Re two batteries, was Miracle switch failures

[WHIP23 at aol.com]

Ok third try, I must be e-mail challenged!!

> >> 
>> Hi Guys
>> 
>> >>> 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.
>>> 
>>> Flame suit on, Bye
>>> 
>>> Bob
>>> 
>> 
> 
> 


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