Is there a maximum indefinite time period charge current that will not harm an AGM battery?

[sdold]

I would guess that disconnecting the battery and keeping it on a bench charger would be more work then necessary?

What do the other pilots do with their batteries?

It would be a lot of work to remove the battery. The guys I know that don't fly often and don't charge or connect anything between flights end up getting about 2-3 years out of the batteries. One or two use the Harbor Freight trickle chargers, I'm not sure what success they have, if any. The batteries in the club airplanes that fly often last 5 or more years.

[SunEagle]

It would be a lot of work to remove the battery. The guys I know that don't fly often and don't charge or connect anything between flights end up getting about 2-3 years out of the batteries. One or two use the Harbor Freight trickle chargers, I'm not sure what success they have, if any. The batteries in the club airplanes that fly often last 5 or more years.

Too bad. Just another reason for me to hate batteries. Most of the time they are a PIA because they do not work when you really need them.

Sorry. I have had years of fighting the problem where other people insisting on installing a UPS in Industrial control equipment cabinets only to have my Instrument Techs have to replace the damn things every couple of years before they died because they would fail when we really needed them. Waste of money and labor IMO.

[PNjunction]

It says that an aviation battery uses a higher specific gravity electrolyte, and that a lower charge voltage should be used than with typical batteries, so an aviation-specific charger should be used. Mine's not aviation-specific, so if that's true I might be getting ready to use the wrong charger, I need to learn more about this. Thanks for the heads-up.

That's exactly right. And of course, like all aviation products they are waaay costly. The temptation to use a cheaper non-aviation product can be strong, but dude - don't mess around.

FBO's that really know the deal might have them. If you see an FBO shop offering automotive chargers, (rare), it's time for them to wise up.

[PNjunction]

What do the other pilots do with their batteries?

Many are neglected and get replaced with the mandatory yearly testing when they fail the load-test. Usually due to neglect, OR automotive chargers that fry the battery since the pilot isn't aware of the difference in chemical makeup.

Think starter-battery on steroids with a much larger percentage of acid than a conventional starter battery has.

[Sunking]

The airplane battery environment seems like a really bad one. A typical flight might be an hour or two, followed by two or three weeks or more of sitting idle, so I'm looking at ways to keep it charged without removing it each time.

Steve you are needless worrywart.

You should not be asking anyone on this forum how to maintain your aircraft batteries. If you are flying at least once a month, you have nothing to worry about. At most disconnect the battery. As part of your annual, the battery will be capacity tested.FWIW the battery is required to test at least 90% capacity. Anything less is toast. An AP mechanic would not allow you to use it at less than 90% capacity.

What Model Series of Concorde battery do you have? RG like RG35? You need to follow Concorde CMM procedures Just guessing but most likely CMM 5-0171. No where will you find any Float Charge procedures. That only applies if the batteries are removed and stored for more than 12 months. Really all you need to do is just disconnect one lead of the battery when you put it in the hanger

Concorde Self Discharge rate is less than Lithium at 1% per month. I am not saying you cannot Float the batteries, but you will not find any Concorde procedure for doing do so if you are using Concorde Aviation batteries. Before each flight you measure the OCV. If it is 12.5 to 13.0 volts fire it up and take off. Anything outside that and you are grounded.

Charging is super simple procedure that does not require any special expensive charger. Just a Plane Jane CC/CV charger. It must be sized no less than C/5 and no greater than 10C. So if you have a RG35 at least 9 amps and no greater than 450 amps. You apply a Constant Voltage of 14.25 volts until charge current tapers to 5% of C or C/20 and on a RG35 is 2.25 amps and terminate charge. If 6 hours have passed and charger has not Terminated, the battery must be Capacity Tested.

Pull up Concorde web site and download the right CMM for your battery. That is the best practice procedure. I think you are looking for CMM 5-0171. If you look in the Concorde RG Owners manual, you are not going to find a lot of info on charging. All they say about long term storage is to disconnect the battery. The CMM is the maintenance, storage, testing, and trouble resolving. FWW I am a PP, not current, and use to be part owner of a Mooney. What you want to know before each flight is the OCV. It either passes or it does not.

If it were me here is what I would do and practiced with my two partners. My two partners are commercial pilots who fly passenger jets on the civilian side, and fighters on the military side. If the battery fell below 25 volts on a 24 volt system (12.5 on 12 volt systems) the battery got a charge. Ironically if the battery is over 26 volts (13 on a 12 volt), is required to have a capacity test. Go figure.

Having said all that, if you really want to Float Charge your battery does not require any special charger. No battery does for that matter. Concorde Specifies CC/CV. We already covered that ground. But call Concorde and see if they will give you a Float Voltage. I seriously doubt they will do that. If they do not tell, you have to take your chances at guessing. Setting to low is no big deal as that is the same as doing nothing. Setting to high and you are screwed with plate corrosion, puffing, venting, and thermal runaway.

Keep in mind if you Float Charge, you invalidate your pre-flight check list because the OCV will be greater than 13.0 volts.

You did not hear it from me

13.1 to 13.2 volts. Click here. Download the document and make sure you can answer all 26 T/F questions correctly.

[sdold]

Steve you are needless worrywart. ... If you are flying at least once a month, you have nothing to worry about

Part of my mindset is from flying Cessna 140s with 12A generators that only started to charge when the rpm was above 1700. I did a lot of night stop and goes to maintain night passenger and tailwheel currency. With the nav lights and landing light using about 20-25A, I'd always park with a partial charge. But now I've moved up (some say down) to a 150 with an alternator. Maybe I don't need to worry about it anymore.

What Model Series of Concorde battery do you have? RG like RG35?

The current one is an RG25. 5-0171 is the correct CMM.

13.1 to 13.2 volts. Click here. Download the document and make sure you can answer all 26 T/F questions correctly.

That's a really good link, thank you. They make a big deal of self-discharge, but they might be speaking of flooded batteries.

I just came back from a big meeting with BTECH where they showed us their battery monitoring system. Maybe you are familiar with them. Their equipment looks at each battery in a plant and does periodic impedance measurements and logs everything and sends it back to an office via ethernet. So today my head is full of battery information.

I always wanted a Mooney. I had a Mooney M-10, but it never seemed like a real Mooney.

[SunEagle]

Part of my mindset is from flying Cessna 140s with 12A generators that only started to charge when the rpm was above 1700. I did a lot of night stop and goes to maintain night passenger and tailwheel currency. With the nav lights and landing light using about 20-25A, I'd always park with a partial charge. But now I've moved up (some say down) to a 150 with an alternator. Maybe I don't need to worry about it anymore.

The current one is an RG25. 5-0171 is the correct CMM.

That's a really good link, thank you. They make a big deal of self-discharge, but they might be speaking of flooded batteries.

I just came back from a big meeting with BTECH where they showed us their battery monitoring system. Maybe you are familiar with them. Their equipment looks at each battery in a plant and does periodic impedance measurements and logs everything and sends it back to an office via ethernet. So today my head is full of battery information.

I always wanted a Mooney. I had a Mooney M-10, but it never seemed like a real Mooney.

Back in NJ my friend would take me up in a 152 every once in a while to get in his T&G's to stay current. That was fun. We even got to rent out a 4 seater 172 once.

[PNjunction]

Let's put it this way - because your head is spinning, a no-brainer solution to make sure it is done right would be an aviation-specific/battery model specific Battery Minder. Done.

If one reads through some of the responses too fast, they may come away with the feeling that just any old automotive type charger will do. NOT SO, and this isn't just snake-oil. Place an overly-agressive Schumacher "speed charger" from the auto-parts store on an agm can easily result in 15.5v EQ being measured at the terminals at the start of absorb despite the front-panel voltage display showing 14.6v. Not good for your aircraft battery. I have a little sticky with this warning about automotive chargers that have unpublished algorithms.

And as always, the devil is in the details, although you are providing some of them.

I was about to ask if your plane was privately owned, or in club use. In a cool hanger, or sitting in the hot sun with tie-downs in Arizona without any charge for a long time? Have 15 club members but NOBODY is flying because it is just so costly to do so and thus the battery doesn't get any charge? Have some knucklehead kill the battery playing with the avionics / gps, forgetting to turn things off and so forth for a weekend, and the battery sits in a discharged state for another month?

Do a summer burger-run to a high-altitude airport, and with a semi discharged battery have that same knucklehead just crank the battery to death trying to overcome vapor-lock because he didn't open the cowlings and let things cool? Short hop back home and battery is already discharged, since the small hop was not enough to fully charge the battery? We had this happen on a trip to L35 (Big Bear, Ca) awhile ago.

I think you get the point. Overly simplistic answers are ok if you are a battery geek or total cheapskate. The thing about batteries is that abuse, even if small, ADDS UP over time and you just aren't going to get the life they are capable of if they aren't treated right.

The aviation Battery Minder will help you achieve what you paid for with a minimum of head-spinning. And they have plenty of aviation connectors for remote charging so you don't have to take the battery out. You could be flying rather than reading.

[Sunking]

OK Steve an RG-25 is fairly small battery of 22 AH. Mind you that is at the 1C rating, not 20 hours rating. If it were specified at 20 hour discharge rate would be much higher like 70 to 80 AH. If you follow the manufactures minimum charge rate of C/5 you need at least 4.4, let's call it 5 amps. Anything from 5 and up can be used on that battery, and anything over 10 is overkill.

I gave you the link for Gill Battery because they are Concorde's direct competitor on the Aviation Market. They just give better maintenance info and facts on the web. You can use the exact same procedures on either Gills or Concorde. Being aviation there really is only one criteria to meet. What the FAA says it is. Battery Minder makes a good charger and a perfect model for you is 128, a 12 volt 8 amp Aviation Grade charger. It is made specifically for Concorde Aviation batteries. At 8 amps can bring that battery back from the dead in 3.5 hours.

But do not fall for the sales pitch you have to use a Aviation Specific charger. Look at the CMM it complies with FAA specs. A CC/CV charger of 14.2 volts until current tapers to 5% and terminate charge. To take that one step further ask you AP Mechanic what all Voltage Regulators are set to in planes? I bet he answers 14.2 volts.

The real issue is FLOAT for storage. For that you have to decide. Whether you want Float or not, there are quite a few chargers that can do that. If it were me being the cheap guy I am, knowing what I know is I would find a nice a god Float Charger of 5 to 10 amps that I can set for 13.2 Volts. I also would not disconnect the battery. That way I let the Engine Alternator do the 14.2 volt charging, then Float Charge the battery to keep it fully charged until next time. Even if you forget to turn Avionics off, no problem.

Anyway good dluck, you will figure it out. You cannot go wrong with the Battery Minder, but there are other options.