Why isn't the 12v battery always charged?

[Grumpy2]

The manual indicates a fully charged 12v battery is required for some software updates, and there are several posts here about that. The manual also suggests a winter driving kit include a jump battery, not jump cables. Clearly the truck is dependent on its 12v battery.

The DC to DC converter apparently provides the 12v power to the vehicle and must recharge the 12v battery but only when the truck is ON???

What is the downside of having the DC to DC converter become active when the truck is OFF, but only when the 12 volt battery needs a boost? It would probably require a separate set of high voltage relays (& more cost); but it seems crazy to put a trickle charger on the truck when it already holds 100,000 watt hours of energy.

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[flyin525]

That Sir, is the $1,000,000.00 question.

 

[TaxmanHog]

The manual indicates a fully charged 12v battery is required for some software updates, and there are several posts here about that. The manual also suggests a winter driving kit include a jump battery, not jump cables. Clearly the truck is dependent on its 12v battery.

The DC to DC converter apparently provides the 12v power to the vehicle and must recharge the 12v battery but only when the truck is ON???

What is the downside of having the DC to DC converter become active when the truck is OFF, but only when the 12 volt battery needs a boost? It would probably require a separate set of high voltage relays (& more cost); but it seems crazy to put a trickle charger on the truck when it already holds 100,000 watt hours of energy.

I believe the HVB contactors engage periodically to supply current to the DC/DC step down converter to charge the LVB. I hear periodic clicks from my truck, interestingly it happens frequently through the day/night.

 

[Grumpy2]

Perhaps this situation has changed, or the system wasn't working for some folks? I just found the following on page 443 of the 2023 manual:

If the 12 volt battery level is low, the high voltage battery transfers energy to the 12 volt battery when the vehicle is off.

 

[sotek2345]

Perhaps this situation has changed, or the system wasn't working for some folks? I just found the following on page 443 of the 2023 manual:

If the 12 volt battery level is low, the high voltage battery transfers energy to the 12 volt battery when the vehicle is off.

No, as far as we know, this has always been working. the challenge is that the level needed for an update may be higher than the level to trigger a recharge.

It is also suspected that the level to trigger a recharge is lower if the vehicle is off, than if it is one, which is why going for a drive can trigger the charge cycle and get the 12V charge high enough for the update.

As to why the update doesn't start by triggering the charge cycle, I have no idea. I suspect we are seeing a lot of legacy ICE assumptions baked into the 12V charging scheme.

 

[queuewho]

I suspect we are seeing a lot of legacy ICE assumptions baked into the 12V charging scheme.

I suspect we are seeing a lot of legacy ICE assumptions baked into the 12V charging scheme almost every function of this truck

 

[COrocket]

There was a similar problem with early Teslas where they were replacing tons of 12V batteries (one of mine included) under warranty because the car would deep cycle the battery and only charge it when it was depleted, which drastically shortens the lifespan of the 12V. They then modified the charging behavior to keep it topped off more frequently and the problem has seemed to resolve itself in the past few years.

I'm sure Ford and other ICE OEMs will learn this lesson the hard way and eventually issue a software update to fix the behavior you are describing. It's unfortunate because at least with the Tesla, when the 12V fails, the car is un-drivable and you are stranded.

 

[Maxx]

When I push the start button once, I see the battery icon. Does that mean all the screen and accessory power comes from 12V battery? when I push it twice (truck is on), does the power come from main pack and stepped dow to 12V leaving the 12 V battery alone? Or it is still coming from 12V Battery, and main pack periodically tops it off?

When I was sitting there messing with the menu while it was on, I could hear a humming sound for a while (heat was off), is that 12V being charged?

Is there any visual indication when 12V is being charged or what the exact Voltage is at the moment?

I suspect we are seeing a lot of legacy ICE assumptions baked into the 12V charging scheme almost every function of this truck

‘That May be the reason it does not have the same level of phantom battery drain as Rivian.

 

[RickLightning]

When I push the start button once, I see the battery icon. Does that mean all the screen and accessory power comes from 12V battery? when I push it twice (truck is on), does the power come from main pack and stepped dow to 12V leaving the 12 V battery alone? Or it is still coming from 12V Battery, and main pack periodically tops it off?

When I was sitting there messing with the menu while it was on, I could hear a humming sound for a while (heat was off), is that 12V being charged?

Is there any visual indication when 12V is being charged or what the exact Voltage is at the moment?



‘That May be the reason it does not have the same level of phantom battery drain as Rivian.

Yes - everything in the vehicle is powered by 12v except the electric motors. The HVB doesn't power any of the displays or accessories. The noise was likely the cooling pumps running.

No, and no.

 

[Maquis]

The reason that manual update instructions state to put the 12V on a charger is because some updates have to temporarily disable the module that normally maintains the 12V.

 

[metroshot]

Time to connect a trickle solar charger to my 12V battery and leave the panel on my dash like I used to do with my older vehicles a long time ago!

 

[Grumpy2]

Ford knows we are thinking about that; on Page 182 of the 2023 manual includes:

Do not plug in any device that supplies power to the vehicle through the power points.

 

[Amps]

Is there any visual indication when 12V is being charged or what the exact Voltage is at the moment?

I find this is a great substitute. It looks good in the 12V port and the cover doesn't get in the way. It's angled a bit away from the driver. The 12V receptacle goes to sleep about 30 minutes after shutdown. You can see how the HVB is charging the LVB, up to 15.65V that I've observed.

https://www.amazon.com/gp/product/B08N4WKJMT

 

[TaxmanHog]

When I push the start button once, I see the battery icon. Does that mean all the screen and accessory power comes from 12V battery? when I push it twice (truck is on), does the power come from main pack and stepped dow to 12V leaving the 12 V battery alone? Or it is still coming from 12V Battery, and main pack periodically tops it off?

When I was sitting there messing with the menu while it was on, I could hear a humming sound for a while (heat was off), is that 12V being charged?

Is there any visual indication when 12V is being charged or what the exact Voltage is at the moment?

While the truck is "RUNNING" the DC/DC converter outputs ~13.5 volts to top the LVB and sustain all chassis 12v operations, this is a diagnostic monitor I ran a on December 9th when trying to get to the bottom of what was delaying my OTA's

 

[GDN]

The reason that manual update instructions state to put the 12V on a charger is because some updates have to temporarily disable the module that normally maintains the 12V.

Really poor design. Do they really think we are all going to get external 12 v chargers?

It is also a lack of trust in their own systems. The SW needs to be broken into 20 to 30 minute install chunks. You have to make an assumption that a 12v battery with a 70% (choose your number that makes sense) or higher charge can run the systems long enough to do said upgrade and then start the upgrade. Or their systems must be able to initiate a charging cycle during the upgrade.

If the 12v battery doesn't have enough charge - then initiate a charge cycle and try the upgrade again later.

I've had Tesla's in the garage for almost 5 years, I'm a member of a large Tesla club, I'm a moderator on a Tesla forum - I don't ever recall once a Tesla didn't start and install a SW update when the user initiated it or when the scheduled time hit. Never did the car say - hold my beer I need a 12v battery charge.

It's just poor design and lack of trust by the engineers for the systems to work.

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