discussion- J230D potential electrical fire - firewall penetration

[Tasmag]

On 22/12/2020 at 3:43 AM, RFguy said:

there is this one

The ATSB simplistically concluded, in my opinion , the possible fire cause by blaming the battery type. I suspect hew ATSB are equally skill starved with electrical systems understandng as other orgs.

 

http://www.atsb.gov.au/publications/occurrence-briefs/2018/aviation/ab-2018-124/

 

If it wasn't the battery, what was it. 

 

 

[Yenn]

If you are going to run a wire through a metal opening you have to provide a smooth, non abrasive surface and that has not been provided here.

[RFguy]

On 23/12/2020 at 10:18 PM, Tasmag said:

If it wasn't the battery, what was it. 

 

 

Lithium Phosphate batteries (and lead acid)  do NOT suffer thermal runaway at engine bay type temperatures.

 

The only way this fire would start, IF it was started by an electrical fire,  is a battery short. Via the wires though the firewall (unfused) , or a wire to the regulator (unfused) , or wires to from the alternator (unfused) , or a starter cable short . 

 

The ATSB report is short of facts and IMO draws premature conclusions with insufficient facts.

 

I already wrote to them and told them their report was bollocks ages ago.

 

 

[Blueadventures]

15 minutes ago, RFguy said:

Lithium Phosphate batteries (and lead acid)  do NOT suffer thermal runaway at engine bay type temperatures.

 

The only way this fire would start, IF it was started by an electrical fire,  is a battery short. Via the wires though the firewall (unfused) , or a wire to the regulator (unfused) , or wires to from the alternator (unfused) , or a starter cable short . 

 

The ATSB report is short of facts and IMO draws premature conclusions with insufficient facts.

 

I already wrote to them and told them their report was bollocks ages ago.

 

 

Have you read the history of the fuel tank ruptures and subsequent fire (some fatal unfortunately) incidents involving R22 and other models? 

[Tasmag]

I believe it was started as a result of the battery being unable to keep a charge and that could with the low internal resistance caused the stator and regulator to fail. Causing the fire/heat to originate at the regulator and quickly overcome a fuel line above it.

 

So no matter the origin of the fire it was the LiFe battery that caused the fire, one reason i chose not to fit one when I was going to.

 

I am not sure that there are sufficient safeguards available for their use with the jabiru charging system at this stage.

 

[RFguy]

Tasmag, I believe your conclusion to be in error.

 

This could have happened with a lead acid battery.
It can CERTAINLY happen with a flat lead acid battery, and a flat battery with say heavy load like halogen landing light.     In fact, the crimp lugs on my J230 on the alternator AC output leads have been very hot- high current and perhaps poor contact.  No doubt occurs when battery is flat and halogen landing light is on and all other EFIS etc are on. (Now LED landing light) 

 

Regulator feed from battery needs fusing

Master feed needs fusing.

Alternator AC feed need  a load dump.  You cannot open circuit the alternator AC leads because it is a current source and high voltages can ensue and the alternator windings may arc and generate a fire. This is misunderstood and is a fault in the existing setup. The alternator regulator MUST load dump with this setup otherwise the alternator and regulator will be damaged. 

 

and the whole lot (battery + ) needs a isolation contactor.

 

Alternator regulator 12V feed needs a contactor also, that drops out when the battery contactor is disconnected. Otherwise the master bus can end up with 30-50 volts on it from an open circuited alternator and mal functioning regulator.   Alternator charge feed should never be able to be connected to the system without battery also beign connected, especially with the permanent magnet style alternator. (which is great, but it needs different thinking compared to what is in there) .

 

Tasmag- you said "I am not sure that there are sufficient safeguards available for their use with the jabiru charging system at this stage." . 

GE : Well a couple of MIDI fuses and heatsunk Transzorb would be a good start !

-glen

 

Edited December 25, 2020 by RFguy

[Tasmag]

Would be interested to here what you think started the fire.

 

[RFguy]

there was another topic  on this, we can continue in the other forum post topic. My point was that this can happen with a lead acid or Lithium phosphate battery. The ATSB people incorrectly loaded the LIFEPO4 battery in with lithium poly batteries which are subject to thermal runaway and much much higher peak current pos and neg capability

 

Anyway, back to the forum topic.

FIREWALL PENETRATIONS, J230D.

 

[Kenlsa]

Looking at weights for a rebuild, the EarthX (LifePO4) at 1.7kg beats my Colt lead battery at 12kg.

It comes with an STC but is spendy at $600 US. Still, I may have to install it if weight becomes a last minute fight.

 

The STC for a Hawker (Odyssey) will come in at 7kg.

 

I am updating the alternator and starter anyway so it has become an option 

 

Ken

[RFguy]

I would recommend CALB cells for LiFEPO4 batteries. I would hesitate to use Thundersky in this service.

 

Before using a LIFEPO4 battery with the Jabiru charging system I would measure the current going into the battery-  a flat or low LIFEPO4 battery with its high capacity will soak up alot of current for a long time, a lead acid battery even if flat is a low capacity and fairly high internal resistance. You might need to come up with some way to limit the charge current. Extra wire length on the heavy regulator wire might do enough of that for you.

 

If the regulator heavy wire has a fuse and if that fuse goes open, the alternator regulator may blow up because there will be no load on the alternator and the diode pack MAY get popped. (as discussed in my previous post) 

 

Additionally, consider the starter current of 150amps will require a LIFEPO4 battery size of at least 75 AH. (as max battery current = 2C).  So, you end up with a 7kg battery anyway.... The lead acid battery is good for this application because it is good at providing starting current, and little else....

Problem with lead acid battery in this environment is that when they are hot their terminal voltage falls and this means for a system trying to regulate to 13.8 V, they are always being overcharged !!! this is because the 'float voltage' for a lead acid battery in a engine bay is about 13V. It goes down as it gets hotter ! (LIFEPO4 battery has essentially flat temperature-voltage coefficient)  

 

-glen

 

[skippydiesel]

1 hour ago, Kenlsa said:

Looking at weights for a rebuild, the EarthX (LifePO4) at 1.7kg beats my Colt lead battery at 12kg.

It comes with an STC but is spendy at $600 US. Still, I may have to install it if weight becomes a last minute fight.

 

The STC for a Hawker (Odyssey) will come in at 7kg.

 

I am updating the alternator and starter anyway so it has become an option 

 

Ken

Unlike RFGuy I am no electronics buff,however I do know you can purchase  sealed motorcycle battery that will easily meet your CCA needs that weighs 6.6Kg for fraction of your  $600 US (Au$800). Check out SSB PowerSport XR  Series Part No RB16CL-B (the one I use). If the configuration of this does not suit there are a host of others to be found on the SSB web site.

[RFguy]

Hi Skippy

Almost -CCA is OK

but...

the max charge rating of 5.7 amps is below what the alternator will try and punch in (17 amps) 

This may damage the delicate glass mat of the lightweight AGM.

 

 

 

[RFguy]

I may have to replace the battery in my Jab, and I'll probably put the original lead acid battery back in, but with a shiny shield to reflect the heat away from it. 

Or put it in the back where the J230D could do with some weight....

The LiFEPO4 really requires minimum 50AH cells (for say 3C discharge which is really hitting it hard) . A $500 battery. If you need extended run time without alternator , that's good I guess.

Another way - a small lead acid battery purely for starting (like what Skippy suggested) , and a SMALL say 10 AH (1kg)  LIFEPO4 for RUN. They would be on different circuits. That is probably the best setup.

 

The other thing to consider:

If you have a big LIFEPO4 battery , it will have ALOT more stored energy to put energy into a short circuit- much more sustained energy for a good fire......so FUSES  are mandatory for every wire running from the battery, suggest MIDI style fuses..... 

 

 

 

[skippydiesel]

33 minutes ago, RFguy said:

Hi Skippy

Almost -CCA is OK

but...

the max charge rating of 5.7 amps is below what the alternator will try and punch in (17 amps) 

This may damage the delicate glass mat of the lightweight AGM.

 

 

 

Is that charge rate  a Jab thing? cause I have no problem with my Rotax.

[RFguy]

well not that you know, or have checked. I would think it equally applies to all.

Anyway, this is a JABIRU forum. no talk of rotax here, thanks. please start another topic or PM

:-) :-) 

[Old Koreelah]

1 hour ago, RFguy said:

...Additionally, consider the starter current of 150amps will require a LIFEPO4 battery size of at least 75 AH...

Being an electronic simpleton, I’m very interested in this discussion. I hope to learn how to get the best out of my LiFePO4 battery, which is rated at 20AH and has been happily spinning my J2.2 for years,  even on cold mornings.

 

 

[RFguy]

Now, while we are on the subject of LIFEPO4 and CCA

There are many high discharge rate RC helicopter LIFEPO4 (as well as LiPol) packs rated for 30C continuous, 60C boost. There is a  8.4AmpHour 30C pack- so 30x is 240 Amps ...

But... I just don't know what quality they are in terms of reliability. 

That much current density in a small space means the battery will likely get hot in the starting exercise, and I don't like that too much.... maybe use as a starting battery on the ground (and then leave it on the ground) glen.

 

 

[RFguy]

Old-K - That Lithumax looks like a good one !

yes on paper is excellent. The only think you DO NOT want in that battery is the on board low voltage cutout- remember- cannot have the jab charging system get disconnected from the battery with everythign else still connected. (over voltage scenario) 

 

So, returns back to the issue of current limiting for the flat-battery  scenario, the lead acid will probably soak up a  charge current greater than the rating of the Jab charging system for the first minute, then back off as the terminal voltage rises of the Lead Acid. Not long enough to overheat the jab charging system.

 

The LIFEPO will just keep on soaking it up for maybe an hour or two !

 

 

 

'

[facthunter]

When you are IFR the battery is presumed to be fully charged at the  time you get airborne. Certainly IF your battery is near flat you have little time when instruments  Pitot heat and radios will work if the generator is inop. Some alternators need battery volts to re-establish on line.  IF you have a plug in point you can use a ground power battery for all your checks and starting , and KNOW that your airborne battery is not at a low charge condition.   NEVER leave a suss battery in an aeroplane.. A good indicator of battery conditions is HOW well it accepts the normal to high charge rate and are any cells getting hot. A paste battery that has become hot is finished  The spaces in the gell remain as it's still a lead acid battery. but deprived of electrolyte in many places due bubbles forming.. Any DOUBT, terf it OUT. Nev

Edited December 25, 2020 by facthunter

[Kenlsa]

Skippy,  any battery that I can put in the Colt (sorry RF not a Jab) must be approved with an STC to make it legal.

[RFguy]

Pitot heat. ahhh  that little chestnut.  another reason not to fly a VFR only equipped aircraft (no pitot heat) in icing condix...Pitot heat 120-200watts. All IFR aircraft I have flown in have been dual alternator. 

[facthunter]

Very few light aircraft would meet de icing capabiity in real icing conditions.  Jets that have an abundance of bleed air heat available (at cost of more fuel) and where the speed rises the outside temp by 25 degrees , fare much better but the power loss may limit climb performance when you are trying to get "on top". of "wet" clouds.  Nev

[Old Koreelah]

27 minutes ago, RFguy said:

Old-K - That Lithumax looks like a good one !

yes on paper is excellent. The only think you DO NOT want in that battery is the on board low voltage cutout- remember- cannot have the jab charging system get disconnected from the battery with everythign else still connected. (over voltage scenario)...

Thanks for the advice Glen, but most of these explanations assume deep knowledge- which I don’t have.

As well as the normal switches, my installation has a Battery negative isolator. I have no idea what this would do to the system.

I presume you are saying that if my battery’s internal BMS disconnects it from the aircraft, the Jab charging system will overload, with nowhere to dump the power.  

If that is the case, I’m open to suggestions about a remedy.

 

 

[skippydiesel]

47 minutes ago, Kenlsa said:

Skippy,  any battery that I can put in the Colt (sorry RF not a Jab) must be approved with an STC to make it legal.

We (The Forum) have had this debate off/on for years - In my opinion a battery conforming to the correct dimensions (will fit the cradle/box safely), able to store/deliver the rated starting power OR better,  is just like any other consumable that an aircraft may use.

 

So if you can use, any engine oil that meets the specification, any tyre, fuel, paint, spark plugs, filters,  etc etc - you do not need to conform to the original product the aircraft was supplied with.

 

If this be true and I believe it is,  then any battery, so conforming, can be fitted.

Edited December 25, 2020 by skippydiesel

[RFguy]

OldK and Skippy

I will expand on your questions etc on this tomorrow. Star Trek wifey time.