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5th year of living dangerously with LiFePo4 batteries



 
 
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  #21  
Old June 5th 18, 08:11 PM posted to rec.aviation.soaring
Martin Gregorie[_6_]
external usenet poster
 
Posts: 699
Default 5th year of living dangerously with LiFePo4 batteries

On Tue, 05 Jun 2018 11:42:49 -0700, Frank Whiteley wrote:

Sadly, not entirely unrelated to this thread. This was the plane used
in the recent glider tow.

https://electrek.co/2018/06/04/sieme...rototype-fire-

crash-death/



A few years back there were a lot of cheap LiIon batteries on sale as SLA
replacements that turned out not to have a BMS system - just cells in the
case. Obviously, these would be at least as flammable as an SLA of
accidentally shorted.

IIRC these were impossible to distinguish from batteries with a proper BMS
inside the case, so, are they still around and being sold to the unwary?


--
Martin | martin at
Gregorie | gregorie dot org
  #22  
Old June 5th 18, 09:32 PM posted to rec.aviation.soaring
jfitch
external usenet poster
 
Posts: 1,134
Default 5th year of living dangerously with LiFePo4 batteries

On Tuesday, June 5, 2018 at 11:21:08 AM UTC-7, K m wrote:
On Tuesday, June 5, 2018 at 9:55:30 AM UTC-6, jfitch wrote:
On Tuesday, June 5, 2018 at 7:08:03 AM UTC-7, kinsell wrote:
On 06/04/2018 09:59 AM, jfitch wrote:
On Monday, June 4, 2018 at 6:55:55 AM UTC-7, krasw wrote:
On Monday, 4 June 2018 02:01:18 UTC+3, jfitch wrote:
On Sunday, June 3, 2018 at 8:29:08 AM UTC-7, Richard Pfiffner wrote:
On Sunday, June 3, 2018 at 8:18:49 AM UTC-7, Nick Kennedy wrote:
So is the problem of a fire caused by a dead short across the battery terminals?
Shouldn't a inline fuse coming off the positive terminal take care of any fire problem? I realize a wrench or something like it placed across the terminals would cause a massive short and possible fire, but lacking that, whats the problem?
Do these things spontaneously combust? I have two in my ship and want to know.

I shorted two different batteries, by placing upside down on a metal plate.

The LiFEPO4 was a non event. The battery management shut down immediately.

On the other hand the Lead Acid got quite hot melted the case.

Richard

There you go bringing real data into the discussion again.

I would like krasw to elaborate on the event, if he knows more. Anything that stores energy is potentially dangerous. The devil is in the details.

So far I have no other info, battery was smoking after removed from the glider. Was it LFP cells or BMS electronics, I don't know.

Keeping sco so far we have one FAA documented fire due to an SLA battery leading to the loss of the aircraft, against a rumor of a smoking battery that may or may not have been LFP which was removed from the glider on landing without damage to it. Other lithium chemistries are irrelevant, unless you are using those in your glider (such as the FES).


Wow! Did you read a different report than I did? What I saw was from
the NTSB (the folks who do the investigations), it used the term "gell
cell" instead of SLA, and most importantly it assigned no blame to the
battery. It said there was enough fire damage that they couldn't
determine if there was arcing on the terminals. They did find signs of
arcing on the wiring. That's quite a jump to calling it a "fire due to
an SLA battery", isn't it?

Apparently a "rumor" is something you don't want to believe, and a
"fact" is something you do.


A couple of facts: A gel battery IS an SLA battery. Its I/V characteristics and chemistry are substantially identical to an AGM, which is also an SLA battery. The only difference is in how the acid is immobilized. Second fact, a battery - any battery - does not spontaneously combust. If they do so, it is while being charged or discharged, usually under out-of-spec circumstances. Another fact: most electrical fires are caused by faults in wiring. Some further facts: the incident in question was caused without question by the SLA battery. It was an electrical fire which would not have occurred had the battery not been present, and therefore a proximate cause. A fact that you will find very inconvenient: had that battery been a properly constructed LFP, the incident would not have occurred. As Richard has pointed out above, the BMS would simply have disconnected the output and the glider would have landed without incident. For mitigation of wiring faults (by far the highest cause of electrical fires) an LFP is much safer than an SLA battery, which has no such protections.

Once again, you can use whatever battery you like, but you don't get to use "alternative facts".

And finally, I do believe in facts, and I don't (necessarily) believe in rumors.


Fitchy, Here is a "Fact" you may find inconvenient, You could stand to lighten up. An electrical fire in ANY glider with a battery installed would not occur if it were not present (Laughing), now would it? Whats your point? Granted they guy got the name a little mixed up (AGM, SLA, Gel Cel, whatever) but a proper SLA or AMG installation is as safe as anything out there.. Why do you think auto manufacturers have been putting terminal covers on batteries for the past 30 years or so? Post crash fire protection.

Kirk

And finally, I believe in facts, but I also like rumors, innuendo, wives tales urban legends, hoaxes, and a lot of the stuff on RAS.


K m, I'm pretty light already . And my point is exactly as you took it: ANY battery stores energy and is a potential hazard unless installed correctly. (The fire in this case was pre-crash, but your point is valid). The difference in risk between SLA or LFP chemistry storing the energy is quite small, if both are correctly installed. There is a valid argument that LFP (with proper BMS) is safer since the protection is inside the case - even if you directly short the terminals, it will fault and disconnect. This is not true of available SLA batteries.

For about the 10th time, I'm not evangelizing the use of a particular battery. I AM correcting errors of fact where they are publicly stated. I didn't say I didn't like rumors. I said I don't (necessarily) believe them.

While we are at it, while the electric plane crash is a tragedy and related to FES sailplanes which use similar batteries, it is unrelated to the LFP batteries used to power instruments in sailplanes. Take a look at the link provided by Tom above (you'll have to hack into his computer to get it....) or any of the many studies on this topic.
  #23  
Old June 5th 18, 09:35 PM posted to rec.aviation.soaring
kinsell
external usenet poster
 
Posts: 546
Default 5th year of living dangerously with LiFePo4 batteries

On 06/05/2018 01:11 PM, Martin Gregorie wrote:
On Tue, 05 Jun 2018 11:42:49 -0700, Frank Whiteley wrote:

Sadly, not entirely unrelated to this thread. This was the plane used
in the recent glider tow.

https://electrek.co/2018/06/04/sieme...rototype-fire-

crash-death/



A few years back there were a lot of cheap LiIon batteries on sale as SLA
replacements that turned out not to have a BMS system - just cells in the
case. Obviously, these would be at least as flammable as an SLA of
accidentally shorted.


Replace "at least" with "far more'. SLA's are way down at the bottom of
the list when it comes to flammability.


IIRC these were impossible to distinguish from batteries with a proper BMS
inside the case, so, are they still around and being sold to the unwary?



Not sure what a "proper" BMS board is. There are a variety of functions
that may be included, the data sheets tend to vague on what's in there.
See Wikipedia for a primer.

If the battery can disconnect itself from the terminals in the event of
excessive discharge current, too high of charging voltage, or too low
voltage on discharge, then it requires some high-current switches to do
the job. It's a dangerous assumption to think that a battery must have
those capabilities included.
  #24  
Old June 5th 18, 10:06 PM posted to rec.aviation.soaring
Jim White[_3_]
external usenet poster
 
Posts: 286
Default 5th year of living dangerously with LiFePo4 batteries

Buy one with a fuse built in?

  #25  
Old June 5th 18, 10:10 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 465
Default 5th year of living dangerously with LiFePo4 batteries

On Tuesday, June 5, 2018 at 2:42:51 PM UTC-4, Frank Whiteley wrote:
On Tuesday, June 5, 2018 at 12:21:08 PM UTC-6, K m wrote:
On Tuesday, June 5, 2018 at 9:55:30 AM UTC-6, jfitch wrote:
On Tuesday, June 5, 2018 at 7:08:03 AM UTC-7, kinsell wrote:
On 06/04/2018 09:59 AM, jfitch wrote:
On Monday, June 4, 2018 at 6:55:55 AM UTC-7, krasw wrote:
On Monday, 4 June 2018 02:01:18 UTC+3, jfitch wrote:
On Sunday, June 3, 2018 at 8:29:08 AM UTC-7, Richard Pfiffner wrote:
On Sunday, June 3, 2018 at 8:18:49 AM UTC-7, Nick Kennedy wrote:
So is the problem of a fire caused by a dead short across the battery terminals?
Shouldn't a inline fuse coming off the positive terminal take care of any fire problem? I realize a wrench or something like it placed across the terminals would cause a massive short and possible fire, but lacking that, whats the problem?
Do these things spontaneously combust? I have two in my ship and want to know.

I shorted two different batteries, by placing upside down on a metal plate.

The LiFEPO4 was a non event. The battery management shut down immediately.

On the other hand the Lead Acid got quite hot melted the case.

Richard

There you go bringing real data into the discussion again.

I would like krasw to elaborate on the event, if he knows more. Anything that stores energy is potentially dangerous. The devil is in the details.

So far I have no other info, battery was smoking after removed from the glider. Was it LFP cells or BMS electronics, I don't know.

Keeping sco so far we have one FAA documented fire due to an SLA battery leading to the loss of the aircraft, against a rumor of a smoking battery that may or may not have been LFP which was removed from the glider on landing without damage to it. Other lithium chemistries are irrelevant, unless you are using those in your glider (such as the FES).


Wow! Did you read a different report than I did? What I saw was from
the NTSB (the folks who do the investigations), it used the term "gell
cell" instead of SLA, and most importantly it assigned no blame to the
battery. It said there was enough fire damage that they couldn't
determine if there was arcing on the terminals. They did find signs of
arcing on the wiring. That's quite a jump to calling it a "fire due to
an SLA battery", isn't it?

Apparently a "rumor" is something you don't want to believe, and a
"fact" is something you do.

A couple of facts: A gel battery IS an SLA battery. Its I/V characteristics and chemistry are substantially identical to an AGM, which is also an SLA battery. The only difference is in how the acid is immobilized. Second fact, a battery - any battery - does not spontaneously combust. If they do so, it is while being charged or discharged, usually under out-of-spec circumstances. Another fact: most electrical fires are caused by faults in wiring. Some further facts: the incident in question was caused without question by the SLA battery. It was an electrical fire which would not have occurred had the battery not been present, and therefore a proximate cause. A fact that you will find very inconvenient: had that battery been a properly constructed LFP, the incident would not have occurred. As Richard has pointed out above, the BMS would simply have disconnected the output and the glider would have landed without incident. For mitigation of wiring faults (by far the highest cause of electrical fires) an LFP is much safer than an SLA battery, which has no such protections.

Once again, you can use whatever battery you like, but you don't get to use "alternative facts".

And finally, I do believe in facts, and I don't (necessarily) believe in rumors.


Fitchy, Here is a "Fact" you may find inconvenient, You could stand to lighten up. An electrical fire in ANY glider with a battery installed would not occur if it were not present (Laughing), now would it? Whats your point? Granted they guy got the name a little mixed up (AGM, SLA, Gel Cel, whatever) but a proper SLA or AMG installation is as safe as anything out there. Why do you think auto manufacturers have been putting terminal covers on batteries for the past 30 years or so? Post crash fire protection.

Kirk

And finally, I believe in facts, but I also like rumors, innuendo, wives tales urban legends, hoaxes, and a lot of the stuff on RAS.


Sadly, not entirely unrelated to this thread. This was the plane used in the recent glider tow.

https://electrek.co/2018/06/04/sieme...e-crash-death/

Frank Whiteley


Not entirely unrelated either - from the memoirs of Dezi Hamvas at the GBSC web site. This is about a "wet" lead-acid battery.

"On a very hot day, the Bird Dog refused to start after a long cranking. After it finally started, I made the first uneventful tow. At touchdown, the 24-volt military battery exploded between my legs right into my face. The cockpit instantly filled with white, very sour tasting, burning smoke. In a panic, I turned off the magneto and rolled out of the Bird Dog while it was still rolling. I ran to the hangar and washed my face and arms, ending up with only a minor skin rash.

While the battery was recharging, it accumulated Hydrogen gas in its chambers.
The gas vented out with a ¼” tube to the bottom of the Bird Dog. The engine
exhaust pipe was pointing right to the end of the Hydrogen exhaust tube. The spark from the backfiring engine ignited the gas, and burned all the way back to the battery. After this episode, we moved the battery to the back seat and rerouted the Hydrogen exhaust. Think about this when you have a ride in the back seat."
  #26  
Old June 5th 18, 10:20 PM posted to rec.aviation.soaring
Martin Gregorie[_6_]
external usenet poster
 
Posts: 699
Default 5th year of living dangerously with LiFePo4 batteries

On Tue, 05 Jun 2018 14:35:42 -0600, kinsell wrote:

Not sure what a "proper" BMS board is. There are a variety of functions
that may be included, the data sheets tend to vague on what's in there.
See Wikipedia for a primer.

I'd say it must have these functions:

- cell-balancing charging management
- low-voltage shut-down
- some sort of high-current limiting
This need not be expensive: I'd accept built-in replaceable fuses
and holders or solid state current limiters that temporarily
disconnect the battery when the load becomes excessive.
Neither are exactly what you'd call new technology.


If the battery can disconnect itself from the terminals in the event of
excessive discharge current, too high of charging voltage, or too low
voltage on discharge, then it requires some high-current switches to do
the job.

Inexpensive built-in fuses can handle that perfectly well.


--
Martin | martin at
Gregorie | gregorie dot org
  #27  
Old June 5th 18, 10:44 PM posted to rec.aviation.soaring
Martin Gregorie[_6_]
external usenet poster
 
Posts: 699
Default 5th year of living dangerously with LiFePo4 batteries

On Tue, 05 Jun 2018 21:06:06 +0000, Jim White wrote:

Buy one with a fuse built in?


Yes, but preferably one with a low voltage cut-off and cell-balancer for
charging as well.

But what I was pointing out is that a year or so back there were brands
that were very similar from the outside and (in some cases) had similar
prices. Some of these had BMS fitted and some just had cells wired to the
terminals. Often the descriptions didn't mention whether they had a BMS
or not.

What I want to know is whether this undocumented mess is still the case
or if you can now read published descriptions and know, with a fair
degree of confidence, whether there is or is not a BMS and current
limiter inside without having to chop the battery open to find out.

If the adverts now give reliable information about this, then I'll
investigate further: if not, I'll stick to SLAs for a while yet.


--
Martin | martin at
Gregorie | gregorie dot org
  #28  
Old June 6th 18, 04:10 AM posted to rec.aviation.soaring
jfitch
external usenet poster
 
Posts: 1,134
Default 5th year of living dangerously with LiFePo4 batteries

On Tuesday, June 5, 2018 at 2:44:10 PM UTC-7, Martin Gregorie wrote:
On Tue, 05 Jun 2018 21:06:06 +0000, Jim White wrote:

Buy one with a fuse built in?


Yes, but preferably one with a low voltage cut-off and cell-balancer for
charging as well.

But what I was pointing out is that a year or so back there were brands
that were very similar from the outside and (in some cases) had similar
prices. Some of these had BMS fitted and some just had cells wired to the
terminals. Often the descriptions didn't mention whether they had a BMS
or not.

What I want to know is whether this undocumented mess is still the case
or if you can now read published descriptions and know, with a fair
degree of confidence, whether there is or is not a BMS and current
limiter inside without having to chop the battery open to find out.

If the adverts now give reliable information about this, then I'll
investigate further: if not, I'll stick to SLAs for a while yet.


--
Martin | martin at
Gregorie | gregorie dot org


You are right to want to know what's in the box. In any case, you should have an external fuse immediately following the battery, since the BMS (if present) is unlikely to limit the current sufficient for most glider wiring. The BMS will protect against short circuited terminals, your fuse should protect the wiring you've chosen.

Another point that should be raised: in lithium polymer and some other chemistries, the BMS is essential to safely charge and discharge the battery. In an LFP, its function has more to do with protecting the cells from an early death due to undercharge, cell balance, or overcharge, than fire safety.. You can probably start one on fire by severely overcharging it, as you can do with any battery (even a flashlight D cell). Undercharging or cell balancing will result in unsatisfactory performance, rather than a fire. You can find some vendors LFP specs that tell you what the BMS does.
  #29  
Old June 6th 18, 05:03 AM posted to rec.aviation.soaring
2G
external usenet poster
 
Posts: 1,439
Default 5th year of living dangerously with LiFePo4 batteries

On Tuesday, June 5, 2018 at 1:32:31 PM UTC-7, jfitch wrote:
On Tuesday, June 5, 2018 at 11:21:08 AM UTC-7, K m wrote:
On Tuesday, June 5, 2018 at 9:55:30 AM UTC-6, jfitch wrote:
On Tuesday, June 5, 2018 at 7:08:03 AM UTC-7, kinsell wrote:
On 06/04/2018 09:59 AM, jfitch wrote:
On Monday, June 4, 2018 at 6:55:55 AM UTC-7, krasw wrote:
On Monday, 4 June 2018 02:01:18 UTC+3, jfitch wrote:
On Sunday, June 3, 2018 at 8:29:08 AM UTC-7, Richard Pfiffner wrote:
On Sunday, June 3, 2018 at 8:18:49 AM UTC-7, Nick Kennedy wrote:
So is the problem of a fire caused by a dead short across the battery terminals?
Shouldn't a inline fuse coming off the positive terminal take care of any fire problem? I realize a wrench or something like it placed across the terminals would cause a massive short and possible fire, but lacking that, whats the problem?
Do these things spontaneously combust? I have two in my ship and want to know.

I shorted two different batteries, by placing upside down on a metal plate.

The LiFEPO4 was a non event. The battery management shut down immediately.

On the other hand the Lead Acid got quite hot melted the case.

Richard

There you go bringing real data into the discussion again.

I would like krasw to elaborate on the event, if he knows more. Anything that stores energy is potentially dangerous. The devil is in the details.

So far I have no other info, battery was smoking after removed from the glider. Was it LFP cells or BMS electronics, I don't know.

Keeping sco so far we have one FAA documented fire due to an SLA battery leading to the loss of the aircraft, against a rumor of a smoking battery that may or may not have been LFP which was removed from the glider on landing without damage to it. Other lithium chemistries are irrelevant, unless you are using those in your glider (such as the FES).


Wow! Did you read a different report than I did? What I saw was from
the NTSB (the folks who do the investigations), it used the term "gell
cell" instead of SLA, and most importantly it assigned no blame to the
battery. It said there was enough fire damage that they couldn't
determine if there was arcing on the terminals. They did find signs of
arcing on the wiring. That's quite a jump to calling it a "fire due to
an SLA battery", isn't it?

Apparently a "rumor" is something you don't want to believe, and a
"fact" is something you do.

A couple of facts: A gel battery IS an SLA battery. Its I/V characteristics and chemistry are substantially identical to an AGM, which is also an SLA battery. The only difference is in how the acid is immobilized. Second fact, a battery - any battery - does not spontaneously combust. If they do so, it is while being charged or discharged, usually under out-of-spec circumstances. Another fact: most electrical fires are caused by faults in wiring. Some further facts: the incident in question was caused without question by the SLA battery. It was an electrical fire which would not have occurred had the battery not been present, and therefore a proximate cause. A fact that you will find very inconvenient: had that battery been a properly constructed LFP, the incident would not have occurred. As Richard has pointed out above, the BMS would simply have disconnected the output and the glider would have landed without incident. For mitigation of wiring faults (by far the highest cause of electrical fires) an LFP is much safer than an SLA battery, which has no such protections.

Once again, you can use whatever battery you like, but you don't get to use "alternative facts".

And finally, I do believe in facts, and I don't (necessarily) believe in rumors.


Fitchy, Here is a "Fact" you may find inconvenient, You could stand to lighten up. An electrical fire in ANY glider with a battery installed would not occur if it were not present (Laughing), now would it? Whats your point? Granted they guy got the name a little mixed up (AGM, SLA, Gel Cel, whatever) but a proper SLA or AMG installation is as safe as anything out there. Why do you think auto manufacturers have been putting terminal covers on batteries for the past 30 years or so? Post crash fire protection.

Kirk

And finally, I believe in facts, but I also like rumors, innuendo, wives tales urban legends, hoaxes, and a lot of the stuff on RAS.


K m, I'm pretty light already . And my point is exactly as you took it: ANY battery stores energy and is a potential hazard unless installed correctly. (The fire in this case was pre-crash, but your point is valid). The difference in risk between SLA or LFP chemistry storing the energy is quite small, if both are correctly installed. There is a valid argument that LFP (with proper BMS) is safer since the protection is inside the case - even if you directly short the terminals, it will fault and disconnect. This is not true of available SLA batteries.

For about the 10th time, I'm not evangelizing the use of a particular battery. I AM correcting errors of fact where they are publicly stated. I didn't say I didn't like rumors. I said I don't (necessarily) believe them.

While we are at it, while the electric plane crash is a tragedy and related to FES sailplanes which use similar batteries, it is unrelated to the LFP batteries used to power instruments in sailplanes. Take a look at the link provided by Tom above (you'll have to hack into his computer to get it.....) or any of the many studies on this topic.


Sorry about that - try this link:

http://www.mdpi.com/2313-0105/3/2/14/htm

Tom
  #30  
Old June 6th 18, 04:38 PM posted to rec.aviation.soaring
kinsell
external usenet poster
 
Posts: 546
Default 5th year of living dangerously with LiFePo4 batteries

On 06/05/2018 03:20 PM, Martin Gregorie wrote:
On Tue, 05 Jun 2018 14:35:42 -0600, kinsell wrote:

Not sure what a "proper" BMS board is. There are a variety of functions
that may be included, the data sheets tend to vague on what's in there.
See Wikipedia for a primer.

I'd say it must have these functions:

- cell-balancing charging management
- low-voltage shut-down
- some sort of high-current limiting
This need not be expensive: I'd accept built-in replaceable fuses
and holders or solid state current limiters that temporarily
disconnect the battery when the load becomes excessive.
Neither are exactly what you'd call new technology.

Not new technology, but the switch needs to handle the maximum current
that the battery can be called on to deliver. Many applications are
going to involve more than an amp or two to power a sailplane panel.




If the battery can disconnect itself from the terminals in the event of
excessive discharge current, too high of charging voltage, or too low
voltage on discharge, then it requires some high-current switches to do
the job.

Inexpensive built-in fuses can handle that perfectly well.


Fuses can handle the overcurrent, but disconnecting on high or low
voltage isn't going to be cheap, if the battery is rated for high current.

Richard had an interesting post a while ago, where he accidentally used
the wrong charger on an FLP, and battery was destroyed due to swelling.
So much for the idea of a BMS protecting the battery.

-Dave






 




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