5th year of living dangerously with LiFePo4 batteries

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.

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

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

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.

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

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

On Wed, 06 Jun 2018 09:38:36 -0600, kinsell wrote:

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.


Using the wrong charger, or a multi-chemistry charger on the wrong
setting, can destroy any battery, regardless of its chemistry.

A BMS probably won't help here because the charger may not trip the max-
voltage switch and the charge balancer is only there to bring any cells
that are under- or over-charged into line with the rest.


--
Martin | martin at
Gregorie | gregorie dot org

One example does not prove all BMS cannot protect the battery.
I see no eveidence that Life is any more prone to failiure than SLA gell cells.

Buy one with a fuse built in?

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