At 19:11 04 December 2008, K M wrote:
I had similar thoughts some months ago. Being the owner of a DG glider, I
asked them for advice on NiMH & lithium based systems. The answers we

"We several times have discussed this topic.

No doubt about that you can store more electric power in the same
compartment with the same weight. But you will need a special charger and
we have to make a "Technical Note" after having tested all technical
questions with this new power system (Temperature, Danger of Fire etc.)

On the other hand the battery of a self launcher always is big enough. And
we are supplying solar cells. With this eqipment you never will have any
electric power problems.

Often we do not have any problems with the weight because the batteries
are used as a counter weight for the correct C/G.

This all is the reason why we have not made such an investigations."

and...

"You just cannot change the battery system by your own. That is a "Major
Change" and must be certified by the manufacturer.
........
When you have any additional instruments and like to have a second battery
for them - strictly separated from the main electric system - you can use
another battery-system on your own risk. Of course this system never may
supply more than 14,4 Volt.

My advice:
Don't change anything! It might be dangerous."


The British Gliding Association picked up this discussion and published
this in their newsletter:

"Glider Batteries. Several new types of battery (NiMH, Li-Po, Li-ion etc)
are now on the market, as suggested alternatives to Lead Acid (gel). There
are a number of safety risks associated with batteries and with replacing
lead acid batteries with
non-lead acid alternatives. More information is available at
http://atsipowermanagement.co.uk, http://dg-flugzeugbau.de/forum-dg0.html
(click on English language forum and follow link to non-lead acid
batteries) and http://www.caa.co.uk/docs/33/CAP562.pdf (note this is a
15Mb document). The BGA advises owners to understand fully the need to use
the correct charging system, whether installed in the glider or not, with
whatever battery type is used; different technology batteries should not
be mixed. In terms of certification, glider parts should be approved by
the type certificate holder or by modification and should either be
released or a standard part. Glider batteries are normally
considered to be standard parts. Owners should ensure that, where
batteries are replaced by alternatives, the installation, aircraft
charging system (if appropriate), weight, balance and use meets type
design approval."


So...there may be certification and insurance implictions.

Cheers

Martyn



Dear List,
It is time to replace one of the battery packs for my sailplane. I
currently use packs consisting of 7 2.5V SLA batteries to make a 14V
pack. This has worked very well for me in the past but the AH on these
cells is somewhat limited. I would like to ad a transponder and
possibly some type of collision avoidance device so I am looking to
upgrade the power supply. I have seen Nickel Metal Hydrate batteries
that come in 12V and 10 to 14 AH sized the same as the SLA batteries
alot of the glider people are using. There is a company in the UK ,
ATSI, who markets these NIMH batteries for aviation use. My question
is does anyone on the list have any experience with these or any other
12V NIMH batteries for glider use. I dont mind using the sealed lead
acid batteries but the NIMH has many advantages . And yea, I know
price isnt one of them.
Thanks