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Batteries (again) - 2 Main Batts plus Tail Fin Batt wiring/switching



 
 
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  #1  
Old November 19th 07, 11:20 AM posted to rec.aviation.soaring
Neil Allison
external usenet poster
 
Posts: 4
Default Batteries (again) - 2 Main Batts plus Tail Fin Batt wiring/switching

Hi,

Time to dust off a perennial topic

I looked through the archives and read Darryl Ramm's battery
presentation. Not an exhaustive search but I didn't find an answer to
my question.

At present we have two (fused) 12V 7Ah "main batteries" connected to
the Master switch via an SPDT "changeover" switch. We are adding a
smaller capacity tail fin battery as a "reserve".

Without using diode switching and keeping it as simple as possible for
multiple club pilots, I can see 3 possibilities that I've illustrated
he
http://www.avon-tech-solutions.co.nz...derBattery.pdf
- select 1 of the three batteries using two SPDT "changeover" switches
in "series"
- separately isolate the tail battery in parallel to the currently
selected master
- separately isolate the tail battery in parallel to the master switch

Each has its advantages and disadvantages. No doubt there are more
possibilities. I expect to add the recommended Volkslogger "hold up"
circuit separately (or power the logger and possibly a PDA from a
dedicated battery, much like the self contained battery/logger systems
previously discussed here on r.a.s.).

What wiring / switching schemes are you using for this 3 battery
arrangement?

Thanks for your suggestions.
Neil

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  #2  
Old November 19th 07, 02:29 PM posted to rec.aviation.soaring
HL Falbaum
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Posts: 133
Default Batteries (again) - 2 Main Batts plus Tail Fin Batt wiring/switching

Schleicher uses a rotary switch
Batt 1, Batt 2, Batt 3, Off.
If you can get one of these, it reduces to one switch.
--
Hartley Falbaum

"Neil Allison" wrote in message
...
Hi,

Time to dust off a perennial topic

I looked through the archives and read Darryl Ramm's battery
presentation. Not an exhaustive search but I didn't find an answer to
my question.

At present we have two (fused) 12V 7Ah "main batteries" connected to
the Master switch via an SPDT "changeover" switch. We are adding a
smaller capacity tail fin battery as a "reserve".

Without using diode switching and keeping it as simple as possible for
multiple club pilots, I can see 3 possibilities that I've illustrated
he
http://www.avon-tech-solutions.co.nz...derBattery.pdf
- select 1 of the three batteries using two SPDT "changeover" switches
in "series"
- separately isolate the tail battery in parallel to the currently
selected master
- separately isolate the tail battery in parallel to the master switch

Each has its advantages and disadvantages. No doubt there are more
possibilities. I expect to add the recommended Volkslogger "hold up"
circuit separately (or power the logger and possibly a PDA from a
dedicated battery, much like the self contained battery/logger systems
previously discussed here on r.a.s.).

What wiring / switching schemes are you using for this 3 battery
arrangement?

Thanks for your suggestions.
Neil



  #3  
Old November 19th 07, 03:17 PM posted to rec.aviation.soaring
JJ Sinclair
external usenet poster
 
Posts: 388
Default Batteries (again) - 2 Main Batts plus Tail Fin Battwiring/switching


Paralleling batteries is Bad Bad Bad.


Its OK to parallel 2 batteries for the brief moment it takes to turn
on battery 2, just before turning off battery 1 (or tail battery on/
off) This way you don't interrupt current flow to your flight
recorder. I have used this method for 30 years. Please don't tell me
it will cause a voltage spike. I have tested it by hooking a dead
battery directly to a freshly charged one...........................no
spike, didn't blow a 3A fuse all that happened was 220 m/a current
flow as the good battery tried to charge the dead battery. While we're
speaking of voltage spikes, you can get one coming out of your radio
when the power is interupted and this can cause trouble with other
units in the system ....................see Ilec manual warning about
this.
JJ
  #4  
Old November 20th 07, 02:26 AM posted to rec.aviation.soaring
Martin Gregorie[_1_]
external usenet poster
 
Posts: 276
Default Batteries (again) - 2 Main Batts plus Tail Fin Batt wiring/switching

HL Falbaum wrote:
Schleicher uses a rotary switch
Batt 1, Batt 2, Batt 3, Off.
If you can get one of these, it reduces to one switch.

I just checked the Maplins online catalog (Maplins is the UK equivalent
of Radio Shack) for their standard range of panel mount rotary switches.
These are 1,2,3 and 4 pole types (12,6,4 and 3 positions). They have a
movable stop so you can blank off unwanted positions. Something like
these is available pretty much anywhere.

They are rated at up to 5 amps, so should be OK in a glider panel.


--
[email protected] | Martin Gregorie
gregorie. | Essex, UK
org |
  #5  
Old November 20th 07, 07:42 AM posted to rec.aviation.soaring
Ian[_2_]
external usenet poster
 
Posts: 86
Default Batteries (again) - 2 Main Batts plus Tail Fin Battwiring/switching

On Mon, 19 Nov 2007 12:45:57 +0000, Tim Newport-Peace wrote:

Not using diodes is good.


I use two diodes to provide a "fail safe" supply to the equipment that
draws low current but requires high availability, like the Volkslogger.

Two very small cheap rectifying diodes do a very effective job with
negligible voltage drop (about 0.1V), no heat sinks etc.

The high current equipment (radio, transponder etc) is powered directly
from alternate batteries via change over switches. But these normally
don't mind a short duration interruption.


Ian
 




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