Prepping AOG for two months

[Max Clark]

Looking ahead in my schedule I’m going to have a ~70 period where I won’t be able to log any flight time.

Anything specific I should do to prepare the plane for this?

First thing that comes to mind is a battery minder - do I need one or two for an M20R? Is the BatteryMINDER the best to buy?

Thanks!

[Brandt]

I use two battery minders. Depending on where you are located, I’d consider an engine dehydrator or a whole hangar dehumidifier.   I don’t think that’s long enough to need to pickle the engine. Suggest you change the oil before you park it and put in w100 w camguard. Wouldn’t hurt to put it on jacks if you have them to relive stress on the donuts and the tires. 

[hammdo]

I’ve used Phillips 20w50 anti-rust. You can fly up to 10 hours with it. If you do your own oil changes, cheap insurance. Change the oil, fly to get temps up, then you can let it sit. Or add up to 10% to your oil …

For sure battery minders…
 

 

[Max Clark]

3 minutes ago, hammdo said:

I’ve used Phillips 20w50 anti-rust. You can fly up to 10 hours with it. If you do your own oil changes, cheap insurance. Change the oil, fly to get temps up, then you can let it sit. 
 

 

 

Interesting thanks!

[ArtVandelay]

Change the oil, make sure you run the engine to check for leaks and circulate the new oil.

[Ed de C.]

I've had similar downtimes due to maintenance (the last annual and other times).  Each time I made sure battery charge was good, tire pressures good, and did a particularly thorough preflight.  Since the downtimes were maintenance related, I would orbit the field for 15 minutes or so to make sure all was OK before venturing off.  Since I was rusty, I followed the checklists extra carefully and made sure weather conditions were very favorable.  Needless to say, these were solo flights without passengers.

I live in Michigan where humidity and salt are low concerns (the downtimes tended to be not summer), so additional engine precautions were not necessary.  

Ed

[hammdo]

Just to give more info…

[Geoff]

5 hours ago, Max Clark said:

Looking ahead in my schedule I’m going to have a ~70 period where I won’t be able to log any flight time.

Anything specific I should do to prepare the plane for this?

First thing that comes to mind is a battery minder - do I need one or two for an M20R? Is the BatteryMINDER the best to buy?

Thanks!

Pass the keys to your friendly CFI and have them fly it occasionally. 

 

In all seriousness, best thing for airplanes is to fly, worst is to sit, even well prepped.

Edited April 28 by Geoff
added info

[Pinecone]

I wouldn't worry that much.  Planes sit for 2 months often.

I agree with the change the oil just before and use CamGuard.

[LANCECASPER]

7 hours ago, Max Clark said:

Looking ahead in my schedule I’m going to have a ~70 period where I won’t be able to log any flight time.

Anything specific I should do to prepare the plane for this?

First thing that comes to mind is a battery minder - do I need one or two for an M20R? Is the BatteryMINDER the best to buy?

Thanks!

I wouldn't worry about the engine in two months. 

Buy the correct battery minder (Concorde or Gill) and get one 210-AY splitter and an extra cord if you don't want to buy two Tenders. https://www.amazon.com/BatteryMINDer-SmarTECHnology-Multiple-Battery-Connector/dp/B00LHVUGXM

I also have one of these and program it so that it comes on for an hour twice a week. https://www.amazon.com/dp/B07G9RK4VV?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

[Pinecone]

The other thing is, if you or someone can get to the plane every week or so, you can use one Battery Minder and swap it between the two batteries.

[Brandt]

14 hours ago, LANCECASPER said:

I wouldn't worry about the engine in two months. 

Buy the correct battery minder (Concorde or Gill) and get one 210-AY splitter and an extra cord if you don't want to buy two Tenders. https://www.amazon.com/BatteryMINDer-SmarTECHnology-Multiple-Battery-Connector/dp/B00LHVUGXM

I also have one of these and program it so that it comes on for an hour twice a week. https://www.amazon.com/dp/B07G9RK4VV?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Do you have any idea what the difference is between the two batteries that require a different charger? Just curious.

[LANCECASPER]

1 minute ago, Brandt said:

Do you have any idea what the difference is between the two batteries that require a different charger? Just curious.

Not exactly the answer you're looking for but Battery Tender says there are specific internal settings in their chargers for Concorde vs. Gill. A few years ago I sent in a Tender that was for Gill and they converted it for the Concorde for $75.

[Fly Boomer]

Use caution with Battery Tender.  Concorde has issued a Service Alert (attached).  BatteryMINDer makes devices specifically for Gill or Concorde.

batterytenderwarning.pdf

[Max Clark]

8 minutes ago, Fly Boomer said:

Use caution with Battery Tender.  Concorde has issued a Service Alert (attached).  BatteryMINDer makes devices specifically for Gill or Concorde.

batterytenderwarning.pdf 45.8 kB · 2 downloads

So what the heck am I supposed to use then?

[Fly Boomer]

10 minutes ago, Max Clark said:

So what the heck am I supposed to use then?

It’s a conundrum.  Concorde also says long term use of the BatteryMINDer is not recommended.  If mine sits for a long period, I try to arrange to plug in my GPU for 24 hours once per month.  I use a voltage that more or less matches Concorde’s recommendation based on ambient temperature in the hangar.

[201Mooniac]

4 hours ago, Fly Boomer said:

Concorde also says long term use of the BatteryMINDer is not recommended.

I wasn't aware of that.  I've had my Concorde on a battery minder for the last 7.5 years and it still passes the load test, it must not be too bad for the battery.

[ArtVandelay]

I wasn't aware of that.  I've had my Concorde on a battery minder for the last 7.5 years and it still passes the load test, it must not be too bad for the battery.

The problem is it will cover for a battery going bad, so you will more likely not have a warning until you’re AOG away from home and the battery minder.

[Fly Boomer]

2 hours ago, 201Mooniac said:

I wasn't aware of that.  I've had my Concorde on a battery minder for the last 7.5 years and it still passes the load test, it must not be too bad for the battery.

If you are getting more than 7 years on a battery, keep doing what you’ve been doing.

[201Mooniac]

1 hour ago, ArtVandelay said:

The problem is it will cover for a battery going bad, so you will more likely not have a warning until you’re AOG away from home and the battery minder.

Understood, but it still passes the load test so I don't think that is really the issue

[Fly Boomer]

1 minute ago, 201Mooniac said:

Understood, but it still passes the load test so I don't think that is really the issue

I’m not looking at their document with the prohibition, but I wonder if dual batteries are more of a problem than singles.

[Jeff Uphoff]

On 4/28/2025 at 4:29 PM, Geoff said:

Pass the keys to your friendly CFI and have them fly it occasionally. 

In all seriousness, best thing for airplanes is to fly, worst is to sit, even well prepped.

Yup!

I let the previous owner of my first Mooney (an M20C), a local who'd moved up to a 231 himself, keep a set of keys and encouraged him to take it up when I was away for more than a week or two. He was a CFII/ATP and a great mentor--hard to beat that.

--Up.

[201Mooniac]

2 hours ago, Fly Boomer said:

I’m not looking at their document with the prohibition, but I wonder if dual batteries are more of a problem than singles.

Could be though it isn't obvious to me why that might be the case.  There may be some environmental issue or something that I just don't experience, we don't get very cold here and I rarely have it on the battery minder when it gets too hot either.  I'll have to look up their documentation to see if they explain why.

[201Mooniac]

1 hour ago, Jeff Uphoff said:

Yup!

I let the previous owner of my first Mooney (an M20C), a local who'd moved up to a 231 himself, keep a set of keys and encouraged him to take it up when I was away for more than a week or two. He was a CFII/ATP and a great mentor--hard to beat that.

--Up.

I wonder who that could have been...

[MikeOH]

2 months?

Fly the plane. Park the plane. Disconnect negative battery cable.

After two months, connect negative battery cable. Fly plane.

AGM batteries (e.g. Concorde) self-discharge at 1-2% per month.