FES&electric system batteries

Snipping from another thread (Per):

"And this is exactly why retrofitting an older glider to FES is impossible. With an max weight of non lifting part typically in the range of 230-250kg is it not enough marginal to put in an extra weight of 40-50kg for motor, electronics and battery in the fuselage unless you are a really light weight pilot.
I have asked the FES guys several times if it would be possible to get batteries suitable for wing installation and the answer is no. "

There might be a lot of practical reasons for that. I quess FES is married with Kokam battery (certification/approval) which has it's own form factor unsuitable for wing installation. FES system also requires weight in the rear fuselage as motor is quite heavy. Cutting old wings open and installing batteries in might not be that easy unless you have nice open root rib and empty wing shell to begin with.

GP has announced that they use Sony battery, it would be interesting to know if that consist of box filled with normal-size cells. Schleicher (ASG 32El) and Binder (EB 29DE) seem to use this kind of approach.

One point that has not been discussed is the lifetime of batteries. So far they cost arm and leg to replace, I wonder what kind of experience people have with FES batteries? Only report I have heard is 70% of capacity left after 4 years use, which is not encouraging. FES manual recommends replacing battery when capacity is 30% of maximum, but range of system is useless at that point.

FES has chosen there system on several aspects. One is that they want to be a competitors to combustion engines in new gliders. Therefor is the extra payload in the fuselage not an issue for them. But for me who wants to retrofit. The Mass and Balance can easily be solved by an extra weight at the fin.

When it comes to lifetime of batteries is my experience that it is severely dependent on the usage and abusage.
Best cast scenarios will they hold up for about 1000 charging cycles, maybe more with good battery monitoring.
What kills them is abuse.
Deep discharging is the main problem, do not discharge your lithiumcells to deep (this also goes for you cellphone or laptop), unless necessary to save your life.
Next is heat, do not let them be hot during charging or discharging.
Third is to discharge them to fast i.e. overload by taking out to much power, this generates heat and is not good. The last is to store the batteries discharged to long time, all batteries have a self discharge and long storage without proper storage charge will put them into deep discharge mode.
I expect the designers of the electrical systems to consider this aspects and therefor put in battery monitoring system that keeps them in charge, in correct temperature and not allow the user to deep discharge them. I would expect them to have a long life time, making 30-50 starts per year give me more than 20 years of usage. This is more than I can foreseen as a glider owner, after 20 year will new batteries be better and the cost be motivated in extra performance compared to just replacing them.

Whilst not strictly comparable the Li Ion cells in the Lange
Antares 20E were initially expected to last at least 10 years of
normal use. Currently there are plenty of Antares 20E's flying
around with their original batteries. I think the batteries are
now expected to last 20 years? (Maybe wrong about that). Of
the 72 cells in my Antares just 3 are now down to about 87%
of their original performance; the batteries are now 11 years
old.

For FES systems, where the batteries might not be used at all
on many flights, I'd expect a similar, or better, battery life
(assuming they are not abused of course; see earlier post).

Dave Walsh, have you installed the Antares hard/soft upgrade yet for "charge plus". The software revision 6 provides for better charging and balancing of the batteries. There are two of us here in the US that are going to have this done in January. The factory is in the process of writing a new software version 7, which ads a number new functionalities.
One of the more interesting functionalities is internet access, which would allow the factory to access the US aircraft remotely and even perform software fixes and upgrades from Germany. On a side note; due to improved monitoring, version 7 will also make the recurring (normally annual) inspection have 3 years of validity, significantly reducing inspection costs for EASA certified aircraft. Version 7 is expected to be certified in the autumn of next year.

At 15:45 08 December 2016, Tom TK wrote:
Dave Walsh, have you installed the Antares hard/soft upgrade
yet for
"charg=
e plus". The software revision 6 provides for better charging
and
balancing=
of the batteries. There are two of us here in the US that are
going to
hav=
e this done in January. The factory is in the process of writing a
new
soft=
ware version 7, which ads a number new functionalities.=20
One of the more interesting functionalities is internet access,
which
would=
allow the factory to access the US aircraft remotely and even
perform
soft=
ware fixes and upgrades from Germany. On a side note; due to
improved
monit=
oring, version 7 will also make the recurring (normally annual)
inspection
=
have 3 years of validity, significantly reducing inspection costs
for EASA
=
certified aircraft. Version 7 is expected to be certified in the
autumn of
=
next year.=20

This thread seems to be drifting into Antares territory; the
Antares and FES (especially an Ultra-light FES self-launcher, i.e.
the Silent Electro) are very different sailplanes. They are only
similar in that electric power should get you to the nearest
airfield/home. In theory the "electrics" option should be more
reliable than the two stroke option, the downside is the much
reduced range of current "electric" systems. In this regard FES is
a much better "get you home" option than a self-launcher.

To answer the previous post I have software version 6.0
("Charge Plus"); it was already installed when I bought the A/C
two years ago. It allows you to charge the batteries to about
118-120%; I don't actually understand this (I'm a biochemist
not an electrical engineer) but what it means is that I can launch
from Sisteron (French Alps 1700 ft elevation, ~30C), climb to
about 5000ft (about the limit before the engine temperature gets
into the red), stow the engine and have about 60% battery
power remaining. If you don't use the "charge plus" feature the
remaining battery power is about 45-50%. These figures are for
10 year old batteries, with a total of 700 flight hours.
Looking at my considerable file of invoices I see that the upgrade
to software 6.0 was not cheap. I am told that one of the big
advantages of version 6.0 is that it prevents catastrophic total
discharge of the batteries which can happen through operator
error (for instance putting the A/C away, going on holiday, whilst
accidentally leaving the radio switched on). This, I am told, can
be a very, very expensive mistake as it requires replacement of
all 72 battery cells.
Version 6.0 "Charge Plus" has some limitations; the batteries
once charged to 120% have to be used, so the A/C has to be
rigged and the engine to be ground run to reduce power back to
100%. This can take quite some time! (There may be some
other way to do this buried in the software, but as all my
documentation is in German, I have never tried it).
Also if you use "Charge Plus" immediately before flight some of
the electronics and the batteries will be hot. I have heard various
opinions on whether this is a significant factor. I avoid this by
running Charge Plus overnight.

Here in EASA land I am not sure that the extended inspection
periods you mention are relevant?

On your side of the pond Dave Nadler (an ex Antares owner)
might be a good source of information?
Dave Walsh

On Thursday, December 8, 2016 at 10:45:29 AM UTC-5, Tom (TK) wrote:
...One of the more interesting functionalities is internet access,
which would allow the factory to access the US aircraft remotely
and even perform software fixes and upgrades from Germany.

Non-USA Antares have had this facility from beginning.
All USA Antares, including yours, already have this capability.
I wrote and installed the facilities required for USA many years ago ;-)

Unfortunately its not so useful in practice.
Poor internet connectivity at many sites makes it dodgy.
Do you want a remote update over a poor connection killing the machine?
For this and other reasons, you always need a qualified tech on site for
updates, which makes this not so useful.

For diagnostics, better is diagnostic dump to USB.
USA Antares, including yours, have had this for years.
You may guess who wrote and installed it ;-)

See ya, Dave

Interesting that while current Kokam batteries for FES cost 8000 euros (2000eur/kWh), at the same time Tesla is building batteries costing under 200 eur/kWh. Assembling FES battery with new Tesla cells would cost one tenth, even doubling or tripling that would still keep it quite affordable. Why use so expensive battery?

On Wednesday, December 7, 2016 at 2:52:26 AM UTC-7, krasw wrote:
Snipping from another thread (Per):

"And this is exactly why retrofitting an older glider to FES is impossible. With an max weight of non lifting part typically in the range of 230-250kg is it not enough marginal to put in an extra weight of 40-50kg for motor, electronics and battery in the fuselage unless you are a really light weight pilot.
I have asked the FES guys several times if it would be possible to get batteries suitable for wing installation and the answer is no. "

There might be a lot of practical reasons for that. I quess FES is married with Kokam battery (certification/approval) which has it's own form factor unsuitable for wing installation. FES system also requires weight in the rear fuselage as motor is quite heavy. Cutting old wings open and installing batteries in might not be that easy unless you have nice open root rib and empty wing shell to begin with.

GP has announced that they use Sony battery, it would be interesting to know if that consist of box filled with normal-size cells. Schleicher (ASG 32El) and Binder (EB 29DE) seem to use this kind of approach.

One point that has not been discussed is the lifetime of batteries. So far they cost arm and leg to replace, I wonder what kind of experience people have with FES batteries? Only report I have heard is 70% of capacity left after 4 years use, which is not encouraging. FES manual recommends replacing battery when capacity is 30% of maximum, but range of system is useless at that point.

This is an interesting discussion. For the record my LAK-17b FES is 5 years old and when fully charged I still have 100% of the battery power. I do take good care of them per the the various messages and bring them home and keep them in my garage during the cold winters at Moriarty, NM. I do not let them discharge too much and keep them charged because you just never know when you are really going to need them...I am very confident these batteries will easily last perhaps 15 or 20 years or perhaps even longer....Thx - Renny

I've noticed that 13.5m FES are advertised as Front Engine Self Launchers and 15m are advertised as Front Engine Sustainers. I did here of a LAK 17b FES launch off asphalt. I wonder if the batteries heat up more from a 15m launching than a 13.5m? Or if the batteries heat up during prolong usage with either the 13.5m or 15m?

I expect Renny will chime in but, for now, I think the LAK-17bfes,
though there's a video demonstrating a self launch, is a sustainer only
because the propeller tips are so close to the runway. If you lift the
tail during a takeoff run, you'll likely have a very noisy and expensive
surprise.

On 12/7/2016 4:21 PM, Casey wrote:
I've noticed that 13.5m FES are advertised as Front Engine Self Launchers and 15m are advertised as Front Engine Sustainers. I did here of a LAK 17b FES launch off asphalt. I wonder if the batteries heat up more from a 15m launching than a 13.5m? Or if the batteries heat up during prolong usage with either the 13.5m or 15m?

--
Dan, 5J