E-Class (W211) 2003-2009

Battery Question

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Old Oct 14, 2015 | 12:15 PM
  #1  
plasma's Avatar
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2003 E320
Battery Question

I checked the voltages of the aux battery when I got home last night and then again this morning after the car sat. Last night the voltage was 11.86 and this morning 11.7. Does that seem normal?
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Old Oct 15, 2015 | 12:55 PM
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From: dmv
2009 E550 2000 Honda civic mash n' go
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Old Oct 15, 2015 | 04:26 PM
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2004 E320
A good battery should be between 12.4 to 12.6v at rest, If that's the original aux batt, I would consider replacing it.

Open Circuit Voltage of 12V battery after car is off for one hour Relative charge
12.6 V 100%
12.4 V 75%
12.2 V 50%
12.1 V 25%
Less than 12 volts Dead
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Old Oct 16, 2015 | 05:58 PM
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wjcandee's Avatar
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From: NYC and LI
2004 Mercedes E500, 2008 Mercedes ML350
Originally Posted by starbrite
A good battery should be between 12.4 to 12.6v at rest, If that's the original aux batt, I would consider replacing it.

Open Circuit Voltage of 12V battery after car is off for one hour Relative charge
12.6 V 100%
12.4 V 75%
12.2 V 50%
12.1 V 25%
Less than 12 volts Dead
The aux batt is fine until it isn't fine. Then the red light will go on on the dashboard. Then, you will go to Amazon and buy the authentic Yuasa YTX battery that we recommend on here. It is the best buy, good mix of quality and performance and price. Then you will install it yourself following the directions on here. Then you will never worry about it again. But until then, there's no need to even think about it. It's not like it's actually an essential part of anything, provided that your electrical system is otherwise working properly. So put it out of your mind, and don't bother testing the voltage again.
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