Charging while parked & unused (over 2 weeks) in cold weather - recorded data

[chl]

FACT, when the HVB contactor closes to energize the 400V bus, offering power to the PTC, it's also offering power to the DC/DC charging converter, that helps keep the 12v system sustained while the higher current devices are running.

Trying to understand the detail more clearly...

1) the HV battery contactors isolate the HV battery electrically from the rest of the system.

2) when the truck is ON, the HVB contactors are closed providing power to the truck including the PTC and the DC-DC converter which charges the 12V battery.

3) when the truck is connected to an EVSE and is OFF but charging the HV battery, the HVB contactors are closed and the DC-DC converter is charging the 12V battery using some of the HV battery charging power.

That I think we all agree and are clear on.

Now, the case that I am not sure I at least am clear on...

When the truck is connected to an EVSE and OFF but NOT charging, I know the PTC may get AC grid power from the EVSE that has been converted to 400VDC when needed.

But are the HVB contactors closed when doing that? I didn't think so.

I could see a case where if extra power was needed the truck could cause the HVB contactors to close to get the extra power, and in that case, the DC-DC converter would be powered and the 12V battery charged.

And I wonder is the DC-DC converter always getting grid power whenever the EVSE is plugged in and the PTC is using grid power, whether or not the HV battery is being charged? Again I didn't think so.

Are the HVB contactors always closed when the PTC is being powered by grid power? I didn't think so.

The HV battery does not always need to be connected when the PTC is using grid power does it?

And why would the DC-DC converter need to be powered when the PTC is using grid power and the HV battery is disconnected?

Does the PTC require the 12V system for something?

Has anyone directly measured 12V battery charging current/voltage under these circumstances?

From the OP data/graphs, it seems apparent that the 12V battery was not kept at 100% while the truck was OFF and using grid power for battery warming.

If the DC-DC converter was on all that time, unless there was some kind of significant load on the 12V system, you would think that the 12V battery would have stayed at or near 100% the whole time. But it didn't.

It would be nice to have some Ford documentation with more detail about this.

There was a recent post where a bad PTC caused the 12V battery to drain, so somehow they are interconencted even though the PTC resistive element(s) run off high voltage DC, not 12VDC.

Inquiring minds want to know.

Sponsored

 

[TaxmanHog]

Now, the case that I am not sure I at least am clear on...

When the truck is connected to an EVSE and OFF but NOT charging, I know the PTC may get AC grid power from the EVSE that has been converted to 400VDC when needed.

But are the HVB contactors closed when doing that? I didn't think so.

I could see a case where if extra power was needed the truck could cause the HVB contactors to close to get the extra power, and in that case, the DC-DC converter would be powered and the 12V battery charged.

And I wonder is the DC-DC converter always getting grid power whenever the EVSE is plugged in and the PTC is using grid power, whether or not the HV battery is being charged? Again I didn't think so.

Are the HVB contactors always closed when the PTC is being powered by grid power? I didn't think so.

The HV battery does not always need to be connected when the PTC is using grid power does it?

And why would the DC-DC converter need to be powered when the PTC is using grid power and the HV battery is disconnected?

Does the PTC require the 12V system for something?

Has anyone directly measured 12V battery charging current/voltage under these circumstances?

From the OP data/graphs, it seems apparent that the 12V battery was not kept at 100% while the truck was OFF and using grid power for battery warming.

If the DC-DC converter was on all that time, unless there was some kind of significant load on the 12V system, you would think that the 12V battery would have stayed at or near 100% the whole time. But it didn't.

It would be nice to have some Ford documentation with more detail about this.

There was a recent post where a bad PTC caused the 12V battery to drain, so somehow they are interconencted even though the PTC resistive element(s) run off high voltage DC, not 12VDC.

Inquiring minds want to know.

I have no idea, if we had a complete set of operating parameters that Ford engineers made requirements for we could answer many of these questions and clarify some 'assumptions'

 

[PrimeRisk]

I'll be honest, I was somewhat surprised to see how much energy it's used - approximately 70kWh in 17 days, so an average of somewhere around ~4kWh per day. I realize I could have unplugged it and put it in "storage", but I was honestly just intrigued to see what would happen if I left it plugged in.

Ack! Talk about your household vampire devices. 70kWh is more than 1/2 of what I charge in an average week of DRIVING the vehicle. Colorado winters are not quite as cold as Vermont, but we have our spells of sub-zero weather. Glad I don't have this thing in the driveway attempting to heat the great outdoors.

 

[Adventureboy]

Has anyone directly measured 12V battery charging current/voltage under these circumstances?

From the OP data/graphs, it seems apparent that the 12V battery was not kept at 100% while the truck was OFF and using grid power for battery warming.

As per my post #29, I have measured this and when plugged in and HVB already at target SOC, on December 25th, my truck did not get moved and was at SOC. When my charge window opened at 11pm, there was no charge cycle since it was already at target SOC. Early December 26th, my heater kicked in twice - once between 12am and 1am for about 18 minutes and once between 6am and 7am for about 14 minutes. For both events, my 12v voltage jumped to 15v. My 12v gained 8% (net) SOC on the first cycle and about 6% (net) SOC on the second cycle. The heat cycles didn't last long enough to charge the 12v fully, but it certainly gave it a bump on both events. Note this is during my charge window. I have not yet seen a heat cycle outside of my charge window.

My read on the OPs data suggests the heat cycles were frequent enough on the left side to keep the 12v fully charged. As the heat cycles spaced out due to warmer temperatures, the 12v SOC started to drop since the heat cycles were not long enough and not frequent enough to maintain the 12v SOC at 100% although it seems to have kept it >89% which certainly wouldn't have happened without the heat cycles.

 

[chl]

As per my post #29, I have measured this and when plugged in and HVB already at target SOC, on December 25th, my truck did not get moved and was at SOC. When my charge window opened at 11pm, there was no charge cycle since it was already at target SOC. Early December 26th, my heater kicked in twice - once between 12am and 1am for about 18 minutes and once between 6am and 7am for about 14 minutes. For both events, my 12v voltage jumped to 15v. My 12v gained 8% (net) SOC on the first cycle and about 6% (net) SOC on the second cycle. The heat cycles didn't last long enough to charge the 12v fully, but it certainly gave it a bump on both events. Note this is during my charge window. I have not yet seen a heat cycle outside of my charge window.

My read on the OPs data suggests the heat cycles were frequent enough on the left side to keep the 12v fully charged. As the heat cycles spaced out due to warmer temperatures, the 12v SOC started to drop since the heat cycles were not long enough and not frequent enough to maintain the 12v SOC at 100% although it seems to have kept it >89% which certainly wouldn't have happened without the heat cycles.

Ok, "this is during my charge window. I have not yet seen a heat cycle outside of my charge window."

That is what I wonder about. Would the 12v battery get charged when only a heating episode occurred (using EVSE suppllied grid power) without a charging episode?

Other previous information (from the Mach-e forum and here) suggested that the ONLY time the 12v battery gets charged when the truck is OFF is during a charging episode.

So that is what I am trying to pinpoint.

The OP said he had left the truck for a bit under 2 weeks with the settings so that the HVB would charge anytime it needed, no specific time limit on charging, but no graph of the HVB SOC to detect a charging cycle. There are little bumps/steps up in energy usage in the Emporia L2 graph which could be charging the HVB, or maybe assisting the PTC with heating, just can't tell.

Around the 17th the 12v SOC begins to drop in steps for 4 days until bottoming out around the 21st. Then up in steps for a while then an even bigger drop on the 26th perhaps because he had returned and started the truck which put a load on the 12v battery.

Anyway, I cannot definitively see any direct correlation between heating and 12v battery SOC because I can't rule out the possibility of an HVB charging episode being the reason.

Some 12v battery usage when the truck is off would be normal which makes me wonder why the SOC held steady from the 11th to the 17th? Maybe the drop was so small as to not be detected.

Around the 17th there was a step up in the L2 usage (energy) graph and a step down in the 12v SOC. One might guess this was the start of a charge cycle and the 12v battery is used to close the HVB contactors from what I have read so that might account for it.

A big drop in 12v SOC occurs around the 18th-19th - the temp is relatively high and there is only a small step up in L2 energy use around then, so why did the 12v SOC suddenly drop from around 99% to 94%? Something happened that put a load on the 12v battery.

Around the 20th the temps had reached a relative high of 50F then went down to 20F, and the 12v battery SOC took another big drop in SOC down to around 90%.

One would think when the temp dropped to 20F, the heater might kick in, and maybe the small step up in L2 energy at that time reflects this. But if it was L2 heating it had no positive or negative effect on the 12v battery SOC at all.

Anyway, it is all pretty inconclusive.

I am curious about why these trucks have so many premature 12v battery deaths, that is, within the 3yr b-to-b warranty period.

As the weather has cooled, there seems to have been an uptick in 12v battery issues (on this forum and another Lightning forum as well).

If just heating the truck with EVSE provided grid power were topping off the 12v batteries, you'd think perhaps the opposite would be happening, assuming people are leaving their trucks plugged in when it gets cold per Ford's recommendation.

 

[chl]

Ack! Talk about your household vampire devices. 70kWh is more than 1/2 of what I charge in an average week of DRIVING the vehicle. Colorado winters are not quite as cold as Vermont, but we have our spells of sub-zero weather. Glad I don't have this thing in the driveway attempting to heat the great outdoors.

I have not noticed anything near that much here in mild northern Virginia when I keep the truck plugged in all the time when not in use.

One "cold" spell last January 2025 when it snowed (so below 32F), I had the truck on the FCSP for over 18 hours - total kWh used was 4kWh, added to battery was 3.92kWh, so only 80Whs grid energy was used for heating over that cold 18 hour period it seems.

Assuming the data from the FCSP is accurate (don't have any other monitoring hooked up).

 

[MattVT]

Just to add, the vehicle is still stationary and parked, and will remain that way for another week. This week is particularly cold with overnight lows below 0°F (-17°C) several times so it’ll be another good cold soak for the vehicle.

In total, the truck will have been sitting ~4 weeks by the time we’re home. Nobody has touched it. Charging settings have stayed the same throughout. The only thing I did is remote start it once, as per my original post. Nothing since.

The only notable new thing to add is that my 12V battery status is now reporting 94% and showing a voltage of 12.5625V. That was reported 4 hours ago.

At the end of the 4 weeks, I’ll share complete graphs of the entire period for every relevant metric I can think of that I have. I need to check if Home Assistant attributes (vs states) are being recorded to InfluxDB. If so, I’ll be sure to include 12V battery voltage.

Again, all of this is just as reported by the Ford API.

 

[chl]

I have no idea, if we had a complete set of operating parameters that Ford engineers made requirements for we could answer many of these questions and clarify some 'assumptions'

Yes, so true!

My curiosity stems from all the 12v battery failures in under 3years that have been reported on the forums and what is going on with that.

It also seems to be an issue on the Nissan Leaf forum I am on as well.

It is so ironic that with all that stored energy in the HVB, it isn't being used effectively to keep the 12v batteries topped off and healthy.

Hence my 2 AGM mode trickle chargers, one on the Leaf and one on the Lightning.

 

[MattVT]

Hence my 2 AGM mode trickle chargers, one on the Leaf and one on the Lightning.

I’m still trying to work out if the data I’ve collected helps to answer whether that’s necessary or not, and if so, in what conditions. I felt I was taking a bit of a risk not using one on this trip, but so far it seems ok.

There seemed to be a hypothesis above that the 12V battery might only be receiving charge when the battery heater kicks in. If that is true, then it would suggest a battery tender is useful if the truck is being left for a prolonged period in temperatures slightly too high to trigger the heater.

I’m also still completely baffled by the deep sleep I’ve read so much about. I don’t see any indication of it whatsoever. I still have full access via the app and am still getting data updates (with new data) via the API. Have I avoided deep sleep somehow? It’s been almost 3 weeks at this point.

 

[chl]

Just to add, the vehicle is still stationary and parked, and will remain that way for another week. This week is particularly cold with overnight lows below 0°F (-17°C) several times so it’ll be another good cold soak for the vehicle.

In total, the truck will have been sitting ~4 weeks by the time we’re home. Nobody has touched it. Charging settings have stayed the same throughout. The only thing I did is remote start it once, as per my original post. Nothing since.

The only notable new thing to add is that my 12V battery status is now reporting 94% and showing a voltage of 12.5625V. That was reported 4 hours ago.

At the end of the 4 weeks, I’ll share complete graphs of the entire period for every relevant metric I can think of that I have. I need to check if Home Assistant attributes (vs states) are being recorded to InfluxDB. If so, I’ll be sure to include 12V battery voltage.

Again, all of this is just as reported by the Ford API.

Well 94% is not too bad. 100% is of course better - only solution for that is a $40 or so trickle charger with an AGM mode.

But one things seems clear - the 12v battery could discharge deeply if the truck sits unused with no charge cycles for an extended period of time.

 

[MattVT]

It is so ironic that with all that stored energy in the HVB, it isn't being used effectively to keep the 12v batteries topped off and healthy.

Not just that, but the truck is plugged in. It has access to All The Power™️.

 

[chl]

I’m still trying to work out if the data I’ve collected helps to answer whether that’s necessary or not, and if so, in what conditions. I felt I was taking a bit of a risk not using one on this trip, but so far it seems ok.

There seemed to be a hypothesis above that the 12V battery might only be receiving charge when the battery heater kicks in. If that is true, then it would suggest a battery tender is useful if the truck is being left for a prolonged period in temperatures slightly too high to trigger the heater.

I’m also still completely baffled by the deep sleep I’ve read so much about. I don’t see any indication of it whatsoever. I still have full access via the app and am still getting data updates (with new data) via the API. Have I avoided deep sleep somehow? It’s been almost 3 weeks at this point.

Yes, even in more temperate climates a battery tender will help prolong the lifespan, and never hurts, assuming it is one with an AGM mode. Seems like a must have for any EV, ironically with all that stored energy inthen HVB...

 

[chl]

Not just that, but the truck is plugged in. It has access to All The Power™️.

There should be a modification to EVs that allows them to access the J1772 energy from an EVSE when plugged in, to trickle charge the battery even when not HVB charging - an on-board trickle charger of some kind, OEM.

 

[TaxmanHog]

There should be a modification to EVs that allows them to access the J1772 energy from an EVSE when plugged in, to trickle charge the battery even when not HVB charging - an on-board trickle charger of some kind, OEM.

I think this could be accomplished with the appropriate logic , no changes needed to hardware at all.

 

[PrimeRisk]

There should be a modification to EVs that allows them to access the J1772 energy from an EVSE when plugged in, to trickle charge the battery even when not HVB charging - an on-board trickle charger of some kind, OEM.

Or we could just to back to the old Block Heater Fashion Days. Just plug her in on cold nights for a sure start tomorrow.

Sponsored