Dead Battery or just a weak pulse...

drgwentzel

drgwentzel

Pre-takeoff checklist
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Hello Flyers,

Gather 'round for the tale of the Master Switch mishap—a saga of drained dreams and electrifying debates! ️

The scene: a mid-life battery, once full of zest and voltage, now as lifeless as a runway at midnight. The culprits: an innocent Master Switch left on, a depleted battery, and a duo of aviators now grounded in a sea of regret.

The conundrum: To charge or not to charge? That is the question! Some aviators, wise as old owls, suggest a gentle overnight trickle charge, followed by a stern load test to prove the battery’s mettle—or metal, if you will. Yet, others cry foul, proclaiming the battery as done for, as expired as last week’s flight plan.

So, what say you, dear Flyers? Shall we give this battery a second wind, or is it time to sing its swan song and lay it to rest in the great hangar in the sky?

Cast your votes, share your wisdom, and may the best current flow!

Gene Wentzel

P.S. ...asking for a friend.
 
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A gentle trickle overnight and then until you’re ready to fly it for a couple of hours. You might need to replace it once the cold sets in, but at a minimum you’ll get a few months of use.
 
The sooner you charge a depleted battery, the better chance of avoiding irreversible sulfation. For a flooded-cell battery, you have more time. For an AGM battery, you really need to get to it within 24-48 hours to have a chance. Charging a dead battery should typically not exceed an initial current of 0.3C where C is the capacity in Ah. So for a 25 Ah battery, no more than 7.5A initial charge. A smart charger should be able to do this automatically. If the battery won't trigger a charge with your smart charger, hook it up in parallel to another, good battery for a few minutes to get an initial charge on it, then try again with the dead battery solo. A full charge may take overnight. If the battery sat dead for a while, it may not be recoverable to full or usable capacity.
 
I'd put a desulfator on it first. It will put a low charge on it in the form of a square wave signal that breaks up the sulfate and encourages it to dissolve back into the electrolyte.

But in the long run, its life is limited.
 
drgwentzel said:
The conundrum: To charge or not to charge?
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No confusion about it. The OEM's guidance will set you free. But the longer you delay putting that battery on the OEM recommended charger the less battery you will have. In the end, a capacity check will tell you how well you succeeded. Good luck.
 
Also, what is your mission?

$100 burger on a CAVU day, uncontrolled fields. Not a huge worry. Especially if the plane can be proped.

Launch into solid IMC? NOPE. I want a battery that I know will get me on the ground in case of alternator and/or vacuum failure.

FYI, I leave my beacon switch ON. As I walk away, a quick glance back will remind me to go back and turn off the master. Just a couple of says ago at the airport. A guy lands and parks. He is walking away from his plane when I yell, "your beacon's on." He says thanks and that he leaves it on to indicate he left the master on. This time, he forgot to look back.
 
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I’d probably try the trickle charge route.

One caveat: Pretty sure all manufacturers recommend against charging a battery while installed in a plane. It may work the vast majority of the time, but batteries can and do explode on occasion. I’ve had it happen twice, fortunately not in a plane. But were you to get unlucky, an exploding battery can do a LOT of damage, with acid going everywhere.

Good luck, regardless.

Edited to add: here’s one that exploded on a battery cart. Made a real mess.

12085518205_d1693bbc71_z.jpg
 
Many plane batteries are AGM these days, so much less likely than a flooded cell to explode.

But that also means you should not use a standard auto type charger on them. Spend the money and get the proper Battery Minder for your battery.
 
Pinecone said:
Many plane batteries are AGM these days, so much less likely than a flooded cell to explode.

But that also means you should not use a standard auto type charger on them. Spend the money and get the proper Battery Minder for your battery.
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Like I said, most of the time you’ll be just fine charging the battery in the plane.

But here’s just one such warning against, from the Cirrus SR22 POH…

1717079775658.png
 
I borrow a battery from another ship or just buy a brand new one on the spot if one is available.


Charge if schedule allows.
 
Pinecone said:
Launch into solid IMC? NOPE. I want a battery that I know will get me on the ground in case of alternator and/or vacuum failure.
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FYI: the OEM capacity check will do just that, determine if the battery is serviceable for IFR flight. While the check is mandatory for Part 135 ops, if your aircraft battery is part of your emergency electrical power for IFR flight, it is highly recommended you still perform a capacity check per the OEM schedule, regardless if it suffered a large discharge event or not. Guidance puts the minimum acceptable limits at 80% C1 capacity level, however, Concorde and others usually use 85% C1 to give a buffer.
FastEddieB said:
But here’s just one such warning against, from the Cirrus SR22 POH…
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The key part is "dead or weak" battery as this condition can be conducive to an unknown internal fault which could create an issue during charging especially on a mx recovery charge sequence. The guidance I've seen and used was if the battery state of charge is below 25% (12.0v/24.0v) the battery should be removed from the aircraft prior to charging.
 
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