When to replace the aux batt and how to know?

[Davexxxx]

It takes between 6-8 hours sometimes longer in the key off state for the BMS/BCM to properly update the battery SOC level.

There hasn't been a key cycle in the last 33 hrs or so.

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[Porpoise Hork]

When you open the door it wakes up multiple modules, such as the door, gateway, apim, BCM etc. These all pull a fair bit on powerup causing a decent dip in voltages. If you want to get an accurate resting voltage you'll need either a bluetooth battery monitor or leave the hood and door open but use a wrench or something to flip the latches closed so the truck thinks they shut. Then you can come back in an hour or so to check resting voltages in the truck.

 

[LostHusker]

All good information, it is not uncommon for my truck to be parked for a couple weeks at a time with no access to it or even being started up, It will be 4 years old next month. I have not really noticed any issues but have noticed that it seems to go into items being disconnected message sooner.

 

[Davexxxx]

Both batts back to 12.72.

 

[Porpoise Hork]

Not far off from where it should be depending on what your SOC level is set to.

All good information, it is not uncommon for my truck to be parked for a couple weeks at a time with no access to it or even being started up, It will be 4 years old next month. I have not really noticed any issues but have noticed that it seems to go into items being disconnected message sooner.

This is due to the BMS algorithim working with the battery's age. If the BMS has never been reset then starting at 3-4 years the BCM will begin putting modules into deep sleep/disconnected state. This is to "protect" the aging battery(s) voltage from being pulled too low and prevent potential damage to the internal plates. The BCM will do this even if there's absolutely nothing wrong with the batteries and they still retain most if not all their original reserve capacity. Just more of Ford's "we know better than you do" engineering. You can reset the BMS with Forscan or the highbeam brake pedal method and it should stop putting modules into a disconnected state but if it starts happening again shortly after then the BMS/BCM is detecting a problem and the batteries should be replaced soon with another BMS reset.

 

[Davexxxx]

Not far off from where it should be depending on what your SOC level is set to.

Its all stock.

 

[Ricksc]

It’s the SOC that will get you. Just replaced my battery again. Resting voltage was 12.4 but SOC was at 50% truck kept going into deep sleep. Put on charger for 2 days still would not hold a charge to keep SOC up.

 

[Davexxxx]

It’s the SOC that will get you. Just replaced my battery again. Resting voltage was 12.4 but SOC was at 50% truck kept going into deep sleep. Put on charger for 2 days still would not hold a charge to keep SOC up.

The voltage charts I'm looking at are all over the map.

Renogy says 12.4 is 85%

https://www.renogy.com/blogs/general-solar/agm-battery-voltage

This one says 75%

https://learnmetrics.com/agm-battery-voltage-charts-12v-24v-deep-cycle-battery-voltage/

Those who have monitored these things for a long time, know where the warnings kick in but I've been through so many threads since the other night, I don't recall.

I'm not opposed to getting a monitor but I'd rather it not be loaded with Chinese spyware.

 

[Ricksc]

Not sure how they get that but this is off my monitor on the battery. After 4 days of being sick on a 3 year old interstate H7

 

[LostHusker]

Not far off from where it should be depending on what your SOC level is set to.




This is due to the BMS algorithim working with the battery's age. If the BMS has never been reset then starting at 3-4 years the BCM will begin putting modules into deep sleep/disconnected state. This is to "protect" the aging battery(s) voltage from being pulled too low and prevent potential damage to the internal plates. The BCM will do this even if there's absolutely nothing wrong with the batteries and they still retain most if not all their original reserve capacity. Just more of Ford's "we know better than you do" engineering. You can reset the BMS with Forscan or the highbeam brake pedal method and it should stop putting modules into a disconnected state but if it starts happening again shortly after then the BMS/BCM is detecting a problem and the batteries should be replaced soon with another BMS reset.

TBH I have no Idea of what my SOC level is, not sure other than hooking up a meter to my batter(s) would I know.

I have only utilized Forscan to change my mirrors when I put tow mirrrors on and a couple other things since I was in there. In fact it was the only reason I have a windows pc now was to do that, have not utilized it since then and that was about 2+ years ago.

 

[Porpoise Hork]

If you have never adjusted it with Forscan then it would be set to Ford's default of 80%.

 

[Davexxxx]

If you have never adjusted it with Forscan then it would be set to Ford's default of 80%.

But thats maximum, right?

Do you know the lower threshold, or when charging from the HV kicks in?

 

[Porpoise Hork]

From what I have been able to learn of Ford's charging strategy is the BMS and BCM work in tandem to attempt to maintain the 12v SOC level what ever it is set to as efficiently as possible. The plus side is reduced engine load on non PB versions from the alternator, but the trade off is significantly longer charge times to bring the 12v up to and maintian the set SOC levels.

For PB's under low 12v load or when the SOC is near the set limit the DC/DC converter will output 12.9v +/- to the low voltage battery. I'm not sure at what SOC level the BCM will raise the charging voltage to 13.8-14.5v but I have seen mine do this when it is showing 10% or more under set SOC (I have mine set to 100%). This also happens when the headlights are off and HVAC fan set below 5. If the headlights are on or fan at 5 or higher the BCM automatically kicks the DC/DC converter to 13.8-14.5v to provide extra current to maintain the 12v and supply power for the increased draw on the low voltage circuit.

 

[Davexxxx]

FYI, did this test back when fan speed 5 was first discovered.

Some swear by it. Some like me, claim no utility.

Post #11

https://www.f150gen14.com/forum/threads/powerboost-12v-battery-charging-tip.18427/#post-361391

 

[Davexxxx]

12.68V at both batts, somewhere around 24hrs. post full charge.

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