Odyssey Battery Failure Modes??

[Finley Atherton]

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/communit...ad.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

[frankh]

Personally I have never heard of a failure in an Odyssey of any kind.

Frank

[kevinh]

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.

[Neal@F14]

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.

[hgerhardt]

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.

[Walt]

Originally Posted by hgerhardt

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.

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).

[gmpaul]

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.

[hgerhardt]

Originally Posted by Walt

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...

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.

[Finley Atherton]

Originally Posted by gmpaul

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.

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

[SHIPCHIEF]

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.