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@DeeK there is always the chance that your truck has a problem, just sharing ideas here.

do you have something that plugs into the cig lighter that uses a good amount of power like a small compressor? Or plug in a trailer with lights? Put a load on it and see if you get more volts out of it.
 

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Discussion Starter #22
I can believe that a low voltage at low current is normally sufficient to run on-board electrical systems and then all is needed is giving the battery a pop every so often to top it off. The thing that makes me question that approach is that my morning charge was typically under 12.5V, which does not indicate a healthy, fully charged battery.
I found almost the opposite of what you found - when my trailer was hooked up, the DICr was sitting at 12.1 virtually all the time and only started charging on long down hills or when I'd unhook. I interpreted that as a sign that as long as the truck was under load it didn't want to "waste" energy charging the battery. I like your charging system better! As I said, I found that my trailer battery was getting drained by being hooked up to the truck and it returned to its normal when I disconnected it while traveling.
I agree that Chevy may have made the calculation that some battery longevity was worth trading to meet fleet fuel standards. They put a very nice AGM battery in that is unlikely to fail until after warranty expires on truck. Then, it looks like it needs to be replaced with a $350 battery that so far I've only found that ACDelco makes, i.e. it becomes another revenue stream for GM. Over time, though, if people have to keep replacing expensive batteries prematurely, you'd think that would erode customers' loyalty to GM. It's also possible that all the big american (foreign too?) manufacturers are playing the same game, who knows. I guess time will tell since we may be among the first generation to experience the effects of manufacturers struggling to meet ever higher fuel efficiency standards.
I have to laugh at myself though because I really like the fuel efficiency but I guess it's unrealistic to think that there's not some trade off.
 

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Discussion Starter #23
oh, good idea about seeing how the system reacts under load. i'll definitely try that.
 

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Discussion Starter #24
After another 3 hour trip where it sometimes charged at 14.5 V but still majority of time at 12.1V, I ended up with battery voltage lower than when I started (12.8 start, 12.4 end). I had used a trickle charger to bring it up to good voltage over the preceding week.
Just talked to my service manager and, he spilled the beans. They started having complaints of low voltage (12ish) a while ago. GM informed them that was the design of the system and that nothing could be changed. When pressed for why the system was designed this way, GM's simple answer was "fuel economy".
I feel vindicated that I wasn't being a conspiracy guy but very disappointed that GM adopted this approach. The battery is covered under the 3 year bumper-to-bumper warranty and Service guy said he had seen quite a lot of premature battery failures on Cadillac but hadn't noticed it on Chevy. A really good battery should be able to stand up to chronic undercharging for 3 years so GM escapes the warranty/financial burden of this practice.
My battery is lower voltage when I finish a long drive and then it slowly recovers as it sits. That's the exact opposite of how it should perform - get charged up well (13+V) on a long drive and then gradually fall down to healthy resting voltage (12.7 or so) and stay there unless it sits for a very long time in which case of course it will very very slowly fall farther.
The only "solution" I see is to leave the battery hooked to a taper rate, trickle charger that will take the battery through a healthy charge cycle and then maintain it at correct voltage (~13V) and hopefully, over time, shed some of the sulfation deposits that have built up because of chronic discharge.
I wouldn't be surprised if other manufacturers are pulling the same crap, but that doesn't make it right.
 

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Have 2017 Colo with 11K miles and just returned from 5,000 mile trip where I spent a lot of time (too much according to herself) watching the battery charge status. Super impressed with truck but have issues with the charging algorithm and wondering what others are experiencing.
Mine sometimes resists going into charge mode but finally does and charges around 14.3-15.0 Volts which is very reasonable for the absorption phase. The problem is that when it leaves that charge phase, it drops the voltage to 12.1-12.2 and holds it there, often for many hours before charging up again and the recharge phase is often very brief, several minutes. A 12.1-12.2V battery is only 50-60% charged. My battery voltage in the morning before I start the truck is usually 11.8-12.1 volts, not the 12.8-13.0 it should be for a fully charged battery. Sulfonation can start occurring when a battery is discharged to less than 90% if it is not quickly taken back through an absorb cycle and that can permanently damage a battery pretty quickly.
I have been off grid at home for years now and "float" voltages, i.e. where the system maintains the battery bank to prevent damage and is considered a full charge is typically 13.5 volts. I can't understand why the truck battery should be much different since the chemistry is the same in home and auto systems.
I'd be sort of OK if the charging system held the battery at 12.7-13.0 volts which is nominally considered to be a full charge but why does the system hold the charge at 12.1 volts? Are others noticing this or is my system having issues? The alternator is absolutely fine because when the charging kicks in, it has no problem delivering enough current to get the battery to good voltage quickly.
Here's a general chart of battery charge versus % charge (SOC - State of Charge).
I been watching the charge also.
And having seen many battery failures on these trucks it’s obvious anything below 12.5 is not good.
Actually I have done a lot of research on battery charge limits and discharge limits.
I also have solar panels on the roof and have read a lot of info on how to get the most life out of your battery bank.

For AGM batteries like we have in our trucks
12.5 is considered as low as it should go. It’s also typical of a battery that has been sitting for a while.
13.8 is considered fully charged. A higher charge will shorten its life.
Now it’s not uncommon to see 14.2
But NEVER HIGHER......

If you watch what the ECM is doing while you drive, you will notice the voltage increase as you go down hill and decrease as you go up hill.
Or
You may notice the ECU stop charging when you have your foot into it.
And charge like crazy while coasting or decelerating.
This tells me it’s all about MPG.

This was a street racer trick used for drag racing
Put a switch on the throttle plate to shut off the charging system and air conditioning when the throttle is wide open.. works great and frees up HP......

Rob
 

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Discussion Starter #27
coloradorob, do you have any documentation for the premature battery failures you mentioned in your comment?
 

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coloradorob, do you have any documentation for the premature battery failures you mentioned in your comment?
No documentation
I read as much as I can about these trucks. Always looking for issues that I should be concerned with.
There has been many posts of batteries being replaced while the truck is under warranty.
Older vehicles had regulators to maintain battery charge. Our trucks charging system is controlled by the ECU. This is very popular now.

I have always thought the best way to get better mpg would be to stop charging when ever possible and charge like crazy when on the brakes or coasting. And that is what GM engineers have done.
But
It should never fall outside the standard limits for the type of battery in
coloradorob, do you have any documentation for the premature battery failures you mentioned in your comment?
No documentation
I read as much as I can about these trucks. Always looking for issues that I should be concerned with.
There has been many posts of batteries being replaced while the truck is under warranty.
Older vehicles had regulators to maintain battery charge. Our trucks charging system is controlled by the ECU. This is very popular now.

I have always thought the best way to get better mpg would be to stop charging when ever possible and charge like crazy when on the brakes or coasting. And that is what GM engineers have done.
But
It should never fall outside the standard limits for the type of battery in the vehicle. The safe charge voltages are different for a flooded acid battery that you can add water to.
AGM do not like 15v.
That is way to high for even a equalize charge.

Do some research
There is a lot of info on batteries and how to get the most life out of them

What kills me is theses are supposed to be engineers.
If they are so smart how can they fuk that up so bad
And how bad is the rest of the vehicles programming. ???????????????????????????????
Leaving any lead acid battery sit at a voltage below 12.5 causes a chemical reaction to take place in the battery that leads to plate damage. Even short term storage as in overnight below 12.5 will lead to drastically shortened battery life.
But they are the engineers.
And replacing a battery is cheap compared to how they in there poorly educated engineering wisdom could cost us a DPF down the road.

I was a GM fan boy for many years.
Until I finally woke up to how bad they really are at engineering.

This is my first GM since 1987

The Japanese vehicles blew them away when it came to quality.

I can only hope they learned (something) since then.
 

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No documentation
I read as much as I can about these trucks. Always looking for issues that I should be concerned with.
There has been many posts of batteries being replaced while the truck is under warranty.
Older vehicles had regulators to maintain battery charge. Our trucks charging system is controlled by the ECU. This is very popular now.

I have always thought the best way to get better mpg would be to stop charging when ever possible and charge like crazy when on the brakes or coasting. And that is what GM engineers have done.
But
It should never fall outside the standard limits for the type of battery in


No documentation
I read as much as I can about these trucks. Always looking for issues that I should be concerned with.
There has been many posts of batteries being replaced while the truck is under warranty.
Older vehicles had regulators to maintain battery charge. Our trucks charging system is controlled by the ECU. This is very popular now.

I have always thought the best way to get better mpg would be to stop charging when ever possible and charge like crazy when on the brakes or coasting. And that is what GM engineers have done.
But
It should never fall outside the standard limits for the type of battery in the vehicle. The safe charge voltages are different for a flooded acid battery that you can add water to.
AGM do not like 15v.
That is way to high for even a equalize charge.

Do some research
There is a lot of info on batteries and how to get the most life out of them

What kills me is theses are supposed to be engineers.
If they are so smart how can they fuk that up so bad
And how bad is the rest of the vehicles programming. ???????????????????????????????
Leaving any lead acid battery sit at a voltage below 12.5 causes a chemical reaction to take place in the battery that leads to plate damage. Even short term storage as in overnight below 12.5 will lead to drastically shortened battery life.
But they are the engineers.
And replacing a battery is cheap compared to how they in there poorly educated engineering wisdom could cost us a DPF down the road.

I was a GM fan boy for many years.
Until I finally woke up to how bad they really are at engineering.

This is my first GM since 1987

The Japanese vehicles blew them away when it came to quality.

I can only hope they learned (something) since then.

My understanding from talking to shop foreman at large GMC dealer. The AGM battery is different than any battery you have ever used. At 57500 miles today 11.8 volts turned engine over and started immediately. Drove from NC to MD.
Charged at 11.8 to 14.9 volts read from DIC. Tonight volt meter across battery terminals 12.4.
This is Apparently the new AGM “normal”
 

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My understanding from talking to shop foreman at large GMC dealer. The AGM battery is different than any battery you have ever used. At 57500 miles today 11.8 volts turned engine over and started immediately. Drove from NC to MD.
Charged at 11.8 to 14.9 volts read from DIC. Tonight volt meter across battery terminals 12.4.
This is Apparently the new AGM “normal”
It’s not the new AGM normal
It is the new way to get extra MPG at the cost of destroying a good battery.
The GM guy was feeding you a line of BS.
If your battery was sitting at 11.8 it’s on its last legs ...
An AGM battery is good for lots of amps, so even though your voltage was extremely low the reserve amps that come from a AGM battery prob got you started.
But I would say your running on borrowed battery time........
 

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I know this thread is a little dormant, but it has really helped me understand what I think is going on with my 2017. Started getting a cel...I think it is P0286...for low PCM voltage. Watching the volt meter, I’m seeing less than 12v after sitting overnight. Sounds like the battery is going and the cel is just a heads up.

So, the ECM controls charging, and GM designed a crappy algorithm. Has any programmer came up with a solution? Or can they even change it?
 

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I know this thread is a little dormant, but it has really helped me understand what I think is going on with my 2017. Started getting a cel...I think it is P0286...for low PCM voltage. Watching the volt meter, I’m seeing less than 12v after sitting overnight. Sounds like the battery is going and the cel is just a heads up.

So, the ECM controls charging, and GM designed a crappy algorithm. Has any programmer came up with a solution? Or can they even change it?
Sounds like your in the 3 year battery end of life like most others. Not much you can do.
ECMs on today’s vehicles are much like a computer program. With thousands of lines of computer code. To change the code that maintains the battery charge section would be a big undertaking.
I bet the guys that write code for tuns could modify the charge sequence while modifying the tune if people asked for it.

Just replaced the battery on my wife’s 2017 Subaru Outback. It was still starting but rolling over very slowly.
Subaru isn’t doing the same as GM, they have a different issue. There is a very high power draw on the battery when the vehicle is turned off. Around 1 amp. Over time the battery goes dead. All new vehicles have a small drain on the battery to keep the radio channel presets programmed, the clock accurate and of course your vehicle listens for your remote door locks and remote start. But Subaru is putting a larger than normal drain on the battery.

I noticed her battery at 11.5 volts after just a few hrs. Even the new battery is having a hard time after a couple of days.
My son sent me a link to a class action lawsuit starting against Subaru for pre mature battery failures.


As in most cases the complaints are wrong about the problem.
They claim the battery is to small.
But it’s not the battery it’s the unusually high drain the vehicle is putting on the battery......
people don’t understand what is going on. They just want there car to start..

Rob
 

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Actually you remind me that my battery is going to be 4 years old this winter bet I have to replace it. Want something to handle accessories for near future upgrades
 

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Actually you remind me that my battery is going to be 4 years old this winter bet I have to replace it. Want something to handle accessories for near future upgrades
What really bugs me is everything we buy now days is supposed to get better fuel milage or is made with less metal or be more efficient with electricity.
But
The truth is we are now disposing of more things than ever.

Take this really bad charge algorithm GMs engineers came up with. It is designed to increase milage and it probably does. But at what cost? How much energy goes into making a battery. How much pollution from the plant goes into the air making the battery ?
How many mpg did we get by destroying the battery before the end of life should have come? In the past I got 6 years easy out of a battery. My 2011 Ranger still has the OEM battery in it.

If you buy a new appliance today they don’t last like they used to.
But they get to put that nice looking energy efficiency tag on it that says how efficient it is.
When in fact if you consider the energy used in making these appliances that don’t last they are more energy intensive than the old appliances...

So because the government says you need to meet energy efficiency standards we are actually using more energy and making more pollution meeting these energy standards.

It’s like these auto start stop engine systems designed to save fuel. The first time you need a new starter or fly wheel you have just caused more pollution than you saved.
The cost of making a new part far out weighs the savings in fuel or pollution...

So what we have is a MFGs product that meets government standards up front but is more energy intensive considering all the parts that will not last. And the short life expectancy.

We throughout more items than ever before................
Its a throwaway world now and we waste more of our resources than ever before.
All do to poorly thought out energy guide lines.

It drives me crazy how stupid engineering has become.
And how these energy standards are so short sited causing more pollution than they actually reduce.

Rob
 

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They might be some day.
i have 27 lithium pouch packs out of an electric bus. This bus was a test mule.
each pouch has 200 amps at 3.6 volts.
Very impressive for how little they weigh.
I built a battery pack with a fully charged voltage of 12.6 volts and 1800 amps
I use it to power my RV when not connected to the grid while camping.

Problem is lithium can be a fire bomb if punctured or shorted.
Lithium is very dirty on the environment to mine.
Lithium is fairly rare.
And there is no true way to recycle it .....yet.

There is some new battery technologies on the horizon.
So maybe in the near future an electric car will be the way to go.

I read something about the new E.Mustange batteries will last 6-10 years then cost 15,000 plus to replace.
Who in there right mind would spend 15,000 on an old car?

So who would buy it?
maybe lease it and get rid of it before the batteries need replacing. Depending on the cost of the lease.

Rob
 

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Discussion Starter #38
I saw this thread was back up and thought I'd update a bit. First off, RCD is right that AGM batteries are tougher than flooded lead acid (FLA) and can withstand longer periods at low charges without significant sulfation. So, even with GM's charge profile, they should last a while. But, sitting below 12.5 volts for long periods of time is not good for any lead-acid battery. Mine is now 3 years old, treated like a princess - always garaged and a not cold starting environment and not too hot in the summer - and it performs exactly as it always has. low, 11.2 V or so in the mornings but still churns it up and starts. We'll have to see what happens as it gets older. I don't know what it's rated for but I've never seen a new car with less than a 7-year battery and I always get longer than rated. If people start seeing failures in shorter than expected lifespan, I'd like to see them post here. Otherwise, it will be impossible for us to show a pattern. I like the idea of having the ECM tuned to a better charge profile but will wait until the first battery fails to pursue that.

As to lithium battery explosions/fires that ColoBob mentions, those are rarely a problem with the LiFePO4 (LFP) batteries used in vehicles and home solar especially if they are charged correctly. They are way safer than the Li-ion batteries in electronics. I switched my home solar from FLA (which I screwed up by stalling too long between checks and they got low on water) to LFP and OMG, they are awesome!

I agree with ColoBob's comments that we seem to miss the big picture sometimes when we make decisions. To me, the classic is all the folks driving their Prius (Pious?) and feeling like they're saving the world but failing to consider the full environmental cost of production.

There's a great little book titled "The Toaster Project" about a british grad student who tries to make a toaster from scratch after he decides that it is ridiculous that he can buy one for $7. I think his ends up costing $1800 and doesn't work either. Funny read and makes the case we are not considering the true costs to the environment when we buy new stuff.
 

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So I'll give you some back ground on my use of the truck since I'm a high mileage user... But I also use the battery more for accessories spend lots of time on the side of the highway in work zones so I don't like idling the truck I rely on the battery but if the low battery light comes on I'll drive around the work zone usually a 16 mile loop on an interstate periodically during a shift. One problem is that every thing cuts of and no hot plugs on truck which results in constantly turning key on and some idling if necessary. Also drive 80 miles of highway one way for a commute 6 days a week. So I know all that sitting with just the battery on is bad for it and with cold starts in the winter and the strain of summer heat my battery is abused.. so I only get 3-4 years. Right now I still have the stock battery truck has 176000 miles on it I dont know how many hours I have on it (Any ideas on how check or track battery hours used?) I can tell when i start the truck it's a little bit strained the other morning temp was 38f. And it was just a little bit weaker then normal and it takes just a little more to start. Could be the starter also but a weak battery can cause starter problems. I'll post up when I have to change the battery.
 
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