A PP3 battery packs in when it is cold as I know to my cost. I lost a
diamond height claim because a brand new batttery in the logger failed. A
suck and blow vario never suffers from lack of power.
If you are not going high enough to get that cold the the below is a
perfectly reasonable approach.

A man with two watches is never quite sure of the time.

At 23:45 16 July 2008, Martin Gregorie wrote:
On Wed, 16 Jul 2008 14:35:28 -0700, Ian wrote:

On 16 Jul, 20:37, Bruce wrote:

So why install mechanical varios in a new high tech glide? Convince
me.

How well do electric ones react to nearby lightning bolts? Apart from
that, isn't it an awful lot easier to fit a mechanical vario than it
is to fit a complete second electrical system?

Depends on which type you pick for your backup vario.

I have a single electric system fitted. I use an SDI C4 as my main
vario and a Borgelt B.40 as backup. Normally the electrical system
drives
both varios, but the B.40 has its factory-supplied backup system. A 9v
PP3
strapped to it and it has a three position power switch (Ext-Off-Int) to
select its power source. As the B.40 is said to run for about 24 hours
on
a PP3, its as likely to get me home as a mechanical unit. I swap the PP3
annually.

The B.40 was no harder to install than a mechanical backup, eliminates
capacity vs pressure sensor problems and is safer in backup mode than a
mechanical because it is an audio vario.


--
martin@ | Martin Gregorie
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org | Zappa fan & glider pilot