the battery and the switch, as once got printed incorrectly, with MY name attached, you won't be able to charge in this configuration) I've been doing this for about 10 years with no problems and it has saved me an airplane, both batteries good on take off one was bad (open) on landing, if only one battery, bye bye airplane. Guess you could argue that the bad battery might have been in someone else's airplane VBG. It is a little more complex, two switches (one of the biggest failure items) two charge jacks, two batteries. Assuming you have an unused channel you can plug the battery into any unused channel (preferred) if not then I would wye it to a non mission critical channel, last choice would be to wye the two batteries together (the wye is then mission critical, I told you I was a worrier) There is also good evidence that the diodes are not necessary, that a 5 cell pack won't charge a 4 cell pack (one shorted cell), sounds right and I've used this scheme, but I have never tested it with a cell shorted so I have no first had experience. I'm not sure I could sleep at night, anymore, with only one battery pack and switch, just seems like unnecessary risk.<br>
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Flame suit on, Bye<br>
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Bob</font>
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