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FYI Battery replacement

Grimmer

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The battery management system (BMS) will adjust the alternator's output based on how much power it thinks the car needs...

Right after start up, it has typically been in the high 13's through the mid 14's and then varies while running, pretty much regardless of RPM. However, I did notice once (with the new battery) that after it sat with an external battery charger/maintainer connected for a couple of days, when I started it up the dash voltage was in the 12's, i.e. battery management must have figured the battery was already full and basically turned off the alternator completely. That didn't last for very long. The BMS, in addition to recharging the battery, also anticipates high electrical needs (like running the cooling fans, lights, etc.) and increases the alternator's output accordingly.

This is part of the reason why the service manual (and probably the owner's manual) advises against charging the battery by attaching directly to the battery posts. Doing so will bypass the sensor the BMS uses to measure power in and power out of the battery and gets it out of sync with the battery's actual state of charge.

I have seen the voltage reading in the cluster vary from 12.X volts to about 14.8 volts with the engine running, always changing... but it spends most of its time between 13.5 and 14.5 ~ish. Second largest chunk of time between 13 and 13.5. Only occasionally on the outer fringes (high or low).

If you have FORScan capabilities, you can reset the battery management system when you install a new fully charged battery. If you don't have FORScan, you can leave the car to sit static (with minimal electrical load, e.g. no significant parasitic draws like a dash cam, no opening doors, key FOB locks/unlocks, etc.) for 8 or 10 hours (if I'm remembering correctly) and the BMS will attempt to self-reset / re-calibrate. I would have to go back and re-read the system description in the Service Manual for the details...
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Grimmer

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That's pretty tight. But not bad, I guess. I just didn't like how the hood felt closing down on it and I noticed some deflection at the left hood pivot so it swayed me. I went with the regular battery for piece of mind.
It is good that you brought this up... For anyone else that comes across this thread later (and has the stamina to read the whole thing), it is important they have all the info and can choose with their eyes wide open.

It may well come down to manufacturing tolerances (car and battery) or model year subtleties as to whether the Group 47 will safely fit or not. I didn't notice any deflection of the hood with mine, but having gone back to take a closer look I'm pretty sure that the hood seal on my setup is literally squeezed as tight as possible may even result in premature degradation of the weather strip material. I couldn't get an exact look due to the sound insulation pad. Although, I did just remember that I also have a bore-scope that attaches to my phone. Maybe I could snake it into the smaller cracks get an even closer look. Now if I can only find it...
 

stratman3

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After replacing the battery, any issues with radio programming or radio lock codes? Or any other electronics? I have a 2017 premium package, just wondering.
 

Armyed

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After replacing the battery, any issues with radio programming or radio lock codes? Or any other electronics? I have a 2017 premium package, just wondering.
I swapped my 19 GT out recently to a group 47 AGM and it literally sat for an hour with no battery and I had no issues with anything. I had to redo my radio stations but that's it.
 

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Dave5.0

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After replacing the battery, any issues with radio programming or radio lock codes? Or any other electronics? I have a 2017 premium package, just wondering.
I had no issues with my 2016 GT.
 

1miracle2

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Just wanted to let everyone know that the D3400R died after 5 months. The battery died a couple days ago and I thought it was the alternator. After taking it to AutoZone they tested both and the battery just wasn't holding a charge at all. I ended up just buying a RedTop Optima battery, which a couple of the employees recommended considering I have a ton of electronics in my car.
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Armyed

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Just wanted to let everyone know that the D3400R died after 5 months. The battery died a couple days ago and I thought it was the alternator. After taking it to AutoZone they tested both and the battery just wasn't holding a charge at all. I ended up just buying a RedTop Optima battery, which a couple of the employees recommended considering I have a ton of electronics in my car.
Cheers
Optima's quality has gone way downhill over the years and they've gained a reputation for being garbage batteries. I bought a cheapo AGM from one of the big stores since basically all batteries are made by like 2 or 3 companies and it's been running like a champ for a good while now. If that Optima dies on you, just go get you a cheapo one that's no more than $150 and it will outlast all those expensive batteries and handle all your electronics.
 

1miracle2

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Funny that you say that because the AutoZone staff commented on how they (Optima) switched manufacturers and recently back because people complained about the quality. I hope this lasts if not ill just go cheapo too. Tired of throwing $$ at this thing lol.
 

Armyed

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Funny that you say that because the AutoZone staff commented on how they (Optima) switched manufacturers and recently back because people complained about the quality. I hope this lasts if not ill just go cheapo too. Tired of throwing $$ at this thing lol.
If they recently changed the people who manufacture their batteries I haven't heard of it and I damn sure wouldn't believe anything a parts store person tells me. If it's true they need to put out a press release about it because I know most people who have done their research are staying away from them and wouldn't go back until they know the quality has gone back to what it used to be. I'll stick with the AGM battery I paid $127 for that will probably last just as long if not longer than an Optima if their quality went back up for 1/3rd the price.
 

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1miracle2

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If they recently changed the people who manufacture their batteries I haven't heard of it and I damn sure wouldn't believe anything a parts store person tells me. If it's true they need to put out a press release about it because I know most people who have done their research are staying away from them and wouldn't go back until they know the quality has gone back to what it used to be. I'll stick with the AGM battery I paid $127 for that will probably last just as long if not longer than an Optima if their quality went back up for 1/3rd the price.
Geeez, I hope the quality went back up lol.
 

MikeZ9

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The battery management system (BMS) will adjust the alternator's output based on how much power it thinks the car needs...

Right after start up, it has typically been in the high 13's through the mid 14's and then varies while running, pretty much regardless of RPM. However, I did notice once (with the new battery) that after it sat with an external battery charger/maintainer connected for a couple of days, when I started it up the dash voltage was in the 12's, i.e. battery management must have figured the battery was already full and basically turned off the alternator completely. That didn't last for very long. The BMS, in addition to recharging the battery, also anticipates high electrical needs (like running the cooling fans, lights, etc.) and increases the alternator's output accordingly.

This is part of the reason why the service manual (and probably the owner's manual) advises against charging the battery by attaching directly to the battery posts. Doing so will bypass the sensor the BMS uses to measure power in and power out of the battery and gets it out of sync with the battery's actual state of charge.

I have seen the voltage reading in the cluster vary from 12.X volts to about 14.8 volts with the engine running, always changing... but it spends most of its time between 13.5 and 14.5 ~ish. Second largest chunk of time between 13 and 13.5. Only occasionally on the outer fringes (high or low).

If you have FORScan capabilities, you can reset the battery management system when you install a new fully charged battery. If you don't have FORScan, you can leave the car to sit static (with minimal electrical load, e.g. no significant parasitic draws like a dash cam, no opening doors, key FOB locks/unlocks, etc.) for 8 or 10 hours (if I'm remembering correctly) and the BMS will attempt to self-reset / re-calibrate. I would have to go back and re-read the system description in the Service Manual for the details...
Hey, my original battery died 2 weeks ago, replaced it with a new battery from Autozone and now I am actually looking at the Voltage readings. For some reason, I remembered the old readings were always around 14V (maybe I was not looking at the readings often enough), but after my mechanic helped me reset the BMS on his computer and driving around, I noticed the Voltage readings fluctuates quite often, ranging from 12.1-14.4ish. My mechanic told me it's normal, are these Voltage readings accurate? Should I be concerned? Also, noticed that everytime I use GPS on my phone through bluetooth, the GPS voice would sometimes stutter. Please help advise, thank you
 

Grimmer

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Mine fluctuate like that too. As I understand it, your 14V reading from before would be from the battery not holding a charge very well putting a more continuous demand on the charging system for power. Now that your battery holds a good charge the charging system can "take some time off" more often.

I vote for it being normal. Keep an eye on it. The car will complain if it isn't getting what it needs.
 

MikeZ9

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Mine fluctuate like that too. As I understand it, your 14V reading from before would be from the battery not holding a charge very well putting a more continuous demand on the charging system for power. Now that your battery holds a good charge the charging system can "take some time off" more often.

I vote for it being normal. Keep an eye on it. The car will complain if it isn't getting what it needs.
Thank you! Hopefully nothing's wrong.
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