Battery capacity checks

[EricJ]

Just now, MikeOH said:

@EricJ

Maybe I need to re-evaluate the risk that my battery minder will burn down my hangar

FWIW, the City of Phoenix only allows two things to be continuously plugged-in in a hangar:  a fridge at least 18" above the ground, and an approved battery minder.    Only some Schauer and BatteryMinder models are approved, including the one for the Concordes.   Since they pass the city lawyer paranoia risk test, you're probably fine.   

They do require the interface kit with the Anderson connectors, too, though.

[PT20J]

21 hours ago, EricJ said:

I had an interesting development lately.   I've been capacity testing my Concorde RG-35AXC battery every year or so, and it's been consistently hitting 95-100% capacity testing both during a capacity test and verified during a recharge cycle with my Topdon charger, which also measures capacity during the recharge.   

But the battery performance has still been dropping during that time, as measured by slower cranks, and deeper voltage sags during starter operation.    I did some engine work a couple weeks ago, and when I went to start it after reassembly it did a quarter turn and stopped.   Erk.  On a second try it turned enough to start, and I figured I'd try a local flight and see what it did.   It started for that as well, but then during a hot start at the fuel pump after returning it was definitely starting to turn a lot slower just before the engine started.

So I got a new replacement, which is now back to spinning the prop like crazy with the skytec, and thought I'd check the old battery to see how it's doing.

Open circuit voltage on the old battery was still great, 12.8V when I took it out of the airplane, which showed as 12.9V with a different multimeter before I started the capacity test after bringing it home.   I got a Kunkin tester to replace my old semi-homebrew unit which could ony test at half current, so this test went more quickly.   The result was 27.13Ah capacity, or 27.13/33 = 82% capacity.    When the Topdon recharged it, it reported a 28.1Ah capacity, which is still only 85% capacity, which is Concorde's recommended threshold for removal from service.   OCV after the recharge was 13.3V.  Since it was already having trouble I didn't think it was worth attempting a rehab cycle, especially since I already had a replacement.   If replacements weren't available a rehab attempt would have definitely been an option.

The battery is nearly six years old, and has lived in Phoenix its entire life and we're not yet through a brutally hot summer with long strings of contiguous record-breaking high temps, so it may have just been enough to push it over the edge.    The more remarkable thing to me is how quickly it went from testing 95+% capacity to notably tired and questionably servicable.   The last capacity test was in March and tested at 34.2Ah, which was confirmed during the recharge by the Topdon at 35Ah (both a little over 100%).   The summer was either hard on it or it was just done, but the change from testing 100% to out-of-service in about six months suggests that other tests, like the voltage sag during start or just observation of starting behavior, may be a more reliable indication of a failing battery.    The capacity test seemed to not provide adequate warning under these particular circumstances.

Anyway, just thought I'd pass that along.    A successful capacity test may not be a reliable indicator of the ability of the battery to make it another year.

That’s an interesting result. Of course, the capacity check only serves to indicate whether the battery can be returned to service as of the date of the check. Since the checks are recommended to be performed annually, I always assumed that the battery would degrade slowly enough near its end of life that it would not fail completely within a year after a successful check. 

I wonder if it might make sense to do more frequent checks after a few years of use? 

[ArtVandelay]

I just replaced my Concord after 5 years, no BM and I fly frequently. Capacity check was 85% and starts seem lethargic. I choose not to push it and have to be AOG somewhere because of battery issues.

[MikeOH]

1 hour ago, EricJ said:

FWIW, the City of Phoenix only allows two things to be continuously plugged-in in a hangar:  a fridge at least 18" above the ground, and an approved battery minder.    Only some Schauer and BatteryMinder models are approved, including the one for the Concordes.   Since they pass the city lawyer paranoia risk test, you're probably fine.   

They do require the interface kit with the Anderson connectors, too, though.

Ruh oh!  My fridge sits on the ground

[PT20J]

1 hour ago, MikeOH said:

Ruh oh!  My fridge sits on the ground

I think the idea is that if someone has a fuel leak, the fuel vapors are heavier than air and so will be near the ground. So, keeping any potential spark producing equipment 18" above the floor might prevent ignition.

[MikeOH]

1 hour ago, PT20J said:

I think the idea is that if someone has a fuel leak, the fuel vapors are heavier than air and so will be near the ground. So, keeping any potential spark producing equipment 18" above the floor might prevent ignition.

Yuup.  Just like a water heater in your garage.

[Hank]

36 minutes ago, MikeOH said:

Yuup.  Just like a water heater in your garage.

In my last house, the water heater sat on the garage floor. In my current home, it's on the floor in the finished part of my basement. 

But the little fridge in my hangar is on a table . . . purely by coincidence rather than planning. 

[PT20J]

I think most building codes only require gas water heaters to be 18” above the floor due to the pilot light. Seems like requiring the refrigerator to be 18” off the floor is overkill, but my hangar has that reg also. 

[Pinecone]

12 hours ago, PT20J said:

That’s an interesting result. Of course, the capacity check only serves to indicate whether the battery can be returned to service as of the date of the check. Since the checks are recommended to be performed annually, I always assumed that the battery would degrade slowly enough near its end of life that it would not fail completely within a year after a successful check. 

I wonder if it might make sense to do more frequent checks after a few years of use? 

Except that the capacity check is hard on the battery.

[Pinecone]

I have run Battery Tenders (similar device) for cars for over 20 years without an issue.  A couple of cars (and my portable generator) are on them pretty much full time.

I thought I heard recently that Concorde is not recommending a Battery Minder for all the time.  IIRC, about 4 hours a day will allow the battery to rest, but stay fully charged.  I was thinking about putting mine on a timer.

[Fly Boomer]

1 hour ago, Pinecone said:

I thought I heard recently that Concorde is not recommending a Battery Minder for all the time.

See page 3 of this Technical Bulletin

TB15 - Maintenance Charging.pdf

 

[PT20J]

3 hours ago, Pinecone said:

Except that the capacity check is hard on the battery.

Agreed, but not that hard if you charge it immediately after the test. It’s a tradeoff. I wouldn’t do it monthly. But maybe 6 month intervals would make sense.

[EricJ]

2 hours ago, Fly Boomer said:

See page 3 of this Technical Bulletin

TB15 - Maintenance Charging.pdf 188.92 kB · 6 downloads

 

That's a good input point.

[Vance Harral]

If Concorde themselves recommend a battery tender, they're obviously the best source of info.

That said, my anecdotal experience matches Mike's - we have absolutely no need for the things.  We've had 3 Concorde batteries over the last 19 years, so average lifetime of over 6 years.  The airplane flies 75-100 hours per year and typically flies at least once a week, but occasionally sits for periods of up to a month.  Sometimes we "tax" the battery during maintenance (e.g. gear cycles), then charge it up with a cheap automotive battery charger after.  That's the extent of our stewardship.

This behavior would be considered downright abusive by the BatteryMinder crowd, but the only battery problems we've ever had didn't actually involve the battery (left the master on once, another time the shower-of-sparks system went kaput and we ran the battery all the way down trying to start the airplane, got the airplane started both times via jump from a car).  We do perform capacity tests, though our test method consists only of "leave the stuff in the airplane turned on and measure voltage with a meter".

This is all anecdotal, so not trying to sway anyone's opinion.  Just providing a data point that I kinda don't get the Battery Minder religion, at least for airplanes that fly on a regular basis.  I might feel differently if the airplane sat for months at a time, or if we lived somewhere with 110 degree summers.  But for our specific situation, given our actual experience, there's just no justification for the extra cost and hassle of a tender (which is admittedly minimal).

Again, though, if Concorde themselves recommend a tender, that's obviously the gold standard.

[PT20J]

It turns out that Concorde has Technical Bulletins discussing adjusting capacity check intervals and maintenance charging.

https://www.concordebattery.com/knowledge-base.html?media=tb

 

[DonMuncy]

24 minutes ago, PT20J said:

It turns out that Concorde has Technical Bulletins discussing adjusting capacity check intervals and maintenance charging.

https://www.concordebattery.com/knowledge-base.html?media=tb

 

C'mon, don't make us read a dozen technical bulletins  How often do they say to do capacity checks?

[PT20J]

13 minutes ago, DonMuncy said:

C'mon, don't make us read a dozen technical bulletins  How often do they say to do capacity checks?

The answer, as you might expect, is, “It depends.” 

[DonMuncy]

19 minutes ago, PT20J said:

The answer, as you might expect, is, “It depends.” 

I should have guessed as much. Thanks.

[MikeOH]

2 hours ago, PT20J said:

It turns out that Concorde has Technical Bulletins discussing adjusting capacity check intervals and maintenance charging.

https://www.concordebattery.com/knowledge-base.html?media=tb

 

Ok, below is the pertinent table from your link. My read is that as long as the capacity check is >90% you perform the check every 12 months.  If the check shows between 85% and 90% then you check every 6 months.  That seems logical to me.

 

[dkkim73]

Does anyone know to what extent a smart tender like the Battery Minder adjusts it's actions to allow it to work well connected full time? The bulleting talks about length of "maintenance charging" with specific but constant voltages, and discusses the negatives of ongoing electrolysis. Does the Battery Minder "back off" and watch? I suspect this would probably require contacting the manufacturer, but the fact it is a "Concorde-specific" model they make raise some hopes... curious if anyone here already worked out this problem. 

The capacity test and recondition were pretty uneventful but, yes, I was halfway expecting it to explode or something... Used an IR thermometer and saw little temp rise. Did not let it sit discharged for hardly any time FWIW. 

[Fritz1]

There is a control algorithm in the battery minder, regular charge up to a predetermined voltage, then trickle charge, also temp dependent, I use only one with two same age Concords charged in parallel, gives you 20 Ah to run avionics in hangar, swing gear, test lights etc. and the minder recharges the batteries thereafter. Regardless I think one of my Concords has had it after 6.5 years, did not swing the engine yesterday, will investigate, maybe main solenoid, but chances are one Concord battery is dead after 6.5 years. Minder does probably not make a difference for an airplane that is flown at least every two weeks, nice to have though as a small ground power unit and in case airplane sits more than 4 weeks.

[EricJ]

7 hours ago, PT20J said:

It turns out that Concorde has Technical Bulletins discussing adjusting capacity check intervals and maintenance charging.

https://www.concordebattery.com/knowledge-base.html?media=tb

 

Nice.   And that bulletin is fourteen years old.   So we're full circle from don't bother, to must test it every year, to mostly leave it alone.   

This does, however, encourage people sharing their capacity test result histories, since that's the recommended basis for determining when to test.   After my recent experience I think my schedule will be to test at five years and go from there.

I'm also backing off how often I connect the minder.   I just finished an inspection cycle today and left it unconnected...oh, my!

 

[PT20J]

Also keep in mind to quote W. Edwards Deming, "There is variation in everything." Some batteries are just going to last longer than others. Everything is on a bell shaped curve.

[T. Peterson]

16 hours ago, Pinecone said:

Except that the capacity check is hard on the battery.

I’m not the expert that are many of you, but the equipment which must be purchased, the time and effort involved, the dubious forecast of reliability and the potential damage to the battery does not make it seem that these capacity checks have a worthwhile return on investment.

[MikeOH]

1 hour ago, T. Peterson said:

I’m not the expert that are many of you, but the equipment which must be purchased, the time and effort involved, the dubious forecast of reliability and the potential damage to the battery does not make it seem that these capacity checks have a worthwhile return on investment.

Hmm, maybe...I don't like 'not knowing' what my battery condition is until it fails.  As in, I doubt that any of my annuals have had a capacity check performed.  It was less than $200 for the equipment to perform the test myself.  Concorde has once a year in their manual, so I don't think it's all that hard on the battery.