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Interpreting battery test results

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Sam

Joined: 18 May 2008
Posts: 135

Posted: Thu Oct 23, 2008 4:00 am Post subject: Interpreting battery test results

I just got hold of a new Oddessey PC310 battery, to use as an endurance backup.  I need to product 12 amps for something like 30-45 minutes. It is rated at 8Ah and here is the product information:

http://www.odysseybatteries.com/battery/pc310.htm

 

Wanting to see what it really had in it, I hooked up the West Mountain tester.  In the test parameters, I called it and 8Ah battery and tried to have it run at 12 amps.  However, the program didn't like that, so I stepped the current draw down to 7 amps.  I set the cutoff voltage at 9 volts.

 

I was surprised the test lasted only 24 minutes, but even more surprised that the resultant Tested Capacity was only 2.82 Ah.

You can see the test results here: http://www.mistakeproofing.net/transfer/PC310_10-22-08.pdf

 

So, why the difference?  Shouldn't the Tested Capacity be near 8Ah? Am I misinterpreting the test results?  Is there something wrong with this brand-new battery?  Was my test set-up flawed? 



Sam Hoskins

 Murphysboro, IL

www.samhoskins.blogspot.com

[quote][b]

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Sam Hoskins
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Neal.George(at)hurlburt.a
Guest

Posted: Thu Oct 23, 2008 5:08 am Post subject: Interpreting battery test results

Well...sorta.

 

You performed a valid test and got roughly the results we'd expect.  The battery you tested is likely rated for 8-ah at a current that would discharge it in about 20-hours.  Closer to 400mA - not 12 amps.

 

neal



________________________________



From: owner-aeroelectric-list-server(at)matronics.com on behalf of Sam Hoskins

Sent: Thu 10/23/2008 6:58 AM

To: Aerolectric List

Subject: Interpreting battery test results

I just got hold of a new Oddessey PC310 battery, to use as an endurance backup.  I need to product 12 amps for something like 30-45 minutes. It is rated at 8Ah and here is the product information:

http://www.odysseybatteries.com/battery/pc310.htm



Wanting to see what it really had in it, I hooked up the West Mountain tester.  In the test parameters, I called it and 8Ah battery and tried to have it run at 12 amps.  However, the program didn't like that, so I stepped the current draw down to 7 amps.  I set the cutoff voltage at 9 volts.



I was surprised the test lasted only 24 minutes, but even more surprised that the resultant Tested Capacity was only 2.82 Ah.

You can see the test results here: http://www.mistakeproofing.net/transfer/PC310_10-22-08.pdf



So, why the difference?  Shouldn't the Tested Capacity be near 8Ah? Am I misinterpreting the test results?  Is there something wrong with this brand-new battery?  Was my test set-up flawed? 



Sam Hoskins

Murphysboro, IL

www.samhoskins.blogspot.com <http://www.samhoskins.blogspot.com/>

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rlborger(at)mac.com
Guest

Posted: Thu Oct 23, 2008 5:35 am Post subject: Interpreting battery test results

Sam,



Check that Odyssey web site document again.  It shows that the battery will provide 25 amps for 9 minutes.  That means that it will only provide 12 amps for 18 minutes at best.  If you want 12 amps for 30-45 minutes you need a bigger battery.  Probably something on the order of a 12 amp-hour battery at a minimum.



Bob Borger

Europa XS, short wings, intercooled Rotax 914, Airmaster C/S prop.

99.999% complete.  Only some extended testing to do.



 

On Thursday, October 23, 2008, at 06:58AM, "Sam Hoskins" <sam.hoskins(at)gmail.com> wrote:

 	  Quote: 	
		  I just got hold of a new Oddessey PC310 battery, to use as an endurance

backup.  I need to product 12 amps for something like 30-45 minutes. It is

rated at 8Ah and here is the product information:

http://www.odysseybatteries.com/battery/pc310.htm



Wanting to see what it really had in it, I hooked up the West Mountain

tester.  In the test parameters, I called it and 8Ah battery and tried to

have it run at 12 amps.  However, the program didn't like that, so I stepped

the current draw down to 7 amps.  I set the cutoff voltage at 9 volts.



I was surprised the test lasted only 24 minutes, but even more surprised

that the resultant Tested Capacity was only 2.82 Ah.

You can see the test results here:

http://www.mistakeproofing.net/transfer/PC310_10-22-08.pdf



So, why the difference?  Shouldn't the Tested Capacity be near 8Ah? Am I

misinterpreting the test results?  Is there something wrong with this

brand-new battery?  Was my test set-up flawed?



Sam Hoskins

Murphysboro, IL

www.samhoskins.blogspot.com

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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mrspudandcompany(at)veriz
Guest

Posted: Thu Oct 23, 2008 6:21 am Post subject: Interpreting battery test results

Sam,  

   

The 8AH capacity of this battery is based on a discharge current rate of 0.4A  over a 20 hr period.  The chart shows a decrease capacity to 7AH if you increase the output current to 0.7A.  

   

As you increase the output current the internal resistance increases resulting in large internal losses at high current.  You can normally get a higher output current with less loss from a larger capacity battery, simply due to the increased plate area, translating to lower internal resistance at a given output current.  

   

Look at Duration of discharge vs. discharge current at Bob’s site:  

   

http://www.aeroelectric.com/Reference_Docs/Battery/Panasonic/LC-LA1233P.pdf  

   

At a 1.65A discharge rate for 20 hrs capacity is 33AH.  At 105.5A rate for 0.7hr.the capacity drops to 12.3AH.  

   

This is a Panasonic battery of a different size, but the characteristics are similar across the lead acid battery spectrum.  

   

Roger  

   

   

   

--

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Sam

Joined: 18 May 2008
Posts: 135

Posted: Thu Oct 23, 2008 7:09 pm Post subject: Interpreting battery test results

Thanks t all who replied.  I now get the picture.  Fortunately, I am friends with the owner of the battery shop and we'll make an adjustment.



Sam



On Thu, Oct 23, 2008 at 8:48 AM, ROGER &  JEAN CURTIS <mrspudandcompany(at)verizon.net (mrspudandcompany(at)verizon.net)> wrote:

 [quote]                

Sam,  

   

The 8AH capacity of this battery is based on a discharge current rate of 0.4A  over a 20 hr period.  The chart shows a decrease capacity to 7AH if you increase the output current to 0.7A.  

   

As you increase the output current the internal resistance increases resulting in large internal losses at high current.  You can normally get a higher output current with less loss from a larger capacity battery, simply due to the increased plate area, translating to lower internal resistance at a given output current.  

   

Look at Duration of discharge vs. discharge current at Bob's site:  

   

http://www.aeroelectric.com/Reference_Docs/Battery/Panasonic/LC-LA1233P.pdf   

   

At a 1.65A discharge rate for 20 hrs capacity is 33AH.  At 105.5A rate for 0.7hr.the capacity drops to 12.3AH.  

   

This is a Panasonic battery of a different size, but the characteristics are similar across the lead acid battery spectrum.  

   

Roger  

   

   

   

--

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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_________________
Sam Hoskins
www.samhoskins.blogspot.com

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