glider battery duration problems

On Monday, October 7, 2013 1:08:14 PM UTC-4, Evan Ludeman wrote:

These are starter batteries. Unsuited for gliders.

From the Shorai FAQ:
.... Not only do they have less than 1/3 the internal resistance per capacity than do lead-acid, they are also the ultimate "deep-cycle" battery.

The internal "completely discharged" capacity of a Shorai LFX is 1/3 the rated "PBeq" capacity. For example, the LFX18 12V series have 6Ah cells internally. But the cells are capable of 80% discharge without damage and while retaining more cranking ability. As such, the USABLE capacity(or "reserve capacity") of an LFX18 12V battery is on or very near par with 18AHr-rated lead acid batteries, while providing superior cranking performance and a vast reduction in weight. The Shorai PBeq AHr (lead-acid equivalent) rating system therefore allows users to compare a very different technology from lead-acid, but on a close apples-to-apples basis when making a choice.

SLA batteries can (and usually are in glider service) discharged 80% DODC or even further. It will shorten their cycle life, perhaps to only 100 cycles or so. Important for only the most active of pilots. For normal pilots the batter will suffer degradation from time than cycles.

I think the main advantage of Li Ion (for a glider battery) is higher energy density, and a flatter voltage discharge curve. I sure hope the "lead acid equivalent amp hours" rating method does not catch on in the industry. Legal lying is what it is, praying mainly on the ignorant.

son_of_flubber wrote, On 10/7/2013 10:17 AM:
On Monday, October 7, 2013 1:08:14 PM UTC-4, Evan Ludeman wrote:

These are starter batteries. Unsuited for gliders.

From the Shorai FAQ: ... Not only do they have less than 1/3 the
internal resistance per capacity than do lead-acid, they are also the
ultimate "deep-cycle" battery.

The internal "completely discharged" capacity of a Shorai LFX is 1/3
the rated "PBeq" capacity. For example, the LFX18 12V series have 6Ah
cells internally. But the cells are capable of 80% discharge without
damage and while retaining more cranking ability. As such, the USABLE
capacity(or "reserve capacity") of an LFX18 12V battery is on or very
near par with 18AHr-rated lead acid batteries, while providing
superior cranking performance and a vast reduction in weight. The
Shorai PBeq AHr (lead-acid equivalent) rating system therefore allows
users to compare a very different technology from lead-acid, but on a
close apples-to-apples basis when making a choice.

Shorai is telling you their starter batteries are GREAT starter
batteries, but they are still intended only for engine starting, which
is why they have the slogan "The World’s Lightest Strongest Powersports
Batteries". They have one-third (0.333) the capacity of a 12 volt, 18 AH
SLA at the 20 hour rate (6AH/Shorai vs 18AH/SLA), the rate that makes
sense when looking for glider batteries.

Shorai's "equivalent" means "equal starting ability". The "reserve
rating" term is used for starter batteries (high currents), not energy
storage batteries (high capacity). For example, the K2 will supply it's
AH rating, but is unsuitable for engine starting, because it has a 30
amp max current output; above that, the BMS will shut it off.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Dan Marotta wrote, On 10/7/2013 9:16 AM:
Eric, I have absolute faith in my ram air parachute. Having said that,
I don't relish the idea of bailing out of a flaming glider!

Since I have no direct knowledge of these new-fangled batteries, I will
listen only to the manufacturer when designing my system. When and if I
get it done, I'll post the design.

I look forward to reading your results.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

son_of_flubber wrote, On 10/7/2013 8:22 AM:
8.LiFePO4 batteries with BMS are compatible with solar panel chargers.

Most solar panel charge regulators use a pulsing output, which may not
be compatible with a BMS. Definitely determine this by asking the
manufacturer, or maybe it's in their data sheet. The regulators I'm
familiar with are intended for direct connection to lead-acid batteries.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On Monday, October 7, 2013 2:43:53 PM UTC-4, Eric Greenwell wrote:

Shorai is telling you their starter batteries are GREAT starter

batteries, but they are still intended only for engine starting, which

is why they have the slogan "The World’s Lightest Strongest Powersports

Batteries". They have one-third (0.333) the capacity of a 12 volt, 18 AH

SLA at the 20 hour rate (6AH/Shorai vs 18AH/SLA), the rate that makes

sense when looking for glider batteries.



Shorai's "equivalent" means "equal starting ability". The "reserve

rating" term is used for starter batteries (high currents), not energy

storage batteries (high capacity). For example, the K2 will supply it's

AH rating, but is unsuitable for engine starting, because it has a 30

amp max current output; above that, the BMS will shut it off.


So when Shorai boasts of being 'the ultimate "deep-cycle" battery.', they are referring to something different than what you call "energy storage batteries (high capacity)? I thought a "deep-cycle" battery was what we were looking to use in a glider.

son_of_flubber wrote, On 10/7/2013 12:50 PM:
On Monday, October 7, 2013 2:43:53 PM UTC-4, Eric Greenwell wrote:

Shorai is telling you their starter batteries are GREAT starter

batteries, but they are still intended only for engine starting,
which

is why they have the slogan "The World’s Lightest Strongest
Powersports

Batteries". They have one-third (0.333) the capacity of a 12 volt,
18 AH

SLA at the 20 hour rate (6AH/Shorai vs 18AH/SLA), the rate that
makes

sense when looking for glider batteries.



Shorai's "equivalent" means "equal starting ability". The "reserve

rating" term is used for starter batteries (high currents), not
energy

storage batteries (high capacity). For example, the K2 will supply
it's

AH rating, but is unsuitable for engine starting, because it has a
30

amp max current output; above that, the BMS will shut it off.


So when Shorai boasts of being 'the ultimate "deep-cycle" battery.',
they are referring to something different than what you call "energy
storage batteries (high capacity)? I thought a "deep-cycle" battery
was what we were looking to use in a glider.

"Deep-cycle" is what we want for a glider battery. I have no idea why
they say that it's the "ultimate" deep-cycle battery; elsewhere, they
clearly state it's for "powersports" applications and the warranty is
void for other uses. "Powersports" means sKidoos, seadoos, motorcycles,
etc. It's very confusing until you realize what is going on.

They do show the AH ratings, and you can see how small they are. The
batteries might actually be suitable for "deep-cycle" use, but be aware
that buying an 18 AH "equivalent" unit gets you only 6 AH of deep-cycle
output.

There is another issue: I don't think they have a BMS in their battery,
and that's why they have strict requirements for the charging system
voltages, and any vehicle with parasitic drains (engine computer, clock,
etc) when it's not running also voids the warranty. Why? No BMS to shut
off the battery if it's drained too low.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

I made some notes in the process of educating myself on LFP batteries last Winter. I've tried to condense them here into something semi-useful.

A non-exhaustive list of things to ask of LFP battery vendors:

1. Get the component cell spec sheets. Especially look for specs on failure modes due to abuse, e.g. short circuits, crushing, piercing. You absolutely want cells that can survive all of this without self ignition. They *will* get hot if shorted in some fashion which is something to keep in mind when finding a home for an LFP battery in your glider. The spec sheets may give you an idea of how hot, probably for a single cell. If the manufacturer has really done their homework, maybe they'll know what a worst case temperature excursion is for the whole pack (you probably won't like the answer).

2. Get the specs on the BMS. You absolutely need under charge & over charge protection. You want a BMS that monitors *individual* cell voltages, not just the whole pack. Internal cell balancing highly recommended (not all BMS do this).

3. Get the specs on charge, discharge and storage requirements. Make certain these specs work for you and your application. These specs will be a function of the BMS as well as the battery. If you fly in wave, try to get some data on low temperature operation.

4. Get as much detail as you can on packaging. I think a sealed ABS case is a minimum requirement for aviation use of any sort, but anything that enhances ruggedness and makes internal damage of any kind less likely over the long haul is a good thing. Here's an interesting dissection of a K2 battery

http://www.etotheipiplusone.net/?p=1991

-Evan Ludeman / T8

Mark et al:
The accu24.de website has the batteries exactly as you can order through Schempp-Hirth. Model number 8000910PSHMPXM is the 12V 10A/H that not only fits but already has the cover that the Schempp battery holders will clip into and the same connector supplied on the Arcus, Quintus and other current production gliders (V2CxM etc).
Or of course you can call Kirchheim. They have the LiFePO4 battery option for everything but motor starting.
And Eric, the Strobl 2-panel 15W array works very well. Had that on 26015 and now on 27053. Does better with LiFePO4, as they seem to charge more efficiently.

The direct link to the ready-to-go Schempp battery might be too long, so here's a tinyurl.
Jim

http://tinyurl.com/kbfjm8p

On Friday, October 4, 2013 10:36:16 AM UTC-7, waremark wrote:
Can someone recommend the best LifePo battery which fits in a completely standard bracket? (In my case for an Arcus M - I have 4 Strobl panels which are supposed to generate 2.4 Ah, but I have the max amount of electronics fitted - I have not run out of power yet with 2 ordinary 7Ah gel cells, but think I might run out if a flight lasted for more than 8 hours).



Thanks for any advice, Mark Burton, 4M, London Gliding Club, UK

On Monday, October 7, 2013 7:25:28 PM UTC-4, Evan Ludeman wrote:
I made some notes in the process of educating myself on LFP batteries last Winter. I've tried to condense them here into something semi-useful.

Oh man. Flying around with two or three cheap plastic buckets filled with hydrochloric acid and lead seems the way go for now (unless you really really need the power capacity).