Hi David,
I think the LAA are taking a very cautious approach to lithium batteries
and this will change with more service experience. It might be worth
someone making a case for the standard Mod to be revised based on your
failure analysis, however, if an electrical fault causes the alternator
fuse to blow and the lithium battery BMS to disconnect the battery I
think you will be in a glider with a 914 but not so in a 912 so there is
a slightly higher risk.
Duncan=99s comment regarding lithium battery capacity is a good
one. The sellers do tend to focus on cranking capacity and tend to
ignore total capacity (endurance). Buying a lithium replacement that
has the same total capacity as the lead acid is an expensive proposition
so the tendency is to go for a smaller capacity. Probably not a good
idea on an electrically dependant aircraft such as a 914 model.
Brian
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of
davidjoyce@doctors.org.uk
Sent: 10 September 2017 10:34
Subject: RE: Europa-List: Battery
Brian, A lot of years ago I found myself over horizon to horizon thick
forest, somewhere near the Czech border with all my electrical
instruments showing no signs of electricity and my assumption was that
my 914 was running on the fuel left in the carb bowls Fortunately my
standard checking system found that both master and alternator switches
were off and order was restored before everything went quiet (I had just
returned my pee bottle to its place under my left thigh support and in
doing so had managed to catch the toggle switches with my trouser
bottom. I felt that I had to share this slightly embarrassing incident
with the Europa community via Matronics in the spirit of the club, and
Andy Draper pointed out that if my wiring was as per manual the 914
would continue as the first pump is driven directly from the alternator
before its output gets to the alternator switch. I have subsequently
deliberately switched everything off and found this to be true.
Which makes me wonder about the exclusion of 914s from the Lithium
battery approval. Clearly if your battery blows up you won't be able to
get started, but on the face of it if it happens in flight you can still
expect to get home, (assuming you can find the way!)
Regards, David Joyce, GXSDJ
On 2017-09-10 08:43, Brian Davies wrote:
For those of you operating under the LAA system there is a Standard Mod
SM 14337 that gives details of approved Lithium batteries. Just a note
of caution when using batteries with a Battery Management System (BMS)
that automatically disconnects the battery if over or under charged.
The Rotax built in alternator produces avionics damaging voltages when
the battery is disconnected. An overvolt protection circuit should be
fitted to guard against this.
At the moment the Mod cannot be used for the 914 because it relies on a
working electrical system. The range of batteries will be updated as
more data becomes available from the manufactures. What has already
become clear is that not all lithium batteries are suitable.
Brian
G-DDBD
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Greg Fuchs
Sent: 09 September 2017 20:30
Subject: RE: Europa-List: Battery
Paul,
The ETX36C has been used successfully for years. The Rotax 914 charging
system needs to be slightly modified to bring the charging voltage into
the range the lithium battery likes (Jim and Heather brought that to my
attention). A diode on the 'C' terminal of the Ducati regulator is
adequate to fool the regulator into thinking the battery is at a
slightly lower voltage than it actually is and so it will up its charge
voltage, placing the battery into proper charging range. I think its
13.9 to 14.6 volts per the data sheet, if memory serves.
This lithium battery has cell protection. It has internal circuitry that
can remove the battery from the circuit due to too low or too high
voltages (i.e. when it is overcharged or drained). A happily charged
battery will not disconnect from the airframe. It is wise to have a
good metal battery box for these in the unlikely event of a thermal
fiasco. A thin Fiberfrax layer can likely do wonders too.
The weight savings is amazing.. When you hold them in your hand, they
feel like a fake toy battery, but they will spin the engine right up for
sure.
Greg
_____
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Paul
McAllister
Sent: Friday, September 08, 2017 7:13 AM
Subject: Europa-List: Battery
Hi All,
My trusty Odessey battery has died and gone to heaven (or wherever
batteries go).
I am seeking peoples experience with the new style Lithium batteries,
and in particular what can be sourced in the US.
Thanks, Paul
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