FES&electric system batteries

On 02/24/2017 10:16 AM, Dan Marotta wrote:
Rich white guys? How about people who simply work for a living as most
home builders are? Since you're a glider pilot you must be a "rich
white guy" too. Or are you a female, or a different color, or does it
really matter? Not to me. Is that you, Dave?

My point was that Jim Bede was always promising more than he could
deliver and asking the hopeful builders to hang in there.

Take a deep breath Dan. Yes Bede overpromised on delivery, so there's
that similarity. But Tesla gets huge government subsidies that reduce
the price to the consumer, but still they're expensive and basically a
luxury item. There's no semblance of the free market at play with
Tesla, so expecting the pricing for FES batteries to be comparable to
Tesla's is never going to happen, unless some government wants to pour
taxpayer money into the things, which is never going to happen.



On 2/24/2017 9:53 AM, kinsell wrote:
Don't think the BD-5 had massive government subsidies to help rich
white guys buy the things. Picking winners and losers didn't extend
down to the homebuilt GA market. Defense contractors, sure.


On 02/24/2017 09:34 AM, Dan Marotta wrote:
Sounds a bit like the BD-5, doesn't it?

On 2/24/2017 8:26 AM, wrote:
On Friday, February 24, 2017 at 8:03:41 AM UTC-6,
wrote:
Tesla makes all their profits off carbon credit games. Thus Tesla
pricing might not match reality.
Plus, they are selling 'vapor ware', what a concept! You give us $$$'s
of your hard earned money for something that doesn't really exist yet
(but we promise you a spot in the line, maybe). Call back in a couple
of years. Oh, and buy our stock, will you?

Tesla uses 18650 sized cylindrical cells, lots of them. This cell size was originally designed for laptops and was driven by the dimensions of the disk drives used at the time. As computers became smaller, so did the form factor for cells. For computers, 14650 cylindrical entered the picture for a while (as drives became flatter) and now flat pouches and prismatic. This left a large overcapacity with 18650 equipment which in turn drove pricing down.

The volumetric and gravimetric energy content of the Kokam cells used in the FES vs. typical 18650 is higher. In a battery configuration, cylindricals waste space. In a rolling platform, the weight/size disadvantage of the 1850 could be tolerated but not so much with an aerial platform.

Additionally with the small 18650 cells, you need a lot of them to get to a desired energy content for a car or airplane battery. That means more BMU (battery management) again increasing weight, size, complexity, and opportunities for failure.

The battery solution (and PC diagnostics) for the FES system is well thought out given the tradeoffs. I am eager to see the final design that the GP guys are going to employ for their gliders. I certainly hope they make their batteries easily removable for charging and storage outside the glider. The volume, mass, and energy content of the proposed GP battery is on par with the FES battery although the dimensions are more long and skinny too fit in the wings.

Danny Brotto

Il giorno mercoledì 7 dicembre 2016 10:52:26 UTC+1, krasw ha scritto:
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.

The cost of Kwh for the car batteries actually is 180 Dollars /kwh.
The Industry is claiming that after Tesla plant will work at full the costs of batteries will drop to 100 dollars/kwh.
At that time I think Feb batteries has to switch to another producer in my opinion.
lak 13.5 GLIDER THAT USE THEW SAME BATTERY PACK OF OTHERS GLIDERS totally(with trailer costs less than 90.000 euro) and I suppose the costs of replacing the battery pack is under 5.000 euro

On Saturday, 25 February 2017 15:22:47 UTC+2, wrote:
Tesla uses 18650 sized cylindrical cells, lots of them. This cell size was originally designed for laptops and was driven by the dimensions of the disk drives used at the time. As computers became smaller, so did the form factor for cells. For computers, 14650 cylindrical entered the picture for a while (as drives became flatter) and now flat pouches and prismatic. This left a large overcapacity with 18650 equipment which in turn drove pricing down.

The volumetric and gravimetric energy content of the Kokam cells used in the FES vs. typical 18650 is higher. In a battery configuration, cylindricals waste space. In a rolling platform, the weight/size disadvantage of the 1850 could be tolerated but not so much with an aerial platform.

Additionally with the small 18650 cells, you need a lot of them to get to a desired energy content for a car or airplane battery. That means more BMU (battery management) again increasing weight, size, complexity, and opportunities for failure.

The battery solution (and PC diagnostics) for the FES system is well thought out given the tradeoffs. I am eager to see the final design that the GP guys are going to employ for their gliders. I certainly hope they make their batteries easily removable for charging and storage outside the glider. The volume, mass, and energy content of the proposed GP battery is on par with the FES battery although the dimensions are more long and skinny too fit in the wings.

Danny Brottoaw

I think glider batterys are not especially critical regarding dimensions. Antares uses large cylindrical cells without problems, as does Schleicher. More importantly, owners would probably be happy replace batteries with, say, one with 80% capacity and 20% of the price of the original.