Alternator Charging too long

[A_User55555]

A few weeks ago, My car battery died and an autoparts store used an 80A fast charger to recharge it. The battery tested good. I made a thread on it here:

No wear on 3 year old Group 94 battery?

After trying to hard wire my dashcam, I wound up with a completely dead battery. I took my battery to Advance Auto Parts to charge it. They used an 80A charger and in 35Mins, the battery was charged. I asked them to do a battery test on it. To my surprise, the battery showed no wear at all. My...

bobistheoilguy.com

Before, Id start my car and the voltage would go up to 15V and after 15 mins of driving, the voltage would go down to 12.9V. Basically the computer detects the battery is charged so it tells the alternator to trickle charge the battery.

Now I noticed that the battery voltage stays at 14.3V for Hour long trips. It's almost as if the car cant detect if the battery is charged so it keeps the voltage high. The car starts up just fine.

Did the rapid charge do something to my battery to make the car think its not charged? Or does the computer need time to re-learn the battery capacity?

 

[StarCaller]

low temperature /

 

[oldhp]

My 2021 JEEP Gladiator stays around 14.4 volts all the time, so does my 2019 Dodge Charger SXT both when running down the road. Both have heated seats / steering wheels with power everything. I don't think that is the correct way to charge a dead battery. I've always been told, and done, no more than 10 amps until the amp draw stays below 2 amps. A fully charged battery should show approximately 12.8 volts, at approximate 2.12 volts per cell.

 

[wrcsixeight]

Is there a ring sensor around a battery cable.?

Votage regulation on modern vehicles, has far less to do.with battery longevity, compared to fuel economy.

And there is little.likelyhood you battery accepted 80 amps for more than 30 seconds.

When a vehicle with a healthy battery inadvertently drained to dead, requires a jumpstart, the alternator can easily feed it 80 amps with engine rpms above idle, if the voltage regulator.is seeking over 14 volts.

Occasional High amp recharging is not the boogeyman the internet will have you believe, and repeat.

 

[billt460]

My Jeep shows right around 15 volts while driving. This never changed before or after I installed a new battery. Even after giving it a full soaking charge with a Noco Genius One..... The voltage never changes on the voltmeter. Be it 40 F Winter mornings, or 122 F Summer days.

And all the engines in my vehicles spend 95% of their lives at between 750 - 2,000 RPM's.

 

[Lubener]

I still would not rule out the battery.

 

[Donald]

I too would not rule out the battery. Why did it die initially? Had you left something on? How are you testing the voltage? With a quality DVM at the battery? With the engine running you should see more than 12.9V at the battery.

A carbon pile load test is the best way to accurately test the battery. The battery does need to be fully charged for the test, which is why the auto parts stores use a Midtronics.

 

[A_User55555]

Is there a ring sensor around a battery cable.?

Votage regulation on modern vehicles, has far less to do.with battery longevity, compared to fuel economy.

And there is little.likelyhood you battery accepted 80 amps for more than 30 seconds.

When a vehicle with a healthy battery inadvertently drained to dead, requires a jumpstart, the alternator can easily feed it 80 amps with engine rpms above idle, if the voltage regulator.is seeking over 14 volts.

Occasional High amp recharging is not the boogeyman the internet will have you believe, and repeat.

There is a ring sensor. I made sure it looked good, but I guess I can check it out again

 

[A_User55555]

I too would not rule out the battery. Why did it die initially? Had you left something on? How are you testing the voltage? With a quality DVM at the battery? With the engine running you should see more than 12.9V at the battery.

A carbon pile load test is the best way to accurately test the battery. The battery does need to be fully charged for the test, which is why the auto parts stores use a Midtronics.

It died because I left a charger plugged in.

I’m reading the voltage from the DIC readout. I also have a phone charger with voltage output. When the car is running the voltage is definitely above 12.9V. But the car didn’t use to keep the voltage at 14.3 for this long

I guess I can get the battery tested elsewhere.

 

[4WD]

My 2021 JEEP Gladiator stays around 14.4 volts all the time, so does my 2019 Dodge Charger SXT both when running down the road. Both have heated seats / steering wheels with power everything. I don't think that is the correct way to charge a dead battery. I've always been told, and done, no more than 10 amps until the amp draw stays below 2 amps. A fully charged battery should show approximately 12.8 volts, at approximate 2.12 volts per cell.

Same with my Wrangler - 14.3 when I just now parked it …
(been watching it since a JLU/JLT owner/friend just replaced both batteries on a 2019)

 

[Donald]

It died because I left a charger plugged in.

I’m reading the voltage from the DIC readout. I also have a phone charger with voltage output. When the car is running the voltage is definitely above 12.9V. But the car didn’t use to keep the voltage at 14.3 for this long

I guess I can get the battery tested elsewhere.

I assume you mean a phone charger? I have one that is powered all the time and I always leave it plugged in. However most of the time if I am not driving, there is no phone attached to the charger. I also have dual group 65 batteries.

 

[A_User55555]

I assume you mean a phone charger? I have one that is powered all the time and I always leave it plugged in. However most of the time if I am not driving, there is no phone attached to the charger. I also have dual group 65 batteries.

It’s complicated.

I was trying to hardwire my dashcam. I saw the glove box light was part of the RAP circuit. Which means power will be cut off after 10 minutes. I even left the glove box open and saw the light turn off after 10 minutes. So I tapped into that circuit to power my charger.

What I didn’t know is that the power feed to the bulb comes from the BCM. It’s not fed from a relay. And apparently that circuit is monitored for current changes. So for example if the dome light goes off because of RAP, you can press the dome light button and RAP will be extended for another 10 minutes.

I measured the current draw of my charger with nothing plugged in, and the current draw was only 2milliamps. That’s not enough to drain a battery overnight.

The only explanation I can think of is by having that charger plugged into the glove box circuit, the car kept extending RAP to the radio and other modules. So stuff that normally loses power after shutdown kept getting power and drained the battery.

 

[sky jumper]

well if it makes you feel any better I've bought about 15 new batteries over the past 10 years and just about every single one took an hour or so to complete an initial absorption charge. they were all 12.6v+ off the shelf. most are still in service. I don't think an extended period of time at 14v is at all indicative of a battery problem. I'd be more concerned if it quickly went straight to float voltage. but like others have said get yourself a $20 load tester and put your mind at ease.

 

[Donald]

It’s complicated.

I was trying to hardwire my dashcam. I saw the glove box light was part of the RAP circuit. Which means power will be cut off after 10 minutes. I even left the glove box open and saw the light turn off after 10 minutes. So I tapped into that circuit to power my charger.

What I didn’t know is that the power feed to the bulb comes from the BCM. It’s not fed from a relay. And apparently that circuit is monitored for current changes. So for example if the dome light goes off because of RAP, you can press the dome light button and RAP will be extended for another 10 minutes.

I measured the current draw of my charger with nothing plugged in, and the current draw was only 2milliamps. That’s not enough to drain a battery overnight.

The only explanation I can think of is by having that charger plugged into the glove box circuit, the car kept extending RAP to the radio and other modules. So stuff that normally loses power after shutdown kept getting power and drained the battery.

Everything is interconnected and nothing is simple. And you might need to be an electrical engineer to be able to read and understand the wiring diagram of a new car.

 

[circuitsmith]

Now I noticed that the battery voltage stays at 14.3V for Hour long trips.

It means your battery is not thoroughly charged.
An 80 amp rapid charge can quickly get the battery functional, but it takes hours of slower charging to complete the job.
Your car's smart charging system can sense this. Thus it elevates voltage to further charge.
A hygrometer would be the best way to tell how fully your battery is really charged, but current measurement while under charge can be informative.
With about 14.5V (depending on temperature) applied I would want to see a drop to less than 1 amp going in.
This check is easy using an adjustable power supply. My preferred tool for battery maintenance.

Amazon.com

 

[Lubener]

A hygrometer would be the best way to tell how fully your battery is really charged, but a current measurement can be informative.

I am sure you mean hydrometer. A hygrometer measures humidity in the air.

 

[A_User55555]

Everything is interconnected and nothing is simple. And you might need to be an electrical engineer to be able to read and understand the wiring diagram of a new car.

I am an Electrical/Computer Engineer. I never thought a 2milliamp draw could drain an entire car battery. Only until I read up on Retained Accessory Power did I realize what could've went wrong.

 

[gathermewool]

It means your battery is not thoroughly charged.
An 80 amp rapid charge can quickly get the battery functional, but it takes hours of slower charging to complete the job.
Your car's smart charging system can sense this. Thus it elevates voltage to further charge.
A hygrometer would be the best way to tell how fully your battery is really charged, but current measurement while under charge can be informative.
With about 14.5V (depending on temperature) applied I would want to see a drop to less than 1 amp going in.
This check is easy using an adjustable power supply. My preferred tool for battery maintenance.

Amazon.com

1A @ 14.5VDC indicates a partially charged battery. I'd want to see a fraction of an amp at that voltage for a full battery. Using a desktop power supply I've even seen a battery stop absorbing charge after an extended period (i.e., overnight) at 14.4VDC (my choice topping off voltage at moderate ambient temps)

As another anecdote, my Legacy (and previous Civic) used to lower the voltage soon after driving if it sensed a full battery. The problem with the Legacy was that it was too aggressive. Subaru had to put out a TSB to change the charging algorithm so that the alternator supplied a constant 14.2-14.3VDC from idle to high RPM, regardless of how long I'd been driving. I know this is fact, because we recently went on a trip to FL from the north-east and the voltage parked itself at 14.2-14.3VDC the entire time. My batteries don't seem to lose too much water this way, either.

As has been mentioned, the best way to determine state of charge is by using a hydrometer (I've never done this, to be honest). The backup method is to monitor how the battery charges (i.e., will it take a charge). The best way to determine the health of a battery is by using some sort of load tester. I don't have a carbon pile, but have a relatively cheap load tester that seems to work well.

 

[A_User55555]

So slight update. Today after driving for 40minutes, the voltage again stayed at 14.3V. I removed the battery out of the car to charge it. The voltage showed maybe 12.7, but I didn’t let the battery sit.

I connected it to a NOCO 1A charger. It took about 7 hours for the charging light to turn green.

I put it back in my car and same thing. The battery voltage stayed around 14.4V. When I turned the lights off, the voltage went up to 15.3. Now 15.3 may seem high, but it’s normal for this charging system. I’ve seen 15.3 before during startup.


I did some more reading on the GM charging system and found this. There’s 6 different charging modes and this is one:

Voltage Reduction Mode–The BCM enters Voltage Reduction Mode when the ambient air temperature is above 32°F, the battery current is less than 1 amp and greater than -7 amps, and the generator field duty cycle is less than 99 percent. The BCM targets output to 12.9 V. The BCM exits this mode once the criteria are met for Charge Mode.

It’s been below 32 in NYC for the past few weeks. So maybe there is no problem at all. I never really paid attention to system voltage. Ive been focusing on it ever since the battery drain. I guess I’ll have to check again when the weather warms up.

 

[slomo]

Not wise to "tap" into other circuits to run some dash cam. Don't mess with any yellow connectors (air bag).

Did you solder and heat shrink? Or some lack luster Scotch Locks?