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art(at)zemon.name
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 Posted: Wed Jul 25, 2018 6:29 am Post subject: Melted battery terminal |
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Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
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cluros(at)gmail.com
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| Posted: Wed Jul 25, 2018 7:09 am Post subject: Melted battery terminal |
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How do you know the connection was tight?
On Wed, Jul 25, 2018, 10:38 Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
|
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art(at)zemon.name
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| Posted: Wed Jul 25, 2018 7:11 am Post subject: Melted battery terminal |
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Correction. The plane has a shunt, not a current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
On Wed, Jul 25, 2018, 10:08 AM Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
|
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echristley(at)att.net
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| Posted: Wed Jul 25, 2018 7:37 am Post subject: Melted battery terminal |
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Looks like a lead post. Lead has a fairly low melting point. Maybe the wire was heated from the other end enough to soften the battery post material. Once soft, the connection was degraded, leading to a high resistance connection. Leading to ... goo running down the side of the battery?
On Wednesday, July 25, 2018 10:31 AM, Art Zemon <art(at)zemon.name> wrote:
Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
-- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
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argoldman(at)aol.com
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| Posted: Wed Jul 25, 2018 7:41 am Post subject: Melted battery terminal |
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Lessee, a loose connection (no matter where it is from or to) is potentially a high resistance connection. With the tremendous power draw of the starter motor it is likely that that was the source of the heat and meltage.
Rich
In a message dated 7/25/2018 10:11:48 AM Central Standard Time, art(at)zemon.name writes:
| Quote: | Correction. The plane has a shunt, not a current limiter.
-- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
On Wed, Jul 25, 2018, 10:08 AM Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
-- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
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art(at)zemon.name
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| Posted: Wed Jul 25, 2018 8:00 am Post subject: Melted battery terminal |
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Because it still is, after the battery terminal melted and the bolt fell off. The lock nut is now soldered in it's compressed state between the bolt head and the washer.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
On Jul 25, 2018 10:30 AM, "Sebastien" <cluros(at)gmail.com (cluros(at)gmail.com)> wrote: | Quote: | How do you know the connection was tight?
On Wed, Jul 25, 2018, 10:38 Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
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ceengland7(at)gmail.com
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| Posted: Wed Jul 25, 2018 8:06 am Post subject: Melted battery terminal |
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On Wed, Jul 25, 2018 at 9:28 AM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
|
If IÂ had to speculate, I'd be looking at the battery type, in addition to the question of whether there really was a clean gas tight connection on the posts. If you look up the specs on that battery, I'll bet you'll find it was intended for service in UPS, powered wheel chair, etc. You can get away with using 'universal' batteries for starting; I've used the SLA universals as starting batteries for a couple of decades. But the terminals are typically a lot smaller than a true starting battery. Even if the terminals were clean/tight, I wonder if a drastically extended cranking session could drive heat up enough to melt the terminals, which are likely sized for, let's say, 20 amps continuous, instead of 200+.
Charlie
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jul 25, 2018 8:25 am Post subject: Melted battery terminal |
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At 09:28 AM 7/25/2018, you wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter. |
Was the current limiter in series with starter
current . . .? If the 'loose' terminal was not
visibly damaged due to electrically induced
heating/arcing, then it did not participate
in this failure.
How did the battery wire terminal look after the 'meltdown'?
Lead has right at 10x the d.c. resistance of copper.
Not sure what comparative gradients for reduction
in compression strength vs. temperature would be
but you can bet that lead is MUCH steeper than copper.
This sorta sets up a weak-link for the low resistance,
high current batteries. An extended cranking scenario
will absolutely warm up these terminals. Joint integrity
falls with temperature rise and the trajectory to destruction
steepens exponentially.
Some suppliers of SVLA products will include a lead
battery bolt kit that includes a Bellville washer
to be used in the joint makeup that provides (1) an
indication as to when design compression in the joint
has been reached and (2) improve retention of joint
quality for small rises in temperature.
[img]cid:.0[/img]
Pretty sure this is why Odyssey and similar products
use a lot of brass in their terminal posts
[img]cid:.1[/img]
[img]cid:.1[/img]
Bob . . .
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Wed Jul 25, 2018 8:56 am Post subject: Melted battery terminal |
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Art:
The current limit circuit has nothing to do with it.
The cable should be going from the battery to the starter relay to the starter.
There are hundreds of amps being sucked out of the battery.
Nothing should be limiting the current flow.
The crank, cranking the engine probably did so WAY TOO LONG!
Many starters stipulate 10 seconds. Well, that is too long! It should be more like 5 seconds.
The only thing indicating the positive terminal was maybe tight is - It did not melt.
It does not matter which terminal is loose, positive or negative, resistance is resistance. And you now have proof of what a poor connection can do.
Also you do not know if the positive terminal was a CLEAN connection or how tight. One ohm of resistance under a terminal increases current drawing a 12 VDC circuit by 12 Amps.
If the plane’s amp gauge reads starting amps, there might be an indication of higher draw than normal. A good indication to stop cranking.
BarryÂ
On Wednesday, July 25, 2018, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
|
--
Barry
"Chop'd Liver"
If you wash your hands before you go to the bathroom you may have the makings of a Crew Chief.
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jul 25, 2018 9:59 am Post subject: Melted battery terminal |
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If I had to speculate, I'd be looking at the battery type, in addition
to the question of whether there really was a clean gas tight
connection on the posts. If you look up the specs on that
battery, I'll bet you'll find it was intended for service in
UPS, powered wheel chair, etc. You can get away with using
'universal' batteries for starting; I've used the SLA universals
as starting batteries for a couple of decades. But the terminals
are typically a lot smaller than a true starting battery. Even
if the terminals were clean/tight, I wonder if a drastically
extended cranking session could drive heat up enough to melt the
terminals, which are likely sized for, let's say, 20 amps continuous,
instead of 200+.
Excellent put Charlie . . .
I'm recalling the first SVLA batteries
B&C offered . . . yeah, they would dump
700A in a load test but also featured
the lead molded terminal tabs. It was important
to educate the buyers about their relative
fragility . . . that's where the soft-n-floppy,
welding cable battery jumpers originated . . .
which remains a good thing to do even with
the more robust terminals.
Bob . . .
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ceengland7(at)gmail.com
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| Posted: Wed Jul 25, 2018 10:04 am Post subject: Melted battery terminal |
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I think we need to review Ohm's Law and power formulas for DC circuits.
http://www.sengpielaudio.com/calculator-ohm.htm
Using P for power, V for volts, R for resistance, and I for current, pick a formula, and plug in value of 12V (or maybe 10 V, with the starter load). Then plug in a value for the starter's resistance. Pick virtually any value you want, but you can get a fairly realistic one by picking an arbitrary current of 200 amps, and using V/I=R: 12V/200A=0.06 ohms.
Now that you have starter resistance, let's use V/R=I: 12/0.06 0 Amps.
Now, add your 1 ohm of extra resistance to the V/R=I formula: 12/(0.06+1.0)=x
Which reduces to: 12V/1.06R=x
Solve for x, and tell us how adding 1 ohm of series resistance increases the current. 
Charlie
On 7/25/2018 11:55 AM, FLYaDIVE wrote:
| Quote: |
Art:
The current limit circuit has nothing to do with it.
The cable should be going from the battery to the starter relay to the starter.
There are hundreds of amps being sucked out of the battery.
Nothing should be limiting the current flow.
The crank, cranking the engine probably did so WAY TOO LONG!
Many starters stipulate 10 seconds. Well, that is too long! It should be more like 5 seconds.
The only thing indicating the positive terminal was maybe tight is - It did not melt.
It does not matter which terminal is loose, positive or negative, resistance is resistance. And you now have proof of what a poor connection can do.
Also you do not know if the positive terminal was a CLEAN connection or how tight. One ohm of resistance under a terminal increases current drawing a 12 VDC circuit by 12 Amps.
If the plane’s amp gauge reads starting amps, there might be an indication of higher draw than normal. A good indication to stop cranking.
BarryÂ
On Wednesday, July 25, 2018, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the current limiter got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the current limiter.
   -- Art Z.
Sent from my phone. Please excuse brevity and bizarre typos.
|
--
Barry
"Chop'd Liver"
If you wash your hands before you go to the bathroom you may have the makings of a Crew Chief.
|
 Virus-free. www.avast.com [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jul 25, 2018 12:35 pm Post subject: Melted battery terminal |
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At 01:04 PM 7/25/2018, you wrote:
| Quote: | I think we need to review Ohm's Law and power formulas for DC circuits.
http://www.sengpielaudio.com/calculator-ohm.htm
Using P for power, V for volts, R for resistance, and I for current, pick a formula, and plug in value of 12V (or maybe 10 V, with the starter load). Then plug in a value for the starter's resistance. Pick virtually any value you want, but you can get a fairly realistic one by picking an arbitrary current of 200 amps, and using V/I=R: 12V/200A=0.06 ohms. |
It's a bit more complex than that. A figure lifted from
the 'Connection will help highlight the details . . .
[img]cid:.0[/img]
A battery has an internal resistance component. So does the starter
motor. As explained in the DC Motors posting on 6/27, we know that the
motor windings moving through the magnetic field flux generates a
COUNTER EMF, i.e. a voltage that opposes the applied voltage.
The starter motor's internal resistance sets the STALL current
which is the same as INRUSH current. That resistance will be MUCH
lower than the hypothesized 0.06 ohms cited above. Using 12v as the
'source' voltage for cranking calculations assumes that OTHER than
motor resistance, there are no additional resistances. The exemplar
cranking scenario speaks to a number of resistances not the least
of which is contained within the battery.
These numbers can be better or worse depending on the system
configuration and condition of the components but suffice it
to say that NONE of these resistances are ever so small as
to be ignored.
Inrush current, while short in duration, is several times
higher than cranking current. Note that ALL resistances cited
are, as Charlie suggested in his hypothetical, are measured
in MILLIOHMS. You don't have to add much resistance to seriously
impact system performance and in all cases, adding or increasing
any resistance causes current to go DOWN.
Bob . . .
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ceengland7(at)gmail.com
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| Posted: Wed Jul 25, 2018 2:18 pm Post subject: Melted battery terminal |
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You have a lot more words at your disposal than I do. I was just shooting for a simple way to show that adding series resistance can't make current go *up* in a DC circuit.
Charlie
On Wed, Jul 25, 2018 at 3:34 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 01:04 PM 7/25/2018, you wrote:
| Quote: | I think we need to review Ohm's Law and power formulas for DC circuits.
http://www.sengpielaudio.com/calculator-ohm.htm
Using P for power, V for volts, R for resistance, and I for current, pick a formula, and plug in value of 12V (or maybe 10 V, with the starter load). Then plug in a value for the starter's resistance. Pick virtually any value you want, but you can get a fairly realistic one by picking an arbitrary current of 200 amps, and using V/I=R: 12V/200A=0.06 ohms. |
 It's a bit more complex than that. A figure lifted from
 the 'Connection will help highlight the details . . .
[img]cid:.0[/img]
 A battery has an internal resistance component. So does the starter
 motor. As explained in the DC Motors posting on 6/27, we know that the
 motor windings moving through the magnetic field flux generates a
 COUNTER EMF, i.e. a voltage that opposes the applied voltage.
 The starter motor's internal resistance sets the STALL current
 which is the same as INRUSH current. That resistance will be MUCH
 lower than the hypothesized 0.06 ohms cited above. Using 12v as the
 'source' voltage for cranking calculations assumes that OTHER than
 motor resistance, there are no additional resistances. The exemplar
 cranking scenario speaks to a number of resistances not the least
 of which is contained within the battery.
 These numbers can be better or worse depending on the system
 configuration and condition of the components but suffice it
 to say that NONE of these resistances are ever so small as
 to be ignored.
 Inrush current, while short in duration, is several times
 higher than cranking current. Note that ALL resistances cited
 are, as Charlie suggested in his hypothetical, are measured
 in MILLIOHMS. You don't have to add much resistance to seriously
 impact system performance and in all cases, adding or increasing
 any resistance causes current to go DOWN.
 Bob . . .
|
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nuckolls.bob(at)aeroelect
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art(at)zemon.name
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| Posted: Sun Jul 29, 2018 1:12 pm Post subject: Melted battery terminal |
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Folks,
I am home now, with access to a real keyboard and a real chair AirVenture was good this year but immediately followed by a hurried trip to New Jersey with no time to even think.
Based on your emails, I figured out my hypothesis of what happened:
- The connector between the cable from the battery to the ammeter shunt got loose, increasing the resistance.
- For unknown reasons, the engine was hard to start and the pilot kept cranking and cranking and cranking.
- There is no circuit protection in the circuit battery positive terminal -> shunt -> master contactor -> starter contactor -> starter motor -> engine block -> battery negative terminal
- Lacking circuit protection, the parts most likely to get hot enough to melt were the lead battery terminals. It was a crap shoot which would fail first, positive or negative. Once the negative got hot enough to loosen up, it got hotter in a hurry and melted.
Several lessons learned.
- I don't think that pilot will do that again.
- I learned that too much cranking puts other components at risk, not just the starter motor.
- The airplane's owner will be checking the other high current connectors.
- In diagnosing this issue, I spotted another damaged connection (unrelated problem) on the master contactor so the airplane's owner will fix that too.
- I have the same battery in my airplane and when it needs replacing, I will choose a model that doesn't have lead terminals.
Thank you for the education!
  -- Art Z.
On Wed, Jul 25, 2018 at 10:08 AM Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the shunt
 got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the shunt
.
|
--
https://CheerfulCurmudgeon.com/"We do not see the world as it is. We see the world as we are."
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ceengland7(at)gmail.com
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| Posted: Sun Jul 29, 2018 1:46 pm Post subject: Melted battery terminal |
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Charlie
On Jul 29, 2018, at 4:39 PM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote: | Quote: |
Charlie
On Jul 29, 2018, at 4:18 PM, Art Zemon < art(at)zemon.name (art(at)zemon.name)> wrote: | Quote: | Folks,
I am home now, with access to a real keyboard and a real chair AirVenture was good this year but immediately followed by a hurried trip to New Jersey with no time to even think.
Based on your emails, I figured out my hypothesis of what happened:
- The connector between the cable from the battery to the ammeter shunt got loose, increasing the resistance.
- For unknown reasons, the engine was hard to start and the pilot kept cranking and cranking and cranking.
- There is no circuit protection in the circuit battery positive terminal -> shunt -> master contactor -> starter contactor -> starter motor -> engine block -> battery negative terminal
- Lacking circuit protection, the parts most likely to get hot enough to melt were the lead battery terminals. It was a crap shoot which would fail first, positive or negative. Once the negative got hot enough to loosen up, it got hotter in a hurry and melted.
Several lessons learned.
- I don't think that pilot will do that again.
- I learned that too much cranking puts other components at risk, not just the starter motor.
- The airplane's owner will be checking the other high current connectors.
- In diagnosing this issue, I spotted another damaged connection (unrelated problem) on the master contactor so the airplane's owner will fix that too.
- I have the same battery in my airplane and when it needs replacing, I will choose a model that doesn't have lead terminals.
Thank you for the education!
-- Art Z.
On Wed, Jul 25, 2018 at 10:08 AM Art Zemon < art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the shunt
got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the shunt
.
|
Art, two things, likely unrelated. There should never be a shunt anywhere in the path from battery to starter.
The external components' heat didn't do the damage to the battery. Current exceeding the design limits of that particular battery for to long is likely wht caused the damage.
Charlie
See my earlier message about the battery type.
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ceengland7(at)gmail.com
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| Posted: Sun Jul 29, 2018 1:48 pm Post subject: Melted battery terminal |
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Charlie
On Jul 29, 2018, at 4:18 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote: | Quote: | Folks,
I am home now, with access to a real keyboard and a real chair AirVenture was good this year but immediately followed by a hurried trip to New Jersey with no time to even think.
Based on your emails, I figured out my hypothesis of what happened:
- The connector between the cable from the battery to the ammeter shunt got loose, increasing the resistance.
- For unknown reasons, the engine was hard to start and the pilot kept cranking and cranking and cranking.
- There is no circuit protection in the circuit battery positive terminal -> shunt -> master contactor -> starter contactor -> starter motor -> engine block -> battery negative terminal
- Lacking circuit protection, the parts most likely to get hot enough to melt were the lead battery terminals. It was a crap shoot which would fail first, positive or negative. Once the negative got hot enough to loosen up, it got hotter in a hurry and melted.
Several lessons learned.
- I don't think that pilot will do that again.
- I learned that too much cranking puts other components at risk, not just the starter motor.
- The airplane's owner will be checking the other high current connectors.
- In diagnosing this issue, I spotted another damaged connection (unrelated problem) on the master contactor so the airplane's owner will fix that too.
- I have the same battery in my airplane and when it needs replacing, I will choose a model that doesn't have lead terminals.
Thank you for the education!
-- Art Z.
On Wed, Jul 25, 2018 at 10:08 AM Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:
| Quote: | Question for y'all. This happened at AirVenture (not my plane, thankfully). The cable from the battery positive terminal to the shunt
got loose at the current limiter end. Just loose, it did not come off. The pilot kept cranking on the starter until he heard a pop. The negative terminal on the battery has melted. See photo.
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the shunt
.
|
Art, two things, likely unrelated. There should never be a shunt anywhere in the path from battery to starter.
The external components' heat didn't do the damage to the battery. Current exceeding the design limits of that particular battery for to long is likely wht caused the damage.
Charlie
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nuckolls.bob(at)aeroelect
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| Posted: Sun Jul 29, 2018 4:47 pm Post subject: Melted battery terminal |
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| Quote: |
I don't understand why this is the party that got hot, since this connector was tight. And why there is no other visible damage to the battery out anything else, not even the
shunt
.
Art, two things, likely unrelated. There should never be a shunt anywhere in the path from battery to starter.
The external components' heat didn't do the damage to the battery. Current exceeding the design limits of that particular battery for to long is likely wht caused the damage.
Charlie
See my earlier message about the battery type. |
Agreed.
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Sun Jul 29, 2018 5:55 pm Post subject: Re: Melted battery terminal |
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The reason for the melted battery terminal was, as others have said, a high resistance connection.
Of course the extended cranking time was a factor. The terminal might have seemed to be tight,
but there was still high resistance. Sometimes the bolt is too long and the nut runs out of threads.
The nut bottoms out and is tight, but the terminal is not tight. One time I found a loose connection
caused by someone using a nut and bolt that did not have matching threads. For instance a 10-24 nut
on a 10-32 bolt. Sure, the nut was tight, but the electrical connection was not tight.
Circuit protection like a fuse or current limiter is not desired in the starter circuit because it would add
resistance which would slow down the starter motor. Circuit protection would not have helped anyway
because the current was not excessive. In fact, the high resistance connection reduced the current.
Lead battery posts are not cause for concern if the terminal is clean and tight.
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art(at)zemon.name
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| Posted: Sun Jul 29, 2018 6:00 pm Post subject: Melted battery terminal |
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Charlie wrote:
| Quote: | | Art, two things, likely unrelated. There should never be a shunt anywhere in the path from battery to starter. |
Charlie,
You bring up a good point. You just make me realize that the shunt is in the wrong place, measuring current to/from the battery instead of from the alternator. I don't remember which end of the shunt is connected to the starter contactor. I'll check, though that will take awhile since I am home and the plane is elsewhere now.
| Quote: | | The external components' heat didn't do the damage to the battery. Current exceeding the design limits of that particular battery for to long is likely wht caused the damage. |
I do understand that.
Cheers,
  -- Art Z.
--
https://CheerfulCurmudgeon.com/"We do not see the world as it is. We see the world as we are."
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