New 12v dead after one month

[chriserx]

Here’s the video when I jumped it. It starts out at 3.8V then I attached another 12V through my jumper leads (jumps to 12V) then I got in and turned the truck on (jumps to 13.4V). I ended up taking the battery out and charging it alone with the 5A Noco as it couldn’t do it attached. It took it 10+ hrs and it was hot (Noco) the entire time but the battery got to 12V and stayed. I drove it around yesterday, had it parked for several hrs at a time, and when I reconnected the Noco it’s able to charge it to green. I turned automatic updates off in the truck. If this seems to work I’m going to turn AU back on and use the breaker that is on the amp to disconnect it and see if it behaves any different.

You really should get that battery tested, no matter how new.
If battery was 3v, you jump started and voltage read 13+ that should rule out DCDC failure, though it could still be intermittent.
You likely could test if it's the amp with a volt meter, it may be somewhat unreliable because there are variables like welcome lighting and approach detection but its worth a shot.
Turn off all 12v sources you can just for good measure, open frunk and door where the amp is, let it sit a while, leave keys and phone in the house.
Measure the voltage with the amp plugged in.
Unplug amp, measure again.
If the voltage realistically increases, you've found your problem.

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[RandyT]

Use an OBD reader and check quiescent average drain

Can a regular BT OBDII dongle pull specific EV data from the Lightning, or do I need a specialized one? And what app are you running to monitor the quiescent drain?

 

[chriserx]

Can a regular BT OBDII dongle pull specific EV data from the Lightning, or do I need a specialized one? And what app are you running to monitor the quiescent drain?

From what I can tell, it's not a live reading so it's likely not 'monitorable' in the traditional sense. Most people on here tend to use car scanner or torque. I'd think you could pull it off of any BT capable OBDII but each app may have a different name and/or location for it. In car scanner, on carplay it's found in the 12v battery page 1/2 iirc.

Which app/dongle are you using?

 

[RandyT]

From what I can tell, it's not a live reading so it's likely not 'monitorable' in the traditional sense. Most people on here tend to use car scanner or torque. I'd think you could pull it off of any BT capable OBDII but each app may have a different name and/or location for it. In car scanner, on carplay it's found in the 12v battery page 1/2 iirc.

Which app/dongle are you using?

Got it. I'm also using Car Scanner, so that’s perfect. Thanks a lot for the tip—I’ll dig through the pages and see if my reader can pull the data.

Have a great weekend!

 

[Mike G]

There have been reports of the trailer module (TRM) causing 12V battery drain and a software update was released recently.

The BCM controls when the 12V battery gets recharged by the HV battery. The threshold for doing this is when the SOC goes below 80%, if I'm not mistaken.

 

[DavidS]

You really should get that battery tested, no matter how new.
If battery was 3v, you jump started and voltage read 13+ that should rule out DCDC failure, though it could still be intermittent.
You likely could test if it's the amp with a volt meter, it may be somewhat unreliable because there are variables like welcome lighting and approach detection but its worth a shot.
Turn off all 12v sources you can just for good measure, open frunk and door where the amp is, let it sit a while, leave keys and phone in the house.
Measure the voltage with the amp plugged in.
Unplug amp, measure again.
If the voltage realistically increases, you've found your problem.

Contained in this reply is really good advice on how to reduce stress on your 12V battery. Minimize how much you walk near your truck with your phone or keys. Every time you walk near the truck it wakes up and places a load on the 12v. Besides battery health, from a vehicle security standpoint, don’t leave your keys in your pocket all day. Keys have motion sensors to put them in sleep mode to help prevent relay attacks on your vehicle.

 

[chriserx]

Keys have motion sensors to put them in sleep mode to help prevent relay attacks on your vehicle.

Is that confirmed for our vehicle, cuz, neat?

 

[DavidS]

Is that confirmed for our vehicle, cuz, neat?

Doing some research, Ford is pretty quiet about which vehicles it has and hasn’t rolled out the timer security function. The best confirmation I could find in the 2024 Lightning manual is a note that the key fob may not function if left stationary for over 1 minute. The timeout is 40 seconds, so this seems about right.

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