F

Finley Atherton

Well Known Member
I am asking this question arising out of a thread on the need for a back-up battery with dual Lightspeeds http://www.vansairforce.com/community/showthread.php?t=80818
In particular is anyone aware of an instance where an Odyssey AGM Battery (amorphous glass mat) or other brand AGM battery eg, Fullriver, has failed so suddenly and completely IN FLIGHT that it has taken down the aircrafts electrical system? I am thinking of something like an internal dead short in the battery.

I don't want to know about alternator failures or failures with other batteries such as wet lead acid, gel or lithium. I am interested in AGM failures and the Odyssey Battery in particular.
Thanks.

Fin
9A
 
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I've never heard of one either. I was probably following the old Matronics RV lists and Aeroelectric lists for a number of years before the VAF - nothing there either.
 
The only failure modes I'm aware of in the AGM batteries is sudden inability to hold a charge or maintain their rated amp-hour capacity shortly after they've every been subjected to deep discharge.... that and the classic failure that any lead-acid battery ultimately suffers... they just die of old age. Never heard of any destructive or thermal runaway type of failures in them at all.
 
Had an AGM (Wesco) in my BMW motorcycle which apparently suffered a failed cell connector. Went from working fine to being almost an open circuit by one push of the Start button. Got a jump start and rode the bike home, but every time I hit the brakes at low RPM, the engine momentarily died from the voltage drop (the bike has a brake booster/ABS servo that's quite a load). Took the Odyssey out of the RV and installed it in the bike and it's been fine since. That PC680 is about 10 years old now and still cranks adequately.

As for how this relates to RV's, the same could happen. If the battery were to have a failed cell connector, it would cease performing as a buffer for the electrical system and the alternator could stop working if there is a momentary sudden drop in the system voltage like you could see if a large consumer is switched on like landing lights. I have a 2nd (small) AGM battery in my -6 with dual Lightspeeds simply for the situation I outlined above. Can't trust a single battery if you have an electrically dependent airplane.
 
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hgerhardt said:
Had an AGM (Wesco) in my BMW motorcycle which apparently suffered a failed cell connector. Went from working fine to being almost an open circuit by one push of the Start button. Got a jump start and rode the bike home, but every time I hit the brakes at low RPM, the engine momentarily died from the voltage drop (the bike has a brake booster/ABS servo that's quite a load). Took the Odyssey out of the RV and installed it in the bike and it's been fine since. That PC680 is about 10 years old now and still cranks adequately.

As for how this relates to RV's, the same could happen. If the battery were to have a failed cell connector, it would cease performing as a buffer for the electrical system and the alternator could stop working if there is a momentary sudden drop in the system voltage like you could see if a large consumer is switched on like landing lights. I have a 2nd (small) AGM battery in my -6 with dual Lightspeeds simply for the situation I outlined above. Can't trust a single battery if you have an electrically dependent airplane.
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Just as a comment to the above example, your alternator did not stop working, you merely had a momentary voltage drop which caused your ignition system to drop below the threshold where it would work. If you increased RPM or reduced the load the voltage will return. So my point is that your alternator did not stop working, it was just turning too slow to supply the current demand so the voltage momentarily dropped.

Once runnning the alternator will supply it's own field current with or without the battery. Without the battery in the system acting as a large capacitor the voltage would have a lot of ripple on it but I doubt it would cause a failure or problem with your ignition or avionics which have their own regulated power supplies.

PS: I've never seen or heard of a PC680 failure other than old age. I have dual EI and install a new battery every 2-3 years just cause it makes me feel good (cheap preventive maintenance).
 
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This is what happened to me, Odesy battery PC=680
In-flight I lost my complete panel ( all glass)
We used a (496) to nav back to my home base 175nm, little pucker factor but went smooth.
This is what I found: battery 10.6volts and a burnt up alternator Vans 60 amp.
This is what I believe happened: 1.Lost cell in battery 2. Alternator started pumping out all it could
3. After some time the alternator got hot and burned up.
This is why I believe this. (2 years later) I noticed my starter was not spinning the engine as strong as it should, and the battery was not staying hot. I found a weak cell.
Even with a small load the battery would drop voltage fairly fast.
My conclusion is that even though people rave about how long they last and how great they are and I am
Still using the Odesy ,But I personally don?t have the warm fuzzy and I keep an eagle eye on it.
 
Walt said:
Just as a comment to the above example, your alternator did not stop working, you merely had a momentary voltage drop which caused your ignition system to drop below the threshold where it would work. If you increased RPM or reduced the load the voltage will return. So my point is that your alternator did not stop working, it was just turning too slow to supply the current demand so the voltage momentarily dropped.

Once runnning the alternator will supply it's own field current with or without the battery. Without the battery in the system acting as a large capacitor t...
Click to expand...

Not necessarily. With a completely failed cell connector, the capacitor function of the battery is lost. By switching on a large consumer like landing lights, the regulator MIGHT not react fast enough and allow the system voltage to momentarily drop to the point where the alternator stops charging. Unlikely, yes... but not impossible.

On my bike, the cell connector didn't completely fail; open-circuit, the battery read ~12 volts... but when the ignition switch was turned on, the voltage dropped to ~2V. Fortunately, that was enough to keep the alternator going.

A completely failed cell connector is admittedly unlikely. But, when a simple 1-lb AGM battery will keep the capacitor function of the system intact and ensure alternator excitement, why not use it? Esp. if you have a dual-EI system.
 
gmpaul said:
This is what happened to me, Odesy battery PC=680
In-flight I lost my complete panel ( all glass)
We used a (496) to nav back to my home base 175nm, little pucker factor but went smooth.
This is what I found: battery 10.6volts and a burnt up alternator Vans 60 amp.
This is what I believe happened: 1.Lost cell in battery 2. Alternator started pumping out all it could
3. After some time the alternator got hot and burned up.
This is why I believe this. (2 years later) I noticed my starter was not spinning the engine as strong as it should, and the battery was not staying hot. I found a weak cell.
Even with a small load the battery would drop voltage fairly fast.
My conclusion is that even though people rave about how long they last and how great they are and I am
Still using the Odesy ,But I personally don’t have the warm fuzzy and I keep an eagle eye on it.
Click to expand...

Could this be a possible alternative theory?

You were flying along happily when you had an unnoticed alternator failure. The battery continued supplying power until it was almost completely discharged at which point you lost the glass panel. Back home you measure a no load voltage of 10.6 volts which is close to the fully discharged voltage of 10.2 volts for an Odyssey battery (from Odyssey Technical Manual).
The slow cranking could have just been due to the battery having a normal gradual death.

Did you try to recharge the battery after this event? If it could be recharged this would indicate the battery was OK?

Fin
9A
 
I have a few years' industrial experience with AGM batteries. Most were the large 8D size, used to start diesel engines.
All failed in a single instant. The last start they gave was perfectly normal. This first failed start was a dead battery. Not a slow crank or anything like that. The ciruit inside the battery went open. Sometimes it would read voltage, sometimes not.
I don't recall any shorted cells, but it could have happened.
In any event, open or shorted, the failure was immediate and permanent.
A new replacement battery was required.
 
My 6-month-old Odyssey just failed in an interesting way. Voltage was good and powered the avionics, but would only barely move the prop when I hit start. After charging, same thing.

Swapped in my 8-year-old Odyssey and it cranked fine. So much for preventive maintenance :(

I'm guessing there's a crack at the post or between the grids. That might explain normal voltage but insufficient current?

Odyssey has a 2 year warranty but they want you to return it to the place you bought it. I bought mine from Amazon who of course want nothing to do with it. May be a write-off...
 
Fin, It's not just the battery that might fail but also the connections at the terminals. On the Odyssey 680 the positive and negative leads are fastened with an M6 screw that as supplied cannot be secured.

And how confident are you of the integrity of the crimped lugs on your leads. It is well known that Vans issued a service bulletin on a run of 2AWG leads a few years back that were faulty. The AMP lugs that Vans uses are very El Cheapo. When I tested mine, one of them pulled out with hardly any effort. I subsequently bought better quality lugs and a crimping tool and redid all of my heavy guage leads (and tested them).

If you lose a battery connection, or an incorrectly crimped lug pulls off its wire that might be a bad day.
 
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8 months

Paul Eastham said:
My 6-month-old Odyssey just failed in an interesting way. Voltage was good and powered the avionics, but would only barely move the prop when I hit start. After charging, same thing.

Swapped in my 8-year-old Odyssey and it cranked fine. So much for preventive maintenance :(

I'm guessing there's a crack at the post or between the grids. That might explain normal voltage but insufficient current?

Odyssey has a 2 year warranty but they want you to return it to the place you bought it. I bought mine from Amazon who of course want nothing to do with it. May be a write-off...
Click to expand...

Paul
I had the same thing happen with my Odessy it lasted about 8 months when Cranking the engine it would turn the prop real slow tried charging several differant times cleaned all connectors but did not help changed the battery with a new one and it's has worked great for the last 3 months
Tim
 
Captain Avgas said:
Fin, It's not just the battery that might fail but also the connections at the terminals. On the Odyssey 680 the positive and negative leads are fastened with an M6 screw that as supplied cannot be secured.

And how confident are you of the integrity of the crimped lugs on your leads. It is well known that Vans issued a service bulletin on a run of 2AWG leads a few years back that were faulty. The AMP lugs that Vans uses are very El Cheapo. When I tested mine, one of them pulled out with hardly any effort. I subsequently bought better quality lugs and a crimping tool and redid all of my heavy guage leads (and tested them).

If you lose a battery connection, or an incorrectly crimped lug pulls off its wire that might be a bad day.
Click to expand...

Hi Bob,

Thanks for pointing out these issues however I think I have it covered.
Whenever I remove a terminal bolt I use a new lock washer plus a small amount of the appropriate Locktite on the first threads of the bolt.

I am on holidays and a long way from my RV but from memory I also soldered all the heavy crimp lugs for extra security. Also any failure of these lugs would not affect the Lightspeed ignition as they have their own positive and negative wires directly to the battery.

Fin9A
 
On the RV-12, the nuts and bolts, that hold the Sensenich propeller on and the bolts that hold the Matco wheel brakes on, are not safety wired. Instead, Nordlock washers are used. I suggest that Nordlock washers also be used with battery bolts, especially on aircraft that depend on the battery for ignition and fuel pumps. When removing my propeller, I was surprised at how much more force is required to loosen the bolts compared to tightening them. After using Nordlock washers, I would never use split-ring washers again in critical applications. Vibration tests have demonstrated that split-ring washers actually cause a bolt to loosen sooner than a bolt without a washer. After using spit-ring lock washers on fasteners my whole life, I was surprised to learn that they do more harm than good. Nordlock aka Wedge Lock washers are available at http://www.mcmaster.com/#standard-lock-washers/=gio1a8
I am not affiliated with Nordlock.
http://www.youtube.com/watch?v=mgwmuZuJ02I
and
http://www.nordlock.com/default.asp?url=2.16.37
Joe Gores
 
Those Nord-locks look pretty cool, I hadn't seen those before. The brakes seem like an awesome place for it. Not cheap though...

Note that the outside faces are ridged and if I understand the physics right, they must bite into both the bolt head and underlying surface to work properly (so that only the cam area turns). I'm guessing not appropriate for thin aluminum applications.
 
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Re PC680.....have two in our RV7A with dual light speed Plasma II. There have been two that have had problems...both our fault. Letting the charge get low in cold WX got one and old age got the other 5years.....we change the oldest batt every other year. The newest is the E Buss battery. As for the cooked alternator mentioned in this thread the most probable senario was the altenator failed due to runaway self excitation and the battery did its usual good job of getting the plane safely on the ground. Talk to the owner of B &C Specialties about the batteries and the internally regulated alternators. He is a wealth of knowledge on both subjects
 
Battery

My PC680 battery is over 7 years old and is getting slow on cranking. I will replace it this year at the condition inspection. It has been a great battery.

Does anyone know what size Nordlock washers I should use. I will order them no?
 
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