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

[Snakebitten]

In my opinion the bendix starter is what Ford would get rid of if they could. It's by far the least used method of cranking the ICE over.

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[Handle]

In my opinion the bendix starter is what Ford would get rid of if they could. It's by far the least used method of cranking the ICE over.

Have you ever been able to hear or isolate the sound of the Bendix operating during usage of your truck? Our friend in the Yukon thread probably uses it everyday…..

 

[Snakebitten]

I admit that I have the luxury of tropical weather and rarely a necessity of remote start.

I need to see if there's some pid that reveals if/when the bendix starter is energized. Or maybe the same for the BISG?

 

[scott011422]

So, Jersey has his SOC set at 80% and has shown his truck is actively attempting to stay there. Has even shown how the charging varies repeatable within 3% of that 80% SOC.

I have my SOC set at 95%. Now that the weather is warmer, the battery is performing better and holding that charge much better from cycle to cycle. It seems that for whatever reason the truck won't approach that 95%. Most I've seen is 88%. I noticed yesterday when I went to break that the voltage never went above 12.9v. I happen to have my laptop with me so I checked it when I got back to work and the SOC was 88%. Now I don't recall what Jerseys voltages were when he hit that 3%, but To me it seems like the truck is aiming for 90%.

So two questions. 1) Charging with CV, Is it possible to overcharge the battery? If not, What's it going to hurt if I set my SOC higher? Say 105%? Looks like currently at 95% the battery is going to sit in the 12.7's. It was at this voltage when I went to break.

 

[scott011422]

So I finished my overhead lights this weekend and went in with Forscan to clear my check engine light. While I was in there I went to increase my SOC Target to 100% and it was only set to 80%? Last month the Target was 95%? So I have no idea what the setting was when I was seeing 86% SOC on the battery. So I set the Target to 98% and we will see what happens. I guess we will find out later in the week.

 

[scott011422]

Im definitely seeing a difference after moving the Target SOC to 98%. I've seen battery voltages of 12.8 a time or two. However, I'm still seeing that digital "ON" "OFF" charging trend. Once the truck gets the battery charged, It doesn't keep it there. It lets the battery fade to a lower voltage+SOC limit before the battery sees any charge again. Yesterday for example, didn't give the battery any charge at all. Battery was 12.79 end of day monday. Was 12.51 end of day yesterday. I actually saw a running voltage of 12.69 steady on my way home yesterday. This morning I was under my 12.5 threshold at 12.49 and the battery charged. 20 min drive later, battery was at 12.79.

Voltage wise I'm happy at the 98% since I'm aiming for a 12.8 resting voltage. Still miffed the truck wont keep the battery charged though. Irritating.

1st pic, day 1, I changed my SOC to 98% the night before, did not drive it that night.
2nd pic, day 2, no charge.
3rd pic, day 3 (today) nice charge this morning.

 

[Snakebitten]

I'm set to 95%, whatever that setting actually means, and even after a nice overnight external charge and the BMS recognizing it as a high SOC, it shows no interest in maintaining it there.

It's stubbornly determined to bring it back down to 12.3-ish as fast as it can.

I'm still waiting for you gurus to discover a hack. Lol

 

[Davexxxx]

I just started reading this massive thread but just a bit in and there is a wide range of realities.

Some have debilitating electrical drains, some don't. I hope to find a sort of constant somewhere.

There will be times, when my yet to come, new PB, will sit for a week or so and what trips it gets during those periods, will primarily be 8 mile one ways. In other words, infrequent, short trips. I have no problem getting into the habit of turning accessories off at shut down, if that would help. I more or less do that now anyway.

A battery maintainer? Don't have one but I do have a couple old style battery chargers and one smart charger, that uses a variable strategy and can do a desulfating regeneration cycle.

About 50/50 on that. It can't fix a shorted cell but it has revived a few that were headed for scrap, before putting them through the cycle. A couple have taken more than one try, which is a 24 hr. cycle but they did wake up enough to get another season out of them.

Complicating things a bit further there is the 7.5ah batt under the rear seat, that there seems to be very little published about and may be wired one way in ICE engines and a different way on PBs?

I did find these 2 vids about it.



And



Yes, I'll continue reading the thread but I'll gladly accept any short cuts too.

 

[HammaMan]

I've found some troubling behavior with the LFP present -- On remote start, the truck won't turn on 12v generation. It just consumes the LFP's power. Now that's not an issue, it can power it for 4hrs like that

Another behavior I've found is that the truck while running, will shutoff 12v generation entirely and consume the batt for a couple minutes, then turn on generation, then shut it off. I haven't seen this behavior constant, more like it's probing the battery to see wth is going on w/ my 13.3v continual. My bat is set to 94% SOC. W/ the LFP, overnight it went to 93% for the first time w/ out external charging. The LFP can really eat some energy and I've capped its max charge to 3.5v / cell which is 14v. It can't actually reach that SOC because the truck can feed it so much amperage. It may be able to eventually due to how the LFP's BMS is behaving. I've set it to shut off charging at 3.5v but it will still let voltage exceed that for 10s before shutting off for 30s. So it can slowly creep its way up there BUT, once the AGM is charged, the truck takes the voltage from 14.5-15.2 down to the AGM float of 13.5-13.7 which is lower than my 14v max charge point. The LFP isn't actually fully charged until 3.65v cell (hard limit) or 14.6v.

When the key is turned off, if the LFP has gotten a healthy charge into the 13.6v+ area, it floats the AGM and slowly drops down into the 13.4 / 13.3v range and power stops flowing out of it as the AGM isn't accepting any more current, despite still being 93/94% SOC as that's a float voltage for it (The LFP's super flat curve has ~10ah of current delta between 100% SOC at 14.6v and 13.4v of 90% SOC) where it sits until it's ~10% SOC). Essentially the truck has more than 2x the amount of available amp hours to burn before it even begins to get into using the AGM's measly 45ah of capacity (it's actually much more, you pull 30ah out of the AGMs and you're bordering on a no-start condition). That essentially boils down to being able to trigger the hell out of the 12v system by opening doors, leaving power points turned on etc... and still being able to go 8-10x longer than the AGMs alone are capable of, before the AGM's reserve capacity even enters the picture.

If I leave the truck alone, that's where it sits. The modem and whatever else it wakes up (I believe the GWM is still awake w/ the modem as it can call on the BCM to turn on something else for updates). I've mapped what actions consume the batts in my LFP thread. I've mapped out all scenarios sans auto updates. I'm not continually connected to the BMS and I'd have to be connected to it and receive an update to see just what exactly is going on. The LFP's BMS is always awake, watching the battery. It uses mosfets as current gates and is able to observe power consumption and control it with a high degree of accuracy. What I can see however is how much energy is missing from the LFP batt at any given point. It's got so much reserve capacity I've stopped watching it.

I will share more about this configuration once I'm satisfied it's a safe arrangement. Simply put, I'm someone who's not afraid to break shit. I'm looking into having a custom BMS made for automotive applications because there are some nuisances that must be satisfied to run a complete LFP 12v system, particularly around cold weather. The chemistry cannot be discharged below -20c or charged unless the temp is 0c (32f). Because it's got SOOO much capacity, it can be insulated and self-heat. However I need custom logic for auto operations so that someone can let their vehicle sit outside in super cold temps and still be able to bring it back to life in the event they let it sit for 2 weeks or longer. There is a lower temp feasibility limit though so it's not something I'd do for an externally kept arctic vehicle. As an aux batt however, with the right logic, it's an easy choice.

 

[scott011422]

HammaMan:
You may be seeing some of these quirks because of how the truck interprets the voltages. Ive already been wondering if tying the two batteries together is causing the truck to see a false high voltage because the smaller battery is going to show charged long before the large battery. Granted the truck monitors amps on both batteries, But there is nothing the truck can DO about it. Its not like the truck is occasionally disconnecting the AUX battery and checking the independent voltages, Even though they could in hindsight, but they don't.

With your LFP battery installed you've made that problem worse. You've basically installed a 4s LiPo battery. The entire safe zone of that battery is above 12.8v. Your truck is going to think that the 12v batteries are overcharged all the time and not charge it, Which you seem to be seeing.

We already see that the truck doesn't like to keep the battery charged, and will cycle the battery from 12.3-12.5 and full at roughly 12.65@80% SOC Target. Your battery si so much higher than that range, If you were to graph that, It probably looks like my graph from yesterday. No Gains.

 

[HammaMan]

HammaMan:
You may be seeing some of these quirks because of how the truck interprets the voltages. Ive already been wondering if tying the two batteries together is causing the truck to see a false high voltage because the smaller battery is going to show charged long before the large battery. Granted the truck monitors amps on both batteries, But there is nothing the truck can DO about it. Its not like the truck is occasionally disconnecting the AUX battery and checking the independent voltages, Even though they could in hindsight, but they don't.

With your LFP battery installed you've made that problem worse. You've basically installed a 4s LiPo battery. The entire safe zone of that battery is above 12.8v. Your truck is going to think that the 12v batteries are overcharged all the time and not charge it, Which you seem to be seeing.

We already see that the truck doesn't like to keep the battery charged, and will cycle the battery from 12.3-12.5 and full at roughly 12.65@80% SOC Target. Your battery si so much higher than that range, If you were to graph that, It probably looks like my graph from yesterday. No Gains.

Well the AGM isn't being used at all so there is no charge curve for it. The battery I'm using is LiFe P04, not lithium polymer. There's a handful of lithium chemistries that people sometimes mix up. Li-ion and LiPo are 2 entirely different chemistries than LFP.

The PB's operation is likely different than the other trucks. That curve you posted looks like it charges and then consumes the batt. The PB will often keep its voltage in the mid 13s once the batts are full. The DC/DC takes up 100% of the power load of the truck, reacting extremely fast to current spikes (it's basically running in a CV mode)

The aux batt isolator (technically it isolates the aux batt and the internal fuse box from the under-hood and starter) is only opened briefly while the flywheel starter is commanded on. On the PB however I haven't seen it open when it uses the belt starter as it's got the DC/DC running. It could be happening really fast as my data has a 1hz refresh. I may try and find it in forscan during a data capture. I expected that to throw a code but I haven't thrown any codes at all except for the missing rear seat.

A side benefit, the powered running boards move quite fast having that happy voltage and low resistance battery powering them. It's a truly noticeable difference with the truck off.

The truck does in-fact charge the LFP up, extremely fast peaking at 75a until it's charged (reaching the 3.5v cell limit) and the LFP's BMS stops inflow current. The LFP is reaching my max charge setpoint though and it's stopping the current, not the truck. I'll have to take it on a long drive and see what occurs. Most of my trips are very short and the AGMs weren't charging satisfactorily and sync hit low power mode too often which started me on this path. I want greeting mode and sync to work 100% of the time because that's my expectations.

 

[Davexxxx]

"Simply put, I'm someone who's not afraid to break shit."

I'm very interested in learning about your LFP experiment but most of what you wrote there, was way over my head so, I'm in the opposite camp.

I AM afraid of breaking shit. Especially on a brand new 70K vehicle, that is so different from anything in my previous experience, of which, seemingly any alteration, could void a very important and valuable warranty.

Anything above reading on board codes, is out of my wheelhouse, so even using Forscan would be a steep learning curve. I just haven't needed such things on my vehicles that are more then old enough to vote.

I know just enough about Lithium batts to be reasonably proficient re RV use, or trolling motor batts but nothing, when hooked to an engine, or it's charging systems.

 

[HammaMan]

"Simply put, I'm someone who's not afraid to break shit."

I'm very interested in learning about your LFP experiment but most of what you wrote there, was way over my head so, I'm in the opposite camp.

I AM afraid of breaking shit. Especially on a brand new 70K vehicle, that is so different from anything in my previous experience, of which, seemingly any alteration, could void a very important and valuable warranty.

Anything above reading on board codes, is out of my wheelhouse, so even using Forscan would be a steep learning curve. I just haven't needed such things on my vehicles that are more then old enough to vote.

I know just enough about Lithium batts to be reasonably proficient re RV use, or trolling motor batts but nothing, when hooked to an engine, or it's charging systems.

Lithium chemistries are great for their really low resistance. This can be an issue when connected to a power source like an alternator because they can eat everything it throws at it and the alternator goes to 100% power output. This changes with battery size so that's why I'm testing this. If it only pulls 70a to charge, that's safe for all F150 alternators. The PB is a great platform to test with as it's got beast mode 12v generation capabilities, and it's primary is water cooled so it can happily produce its 220a output all day long. The aux batt is on a 125a circuit and a ceiling for such a fuse is 100a for prolonged draw. One easy hurdle passed is that it appears to be on a T-class fuse (sand filled) which is the proper way to fuse a low resistance battery.

I'll be more open on the specifics once I'm satisfied with its behavior.

 

[scott011422]

Well the AGM isn't being used at all so there is no charge curve for it. The battery I'm using is LiFe P04, not lithium polymer. There's a handful of lithium chemistries that people sometimes mix up. Li-ion and LiPo are 2 entirely different chemistries than LFP.

The PB's operation is likely different than the other trucks. That curve you posted looks like it charges and then consumes the batt. The PB will often keep its voltage in the mid 13s once the batts are full. The DC/DC takes up 100% of the power load of the truck, reacting extremely fast to current spikes (it's basically running in a CV mode)

The aux batt isolator (technically it isolates the aux batt and the internal fuse box from the under-hood and starter) is only opened briefly while the flywheel starter is commanded on. On the PB however I haven't seen it open when it uses the belt starter as it's got the DC/DC running. It could be happening really fast as my data has a 1hz refresh. I may try and find it in forscan during a data capture. I expected that to throw a code but I haven't thrown any codes at all accept for the missing rear seat.

A side benefit, the powered running boards move quite fast having that happy voltage and low resistance battery powering them. It's a truly noticeable difference with the truck off.

The truck does in-fact charge the LFP up, extremely fast peaking at 75a until it's charged (reaching the 3.5v cell limit) and the LFP's BMS stops inflow current. The LFP is reaching my max charge setpoint though and it's stopping the current, not the truck. I'll have to take it on a long drive and see what occurs. Most of my trips are very short and the AGMs weren't charging satisfactorily and sync hit low power mode too often which started me on this path. I want greeting mode and sync to work 100% of the time because that's my expectations.

Sorry for the confusion, I'm aware of the differences, I was just trying to simplify since most people are familiar with lipo. No Worries.

That's exactly what its doing. Defiantly likes to cycle the battery. Especially with the shorter trips, the PB would see a great improvement if it ran a lithium main and AUX batt. As you said, The DCDC can supply huge amounts of power, Couple that with a fast charging Lithium battery and should have no trouble topping off day to day in a few mile drive.

Have you checked the size of the wire supplying the AUX battery? Its intended more as a system maintainer. With the increased ability to supply and absorb power, Can the existing power wire hold up to that?

 

[Snakebitten]

Again, I'm just waiting for the braintrust of this thread to find a solution that FOR ME is preferable to the effort I currently make to keep the Powerboost AGM 12V battery health above drowning.

In other words, I have been using battery tenders and chargers for years. Common on my motorcycles and sports cars. Some because of casual use. Others because they are notorious for parasitic draw. (Porsche)

I'm coming up on 365 days in service.
I have never reset the BMS

As much as I want my battery to sit at 12.7V when parked, I've come to terms with it not being nearly as scary to be at 12.3 than I once thought. Lol

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