Battery Tender and Load Tester

[outermarker]

I have had my battery on a battery tender since it was new when in the hangar. The battery tender cost more than the battery back then. That was seven years ago and the battery really performs well when starting that difficult IO360 A1A engine after it has been at flight temperatures to this day. I've never had a battery last this long so I'm a bit nervous. Has anyone ever used a battery load tester to see how much capacity their battery still has after five or more years? Is it even a valid test to make?

thanks!

[N201MKTurbo]

It is not only a good idea, it is required. But often overlooked. You should do the test according to the battery service manual.

[Fly Boomer]

16 minutes ago, outermarker said:

I have had my battery on a battery tender since it was new when in the hangar. The battery tender cost more than the battery back then. That was seven years ago and the battery really performs well when starting that difficult IO360 A1A engine after it has been at flight temperatures to this day. I've never had a battery last this long so I'm a bit nervous. Has anyone ever used a battery load tester to see how much capacity their battery still has after five or more years? Is it even a valid test to make?

thanks!

Concorde recommends a capacity check every 12 months.
 

[EricJ]

Another simple test (that I learned from the Concorde rep) is to watch the system voltage during engine start (while the starter motor is running).    If the voltage sags too much during start it may mean that your battery capacity is reduced.   I neglected to ask him how much is too much on a 12V battery.   Their example was a turbine engine starting with a 24V battery that sagged to 12V during start and actually couldn't continue the start.    Turbines are in danger of a hot start when that sort of thing happens (i.e., $$$ engine rebuild).

A year ago last July I did a load capacity test on my six-year-old Concorde and it tested to >95%.   Recently I noticed that during a start it'll sag to 9V, so I need to pull it out and do another capacity check, but I suspect it is either getting near replacement or needs a rehab cycle.

[Ragsf15e]

3 hours ago, outermarker said:

I have had my battery on a battery tender since it was new when in the hangar. The battery tender cost more than the battery back then. That was seven years ago and the battery really performs well when starting that difficult IO360 A1A engine after it has been at flight temperatures to this day. I've never had a battery last this long so I'm a bit nervous. Has anyone ever used a battery load tester to see how much capacity their battery still has after five or more years? Is it even a valid test to make?

thanks!

This should be a standard part of your annual inspection… do you think it’s not happening?  Mine is going on 5 years and passed (>80%) last month.

[outermarker]

Thanks for the replies. The sag test will be part of my starting checklist going forward. 

[Ragsf15e]

1 hour ago, outermarker said:

Thanks for the replies. The sag test will be part of my starting checklist going forward. 

If you use your plane for ifr (or anything else where the battery is critical), please get a legit cap check once in a while.  The “sag” test might give you a ballpark idea, but it’s not a real test.  A battery that fails the capacity test can still start the engine fine but will die quickly if you lose your alternator.

[outermarker]

The manual mentions once capacity falls below 85% on three tests, its time to replace. 

5-0171.pdf

 

[Greg Ellis]

So, if you are not an A&P with a shop but want to do a capacity check on your Concorde battery, besides the "Sag test" what would you use to do this?  The actual capacity and load testers from Concorde are more than 2 grand.  Is there a CB way to do this just to get an idea of the health of the battery?

[EricJ]

55 minutes ago, Greg Ellis said:

So, if you are not an A&P with a shop but want to do a capacity check on your Concorde battery, besides the "Sag test" what would you use to do this?  The actual capacity and load testers from Concorde are more than 2 grand.  Is there a CB way to do this just to get an idea of the health of the battery?

Replacing and servicing batteries is specifically listed as Preventive Maintenance in FAR 43 Appendix A, so owner/operators can do that task.   While the battery is out you can capacity test and recharge it.   There are a number of ways to test capacity and imho the constant-current loads that you can get from amazon or elsewhere are a good way to do it, but require some effort.    The old-school way was to hook up a bunch of headlights or landing lights, but it's not a very well controlled technique so accuracy will suffer.

Whatever you do, use the Concorde battery CMM as your guide:

https://batterymanagement.concordebattery.com/BatteryDocs/5-0171.pdf

Here's an example load tester, there are cheaper ones depending on what you need.

https://www.amazon.com/dp/B09925SZF3

 

[MikeOH]

If I'm reading the Concorde manual correctly, you need to test at a 1C discharge rate; for the RG-35XC, that's 35 Amps.

This was the best (lowest cost $175 with shipping) I could find on Amazon: https://www.amazon.com/KP184-Electronic-Precision-Capacity-Resistance/dp/B0CD7LM5R3/ref=sr_1_25?crid=3CVYHWD9YT856&dib=eyJ2IjoiMSJ9.meSQGHU_0ms1CUhVP44jui5B1Ii4jaBAZwoRbVJYuWvpE-77y6RjlF4zetq_qFoGXoaK_YrLGBUy9ipYP4rZ2TJ8M2tW3auiH_k25ZcEmn6-eHUZcJ_A4ecpGxXcOFUdYqF44jFo-v67GKx7fG4zeb-82UNWJP43TUl3LthaSHxn6LY__ClJEGbxfst9g_lI.J-5J-SIRZd163ZfSklVG7GtXxHZa0eQsH3l9pVlilWo&dib_tag=se&keywords=battery+capacity+tester+kp184&qid=1711387539&sprefix=battery+capacity+tester+kp184%2Caps%2C152&sr=8-25

 

[EricJ]

41 minutes ago, MikeOH said:

If I'm reading the Concorde manual correctly, you need to test at a 1C discharge rate; for the RG-35XC, that's 35 Amps.

This was the best (lowest cost $175 with shipping) I could find on Amazon: https://www.amazon.com/KP184-Electronic-Precision-Capacity-Resistance/dp/B0CD7LM5R3/ref=sr_1_25?crid=3CVYHWD9YT856&dib=eyJ2IjoiMSJ9.meSQGHU_0ms1CUhVP44jui5B1Ii4jaBAZwoRbVJYuWvpE-77y6RjlF4zetq_qFoGXoaK_YrLGBUy9ipYP4rZ2TJ8M2tW3auiH_k25ZcEmn6-eHUZcJ_A4ecpGxXcOFUdYqF44jFo-v67GKx7fG4zeb-82UNWJP43TUl3LthaSHxn6LY__ClJEGbxfst9g_lI.J-5J-SIRZd163ZfSklVG7GtXxHZa0eQsH3l9pVlilWo&dib_tag=se&keywords=battery+capacity+tester+kp184&qid=1711387539&sprefix=battery+capacity+tester+kp184%2Caps%2C152&sr=8-25

 

You can test at a lower rate and apply a correction.   Testing at 1C is best, but not strictly necessary.

[MikeOH]

Just now, EricJ said:

You can test at a lower rate and apply a correction.   Testing at 1C is best, but not strictly necessary.

Is that covered in the manual?  It just seems a less severe, i.e. not really equivalent, test.

[EricJ]

1 minute ago, MikeOH said:

Is that covered in the manual?  It just seems a less severe, i.e. not really equivalent, test.

No, but it's doable.   I mentioned it to the Concorde rep and he didn't even think the correction factor was needed. 

BTW, the tester you linked won't quite do it, either, due to the 400W limit.

[MikeOH]

@EricJ

Interesting...I would have thought ESR would increase with age/condition rendering lower current testing less representative of capacity.  While the correction factor makes sense, the lower the current the less I'd think that factor would be valid. So, Concorde saying it wasn't needed is a bit surprising.  Did he mention how low you could go?  Like 1/3C?

[EricJ]

1 minute ago, MikeOH said:

@EricJ

Interesting...I would have thought ESR would increase with age/condition rendering lower current testing less representative of capacity.  While the correction factor makes sense, the lower the current the less I'd think that factor would be valid. So, Concorde saying it wasn't needed is a bit surprising.  Did he mention how low you could go?  Like 1/3C?

I just mentioned I did it at C/2 and he thought that was fine.   There are quite a few inexpensive testers that will support that.

 

[MikeOH]

1 minute ago, EricJ said:

I just mentioned I did it at C/2 and he thought that was fine.   There are quite a few inexpensive testers that will support that.

 

Seems 1C would require around 420-450 Watt capability, so 1/2C would be 210-225 Watts.  The low cost testers I saw were all under 200W; I believe the one you cited was only 180 Watts.  Do you have a link to one in the required range that is low cost?

[EricJ]

2 minutes ago, MikeOH said:

Seems 1C would require around 420-450 Watt capability, so 1/2C would be 210-225 Watts.  The low cost testers I saw were all under 200W; I believe the one you cited was only 180 Watts.  Do you have a link to one in the required range that is low cost?

This is another one I have that I used previously.   It's just a bit more basic as far as the user interface and software is concerned.

https://www.amazon.com/dp/B07XHLTB4G

[MikeOH]

10 minutes ago, EricJ said:

This is another one I have that I used previously.   It's just a bit more basic as far as the user interface and software is concerned.

https://www.amazon.com/dp/B07XHLTB4G

Thanks!

Looks perfect for 1/2C testing.  Even if not perfectly equivalent, at that price I can at least get a pretty good idea of my battery's condition.  I suspect the IAs for my annuals have never done this (no record in the logs) ...and I'm embarrassed to say I've never asked them!

[EricJ]

I just tested my roughly six-year-old Concorde RG-35AXC and it tested to the 100% discharge time almost to the second.   I was surprised.    It's now on my smart charger which also measures capacity, so I'll see what it says when it's done. 

Edit:   Charger sez the battery is 34.2Ah.

 

[Fly Boomer]

11 hours ago, EricJ said:

I just tested my roughly six-year-old Concorde RG-35AXC and it tested to the 100% discharge time almost to the second.   I was surprised.    It's now on my smart charger which also measures capacity, so I'll see what it says when it's done. 

Edit:   Charger sez the battery is 34.2Ah.

 

I seem to recall that the RG-35AXC is rated at 33, so that's an amazing result for a battery that's been in service for some time.  Do you keep a BatteryMINDer on it?

[EricJ]

6 hours ago, Fly Boomer said:

I seem to recall that the RG-35AXC is rated at 33, so that's an amazing result for a battery that's been in service for some time.  Do you keep a BatteryMINDer on it?

Yes, it's on a minder and the airplane is stored in a hangar that has very good passive ventilation, so it doesn't get as hot as it might otherwise.   The regulator shows 14-14.1V on the engine monitor during operation.

A buddy with a Cherokee that gets stored outside has been going through the same batteries every two years or so, and he just replaced it again.   The one he just removed was about two years old and was showing 20% capacity.   He doesn't (can't) keep it on a minder, and it may get hotter during the summer than mine, and his ancient mechanical regulator keeps it around 13.2V, which varies with load.    We're thinking putting a Zeftronics regulator in there might help it charge more thoroughly when it gets flown.   He thinks the failures have been due to cell failures, which might be heat related.    His battery is in front of the firewall, mine is in the tail.

[Fly Boomer]

On 3/28/2024 at 3:03 PM, EricJ said:

Yes, it's on a minder and the airplane is stored in a hangar that has very good passive ventilation, so it doesn't get as hot as it might otherwise.   The regulator shows 14-14.1V on the engine monitor during operation.

A buddy with a Cherokee that gets stored outside has been going through the same batteries every two years or so, and he just replaced it again.   The one he just removed was about two years old and was showing 20% capacity.   He doesn't (can't) keep it on a minder, and it may get hotter during the summer than mine, and his ancient mechanical regulator keeps it around 13.2V, which varies with load.    We're thinking putting a Zeftronics regulator in there might help it charge more thoroughly when it gets flown.   He thinks the failures have been due to cell failures, which might be heat related.    His battery is in front of the firewall, mine is in the tail.

Oof, that hurts.  I just bought a pair of RG-35AXCs during a dip in availability (premium price).  Painful.