Continuous Trailer Charging Question

[Waterick]

Congratulations on your new-to-you Maverick!

As established you have factory 2k (trailer wiring connector as is on the left):

It's possible but not likely the aftermarket flat tow package is causing additional battery drain. It ain't supposed to do that, it's supposed to provide power to keep the battery from going flat while the vehicle is being towed, because the vehicle needs to be in neutral tow mode which means the onboard computers are active and using 12v power and would drain the battery over time! If it is a well designed accessory if would never cause it's own parasitic drain.

The 14.5 when driving is not the reading from the battery, that is from the converter that is powered by the high-voltage hybrid system. In the old days this reading would mean that the alternator was charging the 12v battery, no so with our hybrids. The 12.2 is a bit low for a resting , non-AGM battery, maybe even of an AGM but they seem to do well even if they are a little "low" at rest.

So for this, you stated that you charged the battery - but that is not the full procedure, and there are some other issues to consider. 1st the "other issues" - in the 2025 and up models Ford switched to an AGM battery type as they seem to know that they have a bug in their 12v battery charging and maintenance strategy (there are many sometimes very long threads about this on the board). If your battery is three years old and has not already been replaced with an AGM battery it may have been damaged (through "sulfation") to the point that it will never be healthy again.

Make sure all recalls and advisories are done, there was at least one somewhere that I think addressed parasitic draw but I don't know the details. You can check with the Ford app or on the Ford owner site, if you haven't set up a profile there with your VIN you should do so.

The battery and procedure:
- If you are going to replace your battery yes you should replace it with an AGM type!
- If your replace the battery yourself, charge the new battery overnight (or as long as it takes) with an AGM-safe charger. If the battery is replaced for you insist that it be charged for you.

If you want to give charging your existing battery another try (or have replaced it with an AGM), once the battery is fully charged you must reset the battery monitoring system (BMS) (it's easy to do). Not doing this means that the BMS has memorized a "State of Charge" (SOC) for your existing battery and will not ever charge it past that state. This is probably why even after driving the truck the voltage read low again, and the many long threads talk about the problem where the BMS charging doesn't seem to get triggered correctly unless you "trick" it into working, for example, drive with your headlights on (not on automatic - force them on) or parking lamps on.

Either way the battery really does need a full charge for the BMS reset procedure to work.

1) Fully charge the battery overnight or for as long as is needed.
2) Remove the charger.
3) Follow the instructions for the BMS reset in the owners manual: put the vehicle in accessory mode (don't start the engine but turn it on), then within 10 seconds complete the following two steps:
a. pull back on the turn signal to flash the high beams five times in a row.
b then press and release the brake pedal three times.

~alternative BMS relearn method, maybe the right one for the hybrid~
1. Fully charge the battery overnight or for as long as is needed.
3. Remove the charger.
2. Lock the vehicle and leave it alone for 8 hours.

BMS reset also also posted here:
https://www.mavericktruckclub.com/f...benefits-of-a-b-m-s-reset.81044/#post-1336750

I hope you can get the battery issue sorted and enjoy the truck!

I agree with this mostly; do not do a BMS reset on a three year old battery however. The reset tells the BMS you have a new fully charged battery when you don't.

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[El Kabong]

I agree with this mostly; do not do a BMS reset on a three year old battery however. The reset tells the BMS you have a new fully charged battery when you don't.

"Either way the battery really does need a full charge for the BMS reset procedure to work."

If the original battery is not sulfated giving it a long slow charge to full should do the trick, of course there isn't an easy way to check for sulfation with a sealed battery. At three years with a known dodgy charging schema I'd have to agree that @hasbro452 probably needs to get a new AGM in there.

 

[denis4x4]

I would seek advice from a shop that regularly installs flat towing equipment. There is a certain added value with that equipment when you go to sell it.

 

[Retro1]

Can anyone tell me how to "see" the battery monitoring state of charge? I don't see it on my display, nor have I found a means to turn it on/off on display menu or infortainment (or whatever it's called) screen. Much obliged.

 

[HeyBales]

Can anyone tell me how to "see" the battery monitoring state of charge? I don't see it on my display, nor have I found a means to turn it on/off on display menu or infortainment (or whatever it's called) screen. Much obliged.

You can't. There isn't.

Must get an OBD2 scanner if you want to see what the truck's BMS thinks the SOC% is.
And that figure is what it bases charging amps on. Voltage reading doesn't give the whole store from a power port - though you can discern a lot from it.
Use the tested adapters from forscan.org - and pair it with Car Scanner app for those readings.
Can use that setup in any vehicle too.
(If Forscan Lite is still available (sounds like not) it's great too.)


A battery tester used in the morning before you drive will give a more industry standard SOC%, and helpful resistance, SOH%, and tested CCA or RC or AH depending on what the tester does.

 

[Retro1]

You can't. There isn't.

Must get an OBD2 scanner if you want to see what the truck's BMS thinks the SOC% is.
And that figure is what it bases charging amps on. Voltage reading doesn't give the whole store from a power port - though you can discern a lot from it.
Use the tested adapters from forscan.org - and pair it with Car Scanner app for those readings.
Can use that setup in any vehicle too.
(If Forscan Lite is still available (sounds like not) it's great too.)


A battery tester used in the morning before you drive will give a more industry standard SOC%, and helpful resistance, SOH%, and tested CCA or RC or AH depending on what the tester does.

Thanks for that; I'd hate to be missing out on something. I guess a scanner is in my future!

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