Battery voltage question
Thread Starter
|
Posting Guru
Joined: Sep 2007
Posts: 2,121
Likes: 0
From: Knoxville, TN
Battery voltage question
What should good batteries test while the truck is not running? And what should they test while the truck is running? I tried to do a quick search, but didn't come up with much. Thanks guys. I am trying to find out if my batteries are weak or not.
Cargo Master
Joined: Jun 2003
Posts: 3,292
Likes: 6
From: Ardenvoir, Washington
The voltage with the truck not running should be around 12.5 volts.. using a digital voltage meter.. Not a very good test however. Running should be about 14.4. I like to check my batteries with a hydrometer occasionally.. It will show the condition of each cell.. If any are weak, I replace the battery.. (note: battery must be fully charged to do this test..) Napa sells a good battery hydrometer for around $20..
Lead Driver
Joined: Jun 2003
Posts: 8,298
Likes: 25
From: Damon (South East Texas)
I have used both methods. My commercial MAC battery charger has a "built in" 200 amp load for testing. I have used a hydrometer to test the % of charge and found my battery cells to be only 50-75% charged. This lead me to discover that my alternator wasn't charging sufficiently and would also discharge the batteries when the engine was off.
Trending Topics
More Turbo
Joined: Mar 2007
Posts: 636
Likes: 7
From: La Mesa, Ca.
A hydrometer is used to measure the state of charge of the cell being tested. It does that by measuring the specific gravity of the cell. A good hydrometer will have a chart for temperature correction. A load testor will tell you the heath of a battery provided the battery is fully charged first. A simple test at home would be to measure the lowest voltage (valley voltage) at the starter terminals when cranking the engine. A valley voltage of 10.5VDC or less would indicate that the batteries were weak.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Thread
Thread Starter
Forum
Replies
Last Post
SmokeBlower
1987 - 1996 F150 & Larger F-Series Trucks
48
Sep 14, 2010 04:26 PM
tetsuo73
Excursion - King of SUVs
8
Jul 29, 2009 07:59 AM
Plat7.3
1999 - 2003 7.3L Power Stroke Diesel
6
Sep 17, 2007 08:18 AM
92F150Flare
1987 - 1996 F150 & Larger F-Series Trucks
3
May 31, 2007 05:23 PM
