Battery voltage before starting


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Old 12-16-12, 05:13 PM
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Battery voltage before starting

My '95 Nissan Hardbody King Cab 2.4L 5 speed 2wd, 165K miles, is giving me some problems starting. A few weeks ago after several stops that day it wouldn't start until jumped. Today, after having sat for a week and a half or so wouldn't start when we tried to use it. Both times it would make a very heavy click noise like I expect, but nothing would spin. This time I had my wife sit in the truck, in fifth gear but with the clutch in, and I pushed it and had her let the clutch out to move the flywheel slightly, but it didn't change anything. I pushed it back into its spot and we took a different vehicle on our errands.

I measured the current across the battery poles at the time. It measured a little under 12.8V.

A few weeks before the original problem I had replaced the starter, only to find that one of the battery cables had corroded about two inches internally from the terminal. I cut that corroded part out and it had started working again until that original time.

What voltage should I see in a battery at rest?
 
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Old 12-16-12, 05:25 PM
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A well charged battery at rest will measure about 13.5 volts. If you measure it while someone tries to start the vehicle and see it drop several volts, then the battery or one of the clamps/cables is the problem. You can repeat this test measuring right on the battery posts and then on the clamps. If it stays solid at the posts but drops when you test at the clamps, it is a clamp or cable.

Meters can vary, so measure the battery in your other car to see what it reads.

Also, did you check the fluid level in the battery?

Bud
 
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Old 12-16-12, 05:27 PM
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12.8 volts is a fully charged battery but that voltage doesn't tell you how much cranking power it has.
If you get your wife to turn it over and read the voltage while she does you may find the voltage drops too low to turn it over.

It should only drop a volt or so while cranking.

At 12.8 volts the alternator is likely working but the battery may be shot.
A load type battery tester would tell you for sure.
 
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Old 12-16-12, 05:28 PM
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Didn't check the fluid level. I checked it with the meter with the ignition off.
 
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Old 12-16-12, 07:30 PM
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Resting voltage tells very little. As GregH said check for a voltage drop when the key is in the start position. The starter will be the load and if the voltage drops to say 10 volts or lower, it's battery time.
 
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Old 12-16-12, 08:31 PM
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Sometimes you don't even have to turn the key to "start" to see the voltage drop off from a dying battery. Often just turning key to "on" will show a significant drop and give you a clue.
 
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Old 12-17-12, 06:25 AM
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Okay. I'll see if I can find the good meter (I have a Fluke but couldn't readily find it, used a Harbor Freight POS instead) and give it a try with a loaded test this afternoon, also will check the water level.

Batteries only last a couple of years around here regardless of how expensive they are for vehicles that reside outdoors 24/7. It's the heat. I've just had enough problems with this truck that I don't usually suspect the battery first thing, and I can't remember when it was last replaced either.
 
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Old 12-18-12, 06:21 PM
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This is peculiar

I went out to check, first measuring voltage across the terminals, and got over 15V, something like 15.4V. Same meter.

My wife turned the key, and it dropped to just over 14V while she held the key to start.

I need to find my Fluke. I'm questioning the accuracy of the HF meter now.
 
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Old 12-19-12, 03:14 AM
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The voltage you should read on a lead acid battery while charging should be between 14 and 15 volts.
When charging is complete you could see anywhere from 13 to 14.5 volts but this voltage will be due to a surface charge.
You need to let the battery rest for at least five hours for the surface voltage to dissipate and you can take a reading.

Generally after the surface charge dissipates, 12.7 volts is seen as 100% charge.

At around11.7 volts a lead acid battery is completely discharged.
If a battery is drained down below this level the battery life will be shortened.
 
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Old 12-19-12, 06:14 AM
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Nothing was touched between the first and second time I took readings. No charging, no lights left on, nothing. The truck sat over a few days. I did not attempt to charge the battery or otherwise work on it.

That's why I'm starting to suspect the meter.

Battery was manufactured September 2009, I don't remember, offhand, when I installed it.
 
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Old 12-19-12, 07:29 AM
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That sounds a lot like the battery in our van when it went this summer.
The van would sit for a couple days (use my summer car for commuting) and then it likely wouldn't start (same signs you have). Throw the chrager on it and it'd charge up pretty quickly. Leave the van. The battery was from 07, so after a quick couple checks, swapped it out.
My battery was showing ~12.8V after the van was shut off, ~14.1V while the vehicle was running (alternator charging). Throw the radio on without the van running and you could watch it drop 0.1V every couple seconds.
 
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Old 12-20-12, 07:33 AM
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I cleaned the top of the battery and added some distilled water. I could see water when I opened the caps, but I went ahead and added a little anyway.

Found the Fluke, took some measurements...

Key off, got just under 12.47V.
Ignition on, not start, 11.95V.
Key turned to Start, 11.40V.
Key off after trying Start, 12.25V.

Wife brought over her car and we hooked up to jump start.
Hooked up to jump start, both cars off, 12.75V.
She starts her engine, mine off, 13.8V.
I start mine, jumps to about 14V.
Unhook, mine continues to read about 14V.

I went around the block, came home and parked it. Didn't sample voltages again, but it did restart after being shut off.
 
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Old 12-20-12, 07:40 AM
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T-W-X, those numbers are very, very similar to what mine was on the van this summer. My issue was an exhausted battery.

Your drive around the block might have helped charge the battery a hair, but the somewhat warmed engine would be a lot easier to start.
 
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Old 12-20-12, 07:46 AM
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A worn starter can draw too much and show excessive voltage drop also. This however wont come and go. To check for loss in a circuit place one lead of your voltmeter on the batt post and the other on the starter post then have someone operate the starter this will measure the loss in that circuit. Ideally it should be 0. Do the ground side the same way going to the case of the starter. Be sure you have the leads connected in the right polarity. You can switch the leads to make sure. Ant test on a batt without a load on it is useless.
 
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Old 12-20-12, 10:13 AM
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I have been following this thread and it sounds like at least one bad cell in the battery. In my opinion pick up a new $100 battery and you will have a happy ending.
 
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Old 12-20-12, 02:18 PM
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Yeah, I'm probably just going to get a battery. The starter has already been changed, this truck seems to go for months without any problems then suddenly it misbehaves. Very annoying. But, it's hard to argue when it only cost me $700 in the first place.
 
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Old 12-24-12, 06:01 PM
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We found the receipt and got a $110 replacement prorated to $62 out the door.

I think I'll buy a battery load tester next time I find a good one for a good price.
 
 

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