Battery going bad, or something else?

FredFenster

FredFenster

Pre-takeoff checklist
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Greg L
Looking for a little insight into a problem that started this past weekend. I had a battery minder hooked up before flying, all indications on the charger show the battery is good to go. Plane starts fine, fly for a little over two hours, land without issue. Fill up with gas, go to restart and barely have enough power to get it started. Luckily I was at home so I taxi to the hangar and shut down. Try to restart again just for the hell of it and there's not enough power to turn the engine over at all. Pushing the starter button only results in hearing the gyros spin down.

I hook up the charger and let it charge for a day. Battery minder shows everything is good to go again. Engine starts up like normal, no issues. Voltmeter shows roughly 13 volts at 1000rpm, 12 with master on but nothing running. Ammeter shows no discharge when engine is running until radios/lights/transponder turned on like normal. Voltmeter drops to 0 while starter is engaged.

Does this sound like a bad battery or something else in the charging system? Battery is a Concorde, I'm guessing it is from 2011 (nothing in logs about replacement since) so it is getting up there in age.
 
That's what I was wondering, although I've got a generator and not an alternator. None of that fancy 1960's alternator tech just yet.
 
What's the voltmeter say when running? 13.5 or so, battery, less, gen or regulator
 
At first blush I would say check connections, sounds like you aren't getting enough current to the starter. Check and clean the battery connections first, make sure ground and other terminals aren't loose or corroded. If you are seeing 13 volts while running it sounds like it is charging. It could be the battery too, but I would start simple, you would hate to buy a new battery and have the same issue.
 
13 volts at 1000rpm? It's definitely keeping the battery from discharging there but what voltage is it at during cruise? 13.5-14.5 is ideal and should definitely mean the battery is charging and not just being maintained.
 
and do you kill your apps when you're not flying? Oh no, not sucking me into YABD!!!!
(Yet Another Battery Discussion)

Oh, and somebody needs to send me a new battery for my ATV ... it didn't survive the winter, since the battery minder got unplugged somewhere along the way.
 
Could be the generator,coupled to a battery,that’s not holding a sufficient charge,you should have the battery load tested.
 
Concorde can give you the Mfg date if you give them the serial no of the batt.
 
Not really enough info but let's try this:
FredFenster said:
I hook up the charger and let it charge for a day. Battery minder shows everything is good to go again
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A Battery Minder is not a battery charger. It is not designed to "charge" but rather maintain a charge on the battery.

FredFenster said:
Voltmeter shows roughly 13 volts at 1000rpm
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This should be closer to 13.5-14.5 volts with an alternator.

FredFenster said:
12 with master on but nothing running
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This should be closer to 12.4 to 12.6 with a fully charged battery

FredFenster said:
Battery is a Concorde, I'm guessing it is from 2011
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It's a little long in the tooth for a lead acid battery. But there is a capacitance check you can perform to verify the health of the battery. Look up the service manual for your model battery online and perform that check.

If the battery fails the check, new battery. But before you install battery verify (using a VOM) aircraft charging system meets specs, no parasitic drains on system, all wires/connectors in good condition, and all ground connections are clean and secure.
 
FredFenster said:
Voltmeter drops to 0 while starter is engaged.
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Might be the battery, but spend some time trouble shooting first. The fact that the voltage drops to zero when the starter is engaged is revealing. It means that there's either almost no capacity left in the battery, or there's significant resistance between the battery and starter. But since that battery is able to start the airplane first start of the day would indicate that it still has enough oomph left in it even if it is seven years old. So we'd start looking at places for resistance to form, resistances that get hot while the generator is trying to charge the battery. A hot connection is a poor conductor compared to a cold one, so the starter doesn't want to go after that first flight. And there are many places for hot connections. The ground connections at the battery and engine mount. The battery cables and their terminals. The master solenoid (which I would put at the top of the Most-Likely list). The cable between the solenoid and starter contactor. All of these can be checked with a voltmeter, looking for voltage drops across the junctions while someone fires the starter. That starter draws a lot of amps, which means that even a tiny resistance causes a huge voltage drop. Voltage = ohms x amps. A 250-amp draw across a .05 ohm resistance...a miniscule twentieth of an ohm...means a 12.5 volt drop. The lights go out. Good, clean connections and contactors are a must, not an option. The dirty, oily, corroded stuff I find in airplanes is inexcusable. It's amazing that some of them work at all.

This topic comes up once or twice a week and this forum has a long history of addressing electrical problems. Too often the advice is to start throwing money at it. Someone needs to write a short book on the basics of aircraft electrical systems and the methods of troubleshooting. With pictures.
 
Bell206 said:
A Battery Minder is not a battery charger. It is not designed to "charge" but rather maintain a charge on the battery.
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It should be noted that while this sentiment is correct, their 8A models are well into the slow charging range of most aviation batteries, so they will slow charge a battery

They’ll also happily get into a fight with a battery that exhibits significant internal resistance and cook it slowly, which will increase in speed if the battery is boiling off water from the electrolyte because of localized internal heat. Great way to utterly destroy a battery that probably is already in the early stages of death, but 8A dumped into a battery in that state will cook off that battery nice and fast.

(Of course so will the alternator on the next few flights so really the effect may actually be positive in that a questionable battery will die quickly. Downside is it’s sitting there boiling and no airflow so nasty corrosion things may be happening in the surrounding area of the battery including the battery box or surrounding aircraft structure. Always clean up and make sure any acid film that’s accumulated anywhere after a battery boils to death is neutralized in the battery box and surrounding area before installing the replacement battery.)

I think they warn about not buying the higher amp rated “minder” if one’s battery is below a certain size, but I’m sure there’s plenty of aircraft owners out there who think “if 4A is good, 8A is mo’ bettah!” LOL. Maybe, maybe not. If a typical aircraft battery needs more than 4A to deal with vampire loads that aren’t run through the master switch (clock usually) and any self-discharge/internal resistance inside the battery, it’s done for anyway. It’d be pretty rare to need an 8A minder. But they sell them.
 
Thanks for all the tips, looks like I'll get the battery load tested and clean all the connections tonight, then go forward from there.
 
I had a nearly identical issue recently in my TBone. It turned out to be a bad battery (I had 11yr old Concordes). Pull the battery, take it to the local auto shop and let them test it. I'm betting it's got a bad cell.
 
mines doing it at exactly 4 years old. drops to 7 volts and slow to crank or stops if it's cold enough, once it starts it does the typical huge amperage and then settles down after 30 minutes. Sure, the braids on those pipers are terrible, but then again they've always been terrible. Occam's razor. It's the battery. Load test it for sure, but on a 2011, I bet ya it's the battery.
 
If this is an AGM batter (e.g. Concorde) it may be nearly dried out. It will hold voltage, but will have limited or no capacity. A load test will sort that out. 7 years is a long time for a battery. I'm used to maybe 3-5 years of good battery life here in the Winter Wonderland. A healthy battery, BTW, should charge to almost 12.6 volts.
 
bradg33 said:
I had a nearly identical issue recently in my TBone. It turned out to be a bad battery (I had 11yr old Concordes). Pull the battery, take it to the local auto shop and let them test it. I'm betting it's got a bad cell.
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Wow. An eleven year old battery. You just about made money on that deal!
 
Dan Thomas said:
...This topic comes up once or twice a week and this forum has a long history of addressing electrical problems. Too often the advice is to start throwing money at it. Someone needs to write a short book on the basics of aircraft electrical systems and the methods of troubleshooting. With pictures.
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If you write it, they will buy it. I'll be first in line at the book signing. ;)
 
Just to update - The battery didn't have much voltage on the load test so I replaced it, seems to have fixed my problem. It must've been on its way out for awhile, the prop spins faster now when starting than I've ever seen it. Flew it for an hour and a half with the new battery running everything I've got electrically and it still restarted normally on the ground. Voltmeter showed just a hair below 13v running at 2500RPM the whole time.

Although when I changed the battery I noticed the power and ground wires look pretty old and ratty, and I saw Bogart makes some overpriced STC'd fancy cables.. Let the slippery slope begin! :D
 
FredFenster said:
Although when I changed the battery I noticed the power and ground wires look pretty old and ratty, and I saw Bogart makes some overpriced STC'd fancy cables.. Let the slippery slope begin! :D
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The Bogert cables are nice and $$$, also since they're 1 gauge they're stiff as a honeymoon....rooster! If you catch my drift. They're a little hard to hook up and route because of this in my experience.
I'd check with this guy and see what he can do
https://pinpointharnessing.com
He's posted some of his work in the Classifieds here and I've read good reviews of his work on the Cessna Pilots Society forums
 
It could be the battery, or maybe the alternator, or perhaps a loose or dirty connection or a bad ground. That's it!! Look for some bad ground underneath the airplane.

Jim
 
FredFenster said:
Voltmeter showed just a hair below 13v running at 2500RPM the whole time.
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May want to check the voltage at battery with a VOM at 2500 rpm. At that rpm should be over 13.5v regardless if generator or alternator.

FredFenster said:
I noticed the power and ground wires look pretty old and ratty,
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Why not have your mechanic fabricate new battery cables? Can buy cable, lugs, heat-shrink at Spruce cheaper and a good auto parts/hardware store will have big crimpers to install lugs.
 
That voltage is low for alternator or generator field engaged. About right for a brand new topped off battery running on its own without the alternator/generator engaged.
 
hindsight2020 said:
That voltage is low for alternator or generator field engaged. About right for a brand new topped off battery running on its own without the alternator/generator engaged.
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You were 100% correct. Flew a little more, voltage slowly started dropping. I figured a new generator would be the next step so I pulled the lower cowling to see if I would be able to remove it without pulling the mags off and found my problem. One of the wires on the generator was broke off from the ring terminal. Got that fixed, along with an overnight on the battery charger and now I'm seeing ~14.5 volts at 2500rpm.
 
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