PowerBoost F150 will run without engine battery hooked up...

[currybob]

I had disconnected my 12 volt battery in the engine bay and noticed the powerboards worked and all the interior lights ect. I thought, what the heck, I hit the start button and the truck turned on like always. I even put it in drive and it drove like nothing was different. I had disconnected the negative and the positive power mounts on the battery post.

Has anyone else noticed this?

I just ran a check with my volt meter and it is hot with the truck off too even when disconnected from the battery.

Here you can see my running lights working with the battery disconnected. I had the truck on here with battery disconnected and everything works and truck will drive like this.

I do remember reading there is a small batter in a box under the rear passenger seat but don't know that anyone figured out what that one is for.

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[Heavishot]

Interesting. I guess the traditional battery is primarily for cranking the engine from a dead start. I suspect starting the engine once you’re moving works sort of like push starting and popping the clutch rather than using the starter. It’s so smooth and seamless!

 

[xtraman122]

When you say it started and drove, did the ICE actually start as well, or was it just running on the electric motor in the test you did? Was it throwing codes or warnings at all? I would have figured it wouldn't be very happy in that state at all.

 

[Vulnox]

I noticed this when trying to fix the CarPlay/FordPass/Hotspot issue as I hoped to reset the modules. Everything worked with that battery unhooked, including starting the ICE engine. There is a shop guide on how to disconnect/discharge the high voltage battery which is needed to fully, really, shut down the truck.

 

[Smitdog]

Good info Bob, thanks for posting.

That would explain why my "Trailer Brake Module Fault" didn't go away / reset when I disconnected the battery! (this was just one of a few troubleshooting attempts to make it go - it's still on )

 

[currybob]

When you say it started and drove, did the ICE actually start as well, or was it just running on the electric motor in the test you did? Was it throwing codes or warnings at all? I would have figured it wouldn't be very happy in that state at all.

Yep, starts and ran the ICE.

Like Vulnox I was trying to do a restart for the tranny, 3rd gear has started doing a slight bump sometimes when it shifts into 3rd gear. Nothing major but had always been silky smooth before, doesn't do it every time but seems to be on the increase. Dealer has to replicate those things to get them to do anything, so I was trying the restart.

I don't know if I have gotten an OTA update or not. When I go to the spot on the screen and check for updates, it states I have the latest.

I still have the 2 recalls to do, the windshield and the heated mirror one. Was waiting to make sure they had enough windshields and was in no hurry. Guess I will have that looked into if it continues.

This really surprised me though, wish the manual had more info about this. Guess I am going to order a hard copy, I really don't like using the electronic version.

 

[xtraman122]

I'm surprised by this, I really would have expected the big high voltage battery to be dedicated to the power delivery system. Almost makes you wonder why they even bothered with a traditional 12v battery at all then if the entire truck functions without it even plugged in.

I guess this also means when people were getting that deep sleep mode thing with the phantom power draw issues it must have been draining both batteries?

 

[Sentinel1201]

Interesting. I was about to run zero gauge wiring for my Edgestar compressor fridge in the bed of the truck - I usually run it along the frame and through the wheel well into the main battery in the engine bay. I suppose this fact that truck will start without main battery doesn't change anything for me? the fridge is smart enough to shut down when it senses battery voltage drop below a certain level, but regardless, I should be good?

 

[Ruffner69]

is it ok to jumpstart someone else’s car/truck with these PB’s?

 

[ColoradoHunter]

I had disconnected my 12 volt battery in the engine bay and noticed the powerboards worked and all the interior lights ect. I thought, what the heck, I hit the start button and the truck turned on like always. I even put it in drive and it drove like nothing was different. I had disconnected the negative and the positive power mounts on the battery post.

Has anyone else noticed this?

I just ran a check with my volt meter and it is hot with the truck off too even when disconnected from the battery.

Here you can see my running lights working with the battery disconnected. I had the truck on here with battery disconnected and everything works and truck will drive like this.

I do remember reading there is a small batter in a box under the rear passenger seat but don't know that anyone figured out what that one is for.

Did you happen to check the voltage at the disconnected battery cable? If it's hot, It would be real easy to get an accidental arc.

 

[PungoteagueDave]

Interesting because in our Tesla the 12-volt battery will go dead if left for a month in storage, despite the main battery being plugged in, due to vampire drain. The main battery only “maintains” the 12-volt when it (the drive battery) is awake and used. So we’ve had to add a trickle charger maintenance dongle to the Tesla’s 12-volt battery because it sits for four months at a time during summer.

 

[schleeb]

I had disconnected my 12 volt battery in the engine bay and noticed the powerboards worked and all the interior lights ect. I thought, what the heck, I hit the start button and the truck turned on like always. I even put it in drive and it drove like nothing was different. I had disconnected the negative and the positive power mounts on the battery post.

Has anyone else noticed this?

I just ran a check with my volt meter and it is hot with the truck off too even when disconnected from the battery.

Here you can see my running lights working with the battery disconnected. I had the truck on here with battery disconnected and everything works and truck will drive like this.

I do remember reading there is a small batter in a box under the rear passenger seat but don't know that anyone figured out what that one is for.

If there is a battery underneath the rear seat, its news to me (2021 F-150 PowerBoost). There IS a small inverter... but I don't think there is a battery.

 

[currybob]

If there is a battery underneath the rear seat, its news to me (2021 F-150 PowerBoost). There IS a small inverter... but I don't think there is a battery.

The PowerBoost has a large inverter underneath the truck the box with the smaller battery has been discussed in another thread, just can't remember where it is.

ColoradoHunter
The voltage I read off the cables with the battery disconnected was 11 volts.

 

[ColoradoHunter]

The PowerBoost has a large inverter underneath the truck the box with the smaller battery has been discussed in another thread, just can't remember where it is.

ColoradoHunter
The voltage I read off the cables with the battery disconnected was 11 volts.

Thanks for the info Currybob, really good to know info before disconnecting for the first time.

 

[Mylriahd]

This news makes an experience I had last month even stranger. I went out to go somewhere and.... the door won't open. Actually, the mirrors didn't pop out to greet me. What is going on? I use the hardware key to open the door and it is absolutely dead inside. No idea how or why, I had driven it the day before no issues. So I hooked up my little jumper pack and jumped it. Of course all hell broke loose, with the alarm and about a million warning messages on the console. (To answer the question of why there is still a 12v battery, I'm assuming so you can jump it when its completely dead.)

The most concerning issue here was there wasn't enough juice to release the auto-parking brake. I was absolutely stuck. I left it running in Tow-Haul mode for 30 minutes, and still it wouldn't release the brake. Stop engine, start engine, didn't matter. I kept getting an error about brake failure. I was able to get this solved by reading some older F150 posts with the brake error: Give it some gas in neutral to increase RPMs, and then hit the brake release, which worked. It's been a month so I forgot the specifics, but that was more or less how I got it all back to normal. And I haven't seen a complete discharge like that since.

So based on this thread, I somehow discharged both the 12v as well as the 48v battery completely, in less than 24 hours. The 7.2kw panel in the back wasn't being used, and I can't think of any other power draw that would have drained that much power.

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