Forums Migration

Please read this thread

Recent Topics
Darker varnish spot on rocker arm
by Spetz - 07/07/20 07:29 PM
AC Delco Dexron VI $18.76 a Gallon Amazon
by Matt1980 - 07/07/20 07:17 PM
ALS labs change in fuel dilution test
by LotI - 07/07/20 06:50 PM
Archery high tech
by CourierDriver - 07/07/20 06:42 PM
Odd filter issue
by fatrap314 - 07/07/20 06:33 PM
Lexus IS 350 AWD 2016 0W-20
by hotp4nts182 - 07/07/20 06:14 PM
Duh-- Didn't know there was a SIM card.
by csandste - 07/07/20 03:54 PM
Running 40 PSI vs 35
by Mr_Luke - 07/07/20 03:05 PM
Kidney Filtration-Secondary Effects???
by TravlinTech - 07/07/20 02:41 PM
When to replace mower deck?
by supton - 07/07/20 02:39 PM
API SN safe for TGDI?
by mdixon26288 - 07/07/20 02:18 PM
borgwarner 4484 t case dexron iii or gear oil?
by apollo18 - 07/07/20 02:12 PM
Hand Sanitizer warning : Methanol
by odie - 07/07/20 02:11 PM
BEST Oil Filter for 2020
by DCMotorsports - 07/07/20 12:39 PM
1997 Lancruiser/Colorado/
4Runner wishbone bolt

by Kamele0N - 07/07/20 12:33 PM
why change oil on low mileage car consuming oil
by NewC-05 - 07/07/20 11:50 AM
Which oil to use?
by HydroxZ - 07/07/20 11:02 AM
What oil for supercharged Lotus Exige?
by mkiv808 - 07/07/20 10:59 AM
Carb Metering Diaphrams
by Fordiesel69 - 07/07/20 10:30 AM
Newest Members
fatrap314, hotp4nts182, LeslieX, Mayuraj, thexeve
71876 Registered Users
Who's Online Now
105 registered members (14Accent, Anthony, Astro_Guy, AlienBug, A_A_G, 16 invisible), 1,989 guests, and 22 spiders.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums67
Topics307,571
Posts5,313,293
Members71,876
Most Online4,538
Jan 20th, 2020
Donate to BITOG
Print Thread
Hop To
LML Duramax charging at 15.3 volts #5262214 11/08/19 11:41 PM
Joined: Sep 2017
Posts: 391
B
BlakeB Offline OP
OP Offline
B
Joined: Sep 2017
Posts: 391
My dads 2016 LML has been turning over a little on the slow side for a while, but this morning it wouldn’t turn over at all. I jumped it with another vehicle and checked the battery voltage with it running after the jump vehicle was disconnected. It was reading in the mid to upper 14’s on the multimeter. I thought ok, it needs batteries... so I take them off and go get new ones.
I ended up getting the Everstart Maxx AGM H6 batteries at WM for ~$150 each. I checked the resting voltage before I installed them, both were at 12.6-12.7 volts.
I got them installed and started the truck up, all seems well until I throw the multimeter on it and find that it is charging at 15.3 volts. I let the truck run for about 30 minutes and the voltage did drop to ~14.5 volts for a minute and then went right back to 15.3 volts.

This truck was manufactured in 8/2016 so the factory batteries were only 3 years and 3 months old. I thought it was odd for them to be dead at just over 3 years old, but now I’m wondering if the charging system/alternator is overcharging and cooking the batteries?

The truck has 48k miles and ~3,300 engine hours. I did not have the old batteries load tested before replacing them but the truck jumped easily and I did verify that the alternator was charging before I removed them so I am confident that at least one of them was bad.

I did check for codes and the only thing it’s showing is a P21DD for the DEF heater. No pending codes.

It runs great and doesn’t have any other symptoms of anything being wrong. I’m just concerning about it charging at 15.3 volts, that seems way too high to me. What do you guys think?

Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262219 11/08/19 11:47 PM
Joined: Nov 2004
Posts: 2,182
Z
zrxkawboy Offline
Offline
Z
Joined: Nov 2004
Posts: 2,182
I wonder if the new batteries had been on the shelf a while and need to charge up a bit.


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262220 11/08/19 11:49 PM
Joined: Nov 2004
Posts: 2,182
Z
zrxkawboy Offline
Offline
Z
Joined: Nov 2004
Posts: 2,182
Also, what was the ambient temp? That will make a difference.


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: LML Duramax charging at 15.3 volts [Re: zrxkawboy] #5262222 11/08/19 11:52 PM
Joined: Sep 2017
Posts: 391
B
BlakeB Offline OP
OP Offline
B
Joined: Sep 2017
Posts: 391
Originally Posted by zrxkawboy
Also, what was the ambient temp? That will make a difference.

23°F here currently

Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262236 11/09/19 12:31 AM
Joined: Nov 2004
Posts: 2,182
Z
zrxkawboy Offline
Offline
Z
Joined: Nov 2004
Posts: 2,182
Colder temps typically equal higher voltage.


"Think of all the Ford owners who will someday want an automobile." John Dodge

Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262380 11/09/19 09:37 AM
Joined: Oct 2008
Posts: 19,679
SteveSRT8 Offline
Offline
Joined: Oct 2008
Posts: 19,679
^^^Exactly. The variable charging setup on most GM vehicles will really pile on the volts when it's cold outside.

Normal behavior. Expect it to drop like a rock when it heats up...


"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix
Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262411 11/09/19 10:19 AM
Joined: Sep 2017
Posts: 391
B
BlakeB Offline OP
OP Offline
B
Joined: Sep 2017
Posts: 391
Thanks for the help guys.

Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262578 11/09/19 02:59 PM
Joined: Mar 2012
Posts: 1,091
T
tiger862 Offline
Offline
T
Joined: Mar 2012
Posts: 1,091
Sounds like you have a voltage regulator going out. 15.3 is to high and will fry battery as well as do goofy things (IE limp mode) if left like this.


Tiger862
2018 Grand Caravan
Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262585 11/09/19 03:15 PM
Joined: Aug 2009
Posts: 2,636
G
Gasbuggy Offline
Offline
G
Joined: Aug 2009
Posts: 2,636
GM's system alternates voltage depending on what it determines is needed, with fuel economy in mind. My CTS-V I've seen anywhere from 15.2 to 13 flat.


Cadillac CTS-V 6.2L 10w30PP
Volvo P1800 Euro L
76 Mercedes 300D Rotella T4
Series III Land Rover VWB
02 Yukon 10w30 PP
01 P71 M1 EP-HM 0W20
95 Accord - 386k. Mobil 2 RIP
Re: LML Duramax charging at 15.3 volts [Re: BlakeB] #5262730 11/09/19 07:16 PM
Joined: Jan 2018
Posts: 470
R
red7404 Offline
Offline
R
Joined: Jan 2018
Posts: 470
try checking all the grounds. body, computer, ect

Re: LML Duramax charging at 15.3 volts [Re: Gasbuggy] #5262733 11/09/19 07:19 PM
Joined: Jun 2003
Posts: 35,783
E
eljefino Offline
Offline
E
Joined: Jun 2003
Posts: 35,783
Originally Posted by Gasbuggy
GM's system alternates voltage depending on what it determines is needed, with fuel economy in mind. My CTS-V I've seen anywhere from 15.2 to 13 flat.


Yes and the "Maintenance free" batteries GM invented need a few tenths more charging voltage for the different chemistry.

Re: LML Duramax charging at 15.3 volts [Re: zrxkawboy] #5263071 11/10/19 08:31 AM
Joined: Jun 2013
Posts: 591
W
willbur Offline
Offline
W
Joined: Jun 2013
Posts: 591
Originally Posted by zrxkawboy
I wonder if the new batteries had been on the shelf a while and need to charge up a bit.



I think you are right. A fully charged AGM is 12.8-12.9 volts (according to East Penn/Deka), and do not charge above 14.6

Previous Thread
Index
Next Thread

BOB IS THE OIL GUY® Powered by UBB.threads™