Battery voltage question before during and after start - Ford Powerstroke Diesel Forum
Powerstroke.org is the premier Diesel Truck Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 12-04-2010, 10:48 AM
Powerstroke.org Rookie
 

Join Date: Dec 2009
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Battery voltage question before during and after start

My question is about the battery voltage. I have a 2005 6.0 seem weak starting. My batteries are 2 yrs old Duralast gold series. I checked the voltage this morning after a 38 degree night and both ahd 12.26 volts in them. Had my wife crank it while I watched the voltage meter it dropped to 10.63 volts after crank it came back up to 12.20 slowly when the alternater kickes in the voltage goes to 13.87 to 14.33 That big of a voltage drop on start up seems way low to me ?? Want some more info before I go to Autozone and complain. Thanks
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 12-04-2010, 11:26 AM
Powerstroke.org Fanatic
 

Join Date: Sep 2010
Posts: 106
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
12.26 is too low to begin with. I would have them load test the batteries. Alternator is good if your showing 13.87 to 14.33 with the engine running.

Mine are 12.58 or higher depending on how long the vehicle sat.
Reply With Quote Quick reply to this message
  #3  
Old 12-04-2010, 02:08 PM
Powerstroke Techie

 

Join Date: Aug 2010
Location: Sassamansville, Pa
Posts: 9,732
Thanks: 93
Thanked 189 Times in 152 Posts
Feedback Score: 3 reviews
When you see the volts go up from 12.20 to 14, that's not the alternator kicking on, it's the glow plugs kicking off.

You also need to test the batteries independently, not in parallel. You need to totally disconnect one of them and test them separately. And always replace the batteries as a pair, not just one battery.
Reply With Quote Quick reply to this message
  #4  
Old 12-04-2010, 10:34 PM
Member
 

Join Date: Sep 2009
Posts: 59
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Here are my results of a bad battery one cold morning (19*). Trickle charged 3 times then was able to get it started. It would crank and almost start, then it wouldn't crank at all second try. Trickle charged for 1/2 hr, then tried again. Same thing. On the 3rd start try, I waited 45 mins and it finally started and smoked good for about 7 mins. Then after warm enough, it didn't smoke at all. My guess the glow plugs weren't hot enough to start.

The fix was 2 new batteries. Bought the truck little 1yr ago. Knew the batts were installed differently by dates on them. It was bound to happen.

Alternator charges just fine.
Attached Thumbnails
Battery voltage question before during and after start-dscf1670.jpg  
Reply With Quote Quick reply to this message
  #5  
Old 12-05-2010, 02:17 AM
Compression Ignition Addict
 

Join Date: Oct 2006
Location: Gods Country/Home
Posts: 1,694
Thanks: 15
Thanked 9 Times in 9 Posts
Feedback Score: 1 reviews
Quote:
Originally Posted by Lilpooh View Post
When you see the volts go up from 12.20 to 14, that's not the alternator kicking on, it's the glow plugs kicking off.
It IS the alternator kicking on. The alternator does not send current to the battery until after the glow plugs go off. It's to keep from seriously stressing the alternator with the extremely high current draw of the glowplugs.
Reply With Quote Quick reply to this message
  #6  
Old 12-05-2010, 07:34 AM
Powerstroke.org Rookie
 

Join Date: Dec 2009
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
yes, this is not the glow plugs kicking off. I checked this voltage at random times after is has been started. the one bettery shows only 12.02 this morning. Going to Autozone for them to check this morning. Every mechanic I have talked with including the senior fors master tech said the bettery should not be that low in voltage just sitting there.
Reply With Quote Quick reply to this message
  #7  
Old 12-05-2010, 08:17 AM
Member
 

Join Date: Oct 2010
Posts: 71
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
12.5V while not running is about typical. 12.2 is low. Are the batteries sealed, or have caps? You might need to add some distilled water to some of the cells. Sometimes that fixes the problem, but that battery may already be done for. From what you described, your alternator is charging good though.

Capped batteries need to be checked periodically for low electrolytes. The underhood heat, especially in hot climes will cook off some. Staying on top of that will keep them lasting longer. I usually check this at the beginning of Spring, middle of Summer, and the end of hot weather for the year. Takes very little time and distilled water is cheap. Also a good time to check everything with the multimeter and the terminals for corrosion.
Reply With Quote Quick reply to this message
  #8  
Old 12-05-2010, 12:35 PM
Powerstroke Techie

 

Join Date: Aug 2010
Location: Sassamansville, Pa
Posts: 9,732
Thanks: 93
Thanked 189 Times in 152 Posts
Feedback Score: 3 reviews
Quote:
Originally Posted by npccpartsman View Post
It IS the alternator kicking on. The alternator does not send current to the battery until after the glow plugs go off. It's to keep from seriously stressing the alternator with the extremely high current draw of the glowplugs.
Then I need to be schooled. Then how come when I start the the truck first thing in the morning, At around 30* outside temp, Not using the block heater, my voltmeter voltmeter starts at 12.5 then drops to 11.5 while cranking, once the motor starts it goes to 12.8 and if I turn on my high idle right away the volts jump up to 13.4. After about a minute of 13.4 and after the glow plugs turn off it jumps up again to 14.3. Now after I drive the truck around and get it up to normal operating temp, I can shut off the warmed up truck, wait almost an hour and now when I start it up and the motor is already still warm, the volts go right up to 14.3, not drop in volts due to the glow pugs not being needed. These readings are showing me that the alternator is charging right away. I also have the dual alternators.

I have also hear of people saying that the voltage regulator is controlled by the PCM, when I picked up my new primary unit from a local performance alternator shop, I asked the owner if my PCM controlled the volt regulator. He told me to look at the module where we plug the wire harness into the alternator. If the module is a gray then no the PCM doesn't control the volt reg. If the module is white, then yes the volt regulator is controlled by the PCM.
Reply With Quote Quick reply to this message
  #9  
Old 12-05-2010, 02:29 PM
Powerstroke.org Rookie
 

Join Date: Dec 2009
Posts: 13
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Took the batteries to Autozone this morning and they checked them both showed near end of life !! They showed 640 cold cranking ampsunder load. He said this was the first set of Duralast Golds that he has seen do this. My luck. Anyway he gave me two brand new ones out the door in 5 min. Many thanks to them !! Now the new baterries show 12.60 constant they do still drop on start but go up fast. Thanks for all the input on this.
Reply With Quote Quick reply to this message
  #10  
Old 12-06-2010, 01:21 PM
Compression Ignition Addict
 

Join Date: Oct 2006
Location: Gods Country/Home
Posts: 1,694
Thanks: 15
Thanked 9 Times in 9 Posts
Feedback Score: 1 reviews
Quote:
Originally Posted by Lilpooh View Post
Then I need to be schooled. Then how come when I start the the truck first thing in the morning, At around 30* outside temp, Not using the block heater, my voltmeter voltmeter starts at 12.5 then drops to 11.5 while cranking, once the motor starts it goes to 12.8 and if I turn on my high idle right away the volts jump up to 13.4. After about a minute of 13.4 and after the glow plugs turn off it jumps up again to 14.3. Now after I drive the truck around and get it up to normal operating temp, I can shut off the warmed up truck, wait almost an hour and now when I start it up and the motor is already still warm, the volts go right up to 14.3, not drop in volts due to the glow pugs not being needed. These readings are showing me that the alternator is charging right away. I also have the dual alternators.

I have also hear of people saying that the voltage regulator is controlled by the PCM, when I picked up my new primary unit from a local performance alternator shop, I asked the owner if my PCM controlled the volt regulator. He told me to look at the module where we plug the wire harness into the alternator. If the module is a gray then no the PCM doesn't control the volt reg. If the module is white, then yes the volt regulator is controlled by the PCM.
The voltage regulator in a single alternator is turned on by the I circuit. In a single alternator setup, that circuit goes to the hybrid electric cluster and is part of what controls the battery warning light.

The HEC does not apply voltage to the I circuit, thus not turning on the alternator, until the glow plugs have shut off.

If you have a dual alternator setup then the second alternator is controlled by the PCM.
Attached Files
File Type: pdf Principles of Operation - Dual Alt[1].pdf (110.6 KB, 195 views)

Last edited by npccpartsman; 12-06-2010 at 01:40 PM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Ford Powerstroke Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -8. The time now is 03:17 PM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.1
Garage Plus, Vendor Tools vBulletin Plugins by Drive Thru Online, Inc.

vB.Sponsors