Connecting battery tender

[Big guy]

Ran across a YouTube video of someone charging the 12V battery in their ICE truck by using the large trailer plug at back of truck. Those plugs have a constant ground and 12 v pins. This guy bought a blank RV style big that plugs into the large plug in the back of the Lightning. He cutoff the original leads from the battery tender and connected them to the hot and the ground lugs in the new RV plug he bought. Seems to me that should work for leaving your battery tender hooked up during long term storage without having to leave the truck open or drilling a hole to get the wiring to the truck 12volt battery. Anyone try this or think of a reason it won't work on Lightning? Maybe too much resistance in the wiring on that long run?

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[Big guy]

the 12volt battery in the Lightning is the same as an ICE vehicle. Many of us leave a battery tender hooked up to our cars that is in storage over the winter. 6 months. I don't see why it would be different for the Lighting.

 

[bmwhitetx]

Ran across a YouTube video of someone charging the 12V battery in their ICE truck by using the large trailer plug at back of truck. Those plugs have a constant ground and 12 v pins. This guy bought a blank RV style big that plugs into the large plug in the back of the Lightning. He cutoff the original leads from the battery tender and connected them to the hot and the ground lugs in the new RV plug he bought. Seems to me that should work for leaving your battery tender hooked up during long term storage without having to leave the truck open or drilling a hole to get the wiring to the truck 12volt battery. Anyone try this or think of a reason it won't work on Lightning? Maybe too much resistance in the wiring on that long run?

I assume you are looking at pin 5 (orange)

The wiring diagram shows Pin 5 is connected to the Trailer Module and not directly to the battery. It does says relay so maybe it connects via relay. Have you confirmed it is hot at all times? The Trailer Module does get 3 VBATT circuits that are hot at all times.

I wonder how old the ICE truck was and if it had a Trailer Module.

 

[Runaway Tractor]

That 12v pin on the trailer connector is not wired back to the 12v battery. It is disconnected when the truck is off. What you want to do may work on some other trucks, especially much older trucks. But not on this one. A battery maintainer will need to be connected directly to the lugs on the battery, on the external side of the little lug mounted BMS module. No other way.

 

[RickLightning]

I hooked up a battery tender cable to the battery (ground to a ground wire, and ran it under the driver's side frunk cover, coming out of the edge of the cover. Open frunk, plug in, close frunk. Put note on front seat to unplug.

Back in 2022 - 2023, Mach-Es (especially) and Lightnings were having battery issues, so people proactively setup this type of setup (Mach-E owners drilling holes in frunk cover and putting caps in). Now, unless you're gone for a month or more, it's probably unnecessary.

Of note, your vehicle will still go into deep sleep after 2 weeks even if a battery tender is connected.

 

[PJnc284]

There's just enough current draw to suck the LVB down within 30 days which is why for extended storage it's best to just disconnect it.

Drilling holes in their frunks? Good grief.

https://www.f150lightningforum.com/forum/threads/charging-12v-battery.16979/post-342839

And then some get real fancy
https://www.macheforum.com/site/thr...les-drilled-for-12v-battery.29891/post-677611

 

[RickLightning]

There's just enough current draw to suck the LVB down within 30 days which is why for extended storage it's best to just disconnect it.

Drilling holes in their frunks? Good grief.

The number of Mach-Es have battery issues were large. Keep in mind there is no key to get in. Battery is dead, you pull cap off bumper and jump to open frunk, then have to charge battery. Battery low, and that doesn't work.

The frunk panels, unlike the Lightning, have no knobs on them. You have to pull the center panel off, possibly breaking permanent connectors, and having the piece connectors separate and fall into the inside of the compartment with all the wiring and such. Then you have to pull off the side panel, and do the same. It's great fun to do when it's 10 degrees out and your hands are cold too...

Ford has changed the battery charging algorithm on the Mach-E several times, including in the past few months, plus the new recall that makes the 12v system stay actively connected to the high voltage for 12 minutes after powering off (which also charges the 12v). I think (top of head) that the new "time to charge the 12v" is now at 60%, it used to be 30%, and often skipped over it (i.e. went from 31 to 29 and therefore didn't trigger charging and battery died).

Here's what many did, including myself. Keep a pry tool in the frunk, so if you need to pop them, you don't even have to use your fingernails.

 

[chl]

Quite a few posts about this topic if you search the forum.
For example: https://www.f150lightningforum.com/...-updates-using-fdrs.11029/page-27#post-343755

 

[flux capacitor]

No, the trailer electrical connector on an F-150 Lightning is not connected directly to the 12V battery. The power for the trailer's auxiliary charging pin is regulated by the Trailer Module and is only active under specific conditions.
This system is a safety and power-management feature that differs from older trucks where the 12V pin might have been a constant, direct connection.
Key details of the F-150 Lightning's trailer electrical system:

• Controlled by the Trailer Module: Power is routed through the Trailer Module, which is a computer-controlled component. This protects the truck's sensitive electrical systems from potential issues like reverse power flow.
• Activation conditions: The 12V power to the trailer connector is only activated when the truck detects that a trailer is connected and the ignition is on. It is not a constant, "hot at all times" connection.
• Trailer battery charging: While the truck can trickle-charge a trailer's battery while driving, the power output is managed and not a direct, high-current connection. For faster or more consistent trailer battery charging, a separate power source or a specialized DC-to-DC converter is recommended.
• Risk of damage: Attempting to backfeed power into the trailer connector to charge the truck's 12V battery can cause serious damage to the Trailer Module.

For these reasons, you must connect a battery maintainer or other 12V accessories directly to the F-150 Lightning's 12V battery terminals, not to the trailer wiring

 

[chl]

https://www.f150lightningforum.com/forum/threads/charging-12v-battery.16979/post-342839

And then some get real fancy
https://www.macheforum.com/site/thr...les-drilled-for-12v-battery.29891/post-677611

I saw where someone put a jump/trickle charger connection under the charge port cover making it available without the need to open and leave open the frunk (which some say may use some LV battery power to do, though I have not confirmed that).

https://www.f150lightningforum.com/...ess-jump-charge-port.24587/page-2#post-475156

See also:

https://www.macheforum.com/site/threads/connecting-trickle-charger.32608/page-2#post-732359

And one put one on the front grill:

https://www.f150lightningforum.com/forum/threads/lvb-easy-access-jump-charge-port.24587/post-474965

 

[chl]

I was thinking about putting this under the charge port cover to trickle charge the battery using the accessory/cigarette plug that comes with the charger. But using the 3ft cable one which should be enough length.

https://www.amazon.com/dp/B0CSSZ4YX...24cd&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWwy&th=1

 

[chl]

I was thinking about putting this under the charge port cover to trickle charge the battery using the accessory/cigarette plug that comes with the charger. But using the 3ft cable one which should be enough length.

https://www.amazon.com/dp/B0CSSZ4YX...24cd&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWwy&th=1

Well I got the 3ft one but too short for where I want to put it, so I ordered a longer one.

The 3ft would work if putting inside the frunk but I decided to try to put it under the charge port door as in one of the other posts.

The 3ft one seemed to be quality, well made and sturdy, just too short for what I want.

 

[chl]

I decided I could put the 3ft one in the plastic cover for the battery compartment at the back of the frunk:

Just need to find a couple M6 nuts to attach it to the battery (the ground down stream of the BMS of course).

I also want to run one of these into the cabin for a lay-on-the-dash solar trickle charger.

And I am thinking I can make a 1/2: hole under the charge port door in the plastic (in an area with nothing in the way near the hinge) so I can run a fused extension with a connector on it to plug into the trickle charger when I don't want to leave the frunk open and the sun isn't shining. The small plug should fit under the charge port without causing any interference when closed.

Like this:

https://www.amazon.com/Terminal-Protection-Disconnect-Extension-Motorcycle/dp/B07XCW4MZZ/?th=1

 

[chl]

LV trickle charger connector under the charge port door:

 

[chl]

Even better I think would be this:

I'm thinking I could mount it inside the charge port where I made the hole in the plastic, a neater solution than to have cord dangling there.

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