Today's Message Index:
----------------------
1. 06:28 AM - Re: LiFe Battery (Ken Ryan)
2. 07:04 AM - Re: LiFe Battery (Charlie England)
3. 08:16 AM - Re: LiFe Battery (Ken Ryan)
4. 09:42 AM - Re: LiFe Battery (Robert L. Nuckolls, III)
5. 11:37 AM - Re: Thermocouple wire extension (Charlie England)
6. 01:52 PM - Re: LiFe Battery (Robert L. Nuckolls, III)
7. 02:11 PM - Re: LiFe Battery (Robert L. Nuckolls, III)
8. 02:49 PM - Re: LiFe Battery (Robert L. Nuckolls, III)
9. 08:47 PM - Dual Battery Question ()
Message 1
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| Subject: | Re: LiFe Battery |
Ivan, you are correct. There are a lot of examples of LiFe batteries being
used without incident. Millions and millions of examples in everything from
motorcycles to jetskis to bicycles to, yes, airplanes. Everyone I know with
an experimental airplane is now using a LiFe battery (admittedly that's not
a large sample).
On Wed, Jun 29, 2022 at 9:33 PM H. Ivan Haecker <hivanhaecker@gmail.com>
wrote:
> Yes, I did mean to write LliFePO4. And I do have it mounted on the engine
> side of the firewall. I have seen others mounted in that position and
> assumed (dangerous word) that the environment would be acceptable. When I
> buy a replacement, I=99ll consider an Odyssey. But my gut feeling i
s that I
> was just unlucky and got a =9CFriday afternoon=9D battery. To
o many examples of
> others having better luck with theirs.
> Ivan Haecker
>
> On Wed, Jun 29, 2022 at 11:55 PM Stuart Hutchison <
> stuart@stuarthutchison.com.au> wrote:
>
>> Good that the battery tender had a Lithium profile maybe the b
attery
>> was ultimately a dud or less than expected quality. I assume by LiFe Iv
an
>> means LiFePO4 (Lithium Iron Phosphate).
>>
>> Actually Ken, the same rated LiFePO4 battery will deliver 80% of its
>> charge at a relatively flat Voltage profile before the BMS protects the
>> battery, but the same rated Lead Acid can only be discharged to 50% befo
re
>> charge is necessary or permanent damage can result. No matter what tech
,
>> we often get what we pay for, hence Odyssey Lead Acids have a good
>> reputation and some LiFePO4s (like Invicta) do as well. Unsure if LiFeP
O
>> degrades in high-heat conditions the same way Li-Ion does if s
o, firewall
>> forward wouldn=99t make much sense, but either way they have huge
energy
>> density and can=99t be extinguished with a typical fire extinguish
er (because
>> the degrading cathode liberates oxygen inside the case), so there's safe
ty
>> issue to consider in that too.
>>
>> Kind regards, Stu
>>
>>
>> On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska@gmail.com> wrote:
>>
>> I'm not sure the 20% cut off number is accurate; I suspect that it is
>> not. But putting that aside, there is another way of looking at this--al
l
>> batteries have a limited capacity. Lead acid batteries will happily
>> discharge until they are dead or badly damaged Lithium batteries with a
BMS
>> will stop discharging before they are ruined. How can this be a bad thin
g?
>>
>> It's bad only if you are relying on the advertised capacity number to
>> size your battery. Bob has taught us all that we cannot rely on the
>> advertised capacity number, rather, we should do annual capacity checks
to
>> verify the actual capacity. It's just a matter of factoring in BMS behav
ior
>> when you decide on the size battery you need.
>>
>> Would it be nice if there was a switch you could throw to disable the BM
S
>> low voltage protection in a real emergency? Sure! Is the lack of such a
>> switch a good reason to write off LiFe technology? Not in my opinion.
>>
>> On Wed, Jun 29, 2022 at 6:00 AM <ashleysc@broadstripe.net> wrote:
>>
>>>
>>> Hi Stu.
>>> The Battery Tender (charger) you mentioned is intended for LiFeO3
>>> batteries. I have one too. I have been through two Li FeO3 batteries. I
n my
>>> case it appeared they didn't like the charging system on board the
>>> aircraft, even though the charging current went to zero soon after star
ting
>>> the engine. I assumed it was not being overcharged, but don't really kn
ow
>>> what caused the problem. Now I have a much cheaper sealed lead acid
>>> battery, which I hope will be bombproof. Installed in the tail cone, ra
ther
>>> than atop the firewall, it will also help with a slightly nose heavy
>>> condition. I have learned latterly that some LiFeO3 batteries will "tur
n
>>> themselves off," when they get down to a 20% charge. Not a good thing i
n an
>>> aircraft.
>>> Cheers! Stu. Ashley
>>>
>>> ----- Original Message -----
>>> From: "Stuart Hutchison" <stuart@stuarthutchison.com.au>
>>> To: aeroelectric-list@matronics.com
>>> Sent: Tuesday, June 28, 2022 10:49:33 PM
>>> Subject: Re: AeroElectric-List: LiFe Battery
>>>
>>> stuart@stuarthutchison.com.au>
>>>
>>> There is much misleading information out there suggesting chargers
>>> suitable for Lead Acid are also suitable for Lithium. Do they work? Yes
. Do
>>> they compromise Lithium longevity? Also yes, absolutely, unless they ha
ve a
>>> Lithium specific mode.
>>>
>>> Kind regards, Stu
>>>
>>> Sent from my iPhone
>>>
>>> > On 29 Jun 2022, at 15:31, H. Ivan Haecker <hivanhaecker@gmail.com>
>>> wrote:
>>> >
>>> > =EF=BBThree years ago I decided to equip my little C-85 powered ai
rcraft
>>> with a B&C starter and LiFe battery ( Shorai 18 Ah). No provision for
>>> charging onboard. It worked great and would easily start the engine a d
ozen
>>> times before I would charge it with an 800mA Battery Tender that was
>>> advertised as suitable for both lead acid and LiFe batteries. It was ne
ver
>>> discharged to the point that it failed to rapidly spin the engine. All
went
>>> well until a few months ago when I noticed that the battery became slug
gish
>>> after only a few starts. Now it=99s only good for one start befor
e it needs
>>> recharging. So the battery is now almost useless. I had (of course!) ho
ped
>>> for a longer useful life. The big question is: have I mismanaged the
>>> battery by recharging it only occasionally instead of more often, or di
d I
>>> use an inappropriate charger, or just bad luck of the draw on this
>>> particular battery? Thanks for any opinions.
>>> >
>>> > Ivan Haecker
>>>
>>>
>>> ==========
>>> -
>>> Electric-List" rel="noreferrer" target="_blank">
>>> http://www.matronics.com/Navigator?AeroElectric-List
>>> ==========
>>> FORUMS -
>>> eferrer" target="_blank">http://forums.matronics.com
>>> ==========
>>> WIKI -
>>> errer" target="_blank">http://wiki.matronics.com
>>> ==========
>>> b Site -
>>> -Matt Dralle, List Admin.
>>> ="noreferrer" target="_blank">https://matronics.com/contribution
>>> ==========
>>>
>>>
>>>
>>>
>>
Message 2
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| Subject: | Re: LiFe Battery |
"I'm not sure the 20% cut off number is accurate; I suspect that it is not.
But putting that aside, there is another way of looking at this--all
batteries have a limited capacity. Lead acid batteries will happily
discharge until they are dead or badly damaged Lithium batteries with a BMS
will stop discharging before they are ruined. How can this be a bad thing?
"
It can be a bad thing in a couple of ways. 1st, if you lose the alternator.
You may need that last few watts to keep the engine turning or the panel
lit to make it safely to the ground. I'd happily trade a battery for the
airframe (or my life). Would you accept an engine controller that went into
'limp mode' or completely shut down the engine with low oil pressure?
2nd, The existence of a disconnect device means that a malfunction in the
device itself can cause a 'false positive' and *create* an emergency.
FWIW...
On Thu, Jun 30, 2022 at 8:31 AM Ken Ryan <keninalaska@gmail.com> wrote:
> Ivan, you are correct. There are a lot of examples of LiFe batteries bein
g
> used without incident. Millions and millions of examples in everything fr
om
> motorcycles to jetskis to bicycles to, yes, airplanes. Everyone I know wi
th
> an experimental airplane is now using a LiFe battery (admittedly that's n
ot
> a large sample).
>
> On Wed, Jun 29, 2022 at 9:33 PM H. Ivan Haecker <hivanhaecker@gmail.com>
> wrote:
>
>> Yes, I did mean to write LliFePO4. And I do have it mounted on the engin
e
>> side of the firewall. I have seen others mounted in that position and
>> assumed (dangerous word) that the environment would be acceptable. When
I
>> buy a replacement, I=99ll consider an Odyssey. But my gut feeling
is that I
>> was just unlucky and got a =9CFriday afternoon=9D battery. T
oo many examples of
>> others having better luck with theirs.
>> Ivan Haecker
>>
>> On Wed, Jun 29, 2022 at 11:55 PM Stuart Hutchison <
>> stuart@stuarthutchison.com.au> wrote:
>>
>>> Good that the battery tender had a Lithium profile maybe the
battery
>>> was ultimately a dud or less than expected quality. I assume by LiFe I
van
>>> means LiFePO4 (Lithium Iron Phosphate).
>>>
>>> Actually Ken, the same rated LiFePO4 battery will deliver 80% of its
>>> charge at a relatively flat Voltage profile before the BMS protects the
>>> battery, but the same rated Lead Acid can only be discharged to 50% bef
ore
>>> charge is necessary or permanent damage can result. No matter what tec
h,
>>> we often get what we pay for, hence Odyssey Lead Acids have a good
>>> reputation and some LiFePO4s (like Invicta) do as well. Unsure if LiFe
PO
>>> degrades in high-heat conditions the same way Li-Ion does if
so, firewall
>>> forward wouldn=99t make much sense, but either way they have huge
energy
>>> density and can=99t be extinguished with a typical fire extinguis
her (because
>>> the degrading cathode liberates oxygen inside the case), so there's saf
ety
>>> issue to consider in that too.
>>>
>>> Kind regards, Stu
>>>
>>>
>>> On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska@gmail.com> wrote:
>>>
>>> I'm not sure the 20% cut off number is accurate; I suspect that it is
>>> not. But putting that aside, there is another way of looking at this--a
ll
>>> batteries have a limited capacity. Lead acid batteries will happily
>>> discharge until they are dead or badly damaged Lithium batteries with a
BMS
>>> will stop discharging before they are ruined. How can this be a bad thi
ng?
>>>
>>> It's bad only if you are relying on the advertised capacity number to
>>> size your battery. Bob has taught us all that we cannot rely on the
>>> advertised capacity number, rather, we should do annual capacity checks
to
>>> verify the actual capacity. It's just a matter of factoring in BMS beha
vior
>>> when you decide on the size battery you need.
>>>
>>> Would it be nice if there was a switch you could throw to disable the
>>> BMS low voltage protection in a real emergency? Sure! Is the lack of su
ch a
>>> switch a good reason to write off LiFe technology? Not in my opinion.
>>>
>>> On Wed, Jun 29, 2022 at 6:00 AM <ashleysc@broadstripe.net> wrote:
>>>
>>>>
>>>> Hi Stu.
>>>> The Battery Tender (charger) you mentioned is intended for LiFeO3
>>>> batteries. I have one too. I have been through two Li FeO3 batteries.
In my
>>>> case it appeared they didn't like the charging system on board the
>>>> aircraft, even though the charging current went to zero soon after sta
rting
>>>> the engine. I assumed it was not being overcharged, but don't really k
now
>>>> what caused the problem. Now I have a much cheaper sealed lead acid
>>>> battery, which I hope will be bombproof. Installed in the tail cone, r
ather
>>>> than atop the firewall, it will also help with a slightly nose heavy
>>>> condition. I have learned latterly that some LiFeO3 batteries will "tu
rn
>>>> themselves off," when they get down to a 20% charge. Not a good thing
in an
>>>> aircraft.
>>>> Cheers! Stu. Ashley
>>>>
>>>> ----- Original Message -----
>>>> From: "Stuart Hutchison" <stuart@stuarthutchison.com.au>
>>>> To: aeroelectric-list@matronics.com
>>>> Sent: Tuesday, June 28, 2022 10:49:33 PM
>>>> Subject: Re: AeroElectric-List: LiFe Battery
>>>>
>>>> stuart@stuarthutchison.com.au>
>>>>
>>>> There is much misleading information out there suggesting chargers
>>>> suitable for Lead Acid are also suitable for Lithium. Do they work? Ye
s. Do
>>>> they compromise Lithium longevity? Also yes, absolutely, unless they h
ave a
>>>> Lithium specific mode.
>>>>
>>>> Kind regards, Stu
>>>>
>>>> Sent from my iPhone
>>>>
>>>> > On 29 Jun 2022, at 15:31, H. Ivan Haecker <hivanhaecker@gmail.com>
>>>> wrote:
>>>> >
>>>> > =EF=BBThree years ago I decided to equip my little C-85 powered a
ircraft
>>>> with a B&C starter and LiFe battery ( Shorai 18 Ah). No provision for
>>>> charging onboard. It worked great and would easily start the engine a
dozen
>>>> times before I would charge it with an 800mA Battery Tender that was
>>>> advertised as suitable for both lead acid and LiFe batteries. It was n
ever
>>>> discharged to the point that it failed to rapidly spin the engine. All
went
>>>> well until a few months ago when I noticed that the battery became slu
ggish
>>>> after only a few starts. Now it=99s only good for one start befo
re it needs
>>>> recharging. So the battery is now almost useless. I had (of course!) h
oped
>>>> for a longer useful life. The big question is: have I mismanaged the
>>>> battery by recharging it only occasionally instead of more often, or d
id I
>>>> use an inappropriate charger, or just bad luck of the draw on this
>>>> particular battery? Thanks for any opinions.
>>>> >
>>>> > Ivan Haecker
>>>>
>>>>
>>>> ==========
>>>> -
>>>> Electric-List" rel="noreferrer" target="_blank">
>>>> http://www.matronics.com/Navigator?AeroElectric-List
>>>> ==========
>>>> FORUMS -
>>>> eferrer" target="_blank">http://forums.matronics.com
>>>> ==========
>>>> WIKI -
>>>> errer" target="_blank">http://wiki.matronics.com
>>>> ==========
>>>> b Site -
>>>> -Matt Dralle, List Admin.
>>>> ="noreferrer" target="_blank">https://matronics.com/contribution
>>>> ==========
>>>>
>>>>
>>>>
>>>>
>>>
Message 3
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| Subject: | Re: LiFe Battery |
I agree with your comment regarding a BMS override switch. Just thought I
would throw it against the wall. I'm glad it's not sticking because I see
no need for such a switch.
With regards to the capacity issue, I cannot make the case more plainly
than this: If you are comparing a LiFe battery that provides x watt-hours
of energy (regardless of what is left after the BMS shuts it down) or a
lead acid battery that provides 0.9x watt-hours of energy before things
quit working, obviously the LiFe battery will keep things running longer. I
was only addressing the previous post (and now your post) that
indicated that because the LiFe batteries still have energy left when
the BMS shuts them down, that is justification for rejecting the
technology. I disagree, based on the above logic. FWIW
On Thu, Jun 30, 2022 at 6:13 AM Charlie England <ceengland7@gmail.com>
wrote:
> "I'm not sure the 20% cut off number is accurate; I suspect that it is
> not. But putting that aside, there is another way of looking at this--all
> batteries have a limited capacity. Lead acid batteries will happily
> discharge until they are dead or badly damaged Lithium batteries with a B
MS
> will stop discharging before they are ruined. How can this be a bad thing
? "
> It can be a bad thing in a couple of ways. 1st, if you lose the
> alternator. You may need that last few watts to keep the engine turning o
r
> the panel lit to make it safely to the ground. I'd happily trade a batter
y
> for the airframe (or my life). Would you accept an engine controller that
> went into 'limp mode' or completely shut down the engine with low oil
> pressure?
>
> 2nd, The existence of a disconnect device means that a malfunction in the
> device itself can cause a 'false positive' and *create* an emergency.
>
> FWIW...
>
>
> On Thu, Jun 30, 2022 at 8:31 AM Ken Ryan <keninalaska@gmail.com> wrote:
>
>> Ivan, you are correct. There are a lot of examples of LiFe batteries
>> being used without incident. Millions and millions of examples in
>> everything from motorcycles to jetskis to bicycles to, yes, airplanes.
>> Everyone I know with an experimental airplane is now using a LiFe batter
y
>> (admittedly that's not a large sample).
>>
>> On Wed, Jun 29, 2022 at 9:33 PM H. Ivan Haecker <hivanhaecker@gmail.com>
>> wrote:
>>
>>> Yes, I did mean to write LliFePO4. And I do have it mounted on the
>>> engine side of the firewall. I have seen others mounted in that positio
n
>>> and assumed (dangerous word) that the environment would be acceptable.
When
>>> I buy a replacement, I=99ll consider an Odyssey. But my gut feeli
ng is that I
>>> was just unlucky and got a =9CFriday afternoon=9D battery.
Too many examples of
>>> others having better luck with theirs.
>>> Ivan Haecker
>>>
>>> On Wed, Jun 29, 2022 at 11:55 PM Stuart Hutchison <
>>> stuart@stuarthutchison.com.au> wrote:
>>>
>>>> Good that the battery tender had a Lithium profile maybe the
battery
>>>> was ultimately a dud or less than expected quality. I assume by LiFe
Ivan
>>>> means LiFePO4 (Lithium Iron Phosphate).
>>>>
>>>> Actually Ken, the same rated LiFePO4 battery will deliver 80% of its
>>>> charge at a relatively flat Voltage profile before the BMS protects th
e
>>>> battery, but the same rated Lead Acid can only be discharged to 50% be
fore
>>>> charge is necessary or permanent damage can result. No matter what te
ch,
>>>> we often get what we pay for, hence Odyssey Lead Acids have a good
>>>> reputation and some LiFePO4s (like Invicta) do as well. Unsure if LiF
ePO
>>>> degrades in high-heat conditions the same way Li-Ion does if
so, firewall
>>>> forward wouldn=99t make much sense, but either way they have hug
e energy
>>>> density and can=99t be extinguished with a typical fire extingui
sher (because
>>>> the degrading cathode liberates oxygen inside the case), so there's sa
fety
>>>> issue to consider in that too.
>>>>
>>>> Kind regards, Stu
>>>>
>>>>
>>>> On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska@gmail.com> wrote:
>>>>
>>>> I'm not sure the 20% cut off number is accurate; I suspect that it is
>>>> not. But putting that aside, there is another way of looking at this--
all
>>>> batteries have a limited capacity. Lead acid batteries will happily
>>>> discharge until they are dead or badly damaged Lithium batteries with
a BMS
>>>> will stop discharging before they are ruined. How can this be a bad th
ing?
>>>>
>>>> It's bad only if you are relying on the advertised capacity number to
>>>> size your battery. Bob has taught us all that we cannot rely on the
>>>> advertised capacity number, rather, we should do annual capacity check
s to
>>>> verify the actual capacity. It's just a matter of factoring in BMS beh
avior
>>>> when you decide on the size battery you need.
>>>>
>>>> Would it be nice if there was a switch you could throw to disable the
>>>> BMS low voltage protection in a real emergency? Sure! Is the lack of s
uch a
>>>> switch a good reason to write off LiFe technology? Not in my opinion.
>>>>
>>>> On Wed, Jun 29, 2022 at 6:00 AM <ashleysc@broadstripe.net> wrote:
>>>>
>>>>>
>>>>> Hi Stu.
>>>>> The Battery Tender (charger) you mentioned is intended for LiFeO3
>>>>> batteries. I have one too. I have been through two Li FeO3 batteries.
In my
>>>>> case it appeared they didn't like the charging system on board the
>>>>> aircraft, even though the charging current went to zero soon after st
arting
>>>>> the engine. I assumed it was not being overcharged, but don't really
know
>>>>> what caused the problem. Now I have a much cheaper sealed lead acid
>>>>> battery, which I hope will be bombproof. Installed in the tail cone,
rather
>>>>> than atop the firewall, it will also help with a slightly nose heavy
>>>>> condition. I have learned latterly that some LiFeO3 batteries will "t
urn
>>>>> themselves off," when they get down to a 20% charge. Not a good thing
in an
>>>>> aircraft.
>>>>> Cheers! Stu. Ashley
>>>>>
>>>>> ----- Original Message -----
>>>>> From: "Stuart Hutchison" <stuart@stuarthutchison.com.au>
>>>>> To: aeroelectric-list@matronics.com
>>>>> Sent: Tuesday, June 28, 2022 10:49:33 PM
>>>>> Subject: Re: AeroElectric-List: LiFe Battery
>>>>>
>>>>> stuart@stuarthutchison.com.au>
>>>>>
>>>>> There is much misleading information out there suggesting chargers
>>>>> suitable for Lead Acid are also suitable for Lithium. Do they work? Y
es. Do
>>>>> they compromise Lithium longevity? Also yes, absolutely, unless they
have a
>>>>> Lithium specific mode.
>>>>>
>>>>> Kind regards, Stu
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>> > On 29 Jun 2022, at 15:31, H. Ivan Haecker <hivanhaecker@gmail.com>
>>>>> wrote:
>>>>> >
>>>>> > =EF=BBThree years ago I decided to equip my little C-85 powered
aircraft
>>>>> with a B&C starter and LiFe battery ( Shorai 18 Ah). No provision for
>>>>> charging onboard. It worked great and would easily start the engine a
dozen
>>>>> times before I would charge it with an 800mA Battery Tender that was
>>>>> advertised as suitable for both lead acid and LiFe batteries. It was
never
>>>>> discharged to the point that it failed to rapidly spin the engine. Al
l went
>>>>> well until a few months ago when I noticed that the battery became sl
uggish
>>>>> after only a few starts. Now it=99s only good for one start bef
ore it needs
>>>>> recharging. So the battery is now almost useless. I had (of course!)
hoped
>>>>> for a longer useful life. The big question is: have I mismanaged the
>>>>> battery by recharging it only occasionally instead of more often, or
did I
>>>>> use an inappropriate charger, or just bad luck of the draw on this
>>>>> particular battery? Thanks for any opinions.
>>>>> >
>>>>> > Ivan Haecker
>>>>>
>>>>>
>>>>> ==========
>>>>> -
>>>>> Electric-List" rel="noreferrer" target="_blank">
>>>>> http://www.matronics.com/Navigator?AeroElectric-List
>>>>> ==========
>>>>> FORUMS -
>>>>> eferrer" target="_blank">http://forums.matronics.com
>>>>> ==========
>>>>> WIKI -
>>>>> errer" target="_blank">http://wiki.matronics.com
>>>>> ==========
>>>>> b Site -
>>>>> -Matt Dralle, List Admin.
>>>>> ="noreferrer" target="_blank">https://matronics.com/contribution
>>>>> ==========
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
Message 4
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| Subject: | Re: LiFe Battery |
At 12:49 AM 6/29/2022, you wrote:
><stuart@stuarthutchison.com.au>
>
>There is much misleading information out there suggesting chargers
>suitable for Lead Acid are also suitable for Lithium. Do they work?
>Yes. Do they compromise Lithium longevity? Also yes, absolutely,
>unless they have a Lithium specific mode.
Excellent question!
For over ten years now I've watched the lithium
based dialog and market . . . and participated
to a small degree.
I've had several maintainers/chargers
with 'mode' switches that claimed to accommodate
various battery chemistries. Even plotted the
charge profiles on a couple to see if different
mode settings produced a significant difference
in performance.
At the same time, virtually all lithium battery
products are advertised as plug-n-play
into applications previously served by
wet or sealed lead-acid.
I've not encountered an alternator voltage
regulator with a lithium/wet/svla selector
switch.
Yes, lithium is not as forgiving as slva . . .
this is why the 'uptown' lithium products
include battery management electronics:
Some combination of O.V. protection, over-discharge
protection, over-heat protection, high discharge
rate protection and perhaps individual cell charge-
balancing.
One assumes that all this 'protection' is to
secure the advertised plug-n-play performance
for replacing lead-acid while standing off
risk of catastrophic, externally induced failures.
If interchangeability of lead-acid and lithium
specific chargers is potentially 'misleading'
then one should refer to the engineering
and marketing literature for the lithium product
under consideration. If the thing is intended
to replace lead-acid without modification to
the vehicle's power system, then it follows
that the same interchangeability would apply
to chargers.
I've had several lithium products run through
my shop over the past ten years . . . still
have an EarthX sample that has been happily
existing tied to the same family of lead-acid
maintainers now pushing 20 or more years old.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 5
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| Subject: | Re: Thermocouple wire extension |
On Wed, Jun 29, 2022 at 4:34 PM Paul Eckenroth <jeckenroth@nbn.net> wrote:
> jeckenroth@nbn.net>
>
> As I redo my Revmaster engine with the burned stator I plan to incorporate
> thermocouples to hopefully allow me to head off a repeat of the burned
> stator. In the past on both the RV and the Onex I ran the full length of
> the suppllied thermocouple wire and then connected to tefzel coated copper
> for the rest of the run to the EIS using Faston connectors. The
> temperature read out for both planes seems reasonable and accurate.
> Although it has never been checked using boiling water. Now that I'm
> looking into thermocouples again I read that only thermocouple wire should
> be used for extensions and copper wire should never be used.
> So, I am looking for some guidance. Is my prior approach totally faulty
> producing meaningless temperature readings or are the practices I read
> about only required for super accurate results and what I have done in the
> past good enough. I will appreciate any opinions. Thanks.
>
> Paul
>
IIRC, if you keep the transitions to copper at the same temperature as the
final termination point (the gauge itself), and the copper extensions are
identical with each other, it's supposed to have little effect on accuracy.
IIRC (again) a lot of the issues with TC accuracy were driven by the old
mechanical gauges that were actually driven by the thermocouple current.
Modern electronic gauges are supposed to help alleviate some of the issues
inherent in the old mechanical gauges.
No recent hotel stays, so you might want to verify the above through other
sources.
Charlie
Message 6
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| Subject: | Re: LiFe Battery |
At 10:14 AM 6/30/2022, you wrote:
>I agree with your comment regarding a BMS override switch. Just
>thought I would throw it against the wall. I'm glad it's not
>sticking because I see no need for such a switch.
Agreed. The BMS 'should' be configured to disconnect
the cell array when voltage per cell drops below the highest
discharge voltage allowed to prevent permanent damage
to the cell(s).
For LiFePO4 this is generally on the order of
The capacity rating of any battery should be stated
in some energy defining units like Watt-Seconds, Joules,
Watt-Hours, etc. The Ampere-Hour is an arcane
unit of measure . . . it works too if that's the
best you've got.
Every manufacturer of a lithium cell will prescribe
a discharge cutoff voltage. Here's one example calling
out 2.5 Volts:
http://aeroelectric.com/Mfgr_Data/Batteries/LithiumCells/Samsung/INR21700-50E.pdf
A typical LiFePO4 discharge profile will look something
like the attached plot. This is a plot published by
A123. Their cutoff for the plots was at 2.0 Volts.
In either case, note the slope of the plots just below
2.5 volts . . . nearly gone and fading fast. The
BMS cuttoff Voltage may or may not be specified by
the manufacturer of your particular battery . . . but
if not, you should ask 'em.
If they have a 4-cell stack, then a battery cutoff
of 10 Volts would not be out of line . . . this is
below the point where any accessory designed for
aviation applications is expected to function . . .
and even if it were still providing service down to
8.0 Volts . . . it would not enjoy that condition
for long.
So yes, unless your battery has an unrealistic
cuttoff voltage, a BMS bypass switch would add
no value. By the time a cell drops below 2.5
Volts, it's time to go to plan-C.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 7
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| Subject: | Re: LiFe Battery |
At 08:58 AM 6/30/2022, you wrote:
>>"I'm not sure the 20% cut off number is accurate; I suspect that it is
not.
It depends on the battery manufacturer's selected
cutoff voltage but it behooves them to set it as
low as practical . . . which is generally below
a voltage where the battery still possesses useable
energy. I think that 20%/80% meme is a spillover
from some of the electric vehicle battery protocols.
I think I read years ago that some EV energy management
systems work to operate the battery at no less than
20, no more than 80 percent for improved cycle
life. Hence improved service life.
This had nothing to do with the chemistry's
best energy performance.
>>. . . batteries with BMS will stop discharging
>>before they are ruined. How can this be a bad thing? "
>>It can be a bad thing in a couple of ways. 1st,
>>if you lose the alternator. You may need that
>>last few watts to keep the engine turning or
>>the panel lit to make it safely to the ground.
>>I'd happily trade a battery for the airframe
>>(or my life). Would you accept an engine
>>controller that went into 'limp mode' or
>>completely=C2 shut down the engine with low oil pressure?
Who did your FMEA for you? What are your battery-only
endurance requirements? What are your plans for periodic
maintenance checks to assure that your endurance goals
are maintained?
>>2nd, The existence of a disconnect device means that a malfunction
>>in the device itself can cause a 'false positive' and *create* an
>>emergency.
Not sure what that would be. The BMS has what you would
consider to be a solid state battery contactor that is
controlled by software and sensors in the management
sytem. It would be no big deal to add a 'low volts
disconnect override' feature to the BMS controller.
Activating such a feature would not be a situational
risk as it cannot inadvertently create a hazard to
ship's electro-whizzies . . . only hazard to the battery's
internal chemistry as a consequence of an over discharge
where one attempted to squeeze a few more percent
of total capacity from the device.
This would be the operational equivalent of adding
a special suction line to unusable fuel sumps
with a control enabling one to truly suck the
tank dry. But what would be the value?
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 8
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| Subject: | Re: LiFe Battery |
>but the same rated Lead Acid can only be discharged to 50% before charge is
>necessary or permanent damage can result . . .
Actually . . . not so. SVLA is rather tolerant of
total discharge as long as you can live with
a reduced service life. The CycleLife profile
attached shows the expected reduction in cycle life
for discharge depths of 30 to 100%
It only takes about 10% of total battery capacity
for pre-flight checks and cranking a Beechjet's engine.
So as long as the generator comes on line to support
cranking the second engine, it's no unreasonable to expect
a rather long cycle life.
The DischargeCurves plots show expected energy
delivered for a discharge to essentially zero
percent on each cycle. This is called 'deep cycle'
service and is not something the battery cannot
routinely handle.
When one cap-checks an SVLA battery, a known
load is applied until terminal voltage drops
to 10.5V. For a LiFePO4 with or without BMS,
I would still terminate the test at 10.5 volts
or BMS trip out . . . which ever occurs first
For BOTH technologies, remaining energy in the
battery will be very low on the order of 5%
or less.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 9
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| Subject: | Dual Battery Question |
Hello
If I connect a second battery via a ground battery socket to assist my
onboard battery what criteria do the 2 batteries use to determine how to
split the load between themselves?
Thanks
Mike Pienaar
m <mailto:ike@vision499.com> ike@vision499.com
Home: +1 250-999-8121
Mike cell: +1 250-885-0554
1-1100 Tulip Ave, Victoria, BC, V8Z 0A2
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