Letter from ABYC President re LiFePo4 safety on boats

[cs1234]

RandyP, let's not cause confusion. The topic is "...LiFePo4 Safety on boats" not Solid State Lithium Ion which is clearly not the same chemistry as the video shows.

I think the confusion comes from @Will Prowse youtube videos screen grab / title. Without the context from the previous video, you might think the flaming wreckage in the window on the upper left is a LiFePO4 in flames and that the answer is: Yes, it will erupt in flames.

 

[Goboatingnow]

From I've heard that the danger is often not the battery itself, but rather by the equipment connected to the battery when the system has a fault.

For example, a battery charging directly from alternator with no DC-DC converter. BMS triggers over-charge-current protection (typically at a low SOC), causes a MASSIVE voltage spike, and this voltage spike is where the danger lies, often blowing up inverters, controllers, ECU's, etc.

Sure, proper design on this equipment often causes fuses to blow when damage occurs, and it doesn't lead to a fire.. but the one system I saw go south had 90vDC on a 12v system...I can see that leading to a fire one way or another.

This is not correct. Because such an alternator without proper protection is an incorrect system. One of the current issues is people are installation half naked li systems and dining understand fully what they install.

Hence a proper li install will never cause the issue you describe as proper alternator protection will be in place. Yes you might loose some sensitive electronics but it WILL NOT start a fire.

Oh and fuses will not protect alternators or electronics. as they are too slow. Fuses protect wires not systems.

Any system you saw that put 90vDC onto a 12v is incorrectly designed or dramatically poorly protected and has no place on a boat.

 

[HighTechLab]

This is not correct. Because such an alternator without proper protection is an incorrect system. One of the current issues is people are installation half naked li systems and dining understand fully what they install.

Hence a proper li install will never cause the issue you describe as proper alternator protection will be in place. Yes you might loose some sensitive electronics but it WILL NOT start a fire.

Oh and fuses will not protect alternators or electronics. as they are too slow. Fuses protect wires not systems.

Any system you saw that put 90vDC onto a 12v is incorrectly designed or dramatically poorly protected and has no place on a boat.

Please read my post again, I believe you misunderstood my point.

Please also consider it as a reply to the original post, for context.

 

[Vigo]

Pretty much every electromagnetic coil on a 12v circuit has a 60-70v spike when you turn it off. Fires are barely a related issue. The thing with fire is you have to have heat being transferred into something flammable for a long enough time to raise the temp to a dangerous level. All kinds of things which are operating normally have very brief conditions where if it WASNT brief it could lead to a fire, and it's normal.

So really, you gotta talk about the time factor when you are worried about a certain voltage or current level as it relates to a fire.

 

[HighTechLab]

you have to have heat being transferred into something flammable for a long enough time to raise the temp to a dangerous level

I do think it is important to consider on a boat fuel vapors may be present which makes this not the whole story...a spark of a blowing component could set off an explosive chain reaction.

 

[RandyP]

RandyP, let's not cause confusion. The topic is "...LiFePo4 Safety on boats" not Solid State Lithium Ion which is clearly not the same chemistry as the video shows.

Agree. But some do not even know there is a difference between LFP and LI battery designation. This set of videos can promote interest in the differnece, and also accentuate 'LiFePO4 Safety in boats'.
I'm glad you replied so all will know the narrow lane of your interpretation of this posts subject.
NOW, LETS STAY ON TRACK, ALL OF YOU (INCLUDING ME). ! Thanks.

 

[RandyP]

RandyP, let's not cause confusion. The topic is "...LiFePo4 Safety on boats" not Solid State Lithium Ion which is clearly not the same chemistry as the video shows.

The cell in the out of scope video is not a Solid State lithium cell, it is a NMC (LI) cell.

 

[Goboatingnow]

From I've heard that the danger is often not the battery itself, but rather by the equipment connected to the battery when the system has a fault.

For example, a battery charging directly from alternator with no DC-DC converter. BMS triggers over-charge-current protection (typically at a low SOC), causes a MASSIVE voltage spike, and this voltage spike is where the danger lies, often blowing up inverters, controllers, ECU's, etc.

Sure, proper design on this equipment often causes fuses to blow when damage occurs, and it doesn't lead to a fire.. but the one system I saw go south had 90vDC on a 12v system...I can see that leading to a fire one way or another.

Just to return to this

Firstly alternator disconnect is in itself not dangerous. The term is known as load dumping

The voltage generated is v= L(di/dt) most alternators are around 300uH for example.

So several conditions must exist primarily significant current must be flowing , and that current must be abruptly terminated

Secondly most though not all alternators are Built to automotive standards such as ISO 7637-2 and SAE J1113-11 and these alternators are specifically designed to survive upto 140v spikes from load dumps.

The issue is of course your other electronics at the rated so.

But the fact is it’s actually easy enough to design and fit TVS based transient protectors that will clamp the voltage to about 20v. All your electronics need of course Be able to handle that. The trouble is some brands of marine electronics are poorly designed for transients.

Hence the whole issue of alternator spikes is utterly overplayed in marine discussions. Virtually no one has actually tested load dumping on boats and too much talk is “ conjecture “ and supposition.

I have an alternator test bed and can actually document what happens.

So the whole debate on LFP in boats is far too based on opinion , personal peccadilloes and unwarranted technical speculation in my opinion. Actual hard data is needed.

An technical analysis of my recent lightning strike suggests about 150v was coupled into the DC system. This took out almost everything connected to the battery , including the alternator , all my Chinese led and Chinese cheap invertor survived , all my Victron and raymarine gear died !

Hence we need to place potential failure mode analysis of LFP in context

 

[audiobill5]

Currently there are three types of lead-acid cell used in the US. Navy's fleet of nuclear-powered submarines...

Apparently the Navy is not ready switch. NASA likes lithium-ion.

In its final configuration, the space station now has three lithium-ion batteries for each channel, each with a service life lasting nearly 10 years. With eight channels, 24 lithium-ion batteries on board replaced 48 nickel-hydrogen batteries.

Spacewalkers Complete Multi-Year Station Battery Upgrades

Spacewalkers Complete Multi-Year Effort to Upgrade Space Station Batteries

www.nasa.gov

| 12V Lithium Batteries for RV, Marine, Solar, Golf Cart and Automotive

CHARGEX® | Lithium Battery Manufacturer for RV, Marine, Golf Carts, Solar & Commercial Applications.

www.lithiumion-batteries.com

I think ChargX has some Navy business.