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FES&electric system batteries



 
 
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  #1  
Old December 7th 16, 10:52 AM posted to rec.aviation.soaring
krasw
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Default 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.
  #2  
Old December 7th 16, 01:08 PM posted to rec.aviation.soaring
Per Carlin
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Default FES&electric system batteries

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.

  #3  
Old December 7th 16, 02:14 PM posted to rec.aviation.soaring
Dave Walsh
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Default FES&electric system batteries

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).

  #4  
Old December 7th 16, 03:09 PM posted to rec.aviation.soaring
Renny[_2_]
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Default FES&electric system batteries

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
  #5  
Old December 8th 16, 12:21 AM posted to rec.aviation.soaring
Casey[_2_]
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Default FES&electric system batteries

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?
  #6  
Old December 8th 16, 01:03 AM posted to rec.aviation.soaring
Dan Marotta
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Default FES&electric system batteries

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
  #7  
Old December 8th 16, 07:26 AM posted to rec.aviation.soaring
Bruce Hoult
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Default FES&electric system batteries

On Thursday, December 8, 2016 at 2:21:34 AM UTC+3, 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?


Any glider with a sustainer can self-launch from a sufficiently long hard surface, with plenty of pressure in the tyre and a push start. Or, better, a tow to 100-120 km/h with a car.
  #8  
Old December 8th 16, 08:30 AM posted to rec.aviation.soaring
krasw
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Posts: 668
Default FES&electric system batteries

I think 20 years of good battery life might be bit optimistic. Antares has very expensive milspec batteries that should have long life, apparently that can be 10 years, but no one knows if that is 20 years. Other systems use cheaper (relatively) off-the-self batteries that might not last so well. Realistically, I would probably budget battery change every 5-10 years.
  #9  
Old December 8th 16, 08:30 AM posted to rec.aviation.soaring
Per Carlin
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Posts: 90
Default FES&electric system batteries

On Thursday, December 8, 2016 at 7:26:05 AM UTC+1, Bruce Hoult wrote:
On Thursday, December 8, 2016 at 2:21:34 AM UTC+3, 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?


Any glider with a sustainer can self-launch from a sufficiently long hard surface, with plenty of pressure in the tyre and a push start. Or, better, a tow to 100-120 km/h with a car.


To be certified as SLG according to JAR 22 do you need to meet specific performance in roll-out distans and climb. The 13,5m FES is only SLG in dry condition, if you load it with water is it only SSG. I guess that the LAK17 is to heavy to meet the performance requirements to be a SLG.
  #10  
Old December 8th 16, 08:56 AM posted to rec.aviation.soaring
Bruce Hoult
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Default FES&electric system batteries

On Thursday, December 8, 2016 at 10:30:26 AM UTC+3, Per Carlin wrote:
On Thursday, December 8, 2016 at 7:26:05 AM UTC+1, Bruce Hoult wrote:
On Thursday, December 8, 2016 at 2:21:34 AM UTC+3, 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?


Any glider with a sustainer can self-launch from a sufficiently long hard surface, with plenty of pressure in the tyre and a push start. Or, better, a tow to 100-120 km/h with a car.


To be certified as SLG according to JAR 22 do you need to meet specific performance in roll-out distans and climb. The 13,5m FES is only SLG in dry condition, if you load it with water is it only SSG. I guess that the LAK17 is to heavy to meet the performance requirements to be a SLG.


Yes I know. I wasn't talking about certification :-)

Of course there are lots of places that you'd be foolish to try it, but given an airfield large enough that you can circle within the boundary with less than 30 degrees of bank, the difference between a car tow with an aerotow rope and an aerotow to a release on downwind at 500 ft (which lots of people do) is probably ... about 300 ft by the time the motor starts.
 




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