Battery Check Anyone do it?

[cliffy]

How many actually do a complete battery capacity check every year at annual as all battery manufacturers recommend? 

[kmyfm20s]

How do you do it? 

[carusoam]

Done at annual...

Love my gills... 

Best regards,

-a-

[Yetti]

I bought the specific gravity tester.    But then just added water and called it good.

[Sabremech]

Since the key word is recommend and not mandatory, not very often for me. 

David

[jetdriven]

I have a pretty fresh battery but it seems that discharging it like that can shorten it's life.  That said, I see a lot of planes where the alternator quits and 5 minutes later everything else quits too, which says the reserve capacity is very low 

[OR75]

how fast it turns the prop is a good test of battery capacity ....

but I do check every quarter or so for battery leaks ( even for a sealed battery)  or loose connection 

[jetdriven]

A lot of them turn the prop fast, but leaving the radio master on for 5 minutes completely kills the battery.  I had a filed wire break on me, an we finished the lesson, flew back to the airport and did 4 landings. Landing light on, gear up and down 4 times, etc.  I did turn the #2 radio off.  Around 30 minutes of flying. It still had enough capacity to start up again twice more while troubleshooting the alternator.

Standing voltage doesnt show this, but putting a load on it for a period of time will.

Edited January 2, 2016 by jetdriven

[DonMuncy]

1 hour ago, jetdriven said:

I have a pretty fresh battery but it seems that discharging it like that can shorten it's life.  That said, I see a lot of planes where the alternator quits and 5 minutes later everything else quits too, which says the reserve capacity is very low 

Byron,

I, too, would worry about discharging a battery that low, but that is only intuitive on my part. Has anyone read anything authoritative that suggests that if a battery is deep discharged and immediately recharged, it would or would not harm it.

[clh]

My understanding is that if you do a deep discharge and immediately recharge, you can cause warping of the plates.  This will reduce the life of the battery.  Back when I was working with battery backup systems, the major causes of battery failures was plate warping or sulfation.  Occasionally, we would degrade the posts, but that was usually due to corrosion and arcing on the terminals.

[N201MKTurbo]

I don't believe the discharge test will deep discharge the battery. If I recall the protocol is to discharge it to a prescribed voltage at a prescribed constant current and record the time it takes to get to that voltage. All within the design limits of the battery.

Starting the plane and immediately charging it back up with a 70 Amp alternator is probably more stressful then the test.

When I was retired six years ago I was designing a USB battery discharge tester that would hook up to your laptop with software to control the discharge and record and display way more information then you would need. I have all the discharge protocols somewhere on my computer if anybody is interested.

It turns out that someone already makes such a device, that I would be hard pressed to beat on price considering how small the market is, so I just went out and got a job... 

[wishboneash]

For the Concorde, there is a recommended discharge procedure. The discharge rate for the RG35-AXC would be 39A (after fully charged at over 20C ambient temp) and recording the time to get to 10V (12V battery). Then calculating the % capacity = discharge minutes * 1.6667. I don't have such a high current load set up yet to do this test. For this, one would need an approx 0.3 ohm resistor that can handle 500W for an hour or so. Note, this is an approximation since the load would need to change (decrease) to maintain constant current as the voltage goes down to 10V. 

[RLCarter]

I have worked with and serviced thousands of Pb-acid batteries over the past 35+yrs, granted these were mostly motorcycle batteries but all lead -acid batteries require the same as far as initial servicing and maintenance. The life of the battery starts with when & how the initial service is performed, adding acid to the correct level and throwing it on the charger until it is fully charged will result in failed battery 1.5 to 2 years down the road. After adding the acid, the battery needs to sit so that the acid fully saturates the plates, most battery manufactures recommend 30 min. or so, I personally wait 3 hrs before hooking it up to a charger. On maintenance free (sealed) batteries I would wait 24hrs before charging, due to the fact all the acid is absorbed into the plates. Do not install the battery before it fully charged as this will shorten the life as well, I have personally seen 7yrs on a properly serviced & maintained battery. Keeping the fluid level up and not allowing the lead plates to be exposed to air is the key to its survival, the water evaporates do to heat, whether it be from charging and/or ambient temperature, so check your water level frequently. The fully charge and “load test” does not drain the battery completely down or it shouldn’t anyway, if it fails the load test generally you recharge and then re-test. Yes it is a pain in the butt to keep a battery serviced correctly and that is why most people just replace them at the first sign of trouble. 

[DonMuncy]

You guys know a lot more than I do. I assumed the test totally depleted the battery. But if it only pulls it down to 10v, I doubt it would be hurt. Somewhere, someone published a diagram for a "poor man's battery capacity tester". If my memory is correct, it was not a perfect constant amperage draw, but was supposed to be close. If anybody cares, I could try to dig it up.

[Yetti]

generally a couple of headlight bulbs to match the proper draw amperage is the old school load.

[larryb]

10v on a 12v battery is fully discharged. Doing the test will reduce life. A lead battery has a life limit on full discharges. It might be just 100 to 200 for a battery designed for deep cycle service. For our starting batteries it can be much lower. I cannot find any graphs on the Concorde website plotting life against discharge depth. That said you are only going to do 3 to 5 of these tests so perhaps it doesn't matter.

[Emmet]

I build one myself using an Arduino microcontrollet board and lamps as the load. It automatcally switches off when reaching the 10V an stores the whole measurement on a micro SD card for later plotting in Excel 

Concerning deep discharge you have to consider that the 10V limit is under load. The idle voltage will be higher.

[wishboneash]

I was thinking the same thinking! Using up to ten 50W 12V lamps as the load. I see yours is not quite constant current so the capacity could be overestimated. Switching in one or two lamps towards the end could make it more accurate. Great idea!

Sent from my iPad using Tapatalk

[carusoam]

Emmet, you have skills!

Data collecting, visualizing and reporting skills!

nice work!

Best regards,

-a-

[Emmet]

I use the actual current for the capacity calculation instead of the time formula given in the Concorde manual. Therefore it should be quite accurate and it is not necessary to have a constant load.

[cnoe]

A couple of Ohmite 300W resistors wired in parallel make a nice load source. I've used this setup using 3.1 ohm resistors for several years to gauge battery condition on underwater diver propulsion vehicles with SLA batteries. I wouldn't recommend discharging below 10.5V though to minimize any chance of battery damage. You will know very quickly whether or not the battery is weak as the voltage curve will begin to crash fairly quickly. A quick look shows these resistors available on Ebay etc. for ~$20 each. I didn't check digikey or elsewhere.

Sent from my iPad using Tapatalk

[cliffy]

#1 Starting does not use very much of the battery's "capacity"

#2  Let's say you have a 1 battery Mooney and you occasionally fly IFR. Now you come to the airport to fly with your 4 year old battery that has never been capacity tested and all you get is a click. Now think back to your last flight (oh ya, it was solid IFR)-

HOW LONG DO YOU THINK THAT BATTERY WOULD HAVE LASTED FOR YOU IN IFR IF YOUR ALTERNATOR HAD FAILED IN FLIGHT?  ( Not yelling, just making a point of how important the aircraft battery is )  

What about those who have dumped their vacuum systems for an all electric airplane?

Maybe something vacuum ain't so bad? Maybe a correctly done capacity check ain't a bad idea either?

Just askin' 

[Tom]

Mike Busch has a good write-up on this subject, including a DIY load testing (using the components in your plane like landing lights, pitot heat, etc):

http://www.avweb.com/news/savvyaviator/191348-1.html

The Concorde AGM battery maintenance manual:

http://www.concordebattery.com/otherpdf/5-0171.pdf

Concorde's ICA calls out only load testing and load testing indeed seems to be the only reliable way to see if the battery truly has what it takes to do the job.  I'm curious, though, if resistance measuring, which is non-destructive (unlike loading) could be a good way to monitor the life cycle of the battery, help predict demise, etc.

FWIW, Harbor Freight sells a carbon pile unit for about $50 and a digital tester for about $80. 

 

[DonMuncy]

The Harbor Freight ad for the digital tester had no information about how it works or what it tests. Does anyone with knowledge have an opinion on the unit.

[Tom]

7 minutes ago, DonMuncy said:

The Harbor Freight ad for the digital tester had no information about how it works or what it tests. Does anyone with knowledge have an opinion on the unit.

See the "AC Conductance" section on this website.