Replacement AGM Battery?

J17GT

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Letting the car sit overnight will allow the BMS to relearn its state of charge. If that's all you want, then a BMS reset isn't necessary.

But that's just one part of the equation.

The BMS also knows the age of the battery and takes it into consideration when choosing the charging strategy. The age counter must be reset when you install a new battery, otherwise the BMS will treat your new battery as if it were old and will charge it accordingly.
I know of instances where some systems (particularly the stop&start, but also the heated steering wheel, or heated windscreen if fitted) had stopped working due to the load shedding caused by a weak battery, and they continued not to work after having the battery replaced. A BMS reset fixed that.

Here's the battery replacement procedure from the service manual.

Screenshot 2021-01-12 at 08.37.03.png


It doesn't say it's optional. It doesn't say that simply leaving the car parked overnight will do.
Right...a dealer is not going to let a vehicle sleep for 8 hours, so they do the reset with the scan tool.

I put an AGM battery in my 2011 5.0 F150 and just let the truck sit overnight for 8+ hours per the manual. Been fine for years.
 

CS19

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Take a wild guess. If it was 'cost cutting', it'd be the correct one :).

My car sat at a dealer for months, so my battery was toast, and didn't want another crappy wet cell, or to deal with a dealer, so bought a DieHard AGM OEM replacement (96R) at Advanced Auto out of pocket. Same specs as stock, so just reset the BMS, although it was probably unnecessary due to the car only being 6 months old.
How was the fit with the Advance Auto AGM?
 

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Fly2High

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Getting low voltage warnings on my battery, low temps are probably exposing a battery that got heavily discharged a few times.


So rather than be let down when I need it most just going to replace the battery. However I have heard that if I change the battery type and Capacity the BCM needs to be reset or programmed?

I have forscan if that helps.

John
Just curious. How often do you drive your car?
Do you store it away for the winter? If you do store it, do you disconnect the battery?

I ask because the car has enough drain to discharge the battery. Not everything is off when your car is off. Some find that the car's passenger side door lock will stop working, for example, when it discharges below a certain voltage and some refer to this state as being in Sleep Mode. In reality, it is the computer trying to prevent the car from discharging too low and is shutting off unneeded systems.

You might just need to drive more often or at least put a good battery charger, like BatteryTender or BatteryMinder, on it during longer periods of inactivity. In the old days you could disconnect the negative but with all this computer crap in cars these days, not sure if that is advisable still. Might have to check the manual on long term storage.
 

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