Stop Safely Now on start

[RLXXI]

read the documents

Believe what you want, your truck not mine but don't complain when you start experiencing electrical gremlins.

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[RLXXI]

The blue circle negative connection is downstream of the BMS and electrically the same as the negative jump post per the wiring diagram.

What happens when you get a spark connecting directly on top of a battery full of explosive gas? There's more than one reason to NOT connect the way you illustrated.

 

[chl]

What happens when you get a spark connecting directly on top of a battery full of explosive gas? There's more than one reason to NOT connect the way you illustrated.

Never had that happen, jumped many a car over the years.

Plus our Ford F-150 Lightning AGM batteries are SEALED batteries, so unless you puncture it somehow, no gasses to worry about.

But with a trickle charger, which was what I was talking about, you connect the clamps BEFORE plugging it in to the 120V outlet so no sparks.

The following post has from this forum never got anyone saying it was wrong or dangerous, but maybe you know something I don't know about the electrical system of the Lightning?

For what it is worth.

 

[TaxmanHog]

There is a vent on the side.

 

[RLXXI]

Never had that happen, jumped many a car over the years.

Plus our Ford F-150 Lightning AGM batteries are SEALED batteries, so unless you puncture it somehow, no gasses to worry about.

But with a trickle charger, which was what I was talking about, you connect the clamps BEFORE plugging it in to the 120V outlet so no sparks.

The following post has from this forum never got anyone saying it was wrong or dangerous, but maybe you know something I don't know about the electrical system of the Lightning?

For what it is worth.

Not going to argue with you, you obviously don't have the extensive training and decades of experience dealing with automotive systems as I do and that's ok. I bet you've never had a battery blow up on you either, I have 3 different times and vehicles one of which was my personal vehicle.

Here's the proper place to connect to the battery, lift up the red protective cap and connect your positive source there, may as well use that huge grounding stud right next to it.

 

[CD4TNF]

I had an experience of accidentally leaving the headlights on at a parking lot. Left for a few hours (4-6 hrs?). At some point I got a push notice on FordPass app that my 12V battery was getting low. I was in the middle of doing stuff, couldn't break away, and a pretty far walk back to the truck.

I must have gotten 5-9 notices from the truck letting me know the 12V was progressively getting low and to charge up.

I got back to the truck 1-2 hours after the notices started. I was nervous. The lights were on when I walked up. I had a jumper battery pack in the truck, so I was prepared.


Got in the truck. Turned it on. It was fine. That was over a year ago. That's the truck's behavior I experienced with the 12V getting low.

 

[TaxmanHog]

I had an experience of accidentally leaving the headlights on at a parking lot. Left for a few hours (4-6 hrs?). At some point I got a push notice on FordPass app that my 12V battery was getting low. I was in the middle of doing stuff, couldn't break away, and a pretty far walk back to the truck.

I must have gotten 5-9 notices from the truck letting me know the 12V was progressively getting low and to charge up.

I got back to the truck 1-2 hours after the notices started. I was nervous. The lights were on when I walked up. I had a jumper battery pack in the truck, so I was prepared.


Got in the truck. Turned it on. It was fine. That was over a year ago. That's the truck's behavior I experienced with the 12V getting low.

Hope that never happens again, next time just hit the remote climate start, let it run .... 5 to 30 minutes based on your settings, that should help recover some of the charge on the LVB until you could get to the truck.

 

[Ry2023]

I have had this same issue … happened to me twice but …. It hasn’t happened since …and that was two years ago…. But I have noticed both times it was doing an update……

 

[AlaskaFlash]

I have not had that issue, but there have been a lot of issues with the 12V battery running low.
When the 12V battery gets low, "funny" things can happen and the other message SSN could have been a result of the low battery causing a sensor or test routine to error out and give the SSN.

According to the AI search (for what it is worth):

"Full accessory power active" means the vehicle's electrical system is on, allowing use of accessories like the radio and power windows, but the engine is not running. This state is usually achieved by pressing the start button twice without depressing the brake pedal. While it indicates the battery is functional enough to power these features, a continued message of "full accessory power active" when the car won't start can signal a problem with the battery, electrical system, or software, requiring a manual reset or professional diagnosis."

It then refers to this youtube video which seems to be your situation where the truck wouldn't start at first after getting the messages:



Your best bet is:
1) don't use the Accessory mode and
2) plug the truck in every night which should keep the 12V battery at a higher state of charge, and it will keep it warm if it gets cold (below 40F) at night up there in Alaska.

Another issue you could have if the battery gets low is over the air updates may not install.
One of those recently improved the routine that keeps the 12V battery charged so it should not fall as low.

Quite a number of owners seem to get the 12V battery replaced under warranty due to charging issues which let it get below 50% soc which can shorten the lifespan of AGM batteries.

Good luck!

Thanks for this informative reply. When this happened, the 12 Volt red battery icon was also lit, so, I think this may have been the issue. I have driven the truck numerous times every day since last Thursday when this happened without any problems.

 

[chl]

Thanks for this informative reply. When this happened, the 12 Volt red battery icon was also lit, so, I think this may have been the issue. I have driven the truck numerous times every day since last Thursday when this happened without any problems.

Glad to hear it's working now.

According to the customer service folks when my 12V battery got low last summer and OTA updates were stalled, they told me to drive around for at least an hour to charge up the battery - that didn't work to get the SOC up enough for the OTA updates (somewhere over 80%), so I saw a post on this forum about plugging into the EVSE and charging overnight and that did the trick.

The 12V battery has caused quite a few problems based on forum reports anyway.

It seems to be the weakest link - nothing will work right or even at all with a low 12V battery - strange they couldn't have done a better job with it since the HV battery holds so much capacity. Go figure.

 

[CD4TNF]

Hope that never happens again, next time just hit the remote climate start, let it run .... 5 to 30 minutes based on your settings, that should help recover some of the charge on the LVB until you could get to the truck.

Ohh clever. Good idea. I'll keep that in mind as a emergency trick.

 

[rdt7]

The truck would not start and gave the message "Stop Safely Now", and then "Full accessory power active". After turning the truck off and back on several times, it finally started.

This exact same scenario happened to me yesterday on my 2023 Lariat. I've only had it since May and this is the first issue I've had. It really shakes my confidence in the vehicle.

 

[NW Ontario Ford Lightning]

Considering the issues with low 12v SOC especially for those of us with "real winter" half the year...has anyone looked at using a larger capacity 12v battery? or even connecting two in parallel?

 

[Heliian]

Considering the issues with low 12v SOC especially for those of us with "real winter" half the year...has anyone looked at using a larger capacity 12v battery? or even connecting two in parallel?

No, it's fine. When it gets cold, say consistently below 5-10degC, I plug my truck in nightly. 3 winters in sudbury and no problems.
Some things about my vehicle:

-Never have any dongles plugged into the obd port or aftermarket acc. drawing power.

-I drive 25km each way to work 5 days a week, that's 40minutes minimum per day that the battery is getting charged by the truck.

-plugged in after 7pm in the winter to maintain battery temp regardless of soc.

-usually have a small jump pack with me, not only for me but since the lightning shouldn't jump vehicles, it gets other people going.

I've never had a problem, one day the 12v will lose its capacity and I'll replace it, just like every other vehicle I've ever owned.

 

[NW Ontario Ford Lightning]

Good to hear.
I bought my truck in January 2025 so had a bit of winter experience.
I park in an open car-port where my charger is set up. I plug in as soon as I get in each day and leave it plugged in until I am about to drive away again the next day.
I set up the Departure Times,
The cabin prepared on scheduled departure times is Awesome during some -30's stuff gotta say.
And since it is just electricity - so much cheaper than remote starting the 2500 Ram to warm up in that kind of temperature.

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