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LiFe Battery

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hivanhaecker(at)gmail.com
Guest

Posted: Tue Jun 28, 2022 9:23 pm Post subject: LiFe Battery

Three 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. All went well until a few months ago when I noticed that the battery became sluggish after only a few starts. Now itâ€™s only good for one start before 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

stuart(at)stuarthutchison
Guest

Posted: Tue Jun 28, 2022 9:50 pm Post subject: LiFe Battery

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.



Kind regards, Stu



Sent from my iPhone



 	  Quote: 	
		   On 29 Jun 2022, at 15:31, H. Ivan Haecker <hivanhaecker(at)gmail.com> wrote:

 

 ï»¿Three 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. All went well until a few months ago when I noticed that the battery became sluggish after only a few starts. Now itâ€™s only good for one start before 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

hivanhaecker(at)gmail.com
Guest

Posted: Tue Jun 28, 2022 10:03 pm Post subject: LiFe Battery

The charger has two modes. One for lead acid and one for LiFe . I assume the LiFe mode charges at a slightly higher voltage?

Ivan Haecker



On Wed, Jun 29, 2022 at 12:52 AM Stuart Hutchison <stuart(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: Stuart Hutchison <stuart(at)stuarthutchison.com.au (stuart(at)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.

 

 Kind regards, Stu

 

 Sent from my iPhone

 

 > On 29 Jun 2022, at 15:31, H. Ivan Haecker <hivanhaecker(at)gmail.com (hivanhaecker(at)gmail.com)> wrote:

 > 

 > ï»¿Three 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. All went well until a few months ago when I noticed that the battery became sluggish after only a few starts. Now itâ€™s only good for one start before 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

 

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ashleysc(at)broadstripe.n
Guest

Posted: Wed Jun 29, 2022 5:58 am Post subject: LiFe Battery

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 starting 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 "turn themselves off," when they get down to a 20% charge. Not a good thing in an aircraft.

Cheers!   Stu. Ashley



---

kenryan

Joined: 20 Oct 2009
Posts: 429

Posted: Wed Jun 29, 2022 8:16 am Post subject: 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?Â 



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 behavior when you decide on the size battery you need.Â 

Would it be nice if there was a switch you could throw to disable the BMS low voltage protection in a realÂ 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(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:



[quote]--> AeroElectric-List message posted by: ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)

 

 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 starting 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 "turn themselves off," when they get down to a 20% charge. Not a good thing in an aircraft.

 Cheers!Â  Â Stu. Ashley

 

 ---

Ceengland

Joined: 11 Oct 2020
Posts: 394
Location: MS

Posted: Wed Jun 29, 2022 10:55 am Post subject: LiFe Battery

On Wed, Jun 29, 2022 at 12:25 AM H. Ivan Haecker <hivanhaecker(at)gmail.com (hivanhaecker(at)gmail.com)> wrote:



 	  Quote: 	
		  Three 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. All went well until a few months ago when I noticed that the battery became sluggish after only a few starts. Now itâ€™s only good for one start before 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

	
Could have been something as simple as a defective battery (atypical lifespan). But if you were going 10-12 starts before recharging, that could well have seriously stressed it. Most batteries like to be kept within a range of charge states. Lithium might have a slightly wider range while maintaining full output voltage, but repeatedly taking them to near full discharge isn't healthy for them, either.

My personal choice is for me to be 5-10 lbs lighter than average, be healthier, and keep the extra Â $150 in my bank account. 

Charlie

_________________
Charlie

stuart(at)stuarthutchison
Guest

Posted: Wed Jun 29, 2022 8:52 pm Post subject: LiFe Battery

Good that the battery tender had a Lithium profile â€¦ 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 the battery, but the same rated Lead Acid can only be discharged to 50% before 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 LiFePO degrades in high-heat conditions the same way Li-Ion does â€¦ if so, firewall  forward wouldnâ€™t make much sense, but either way they have huge energy density and canâ€™t be extinguished with a typical fire extinguisher (because the degrading cathode liberates oxygen inside the case), so there's safety issue to consider in that too.

  

 Kind regards, Stu   [quote] On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)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 thing?   

 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 behavior 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 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(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote: 

 [quote] --> AeroElectric-List message posted by:  ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)  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 starting 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 "turn themselves off," when they get down to a 20% charge. Not a good thing in an aircraft. Cheers!   Stu. Ashley  ---

hivanhaecker(at)gmail.com
Guest

Posted: Wed Jun 29, 2022 9:30 pm Post subject: LiFe Battery

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, Iâ€™ll consider an Odyssey. But my gut feeling is that I

was just unlucky and got a â€œFriday afternoonâ€ 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(at)stuarthutchison.com.au> wrote:



[quote] Good that the battery tender had a Lithium profile â€¦ 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 the

 battery, but the same rated Lead Acid can only be discharged to 50% before

 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 LiFePO

 degrades in high-heat conditions the same way Li-Ion does â€¦ if so, firewall

 forward wouldnâ€™t make much sense, but either way they have huge energy

 density and canâ€™t be extinguished with a typical fire extinguisher (because

 the degrading cathode liberates oxygen inside the case), so there's safety

 issue to consider in that too.



 Kind regards, Stu

 On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska(at)gmail.com> wrote:



 I'm not sure the 20% cut off number is accurate; I suspect that it is not

kenryan

Joined: 20 Oct 2009
Posts: 429

Posted: Thu Jun 30, 2022 5:28 am Post subject: 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).Â 



On Wed, Jun 29, 2022 at 9:33 PM H. Ivan Haecker <hivanhaecker(at)gmail.com (hivanhaecker(at)gmail.com)> wrote:



[quote]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, Iâ€™ll consider an Odyssey. But my gut feeling is that I was just unlucky and got a â€œFriday afternoonâ€ 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(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:



[quote]     Good that the battery tender had a Lithium profile â€¦ maybe the battery was ultimately a dud or less than expected quality.Â  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 the battery, but the same rated Lead Acid can only be discharged to 50% before charge is necessary or permanent  damage can result.Â  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.Â  Unsure if LiFePO degrades in high-heat conditions the same way Li-Ion does â€¦ if so, firewall  forward wouldnâ€™t make much sense, but either way they have huge energy density and canâ€™t be extinguished with a typical fire extinguisher (because the degrading cathode liberates oxygen inside the case), so there's safety issue to consider in that too.

 

 

 Kind regards, Stu

 

 

 [quote] On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)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 thing?Â  

 

 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 behavior when you decide on the size battery you need.Â 

 

 

 Would it be nice if there was a switch you could throw to disable the BMS low voltage protection in a realÂ 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(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:

 

 [quote] --> AeroElectric-List message posted by:  ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)

 

 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 starting 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 "turn themselves off," when they get down to a 20% charge. Not a good thing in an aircraft.

 Cheers!Â  Â Stu. Ashley

 

 ---

Ceengland

Joined: 11 Oct 2020
Posts: 394
Location: MS

Posted: Thu Jun 30, 2022 6:04 am Post subject: LiFe Battery

 	  Quote: 	
		  "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 completelyÂ 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(at)gmail.com (keninalaska(at)gmail.com)> wrote:



[quote]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).Â 



On Wed, Jun 29, 2022 at 9:33 PM H. Ivan Haecker <hivanhaecker(at)gmail.com (hivanhaecker(at)gmail.com)> wrote:



[quote]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, Iâ€™ll consider an Odyssey. But my gut feeling is that I was just unlucky and got a â€œFriday afternoonâ€ 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(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:



[quote]     Good that the battery tender had a Lithium profile â€¦ maybe the battery was ultimately a dud or less than expected quality.Â  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 the battery, but the same rated Lead Acid can only be discharged to 50% before charge is necessary or permanent  damage can result.Â  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.Â  Unsure if LiFePO degrades in high-heat conditions the same way Li-Ion does â€¦ if so, firewall  forward wouldnâ€™t make much sense, but either way they have huge energy density and canâ€™t be extinguished with a typical fire extinguisher (because the degrading cathode liberates oxygen inside the case), so there's safety issue to consider in that too.

 

 

 Kind regards, Stu

 

 

 [quote] On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)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 thing?Â  

 

 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 behavior when you decide on the size battery you need.Â 

 

 

 Would it be nice if there was a switch you could throw to disable the BMS low voltage protection in a realÂ 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(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:

 

 [quote] --> AeroElectric-List message posted by:  ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)

 

 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 starting 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 "turn themselves off," when they get down to a 20% charge. Not a good thing in an aircraft.

 Cheers!Â  Â Stu. Ashley

 

 ---

_________________
Charlie

kenryan

Joined: 20 Oct 2009
Posts: 429

Posted: Thu Jun 30, 2022 7:16 am Post subject: 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 yourÂ post) that indicatedÂ that because the LiFe batteries still have energy left when theÂ BMS shuts them down, that is justification for rejecting the technology. I disagree,Â based on the above logic. FWIW





On Thu, Jun 30, 2022 at 6:13 AM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:



[quote] 	  Quote: 	
		  "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 completelyÂ 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(at)gmail.com (keninalaska(at)gmail.com)> wrote:



[quote]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).Â 



On Wed, Jun 29, 2022 at 9:33 PM H. Ivan Haecker <hivanhaecker(at)gmail.com (hivanhaecker(at)gmail.com)> wrote:



[quote]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, Iâ€™ll consider an Odyssey. But my gut feeling is that I was just unlucky and got a â€œFriday afternoonâ€ 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(at)stuarthutchison.com.au (stuart(at)stuarthutchison.com.au)> wrote:



[quote]     Good that the battery tender had a Lithium profile â€¦ maybe the battery was ultimately a dud or less than expected quality.Â  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 the battery, but the same rated Lead Acid can only be discharged to 50% before charge is necessary or permanent  damage can result.Â  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.Â  Unsure if LiFePO degrades in high-heat conditions the same way Li-Ion does â€¦ if so, firewall  forward wouldnâ€™t make much sense, but either way they have huge energy density and canâ€™t be extinguished with a typical fire extinguisher (because the degrading cathode liberates oxygen inside the case), so there's safety issue to consider in that too.

 

 

 Kind regards, Stu

 

 

 [quote] On 30 Jun 2022, at 2:15 am, Ken Ryan <keninalaska(at)gmail.com (keninalaska(at)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 thing?Â  

 

 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 behavior when you decide on the size battery you need.Â 

 

 

 Would it be nice if there was a switch you could throw to disable the BMS low voltage protection in a realÂ 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(at)broadstripe.net (ashleysc(at)broadstripe.net)> wrote:

 

 [quote] --> AeroElectric-List message posted by:  ashleysc(at)broadstripe.net (ashleysc(at)broadstripe.net)

 

 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 starting 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 "turn themselves off," when they get down to a 20% charge. Not a good thing in an aircraft.

 Cheers!Â  Â Stu. Ashley

 

 ---

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 30, 2022 8:42 am Post subject: LiFe Battery

At 12:49 AM 6/29/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Stuart Hutchison <stuart(at)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?"

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 30, 2022 12:52 pm Post subject: LiFe Battery

At 10:14 AM 6/30/2022, you wrote:

  	  Quote: 	
		  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?"

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 30, 2022 1:11 pm Post subject: LiFe Battery

At 08:58 AM 6/30/2022, you wrote:

  	  Quote: 	
		    	  Quote: 	
		  "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.



  	  Quote: 	
		    	  Quote: 	
		  . . . 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 completelyÂ 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?



  	  Quote: 	
		    	  Quote: 	
		  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?"

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 30, 2022 1:49 pm Post subject: LiFe Battery

 	  Quote: 	
		    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?"

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wsimpso1

Joined: 04 Nov 2018
Posts: 33
Location: Saline MI

Posted: Fri Jul 01, 2022 5:08 am Post subject: Re: LiFe Battery

The concerns I have with LiFe batteries - and these are not disqualifies - are:



Our baseline is SVLA battery and its connections, and they do have low but real chance of failing and dropping the battery out of the power loop, and we design our systems knowing this can happen. We live with the set of risk (severity times frequency) that this gives us, and we seem comfortable with it tooâ€¦



Go to LiFe batteries, and we probably have similar low levels of likelihood of a mechanical failure causing us to lose the battery, but now we have added to that there is a set of gadgets internal to the battery that is designed to remove the battery from the power loop. At some level, it too can have failures that cause us to lose the battery, even if nothing is wrong. This is adding failure modes to our system. 



In most industries, when we add failure modes, we have to be able to show that aggregate risk is actually made smaller by doing so. In order to make up for adding some risk (sum of severity times frequency for new failure modes) to the already present risk from the battery, well, the new risk has to be really small AND the existing risk has to be made smaller. 



Maybe the LiFe batteries do pose small enough risk compared to SVLA batteries and our failure tolerant design covers battery failure adequately. I will remain skeptical until there is a lot more data indicating LiFe are in total of lower risk to us. 



Bill

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 01, 2022 3:24 pm Post subject: LiFe Battery

 	  Quote: 	
		  Our baseline is SVLA battery and its connections,

 and they do have low but real chance of failing and

 dropping the battery out of the power loop,

 and we design our systems knowing this can happen. 	


  I've never had occasion to consider this as

  a 'factor' in either OBAM or TC aircraft 

  designs. What is your evidence for frequency

  of the event . . . and what are the design

  rules for mitigating effects of such an event?



  	  Quote: 	
		  Go to LiFe batteries, and we probably have similar low

 levels of likelihood of a mechanical failure . . .

  <snip 	
 . . . is adding failure modes to our system.



   Okay, are you aware of any such incident and what

   was the outcome of that incident?



  	  Quote: 	
		  Maybe the LiFe batteries do pose small enough risk

 compared to SVLA batteries and our failure tolerant

 design covers battery failure adequately. I will

 remain skeptical until there is a lot more data

 indicating LiFe are in total of lower risk to us. 	


   Okay, BOTH technologies will no doubt be controlled

   with a battery contactor and master switch. Artful

   FMEA says account for risk of loss for those

   components.



   Now, what difference does it make if your add

   more electro-whizzies into the analysis? Accommodating

   failure of the battery contactor, by extension, covers

   all other failures that manifest as a battery-disconnect

   event.



   So how does failure of the BMS to convey energy

   out of the battery become more than a maintenance

   event?



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

wsimpso1

Joined: 04 Nov 2018
Posts: 33
Location: Saline MI

Posted: Sat Jul 02, 2022 7:24 pm Post subject: Re: LiFe Battery

All things can break. The question of this experienced product engineer is then how often does this occur and how severe is the result of a failure. Some might take the perspective that the risk of completely losing the battery is vanishingly small. Others might say we already have that failure mode covered, so it is no big deal. OK for you guys.  



I do know of two pilots I have reason to trust who have described their own experiences with a total failure of a battery (not wiring, but an internal failure that isolated the battery electrically from the airplane) while in flight. While anecdotal, I suspect that gives us some reason to believe that such a failure has some real frequency in our airplanes. I have no idea how small this frequency is and admit that I know nothing of the rest of the maintenance state of these batteries. 



The two events occurred in flight. One was detected by an oscillating ammeter reading then the alternator field breaker tripped (or a reset was attempted), resulting in a total electrical failure. In the other case the alternator stayed online until shut off on the ground, and was found that the battery was off line. In both cases the airplanes were simple magneto fired engines being flown in VMC, and were flown to airports for safe landings, which only reinforces our training here that adequate backup really should be present for the failures we think are real.



Adding failure modes to a system does increase total risk from the system (risk = severity * frequency) unless other parts of the system have been made more reliable in the same process. I suspect that internal battery connections are not much different in SVLA and in LiFe batteries, but I could be wrong.



As we are trained on AEC, the concerned designer can examine the failure modes and see to it that any failure mode does not result in a severe outcome nor unnecessarily raise total risk by checking for and perhaps adding suitable redundancy. That issue does not change, but I do suspect that batteries with added internal gadgets may well have higher likelihood of total failure. Be forewarned and design accordingly.



Bill Simpson

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 04, 2022 8:49 am Post subject: LiFe Battery

 	  Quote: 	
		  Others might say we already have that failure mode

 covered, so it is no big deal. OK for you guys. 	


   How does one arrive at a conclusion of

   'no big deal'?  There are no suppositions

   allowed in the conduct of an FMEA. Some things

   are known by simple deduction . . . if that

   wire becomes unhooked, some electro-whizzy

   ceases to function.



   But what about that battery disconnect

   thing? There are a number of variables that

   drive the system's ability to function.

   Regulator design, alternator dynamics,

   nature of operating loads. FEMA credit

   for any particular failure cannot be

   claimed without CONFIRMATION of a

   condition for which there is no obvious

   or first-hand knowledge.



 

  	  Quote: 	
		  I do know of two pilots I have reason to trust who have described their own experiences with a total failure of a battery (not wiring, but an internal failure that isolated the battery electrically from the airplane) while in flight. While anecdotal, I suspect that gives us some reason to believe that such a failure has some real frequency in our airplanes. I have no idea how small this frequency is and admit that I know nothing of the rest of the maintenance state of these batteries. 	




   It would have been interesting to do a 

   failure analysis on the subject batteries. 



   Exactly. Yes, there are cases where batteries

   have gone open-circuit. Skip Koss (Concorde

   battery guru) related several events to

   me . . . post event teardown revealed

   manufacturing defects. In his tenure with

   Concorde, he could count those events 

   the fingers of one hand.



 

   All cases occurred in aircraft that would

   function alternator-only. The famous

   (or infamous) split-rocker switch was

   birthed out of a concern for alternator-

   only operations. Generators would run

   happily sans-battery but those alternators

   were a new thing. I was a lowly tech-writer

   back then an not privy to any testing

   or perceptions of risk experienced by the

   engineers. Nonetheless, whether or not it

   was really necessary in all cases, the split

   rocker became firmly embedded in aviation

   zeitgeist for about 60 years.



   A few years later, I was tasked to craft a

   new regulator design for the Bonanzas and

   Barons. I was astonished to read that Beech

   expected an alternator to start up cold and

   run sans-battery. Cold start? No battery?

   Seems that these airplanes had independent

   alternator and battery switches. There was

   no prohibition in the POH for alternator-only

   operations. Further, the alternators being

   used at the time had residual field flux that

   would permit start-up sans battery. That's

   a long story!



  	  Quote: 	
		  The two events occurred in flight. One was detected by an oscillating ammeter reading then the alternator field breaker tripped (or a reset was attempted), resulting in a total electrical failure. In the other case the alternator stayed online until shut off on the ground, and was found that the battery was off line. In both cases the airplanes were simple magneto fired engines being flown in VMC, and were flown to airports for safe landings, which only reinforces our training here that adequate backup really should be present for the failures we think are real. 	


   To be sure, artful FMEA discovers and mitigates

   real risks. Suppositions requiring verification

   need to be tested. While doing the obligatory

   test-area-flyoff with a new or recently modified

   airplane, one is well advised to do the good

   test pilot things and confirm/refine your

   plan-A/plan-B operations.

  



  	  Quote: 	
		  Adding failure modes to a system does increase total risk from the system (risk = severity * frequency) unless other parts of the system have been made more reliable in the same process. I suspect that internal battery connections are not much different in SVLA and in LiFe batteries, but I could be wrong. 	


   The unfortunate thing about the dark-n-stormy-night

   stories is that they very seldom achieve resolution

   of root causes. The instances you've cited

   cannot rise above anecdotal status without

   investigation and discovery of root cause.

   But they certainly contribute to builder/pilots

   who have 'worries' but lack tools for mitigation.



   This is the beauty of FMEA . . . we don't wrestle

   with failure rates we only study outcome of flight

   assuming that the failure will occur. It matters

   not if MTBF on the thing is 1000 or 100 hours.



 

  	  Quote: 	
		  As we are trained on AEC, the concerned designer can examine the failure modes and see to it that any failure mode does not result in a severe outcome nor unnecessarily raise total risk by checking for and perhaps adding suitable redundancy. That issue does not change, but I do suspect that batteries with added internal gadgets may well have higher likelihood of total failure. Be forewarned and design accordingly. 	


   True . . . but artful design is limited by

   a lack of information. The 'scientific method'

   demands that every supposition be questioned.

   The more folks participating in the conversation

   the better. 



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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