Looking for a Battery Capacity Tester

[M20F-1968]

I am looking for a reasonable and cost effective method to test battery capacitance.  Does anyone have a used unit for sale?  My system is 14 volt and I understand that it needs a load of 35 amp per hour.  Correct me if I am wrong.  Are there alternatives to the $1500.00 plus units designed for the aviation market?

John Breda

[Niko182]

You could probably take it out and just give it to an auto shop. Maybe?

[N201MKTurbo]

Look in the ICA for the battery for the discharge current for the capacity test.

Go to the auto parts store and buy enough headlight bulbs to get near the proper discharge current.

Go on eBay and order a combination amp and volt meter that covers the current you need.

The ICA will tell you the discharge voltage. 
 

Start it up. Write down the time, voltage and current every minute or two until the voltage goes down to the discharge voltage.

Calculate the AH for each time interval and sum them up. Make a spread sheet for this.

True CB battery capacity tester. <$50

 

https://www.ebay.com/itm/154414886759

You need about 500 watts of load. 5 of these is your cheapest route. They have spade lugs, so they are easy to connect.

https://www.summitracing.com/parts/hla-h410080w

 

Edited September 17, 2021 by N201MKTurbo

[Will.iam]

or just goto walmart and get a battery load tester for $38?

https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwi8yseR-YbzAhUPc28EHUOeDRQYABAFGgJqZg&ohost=www.google.com&cid=CAESQOD21n8-0Fyeu8ZjhYtqkg8Uc28cLYAc67a0pjCqVn_YlzfW4PbtGslyKKhTeV58CaVchfBw65JHMq3F4Y2lX2M&sig=AOD64_3T0he9Y6gBGuUJHkLZJ7E1muwPaw&ctype=5&q=&ved=2ahUKEwiXpruR-YbzAhXIlWoFHfwvDFgQ9aACegQIARBo&adurl=https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwi8yseR-YbzAhUPc28EHUOeDRQYABAFGgJqZg&ohost=www.google.com&cid=CAESQOD21n8-0Fyeu8ZjhYtqkg8Uc28cLYAc67a0pjCqVn_YlzfW4PbtGslyKKhTeV58CaVchfBw65JHMq3F4Y2lX2M&sig=AOD64_3T0he9Y6gBGuUJHkLZJ7E1muwPaw&ctype=5&q=&ved=2ahUKEwiXpruR-YbzAhXIlWoFHfwvDFgQ9aACegQIARBo&adurl=https://www.walmart.com/ip/Schumacher-Battery-Load-Tester-and-Voltmeter-100-Amp/21642133?wmlspartner=wlpa&&adid=22222222227000000000&wl0=&wl1=g&wl2=c&wl3=42423897272&wl4=pla-51320962143&wl5=9027291&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=21642133&veh=sem&gclid=CjwKCAjw-ZCKBhBkEiwAM4qfF7FBuSn0RLFo3ykWWFQ5MPvgpmG2_Ax-sax5cw83mkBbbweK03I_EhoCguUQAvD_BwE&gclsrc=aw.ds

[N201MKTurbo]

9 minutes ago, Will.iam said:

or just goto walmart and get a battery load tester for $38?

https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwi8yseR-YbzAhUPc28EHUOeDRQYABAFGgJqZg&ohost=www.google.com&cid=CAESQOD21n8-0Fyeu8ZjhYtqkg8Uc28cLYAc67a0pjCqVn_YlzfW4PbtGslyKKhTeV58CaVchfBw65JHMq3F4Y2lX2M&sig=AOD64_3T0he9Y6gBGuUJHkLZJ7E1muwPaw&ctype=5&q=&ved=2ahUKEwiXpruR-YbzAhXIlWoFHfwvDFgQ9aACegQIARBo&adurl=https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwi8yseR-YbzAhUPc28EHUOeDRQYABAFGgJqZg&ohost=www.google.com&cid=CAESQOD21n8-0Fyeu8ZjhYtqkg8Uc28cLYAc67a0pjCqVn_YlzfW4PbtGslyKKhTeV58CaVchfBw65JHMq3F4Y2lX2M&sig=AOD64_3T0he9Y6gBGuUJHkLZJ7E1muwPaw&ctype=5&q=&ved=2ahUKEwiXpruR-YbzAhXIlWoFHfwvDFgQ9aACegQIARBo&adurl=https://www.walmart.com/ip/Schumacher-Battery-Load-Tester-and-Voltmeter-100-Amp/21642133?wmlspartner=wlpa&&adid=22222222227000000000&wl0=&wl1=g&wl2=c&wl3=42423897272&wl4=pla-51320962143&wl5=9027291&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=21642133&veh=sem&gclid=CjwKCAjw-ZCKBhBkEiwAM4qfF7FBuSn0RLFo3ykWWFQ5MPvgpmG2_Ax-sax5cw83mkBbbweK03I_EhoCguUQAvD_BwE&gclsrc=aw.ds

Those are not capacity testers. Neither are the ones they have at the auto parts store. A capacity test takes between 1/2 hour and an hour to accomplish. The testers you mention just measure the voltage with a load on the battery. 

Edited September 17, 2021 by N201MKTurbo

[jaylw314]

7 hours ago, M20F-1968 said:

I am looking for a reasonable and cost effective method to test battery capacitance.  Does anyone have a used unit for sale?  My system is 14 volt and I understand that it needs a load of 35 amp per hour.  Correct me if I am wrong.  Are there alternatives to the $1500.00 plus units designed for the aviation market?

John Breda

If you're just measuring battery capacity for your information only (i.e. not for any FAA requirement), all you need is a ammeter and good digital voltmeter.  You need an ammeter to partly discharge the battery a specific number of amp-hours (say 50% of the factory capacity).  then you measure the open-circuit (no-load) voltage after it settles.  The open-circuit voltage tells you the percentage capacity fairly accurately for lead-acid chemistry, there are charts you can find.

So if your battery started with 30 amp-hours, and you run it at 15 amps for one hour using the ammeter, the battery SHOULD be at 50% capacity.  When you check the open-circuit voltage and it corresponds to 30% capacity, that means you've lost 20% of the battery's capacity, or 6 amp-hours.  Now your battery only has 24 amp-hours of capacity.

Luckily, most Mooney's have an ammeter already built in.  You can just discharge your battery by turning on enough electrics and using your watch.  IIRC my Mooney uses between 15-20 amps with just the master on, and 25-30 amps with the panel running.  It's not terribly accurate, but neither is figuring battery capacity.  The phrase "good enough for government work" is somewhat ironic here

 

Edited September 18, 2021 by jaylw314

[PT20J]

Check the battery manual. There are specific procedures for testing and doing so will run the battery down low enough that it needs to be recharged immediately so you need a charger also. If it fails, there are procedures for a conditioning charge and retest. 

Skip

[A64Pilot]

 A landing light etc will suffice, it’s not rocket science, close is good enough. Just err to the conservative side, if it’s close, buy a new battery, if your alt fails IFR you’ll be glad you did.

If you decide to try to be accurate, remember it’s the amp draw that your trying to keep constant, and unfortunately as voltage changes, amps change so that your going to need a variable load to maintain constant amps, and make constant adjustments to the load, or buy an expensive one that is automatic

Battery cap check is a required annual inspection, one that is almost never done, but if you fly IFR, it’s important.

A batteries capacity and it’s ability to start an engine often aren’t related surprisingly, only way to be sure your battery has enough power to get you down IFR is to perform a cap check.

Interesting to me is only one battery comes from the factory not legally requiring a capacity check and that’s a Concorde, every Concorde battery is capacity checked prior to being shipped, all others legally are required a capacity check prior to being placed into service.

Anyone ever seen that done? 

Load banks don’t have to be complicated or expensive, this is one I used for Aircraft Certification test flights, it’s eight 600W landing lights that we put in the hopper of an Ag plane to load the Starter / generator to max output. Put out so much heat, had to have the hopper filled with water.

Edited September 18, 2021 by A64Pilot

[RobertGary1]

The only thing that matters is what voltage it can hold while cranking. Just hook it to the plane and crank. 

[N201MKTurbo]

38 minutes ago, RobertGary1 said:

The only thing that matters is what voltage it can hold while cranking. Just hook it to the plane and crank. 

The FAA could give a rats ass about that. If you can’t start your plane, it is very safe.

What they care about is how long it will power the avionics and other required loads after your alternator fails. That time is measured with a capacity test.

[PT20J]

I recently purchased a 24V Gill LT. Cheaper and higher capacity than the Concord. The ICA only requires it be charged if necessary before installing. No capacity test for 18 months. 

I replaced the 5 year old Concord because it was marginal on the capacity test and barely passed after a couple of charge/test cycles. It cranked the engine just fine.

A lot of people seem to think that it’s good if it cranks. I had a 6 year old battery in my Subaru tested with one of those quickie automotive testers and it tested good. Always started, too. But I left the hatch open for about an hour and that little light bulb in the cargo light ran it completely down so I had to get a jump to start it.

Skip

[McMooney]

Fluke and an appropriate load should work

[RobertGary1]

46 minutes ago, N201MKTurbo said:

The FAA could give a rats ass about that. If you can’t start your plane, it is very safe.

What they care about is how long it will power the avionics and other required loads after your alternator fails. That time is measured with a capacity test.

Which reg are you referring to?

[N201MKTurbo]

41 minutes ago, RobertGary1 said:

Which reg are you referring to?

Which battery do you have?

[N201MKTurbo]

1 hour ago, RobertGary1 said:

Which reg are you referring to?

23.1353

(h) In the event of a complete loss of the primary electrical power generating system, the battery must be capable of providing at least 30 minutes of electrical power to those loads that are essential to continued safe flight and landing. The 30 minute time period includes the time needed for the pilots to recognize the loss of generated power and take appropriate load shedding action.

Edited September 19, 2021 by N201MKTurbo

[RobertGary1]

44 minutes ago, N201MKTurbo said:

23.1353

(h) In the event of a complete loss of the primary electrical power generating system, the battery must be capable of providing at least 30 minutes of electrical power to those loads that are essential to continued safe flight and landing. The 30 minute time period includes the time needed for the pilots to recognize the loss of generated power and take appropriate load shedding action.

Ok. I use the Garmin method for this test.  In the Garmin case it’s more “supervised” but you go into that menu and say you’re doing a battery test. Then go come back some hours later snd it says if it passes or not. But you could easily do the same yourself. Just turn on the required equipment and come back later and see if the voltage is still sufficient. 

[PT20J]

1 hour ago, N201MKTurbo said:

23.1353

(h) In the event of a complete loss of the primary electrical power generating system, the battery must be capable of providing at least 30 minutes of electrical power to those loads that are essential to continued safe flight and landing. The 30 minute time period includes the time needed for the pilots to recognize the loss of generated power and take appropriate load shedding action.

That’s a certification requirement to size the battery.

I don’t know of any requirement for an owner/operator to perform a capacity test unless the test is required in the limitations section of the ICA or AFM. However, I would not want to fly IFR with a battery that had not been recently tested if it were more than a couple of years old.

Skip

[N201MKTurbo]

33 minutes ago, PT20J said:

That’s a certification requirement to size the battery.

I don’t know of any requirement for an owner/operator to perform a capacity test unless the test is required in the limitations section of the ICA or AFM. However, I would not want to fly IFR with a battery that had not been recently tested if it were more than a couple of years old.

Skip

The airplane isn’t airworthy unless it meets the the provisions of the type certificate. The type certificate is based on part 23. The type certificate specifies the battery. The battery has instructions for continued airworthiness. If you don’t follow the instructions, you can’t prove the battery meets its specifications.

when an IA does an annual, they are certifying that the airplane is airworthy. That means that it meets all the provisions of the type certificate.  

[carusoam]

To put some guidelines for how important this can be…

1) You have to be flying in or above IMC to make this really important…

2) If all of your AIs are depending on it… it becomes incredibly important…

3) Once that important wire from the VR vibrates itself loose or breaks…. The charging system goes off line.

4) Once the charging system is done… The amount of electrons in the battery are at their highest, and the clock has started….

5) Battery capacity changes over time, and use, and temperature…..

6) If everything in the panel is electric, and your ship has one battery… it’s capacity just became really important …

7) Your panel may have a few other batteries for back-up… their capacity is also important….

 

8) Lets say your ship has two batteries, it hasn’t seen the inside of a cloud in decades…. you are IR, but not current any longer….  Battery capacity may not be your biggest priority… 

 

9) The reason new batteries may not get tested for capacity…. They are built to specifications… when all of the construction procedures are followed… this pretty much guarantees the performance out of the box… leaving the factory….   If the battery has sat in the box, it may have limitations on how long it can sit that way…

10) Nothing worse than finding out your generator has croaked, you got no warning, until all your electric displays start to blink…. In this case whatever capacity you had got used up…. Shutting every electric device down, and letting it rest may allow some charge to come back out of deep storage and show for the final moments of the flight…

11) It’s too bad that capacity testing is so stressful for some batteries…. This destructive test method may be getting to be less destructive with the newer generation of batteries…

12) My firebird has a hybrid drive system… a 350 cubic inch gas engine…. And when it croaks… the starter motor is pretty good at driving the car to the nearest parking space….   Battery capacity is going to be really important on a rainy day… 

PP thoughts only, the clutch lock-out switch needs to be defeated for the hybrid option to be available…

Best regards,

-a-

[RobertGary1]

I wonder if the same goes for the engine. The type certificate on mine says 200hp but I’ve not put it on a dyno. Probably a lot of tired engines out there not making rated. 

[A64Pilot]

I can’t quote chapter and verse, but the annual requirement for battery capacity testing does exist but as I said it’s not often done.

80% of rated capacity is the min acceptable, I know this is in Concorde’s component maintenance manual, but as I’ve not used other batteries I can’t say for sure if it’s in all manuals or not.

An annual capacity test assuming the battery is immediately recharged isn’t hard on the battery. Lead acid batteries primarily die from sulphation, sulphation occurs most often from sitting at a discharged state.

Actually if it’s an AGM battery and charged at a high rate, that can to some extent reverse sulphation, and recover capacity

Ome of the myths about battery charging is don’t charge them at a high rate, if the voltage is correct you can’t charge a battery too fast, the battery will only accept the rate it can, as it charges the current will slowly drop.

If your curious this manual is full of information, Lifeline is Concorde’s non aviation batteries but they are essentially identical.

I am not saying use this manual for aircraft batteries, but as for example it’s not uncommon for deep cycle banks to be very large and expensive, they are usually maintained better so they manual contains a lot of additional information.

https://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101F-Lifeline-Technical-Manual-Final-5-06-19.pdf

 

The capacity check time is different on these batteries as they are used as deep cycle batteries and due to Peukert’s law that basically says if you discharge a battery slowly you can get more amp hours than a quick discharge 

https://en.wikipedia.org/wiki/Peukert's_law

Edited September 20, 2021 by A64Pilot

[carusoam]

51 minutes ago, RobertGary1 said:

I wonder if the same goes for the engine. The type certificate on mine says 200hp but I’ve not put it on a dyno. Probably a lot of tired engines out there not making rated. 

There are two popular methods of dyno-ing your engine…. With enough accuracy to be meaningful….

1) Use a WAAS source to measure your T/O distance….

2) Use a consistent climb rate, use the same WAAS source for data…

3) Compare to Book Numbers…

4) It takes a bit of an engineering mind set… DA is important for the numbers to work properly…

5) It was the first thing I did after the OH’d engine got installed….  I also compared to @Cris’ plane… Screamin’ Eagle…

6) When your plane performs to book numbers… under a couple of different conditions…. The whole collection of book numbers becomes way more meaningful than numbers on a page in a dusty book….

7) That 310hp was about a 20amu (prop, STCs, etc) project that was hinging on actual performance….  

8) My WAAS source for the project… portable SkyRadar and CloudAhoy app on an iPad….

9) either way… no need to wonder how well your engine is performing… no actual dyno is required.

10) Safety margins still apply… just not overly huge ones…

11) You may not like putting your engine through the tests as hard as a factory test pilot… so measure with your style, and see how well your plane actually responds…  you may be surprised… 

12) MP, RPM, and FF… if you have all three, you probably have the HP stated in the book…

13) There are also similar methods to know if the firebird is producing rated power, or the ignition timing has been retarded…  the opti-spark system can need to be cleaned… The user won’t know the timing got automatically adjusted… until a simple test of torque is performed….

(simple test, go / no go… if the bird can spin the wheels on a wet road in second gear… Go!) if not… clean the opti-spark… 

14) Let’s say you wanted to know if your engine was tired… you think there has been metal filling your oil filter… the pics of your cam are showing nubs… but the plane has been still flying for a year….

Cams are responsible for the engine’s breathing… if the engine can’t breathe, it can’t produce rated power…. This will show up when compared to performance charts…

Go collect data!  

PP thoughts only, not a CFI…. Or mechanic… or gear head… mostly stuff seen around here…

Best regards,

-a-

[PT20J]

Well, I respectfully disagree with @N201MKTurbo and @A64Pilot. 

First of all, the certification basis for Mooneys is, per the TCDS, CAR 3, so Part 23 requirements are irrelevant.

Second, it is established FAA policy that for light, non-turbine aircraft operated under part 91, TBO, Service Bulletins, and Aircraft Maintenance Manual inspection/overhaul/replacement intervals, and ICAs are not required EXCEPT when specifically included in a LIMITATIONS section (which is rare).  What is required is described in FARs 91 snd 43.

So, for a Mooney operated under Part 91, you are not required to replace the landing gear actuator no back spring at 1000 hours even though the Mooney Service and Maintenance Manual says to do so. Similarly, you do not need to perform a capacity check although the battery manufacturer’s ICA says to do so.

Here is Mike Bush’s explanation.  https://www.aopa.org/news-and-media/all-news/2019/september/pilot/savvy-maintenance-safety-continuum

Skip

 

[RobertGary1]

1 hour ago, carusoam said:

There are two popular methods of dyno-ing your engine…. With enough accuracy to be meaningful….

1) Use a WAAS source to measure your T/O distance….

2) Use a consistent climb rate, use the same WAAS source for data…

3) Compare to Book Numbers…

4) It takes a bit of an engineering mind set… DA is important for the numbers to work properly…

5) It was the first thing I did after the OH’d engine got installed….  I also compared to @Cris’ plane… Screamin’ Eagle…

6) When your plane performs to book numbers… under a couple of different conditions…. The whole collection of book numbers becomes way more meaningful than numbers on a page in a dusty book….

7) That 310hp was about a 20amu (prop, STCs, etc) project that was hinging on actual performance….  

8) My WAAS source for the project… portable SkyRadar and CloudAhoy app on an iPad….

9) either way… no need to wonder how well your engine is performing… no actual dyno is required.

10) Safety margins still apply… just not overly huge ones…

11) You may not like putting your engine through the tests as hard as a factory test pilot… so measure with your style, and see how well your plane actually responds…  you may be surprised… 

12) MP, RPM, and FF… if you have all three, you probably have the HP stated in the book…

13) There are also similar methods to know if the firebird is producing rated power, or the ignition timing has been retarded…  the opti-spark system can need to be cleaned… The user won’t know the timing got automatically adjusted… until a simple test of torque is performed….

(simple test, go / no go… if the bird can spin the wheels on a wet road in second gear… Go!) if not… clean the opti-spark… 

14) Let’s say you wanted to know if your engine was tired… you think there has been metal filling your oil filter… the pics of your cam are showing nubs… but the plane has been still flying for a year….

Cams are responsible for the engine’s breathing… if the engine can’t breathe, it can’t produce rated power…. This will show up when compared to performance charts…

Go collect data!  

PP thoughts only, not a CFI…. Or mechanic… or gear head… mostly stuff seen around here…

Best regards,

-a-

Without analytical numbers I have no doubt that my 50 hr since factory overhaul motor beats the book performance data epecially in take off distance. 
of course that also assumes ordinary pilot skills.

[DonMuncy]

I won't argue with people who use alternative methods of assuring their battery is up to snuff, but as I understand it, a battery capacity test is necessary at each annual (and is the best test to determine whether your battery will provide you juice enough to run your instruments long enough if you have an alternator/generator failure). As others have pointed out, most IAs do not do capacity checks at annual. 

The equipment to do the test properly is expensive, primarily because it takes  some pretty sophisticated stuff to maintain a constant amperage, because the amp draw constantly changes as the voltage changes.

I built a relatively inexpensive but admittedly not super accurate tester, using two 6 amp bulbs to draw the battery down. But (assuming the bulb labels are accurate) when the voltage is above 12, the amp draw will be high, and when the voltage drops below 12, the draw is increasing lower. Good enough for government work? Who knows.