Battery not holding charge

[BravoWhiskey]

My #2 Battery is pretty much shot.  I was loading a flight plan before firing up and saw the battery drop down from 23.4v to 13.1v in just a few minutes.  It gains back voltage from alternator but then drops again quickly at low RPM or when the engine is shut down.  So I have a new battery and replacing in the next day or so.  
My question here is about legal flight.  POH min Equipment list says I need 2 batteries for all flight conditions.  So at what point is flying with this battery not legal?  

[mike_elliott]

A quick reminder Concorde has donated a 12 or 24v battery to the Mooney Summit Silent Auction

Here is an easy way to contribute to the Mooney community while buying something you might need anyway.

https://app.galabid.com/summitix/items

Yo do not have to attend the Mooney Summit to bid on items in our silent auction. All money goes to assisting downed Mooney Pilots families thru the Bill Gilliland Foundation

 

[1980Mooney]

2 hours ago, BravoWhiskey said:

My #2 Battery is pretty much shot.  I was loading a flight plan before firing up and saw the battery drop down from 23.4v to 13.1v in just a few minutes.  It gains back voltage from alternator but then drops again quickly at low RPM or when the engine is shut down.  So I have a new battery and replacing in the next day or so.  
My question here is about legal flight.  POH min Equipment list says I need 2 batteries for all flight conditions.  So at what point is flying with this battery not legal?  

Per @LANCECASPER the answer is “NO” - Not legal to fly  

 

Edited September 30, 2023 by 1980Mooney

[BravoWhiskey]

I understand not legal to fly, nor is it smart… but at what point to you recognize such a discharge?  Is there a discharge rate we should be looking for?  I’m already swapping out the battery.  This is more of a diagnostic question.

[BravoWhiskey]

2 hours ago, mike_elliott said:

A quick reminder Concorde has donated a 12 or 24v battery to the Mooney Summit Silent Auction

Here is an easy way to contribute to the Mooney community while buying something you might need anyway.

https://app.galabid.com/summitix/items

Yo do not have to attend the Mooney Summit to bid on items in our silent auction. All money goes to assisting downed Mooney Pilots families thru the Bill Gilliland Foundation

 

I was unaware, and have already received the new battery this week.  

[PT20J]

15 minutes ago, BravoWhiskey said:

I understand not legal to fly, nor is it smart… but at what point to you recognize such a discharge?  Is there a discharge rate we should be looking for?  I’m already swapping out the battery.  This is more of a diagnostic question.

Batteries lose capacity (amp hours) long before they won’t run the starter or they fail to hold a charge. Aircraft batteries are considered unairworthy when they fail a capacity test as specified by the manufacturer. So, unless that battery suffered a sudden failure, it has likely been unairworthy for a long time.  If you fly IFR, you really should get a capacity test done annually.

[mike_elliott]

30 minutes ago, BravoWhiskey said:

I was unaware, and have already received the new battery this week.  

You will need another soon

 

[LANCECASPER]

2 hours ago, 1980Mooney said:

Per @LANCECASPER the answer is “NO” - Not legal to fly  

 

In that post from almost 4 years ago there was a little bit of hair-splitting. Even though I showed a screen shot of the POH required-equipment page that said otherwise, some said that yes two batteries are required but they don’t both have to be functional.

To me that would be a little like saying that for an airplane that requires two crewmembers that one could be alive and the other one could be embalmed, but you’d still be ok . . lol.

[BravoWhiskey]

18 minutes ago, LANCECASPER said:

In that post from almost 4 years ago there was a little bit of hair-splitting. Even though I showed a screen shot of the POH required-equipment page that said otherwise, some said that yes two batteries are required but they don’t both have to be functional.

To me that would be a little like saying that for an airplane that requires two crewmembers that one could be alive and the other one could be embalmed, but you’d still be ok . . lol.

Ha! Well in my POH it does say it must be installed and in operable condition.  

[Rick Junkin]

I found this through another aviation web board, can't remember which one, and ordered one last week. I should have it in a couple of weeks and I'll give a PIREP. I think it was the RV board where someone was recommending it, may have been Beechtalk.

https://www.ebay.com/itm/122893917064

 

I too just replaced a battery I knew was bad and I got this to keep a better eye on both. #2 still passes my approximated capacity test (turn on 14ish amps worth of avionics and lights and verify it still has 20 volts at 48 minutes) but I'd prefer to be able to see and verify the data. I'm using Gill LT 7243-14 batteries. I know, once again I'm the outlier. 

Cheers,
Rick

[LANCECASPER]

16 minutes ago, BravoWhiskey said:

Ha! Well in my POH it does say it must be installed and in operable condition.  

Mine too.

[Pinecone]

BTW, you do not want to capacity check your battery often.  It stresses the battery.

Concorde has a table of how often to test based on age of the battery and last test.

[tls pilot]

21 hours ago, mike_elliott said:

You will need another soon

 

Exactly what is the point you are trying to convey? 

[BravoWhiskey]

The capacity check is part of my annual, which is 2 months away.  My batteries were not installed at the same time so I don’t believe a staggered replacement is unreasonable.

[mike_elliott]

7 hours ago, tls pilot said:

Exactly what is the point you are trying to convey? 

The Batteries dont last forever and with one gone, the other will probably be weak soon enough. I simply pointed out an opportunity to get a certificate good for a new Concorde Battery and help out the Mooney Community. One of course could wait and take their chances of them even being available from the distributor as Mimi unfortunately found out the hard way recently when she needed one and couldnt scrounge one up.

Thanks Concorde for donating this to the Mooney Summit Silent auction.