Ford BMS Battery Monitoring System: How it Works, How to Properly Charge, How to Power Accessories

[Porpoise Hork]

Excellent video, I'd be curious to see how the PowerBoost handles this... can the traction battery keep the AGM topped up when the truck is off? Or can it supply enough current fast enough to offset the 12V demand during short drives?

I was wondering the same thing. One of the first Forscan mods I did was change the battery SOC from 80 to 95%. In the 4 months of ownership the vast majority of my drives are 10-15 miles and so far no issues at all with the 12v system. Any time I have looked at the voltage with the engine off with Forscan or CarScan app it's been at 12.7v. I'm guessing that because the hybrid battery acts like the alternator on the PB it does a better job at maintaining the 12v SOC level on short trips than traditional alternators do.

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[Doughecka]

I was wondering the same thing. One of the first Forscan mods I did was change the battery SOC from 80 to 95%. In the 4 months of ownership the vast majority of my drives are 10-15 miles and so far no issues at all with the 12v system. Any time I have looked at the voltage with the engine off with Forscan or CarScan app it's been at 12.7v. I'm guessing that because the hybrid battery acts like the alternator on the PB it does a better job at maintaining the 12v SOC level on short trips than traditional alternators do.

Hmmm, I didn't realize I could change the SOC... this is for the high voltage battery right?

 

[RickBullotta]

Good info, still think a higher capacity battery should be in these trucks so when you do drive it for longer periods it can build up a higher reserve capacity.

Mine does have the 760 CCA battery, but have seen Spec sheets that says the Lariat and above should have an 800 CCA battery installed if it has the EcoBoost V6 or a 850 CCA for the Turbo Diesel.

Here's what I put in my Lariat PB (new battery is 850 CCA):

https://www.autozone.com/batteries-...tery-h7-agm-group-size-94r-850-cca/319458_0_0

 

[Porpoise Hork]

Hmmm, I didn't realize I could change the SOC... this is for the high voltage battery right?

No it's the SOC for the 12v in the engine bay. As far as I know there is no way to alter Ford's configuration on the hybrid charge levels that keep the lithium battery pack between 40-70%.

Ford's default is 80% (12.5v). If you run into issues with the truck entering deep sleep (SOC 50% 12.05v) after a few days of not starting, up this with Forscan in the BCM to 95% (12.7v) and drive it around for about 30+ minutes to bring the battery SOC up. After that the truck should go 7-10+ days before entering deep sleep. Provided there are no gremlins keeping modules on. I did this on my 20 Ranger during covid and could go upwards of 2 weeks and not get the deep sleep warning. Have never gotten the deep sleep warning on the PB with it at 95%. Even with not driving it all last week (9 days) with temps below freezing for days too.

 

[Jersey Jim]

Interesting video. I searched for what that component was on the negative battery terminal, with the 2 small sensing wires. I assumed it was a shunt of sorts, with the mV drop across the shunt being monitored. I have installed 50mV shunts in my motorhome 300 Ah Lithium house battery, and also in my 25kW off grid residence battery bank. It drops from 0 to 50mV across the shunt when up to the maximum current of 500 amps passes through.
I am particularly interested in this feature, as I have a 175 amp Anderson SB power receptacle mounted under my rear bumper. This is only fed with 4 Ga. wires, and I use it to power a boat winch and an inverter to charge Stihl chainsaw batteries in the woods.

Here's my question(s)..... 1) on a 2021 F-150, is there a screen where I can monitor the BMS state of charge? And 2) are those 2 small sensing wires measuring the voltage drop across the shunt? In the video the narrator said it was networked information. If it was sensing across the shunt, l could tap into it and monitor at least the "instantaneous" current flow.

I"d be interested in hearing from someone who knows this feature inside and out. Thanks.

 

[Jersey Jim]

.....Also, be aware that when installing a larger battery, the BMS software is set up to totalize for a given Amp-Hour capacity battery. For example, if BMS is calibrated for a 100 Amp-Hour battery, it will assume 100% SOC when approximately 100 "charge" amp hours pass through the shunt. If you install, for example, a larger 150 amp-hour battery in the vehicle, the BMS will think the battery is at 100% SOC when the larger battery is actually only holding 66% SOC. The bigger the battery, the bigger the "AMP Bucket". Problem is, Ford set their BMS software for measuring/totalizing a smaller bucket. Once achieving 100%, the charging system may throttle back on charging that larger battery once it reads 100% in order to not over charge it, even though the larger battery may only be at 66% of it's greater capacity.
With a truly flexible BMS, like I've installed on my own systems listed in the post above, the size of the "amp Bucket" can be configured in the BMS parameters. When I changed out my motorhome house battery to a 300Ah Lithium Iron Phosphate, I had to set the BMS to 300 Ah so it would know that 100% would be displayed after 300 amps of net charge. Maybe Ford allows this parameter to be altered... I don't know.

 

[Snakebitten]

@Jersey Jim

With a smartphone app and a Bluetooth OBD adapter, you can monitor as many Battery Management parameters as your heart desires.

I personally use the OBDLink MX+ adapter and the app developed by the same folks.
https://www.obdlink.com/

I dig those cordless Stihl chainsaws. I have a couple and they are a game changer for my needs.

 

[Jersey Jim]

Snake... what a great idea! I hope I can display that SOC parameter, as like I said, I plug a 4 gauge plug/cable into my rear bumper outlet and draw as much as 60 to 75 amps. I like to know when the alternator keeps up, and when the battery has to start "chipping in".
Do you happen to know how many amps a 2021 2.7 Ecoboost alternator will output at idle?

BTW, I forgot I even bought one of these 5 or so years ago!..... I found the box, now to hunt through the barn...

 

[Snakebitten]

Be sure to update the firmware on that one before you...... Well, you know. Lol

It's an easy enough procedure.
Also, it's worth the extra few buck$ for the extended Ford/Lincoln/Mercury software addon in the app itself if you want to see all the parameters that the BMS module on your specific truck will allow you to monitor. (I think it's $7.00?)

 

[Jersey Jim]

Snakebitten, My bluetooth OBDLink MX does not show anything charge related on my 2.7 F-150 other than voltage. I need to see charge current at a minimum, and preferrably SOC. They make so many different plug-in OBD2 modules, and the OBDLink MX I have has been discontinued. I don't want to keep buying the wrong module, and would rather be sure.

 

[Snakebitten]

Are you saying that OBDLink doesn't currently support your device with new firmware as well as the Ford/Lincoln/Mercury enhanced PIDs? (purchased separately)

I have a Powerboost, and the number of PIDs related to the Hybrid (high voltage) battery is impressive. I built the gauges below to monitor the charge/discharge rate and SOC. Note: it's the lower 50% of the dashboard. At the moment of the screenshot the battery was in charging state at 28.8 Amps at ~280V. That's a fairly fast charge rate from ICE alone, although regenerative breaking can increase to better that 60Amps. You can literally watch the SOC climb quickly.

Admittedly I haven't tried to duplicate the effort for the low voltage side, but there's another member with a Coyote that has recently been logging such things.

Maybe he'll stop in and share?
@Big Dog Daddy

 

[imnuts]

I don't know of a way to get the 12V battery SOC easily. I think only the hybrid charge level can be monitored with most apps. You can probably find it in Forscan though.

 

[imnuts]

I made a couple Forscan changes today, so decided to look for 12VDC battery charge level. I didn't see it there either. I'm sure there's probably a way to get it from the module, but it may be FDRS only for now until someone figures out where it's hiding.

 

[Jersey Jim]

Snakebitten.... I updated the firmware on my OBDLink MX, and even paid the $14.99 to get the extended features for the Ford, but still no parameter listed for charge current, or SOC. However, I did see a video of a guy monitoring exactly what I need, using an OBDLink "MX+" adapter, and Forscan Lite on his phone. The MX+ seemed to be way pricier than I recall paying for the "MX", and I don't even know what Forscan Lite costs.
Anyone know what it would take take to "economically" show me all the charge/alternator parameters for my 2021 2.7L ecoboost? This guy's video even showed the 125 hz command data and alternator Feedback handshaking pulse width modulation transfer. Maybe not the waveform, but his gauges showed the duty cycle % of those commands to and from the alternator. Amps too along with much more charge related data.

......... Since the smart alternator/charging is controlled by the powertain control module, what adapter and android app would get me all the charge PIDs being controlled by the pcm? ..... on a budget.

 

[Snakebitten]

Sorry that your MX isn't getting you what you are looking for.

Are you Android?
Forscan Lite is free.
And while it IS a nice app, I found far more PIDs with the MX+ and the OBDLink app. (more than 1500 pids)

However, none of the apps I have tried are as good as Full Forscan on windows. I dream that someday the Forscan guys will add all the support in the app that the full version has. (regarding monitoring)

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