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Battery Load Testing

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nuckolls.bob(at)aeroelect
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Posted: Sun Sep 10, 2017 6:31 am Post subject: Battery Load Testing

At 11:20 AM 9/9/2017, you wrote:

  	  Quote: 	
		  A few weeks (?) ago, Bob posted a link to a Harbor Freight 500 Amp Carbon Pile Load Tester:



  https://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html 



 I thought that this is what we would use to annually test the capacity of our batteries. I thought that we would connect the battery, set the amps to our expected load (for example, 12 amps) and then time how long until battery voltage reaches an unacceptably low level.



 But, upon reviewing the user manual for this tool, it does not look like that is what this thing is for. It appears to just load the battery for a short period of time and then extrapolate the battery condition based on how it behaves for that very short test period.



 What's the deal? How do we use this tool to check on our battery condition, annually? 	


   It is one of TWO tests, and the least $time$ consuming

   of the two. There are two qualities of a battery that

   described its performance. One is internal resistance,

   the ability to DELIVER what ever energy is contained

   to the outside world.  This quality goes to getting

   the engine started and is loosely linked to overall

   quality of the battery . . . a battery whose internal

   resistance is rising is loosing active material . . .

   active material is directly related to the second

   quality of interest: CAPACITY.



   To capcheck a battery, you need to literally run

   it down with some load that approximates your

   anticipated ENDURANCE requirements. Then track

   how many minutes that load is supported. There

   are test sets that do this automatically and give

   you data plots.



   Here's one such device



  http://tinyurl.com/mas7ea9



   I've had these in the shop for over a decade.

   Very handy. This tool produces data plots like

   this:



 [img]cid:.0[/img]



   This was a new battery in installed in Dr. Dee's Saturn

   just over two years ago. With a 5a load, it produced

   just over 32 a.h. of energy output. I just replace that

   battery yesterday . . . it had suffered a couple of run-down-

   and-sit events . . . the worst thing you can do to a

   battery.  The new one is sitting in the garage with

   a Battery Tender on it like my lab batteries.



   The HF load tester is the quick'n dirty battery evaluator.

   When you install a NEW battery. Make sure it's topped off

   (Go flying for an hour).  After landing, put the load tester

   on, start the timer (15 seconds) and quickly crank the

   knob up until the voltage FALLS to 9 volts. Adjust the

   knob to maintain the 9v reading until the timer light

   goes out. Then quickly observe and record the CURRENT

   being delivered.



   Repeating this test at intervals will reveal a slow

   decline in that current reading. When it falls to 75%

   of new, then about 1/4th of the battery's chemistry

   has become inactive.



   Now, if you subscribe to the legacy notion of replacement

   at 75-80% of new capacity, then you know when to do it

   based on this admittedly coarser measurement.



   But if you'd care to do a ground check on ENDURANCE

   then you need something like the West Mountain Radio

   instrument -OR- you simply set up an ENDURANCE mode

   load scenario in the hangar and watch a voltmeter. When

   the voltage drops to 11.0 volts the battery is 90+

   percent used up. If that TIME does not meet our exceed

   your personal design goals for alternator-out operations,

   THEN is when you replace the battery. 



 

 

   Bob . . .

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rnjcurtis(at)charter.net
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Posted: Sun Sep 10, 2017 7:12 am Post subject: Battery Load Testing

The HF load tester is the quick'n dirty battery evaluator.

  When you install a NEW battery. Make sure it's topped off

  (Go flying for an hour).  After landing, put the load tester

  on, start the timer (15 seconds) and quickly crank the

  knob up until the voltage FALLS to 9 volts. Adjust the

  knob to maintain the 9v reading until the timer light

  goes out. Then quickly observe and record the CURRENT

  being delivered.

 

Â Â Â Â Â Â Â Â Â Â Â Â Â Â  HF has a slightly different approach to this test.Â  

Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Are there pros and cons of either method?

 

Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Roger

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 10, 2017 9:03 am Post subject: Battery Load Testing

 	  Quote: 	
		  At 10:10 AM 9/10/2017, you wrote:

  

   The HF load tester is the quick'n dirty battery evaluator.

   When you install a NEW battery. Make sure it's topped off

   (Go flying for an hour).  After landing, put the load tester

   on, start the timer (15 seconds) and quickly crank the

   knob up until the voltage FALLS to 9 volts. Adjust the

   knob to maintain the 9v reading until the timer light

   goes out. Then quickly observe and record the CURRENT

   being delivered.

  

  HF has a slightly different approach to this test.Â  

  Are there pros and cons of either method? 	




    One could debate that for a long time. This

    is comparative test . . . How much does

    test #2 depart from test #1?  Then test #3,

    #4, etc.



    Use any protocol that pushes the battery to

    the edge of its performance capability and

    keep track of results.



 

 

   Bob . . .

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