A very lucky pilot! (LI Iron Battery)

[ChiefPilot]

Originally Posted by 1001001

Folks, if you are considering a lithium ion battery of any type in your aircraft or other vehicle, do yourselves a favor and read the recently released NTSB report on the JAL 787 Yuasa battery failure. It includes information related to two other lithium chemistry battery failures on the 787 fleet.

Lithium Colbalt Oxide is a very different makeup than Lithium Iron Phosphate, with significantly different characteristics.

A much better link for learning about the characteristics of lithium chemistry batteries will take you to Battery University: http://batteryuniversity.com/learn/a...of_lithium_ion

[1001001]

Originally Posted by ChiefPilot

Lithium Colbalt Oxide is a very different makeup than Lithium Iron Phosphate, with significantly different characteristics.

A much better link for learning about the characteristics of lithium chemistry batteries will take you to Battery University: http://batteryuniversity.com/learn/a...of_lithium_ion

I am aware of the difference in chemistries. The report notes mechanically induced failure modes that could be common to any number of different battery chemistries. In addition, there are other items that users should want to be aware of that are addressed in the report, such as the quality of manufacturing quality control processes. Again, I'm not making a case for or against these batteries, merely suggesting that everyone avail themselves of all sources of information.

[BillL]

Originally Posted by 1001001

I am aware of the difference in chemistries. The report notes mechanically induced failure modes that could be common to any number of different battery chemistries. In addition, there are other items that users should want to be aware of that are addressed in the report, such as the quality of manufacturing quality control processes. Again, I'm not making a case for or against these batteries, merely suggesting that everyone avail themselves of all sources of information.

The NTSB report is so-so for understanding Li battery performance limitations, and considerations for abuse testing. It implies that Boeing (contractor/) was either naive or ignored the vast amount of information, chemistries, research, and testing that has been done by a wide array of companies. This includes our own government sponsored work for hybrid transportation, NREL, in Golden, Co. Many of these reports are public that are incomplete but give a much better picture of failure modes, abuse testing and odd discoveries. Like internal temperature rise onset and testing for 7 days, yes 7 days waiting following the abuse performance levels to determine if the cell will ramp to failure.

EarthX has done many of these tests on cells and packs with the BMS. Whether these tests, alone, sufficient to yield a drop-in replacement is unknown, but they did not just make a pack for sale. Along with a sealed box, (a vault) and crowbar circuit for runaway voltage regulator mitigation we just might have a winner.

Regardless of testing, until there is enough volume and usage, and quality control all along the line from raw materials to the completed pack, we should be careful. Don't expect that it is an on the shelf, blister pack, use it anyway you want and sue the manufacturer when it fails product, not yet. And, maybe never for aviation. We ARE experimental, so care, learning and understanding should be taken in the application of everything we do. Never be complacent. Never stop questioning, and don't discourage (please!) those who do.

Sorry, that was not intended to sound like a lecture, just some thoughts on the subject.

[1001001]

BillL, I agree with what you've written. The NTSB is often circumspect in its conclusions when the data lean in a direction but there is not conclusive evidence of a specific root cause.

When you say that it is implied that Boeing was naive and placed too much trust in its contractors' processes I agree, that was my take as well. The battery manufacturer as well may have had the chemistry down pat, but the mechanical flaws introduced in the assembly process may have contributed to the failure. As experimenters, the individuals in the community here take on the role Boeing had as a systems integrator, and need to exercise skepticism and good judgment when selecting suppliers.

Probably too much of a lecture here as well. I really want to see light, high density power supplies succeed, but success implies safety as well as performance.

One other note...if you take the "contain it and vent it" approach to risk mitigation, make absolutely sure the materials you use in your containment and vents are suitable for the environment surrounding a runaway battery.

[judoka5051]

I've got a Shorai in the front baggage compartment of my 8. However, it is in a stainless box, I have my EIS set to alarm for an over voltage condition, and I have a very small alternator (SD20 only) which will likely fry itself even before the crowbar fails.

I am not going to get rid of the Shorai, but having read this and using the 'just in case' rule, it will soon be moved to the firewall as low and cool as possible. That's enough caution for me. If I want to rule out every possible battery incident, I'll fly my no-electrics Biplane. But then I have to hand prop...

[Low Pass]

Originally Posted by judoka5051

I've got a Shorai in the front baggage compartment of my 8. However, it is in a stainless box, I have my EIS set to alarm for an over voltage condition, and I have a very small alternator (SD20 only) which will likely fry itself even before the crowbar fails.

I am not going to get rid of the Shorai, but having read this and using the 'just in case' rule, it will soon be moved to the firewall as low and cool as possible. That's enough caution for me. If I want to rule out every possible battery incident, I'll fly my no-electrics Biplane. But then I have to hand prop...

Having on the other side of the firewall would be better. But would you not be comfortable directing the battery box vent through the firewall and overboard somehow? Is the box vented currently?

[Greg_Toman]

If the Challenger had a Rotax 2-cycle engine, which is very likely, the charging system is not the most sophisticated. I suspect the battery was being overcharged, and apparently that battery is not as tolerant of this as a lead-acid battery.

[BillL]

Originally Posted by judoka5051

I've got a Shorai in the front baggage compartment of my 8. However, it is in a stainless box, I have my EIS set to alarm for an over voltage condition, and I have a very small alternator (SD20 only) which will likely fry itself even before the crowbar fails.

I am not going to get rid of the Shorai, but having read this and using the 'just in case' rule, it will soon be moved to the firewall as low and cool as possible. That's enough caution for me. If I want to rule out every possible battery incident, I'll fly my no-electrics Biplane. But then I have to hand prop...

It sounds like you are taking quite reasonable precautions. I was thinking about the "vault" Would it be prudent to provide some forced ventilation to the box to ensure that there is some cooling to the box, and if the plastic begins to smoke, that there is some velocity to the exiting gas? Do you have some thoughts about the sealing of the wire exits to ensure that the solution to one issue does not present others?

[lrgabriel]

I just wanted to pass along an idea for those with LiFePo4 batteries--In addition to monitoring voltage (which I think is critical), I've also installed a couple of surface-mount thermocouples to monitor individual battery temperature.

If either parameter goes out of limits, I plan on disconnecting the offending battery from all charging or load. So far so good, and I wouldn't feel comfortable experimenting with a low-volume technology without the added data.

[judoka5051]

Hey Bill, that's what I'm planning. Battery forward of the firewall, with forced air cooling. I'm as concerned about battery longevity as anything else.