12V Battery - Something has to be done!

[Maquis]

I just replaced the 12V battery. It took 44 minutes including getting all the tools out, dropping a few of them (why does this always happen?), putting the tools away and performing the BMS reset procedure. I didn't lose any new clips! I think.

I followed the process that does not require removing the tub. It was very easy and it would have taken me longer to drop off and pick up my car if I had paid the dealer to do it. And it only cost me $27 because I used points to buy the battery.

Now I am good to go for another 3 years!

Did you charge the new battery before installation?

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[mkhuffman]

Did you charge the new battery before installation?

Yes. I put it on a charger/maintainer a few days ago. So it was fully charged when I installed it.

 

[Maquis]

Yes. I put it on a charger/maintainer a few days ago. So it was fully charged when I installed it.

I figured you did, but thought it worth mentioning in case a less experienced person uses this thread to guide their replacement.

 

[Maui]

i know nothing about EV builds and little about how they work but if I have the car plugged in, why doesn’t this effectively allow the car charger to work as a “charger/maintainer”. It seems silly to have to buy another charger just for the 12v when we have a very expensive charger sitting right there and already plugged in.

 

[mkhuffman]

i know nothing about EV builds and little about how they work but if I have the car plugged in, why doesn’t this effectively allow the car charger to work as a “charger/maintainer”. It seems silly to have to buy another charger just for the 12v when we have a very expensive charger sitting right there and already plugged in.

Because turning on the HVB requires multiple systems to run so that it is safe. As Tesla discovered years ago, utizing the HVB when the car is off causes vampire drain. Bing search for "HVB vampire drain" and you will find it is a big problem for some cars, like Rivian for example.

Nobody wants to park their car and have the HVB drain while it just sits there. You could park at the airport and return to a dead vehicle. Some Rivians are losing 2kWh or more per day just sitting.

Ford takes a different approach and you will never see vampire drain in your MME.

Just replace the LVB every 3 years and don't worry about it. (You can also try the desulfating procedure @Mach-Lee provided. I do that yearly.)

 

[Maquis]

i know nothing about EV builds and little about how they work but if I have the car plugged in, why doesn’t this effectively allow the car charger to work as a “charger/maintainer”. It seems silly to have to buy another charger just for the 12v when we have a very expensive charger sitting right there and already plugged in.

The 12V battery is maintained (charged) from the HVB under normal conditions. When the 12 V battery is at end of life, an external charger is only a band-aid. Just replace it.

 

[Mach-Lee]

I just replaced the 12V battery. It took 44 minutes including getting all the tools out, dropping a few of them (why does this always happen?), putting the tools away and performing the BMS reset procedure. I didn't lose any new clips! I think.

I followed the process that does not require removing the tub. It was very easy and it would have taken me longer to drop off and pick up my car if I had paid the dealer to do it. And it only cost me $27 because I used points to buy the battery.

Now I am good to go for another 3 years!

That’s the spirit!

 

[DeltaDelta]

Did you charge the new battery before installation?

A week ago, I got a battery from the dealership, put it in myself, and reset the BMS.

I assumed it was fully charge.

Are they not fully charged when you get them?

 

[stinsvic]

oohhhhhhhhh, you did it NOW! Had to go and say something like that.....

lol!!!!

 

[mkhuffman]

A week ago, I got a battery from the dealership, put it in myself, and reset the BMS.

I assumed it was fully charge.

Are they not fully charged when you get them?

No, they are definitely not fully charged when you get them.

 

[4wheeldog]

A week ago, I got a battery from the dealership, put it in myself, and reset the BMS.

I assumed it was fully charge.

Are they not fully charged when you get them?

Nope. Batteries off the shelf used to be charged to maybe 80%. The last couple (Not for the MME, but batteries aren’t produced differently for specific vehicles) were more like 60-70%, and took a minimum of 12 hours to charge to 100%. It is good practice to always fully charge any new lead acid battery before installation.

 

[DeltaDelta]

Nope. Batteries off the shelf used to be charged to maybe 80%. The last couple (Not for the MME, but batteries aren’t produced differently for specific vehicles) were more like 60-70%, and took a minimum of 12 hours to charge to 100%. It is good practice to always fully charge any new lead acid battery before installation.

So, if I level 1 charge for 12 hours will that top it off and then I should reset the bms again or will it not charge it correctly now?

 

[Snakebitten]

That H3 is just very few AH for a vehicle loaded with 40+ modules and lots of approach technology. There's not very much headroom for the multiple taxes that battery is asked to pay.

I forgot to "disconnect" the Car Scanner app when I got to the office ~11:20am this morning. I left the office at ~3:25pm

You can clearly see (white box) how quickly that H3 drops with the OBD being kept alive with the Bluetooth monitoring app left connected.


Arrival 11:21am 12.47 Volts (red vertical timestamp)

At 1:41 pm, voltage had dropped to ~11.94 Volts and FordPass sent two notifications

The BMS initiated a battery charging event. Note the car is parked in an aircraft hangar. No EVSE involved. So is dropping below 12.0 Volts the charge trigger?
The white circle is the charging event. It looks like it lasted about 1 hour.
It ended and the Car Scanner app began to bleed the AGM again until I arrived at the car (3:25pm) and started it to go home.

 

[4wheeldog]

So, if I level 1 charge for 12 hours will that top it off and then I should reset the bms again or will it not charge it correctly now?

How will you know the state of charge if you don’t use a separate battery charger?

 

[Mach-Lee]

That H3 is just very few AH for a vehicle loaded with 40+ modules and lots of approach technology. There's not very much headroom for the multiple taxes that battery is asked to pay.

I forgot to "disconnect" the Car Scanner app when I got to the office ~11:20am this morning. I left the office at ~3:25pm

You can clearly see (white box) how quickly that H3 drops with the OBD being kept alive with the Bluetooth monitoring app left connected.


Arrival 11:21am 12.47 Volts (red vertical timestamp)

At 1:41 pm, voltage had dropped to ~11.94 Volts and FordPass sent two notifications

The BMS initiated a battery charging event. Note the car is parked in an aircraft hangar. No EVSE involved. So is dropping below 12.0 Volts the charge trigger?
The white circle is the charging event. It looks like it lasted about 1 hour.
It ended and the Car Scanner app began to bleed the AGM again until I arrived at the car (3:25pm) and started it to go home.

Yes you get those two FordPass messages when the automatic 12V recharge is triggered because of a high drain.

The 12V battery is big enough, just not managed the best sometimes. Teslas only have 7 amp hour batteries now vs. our 35.

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