battery and charging question

naford · Oct 16, 2013

I have an 02 ranger 4.0. The battery was the original until this past week. I have been noticing that when I go to start the truck up the voltage gauge (gauge is factory on the instrument panel) is down then comes right back up slow but not that slow. The battery voltage before I started was 12.2 and when running 14.5. The battery is almost 12 years old so I figure I'll take it in and get a new one. I have it tested and the machine prints out 420 CCA ( cold cranking amps ) at 67 degrees. The battery is supposed to be 540 CCA. That is within spec. but I buy a battery anyway before winter sets in. After the install I watch the voltage meter again but this time it doesn't seem to be down at all. I wondering if watching the voltage gauge would be a good indication of when the battery is going bad? I know that on my old Toyota back in the day before the battery went bad the voltage gauge was doing the same thing.

ab_slack · Oct 16, 2013

12 years is very good on a battery. I just had to replace battery in my 02 Explorer and it probably isn't more than 5 years old.

I don't know how much use the gauge is in the ranger. The gauge in my 02 Explorer always sits right in the center. I can go key on, engine off and it is in the center. Headlights on, high beams on, still no movement. Start the engine again no movement. If it was a voltmeter or ammeter, it should have moved under different conditions.

This leads me to believe it is like the fake oil pressure gauge which has a simple switch behind it that causes it to read center or zero and that is it. I have no idea what logic is behind the battery gauge.

Now the battery voltage is a reasonably good indicator battery and alternator health. After the engine has been running and battery should be fully changed, the battery voltage when engine is off can give some clues. What it drops to over an hour or overnight really can highlight problems.

A quick load test can be performed by turning headlights on and seeing what the voltage drops to with that much load.

Conversely, what the voltage goes to when running the engine tells a great deal about alternator. Someone around here, RonD I think in another topic posted some good information fairly recently.

I don't know the specifics very well. I usually know I am getting into trouble with my battery when I have trouble starting the car after it has sat a couple days or seriously getting bad if it doesn't crank in the morning after having driven it the night before. Then I look at the voltage and usually find it sitting down between 11V and 12V within an hour of it having last been driven.

RonD · Oct 17, 2013

It would be the 2nd battery, should be a date code on it, unless truck has 60,000 miles or less on it, then it would be equivalent to 6 years old battery
Car batteries last for 5 years for the most part, depends on use, that would be a daily driver use, the discharge/recharge count is what that's based on.

Battery with 12.2 volts has a 50% charge, so time to shop for a sale, next cold night will make for slow cranking the next morning.
Over 14.2 volts from alternator shouldn't last very long, that's just to recharge after starting, after a few minutes it should be down to 13.6-13.8 volts
Higher average voltage than that will shorten life of the battery.
Batteries need 1 volt above their voltage to maintain their charge, 1.5-2volts to recharge after starting

New battery will be 12.8 volts
12.8/9volts = 100%
12.5volts = 75%
12.2volts = 50%

Best time to measure battery voltage is after it sits overnight
Once battery gets down to 50% it probably has a residue build up at the bottom of the cells, this will eventually cause a short in one of the cells, so battery will self discharge.
Most have experienced this.
You go out one morning usually chilly morning and try to start engine, maybe it turns slowly then the dreaded "CLICK, CLICK,CLICK"
You jump it and it starts right up
You drive to work, turn it off and restart, just to see, works fine
Come out from work and it cranks slowly but starts, "must just need a longer drive to charge up"
So you drive an extra 20 minutes and turn in
Next morning, "CLICK, CLICK,CLICK", lol

Ain't no fun, been there done that

Battery has a shorted cell, it drains the battery when it sits
If it was the alternator the engine would stall out after jumping it as the battery had no juice to start the engine so would have little left to run it with no alternator output

Road Angels · Oct 17, 2013

12 years on a battery I want one of those!!!! Oh wait it has been replaced with a factory (dealer battery) I got 7 years out of one battery but I lived on a hill so winter starts where not a problem, just pop the clutch, but it was shot, so is yours

battery and charging question

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