DC to DC Charger ?s

[John in Santa Cruz]

Originally Posted by SageRpod

Even with the smart DC-DC that breaks the TV to house battery circuit, I still unplug. Old habits are hard to break and I have trust issues as well.

Never had an issue with a Ford or Toyota truck, they disconnect the 7-blade when the truck is switched off.

[Centex]

Originally Posted by SRS

Hi Centex, I'd be interested in Fords explanation regarding the behavior of the smart charging system if it isn't too big a deal to post. TIA

Attached for your reading enjoyment.

These sections from the Service Manual for 2022, should be the same for all Gen 14 F150 2021-current; previous years may differ.

[John in Santa Cruz]

awesome thanks for those docs, I have a 2019 ford with the 3.5 and that exact same electrical setup.

for those unfamiliar, LIN referenced in those docs is a specialized digital communications bus used to tell the alternator's voltage regulator what to do, and to monitor the state of the alternator.

This system is very similar to whats in my wife's 2016 Mercedes E350 wagon. On the MB, the goal is to minimize the engine drag from the alternator once the battery is reasonably close to a full charge, it does this by reducing the alternator output to just 12.7V or so so the alternator is supplying the vehicle loads without trying to push more current into the battery.

I haven't looked in the Ford yet, but on the Mercedes the battery monitor is a Hyundai device... this is almost exactly the same sort of function as the Victron SmartShunt many of us have added to our Escapes for battery monitoring.

[Centex]

Originally Posted by John in Santa Cruz

.... I haven't looked in the Ford yet, but on the Mercedes the battery monitor is a Hyundai device... this is almost exactly the same sort of function as the Victron SmartShunt many of us have added to our Escapes for battery monitoring.

This prompts mention that the same rules apply regarding connections of loads or vehicle charger inputs to the ground side of the 'shunt' (BMS) vs the negative vehicle battery terminal.

Never connect a load (e.g. DC-DC trailer battery charger) or vehicle battery charger (e.g. battery-tender) directly to the vehicle negative battery terminal. The 'shunt' (BMS) must always be between the loads / battery inputs and the battery negative terminal.

Bypassing the BMS with loads or charger inputs will totally foul-up your vehicle's "Smart" charging algorithms / strategies.

My 2022 F150, to illustrate:

[John in Santa Cruz]

yeah... our Mercedes has the battery buried in a cave, and a very easy to connect + and - jump terminal outside said cave.

[SRS]

Thanks Alan, appreciate both posts. Very informative.

[SRS]

Originally Posted by Centex

Bypassing the BMS with loads or charger inputs will totally foul-up your vehicle's "Smart" charging algorithms / strategies.

My 2022 F150, to illustrate:

I have had to charge my 2021 F-150's battery a couple of times because I don't drive too much this time of year-lots of parasitic drains with all the computer stuff. Based on your info, I did it incorrectly by attaching the negative to the the battery lug negative. So, I've probably messed up the charging algorithms Any idea how one would fix that?
Thanks Sherby

[Centex]

Originally Posted by SRS

I have had to charge my 2021 F-150's battery a couple of times because I don't drive too much this time of year-lots of parasitic drains with all the computer stuff. Based on your info, I did it incorrectly by attaching the negative to the the battery lug negative. So, I've probably messed up the charging algorithms Any idea how one would fix that?
Thanks Sherby

With the passage of time the system will figure out ('recalibrate') the correct battery SOC and all will be good. The fact that your truck 'sits undisturbed' for extended periods helps that 'recalibration' process which occurs during many-hours-long periods of 'deep sleep' when your vehicle is not disturbed at all (not even opening a door or approaching it with a key fob which 'wakes' various vehicle systems).

Sorry if I gave the impression that your (common) error is permanently fatal, it's not. Just don't keep repeating, in the future I suggest the 'best practice' of connecting the charger negative clip to a solid chassis ground rather than the negative battery terminal or the BMS stud.

The applicable section from the Service Manual is attached FYI, I've highlighted the preferred procedure in a red box.

[SRS]

Originally Posted by Centex

With the passage of time the system will figure out ('recalibrate') the correct battery SOC and all will be good. The fact that your truck 'sits undisturbed' for extended periods helps that 'recalibration' process which occurs during many-hours-long periods of 'deep sleep' when your vehicle is not disturbed at all (not even opening a door or approaching it with a key fob which 'wakes' various vehicle systems).

Sorry if I gave the impression that your (common) error is permanently fatal, it's not. Just don't keep repeating, in the future I suggest the 'best practice' of connecting the charger negative clip to a solid chassis ground rather than the negative battery terminal or the BMS stud.

The applicable section from the Service Manual is attached FYI, I've highlighted the preferred procedure in a red box.

Thanks again Alan, and not a problem. Online videos helped a lot to clarify my concern and question I asked. I've linked two of the videos below in case anyone else is interested, enjoy.

https://www.youtube.com/watch?v=I_KmO-KaR4A

https://www.youtube.com/watch?v=V5gz14VODZY