larryh

The following link provides some details about the BMS for the Ford F150, which is probably similar to the Ford Fusion Hybrid BMS: http://www.f150forum.com/f38/battery-management-system-reset-109656/. The post talks about the BMS using a Hall Effect Sensor near the negative battery terminal, which implies that the BMS is measuring current flow. It also refers to SOC drain timers and load shed. I assume load shed refers to shutting down non-essential functions to conserve 12 V battery charge when SOC is low, i.e. battery saver mode. The BMS SOC can be reset to a default of 85% (FORScan offers that option) along with the SOC drain timers. This stops load shedding, and probably battery saver mode (at least until the car learns the actual SOC). It takes approximately 8 hours for the BCM to learn the correct battery SOC, when the car is left undisturbed.

The ICE supplies more power (by burning more fuel) to charge the HVB when the charge is low vs. when it is high.

When I look at the 60 mile commutes, the SOC of the 12 V battery generally increases by 2-3%. For the 15 minute commutes to and from work, it increases by 1-2%. Overnight and during the day the SOC decreases by at least 2-3%, probably more. So once the charge on the 12 V battery starts getting low, I don't see how the car can keep up if the only opportunity to charge is when the car is on while driving to and from work or during the 60 mile commutes. The only way my car keeps up is by charging the 12 V battery when it is plugged in overnight to charge the HVB. The question is should the car be able to keep up to maintain 100% SOC, and if so, why isn't it doing so?

I don't think there is anything wrong with the 12 V battery. I am only posting my observations in the hopes that they may provide some insight into how the car maintains the 12 V battery. My typical week consists of a 60 mile round trip plus 15 minute commutes one-way to and from work. Since I have the Fusion Energi, the car also has the opportunity to charge the 12 V battery overnight while charging the HVB. Prior to applying the TSB, the SOC of the 12 V battery averaged 69% over two months. I check the SOC each morning. It ranged from 55% to 84%. I think it needs to get below 50% for battery saver mode. So even with the opportunity to charge each night, the car was unable to maintain full charge to the 12 V battery. Now after applying the TSB, the car is much more aggressive in charging the HVB. It has spent many hours drawing power from my 240 V charger to charge the 12 V battery, at least 24 hours, and has only managed to get the SOC up to 91% (I'm not sure that the SOC measurement is accurate. I think the typical accuracy of most battery management systems in measuring SOC is about 5% to 10%). I will have to see in the coming weeks how effective the new programming will be in maintaining the 12 V battery. If the Fusion Energi has so much difficulty in maintaining 100% SOC, the Fusion Hybrid will have a much more difficult time since there is no opportunity to charge the Hybrid overnight by plugging the car into a 240 V charger. Since I don't experience the battery saver message, it would be informative to compare my observations with a Hybrid that does experience the problem.

Now I am confused what the car is doing. If I turn the car on and off when it is plugged into the charger, it will start charging the 12 V battery for up to four hours at about 14.5 V. It did not do that prior to applying TSB 14-0020. It currently claims the SOC is 91%. When I measure the voltage of the 12 V battery with no load after sitting for 20 minutes, it reads 12.99 V. That seems rather high. I wonder if it is underestimating SOC and now overcharging the 12 V battery. I notice that the count of start/stop events recorded by the BCM was zeroed out when they reflashed by the modules. I wonder if there are parameters associated with the 12 V battery that are incorrectly set. It reports the correct age for the 12 V battery, 444 days.

FORScan provides access to hundreds of PIDs. You can download it from forscan.org. You should be measuring the 12 V battery level when there is no load on the battery, about 20 minutes after the car is turned off and all the doors are closed. The voltage should be at least 12.6 V. A more complete list of PIDs is here, but you have to translate the X-Gauge codes: "http://fordfusionhybridforum.com/topic/6503-scangauge-ii-x-gauge-codes/?p=50199". See the following thread: http://fordcmaxhybridforum.com/topic/2757-obd2-%E2%80%93-elm-327-%E2%80%93-torque/ The lists are missing the headers, which are needed to specify the module containing the PIDs.

I tried the EBH after applying TSB 14-0020 twice now. The SES light did not come on either time. For the second trial, the outside temperature was 70 F. The coolant temperature reach 149 F. The inverter temperatures for the generator and motor were 87.8 F and 91.4F. The temperature differences between the inverter temperatures and the coolant temperature was more than 30 C, which was the threshold for turning on the Service Engine Soon light. The temperature thresholds were also exceeded for the first trial. The real trial will be this coming winter.

The dealer was supposed to check the 12 V battery during the inspection. I let the service manager know. He claims everything was fine. But, I didn't talk to the technician servicing the car, so I can't verify that they actually tested it. The service manager just seems to say yes to all your requests, but I have a suspicion they don't actually make it to the technician servicing the car and they don't actually ask the technician if your requests checked out OK.

My college degrees are in Physics/Math/Computer Engineering, so I should be able to figure these things out. After the upgrade to the SOBDMC, SOBDM, PCM, and BECM, the car is now very persistent in charging the 12 V battery when the charger is plugged in. Prior to the upgrade, the only time it charged the 12 V battery was when the HVB battery needed charging. Now, it charges the 12 V battery if the car is plugged in and the HVB is fully charged. It charged the battery for four hours this morning until the timer shut off the charger. The SOC has gone from 86% to 88%.

From what I have read, the Ah capacity of a car battery is usually measured using a discharge rate that results in a full discharge over 20 hours. The rated capacity of the battery is 43 Ah, so a discharge current of about 43 / 20 = 2.15 amps should be used to measure the battery capacity. I was using 23 amps. The observed battery capacity decreases with increasing current draw according to Peukert's law: the capacity of the battery in Ah at a one-amp draw rate is where I is the actual draw rate, k is the Peukert constant which ranges between 1.1 and 1.3 for a lead acid car battery, and t is the time to discharge the battery. Going through the math, it should take between 0.92 to 1.48 hours to fully discharge the battery at 23 amps assuming a capacity of 43 Ah (for k ranging from 1.1 to 1.3). I estimated 1.32 hours if the battery were fully charged. But I doubt the current flow would remain 23 amps as the SOC reaches 0%. There are too many unknowns and assumptions to draw any firm conclusions regarding if the SOC is being measured correctly or the capacity of the 12 V battery is actual 43 Ah.

I had some TSBs applied yesterday to the car. TSB 14-0020, to fix the issue I was having with the Service Engine Soon light coming on when using the Engine Block Heater, seems to have changed the car's behavior with respect to charging the 12 V battery. It appears the technicians reflashed the SOBDMC, BECM, SOBDM, and PCM. For the past three trips, the DC to DC converter voltage setpoint has been 14.7 Volts the entire time. Before, it initially started at 14.3 Volts and later dropped to 13.3 Volts. I will have to monitor to see if the behavior has also changed while charging the HVB. At the end of the third trip, the SOC was 84%.

Note the car is running both the AC and the heater at the same time.

The Fusion Energi turns on the electric heating element when the AC is on (and the AC light is illuminated). The higher the temperature setting, the more likely the heater will be on. If the temperature is set to LO, the heater does not come on. If you raise the AC temperature setting past a threshold that I have yet to determine, the heating element turns on. Then to turn it off again, you have to lower the AC temperature setting past a different threshold. This is very inefficient. You want to raise the temperature setting to reduce energy usage by the AC. But instead, the heater comes on and consumes even more energy than had you left the setting at a lower temperature. You need to monitor the energy usage of climate on the car's left display and choose a temperature setting that minimizes energy usage. It was 80 F outside. The inside temperature was also 80 F. As I varied the temperature setting, the AC power ranged from 0.5 kW to 0.8 kW. The heating element power ranged from 0.0 to 1.2 kW. During the 6.5 minutes I observed the power usage of the AC and heater, the AC used 0.06 kWh of energy and the heater used 0.07 kWh of energy. The heater used more energy than the AC. Why is the car wasting energy running the heating element when its hot out?

When looking through the logs I have made while driving and charging the car, I observe the DC to DC converter voltage applied to to the 12 V battery as follows: Percentage of Time Voltage 44% 14.3 50% 13.3 5% Off

After my drive this morning, I am now charging the HVB. Initially, the DC to DC converter was not even enabled--the car was not charging the 12 V battery at all while charging the HVB. About half an hour later, it enabled the DC to DC converter and is now charging the 12 V battery at the lower voltage level of about 13.3 V.

When I connected a charger to my 12 V battery this weekend, within a minute the green light indicating the 12 V battery was full came on. The car reported that the SOC was 72% before connecting the charger. Just like when I turn the car on, the current started out at about 20 amps and then dropped to about 2 amps within four minutes. So I believe the 12 V battery is just fine. I'm not sure charging it with an external charger is going to do anything useful.

It would be nice to know how they are determining the 12 V battery SOC and how accurate it is. I suspect they keep track of the amount of current flowing into and out of the battery. Obviously, the car tracks the 12 V battery current and voltage, or I wouldn't be reporting it. It also tracks the 12 V battery estimated temperature, age, and type. Finally, it has several counts that it maintains: Cumulative Battery Charge When Ignition Is On, Cumulative Discharge From Battery When Engine Is Off, Cumulative Discharge From Battery When Engine Is On, and Cumulative Discharge From Battery in Sleep Mode. I suspect this method requires a good model of how the battery works. Unfortunately, batteries don't always work as expected, and then the model would no longer accurately describe how the battery works and would yield incorrect results.

Note the first time that I did this unintentionally, the voltage fell significantly more after 25 minutes than the other day. But that was when it was cold at the beginning of February. Both times, the voltage started out the same at 11.65 V. In February, the voltage dropped to 10.85 V after 25 minutes. This time, it fell to 11.3 V.

I have an annual inspection coming up with the dealer soon. They check the battery as part of the inspection. People might find my observations useful.

This morning, the car charged the HVB and the 12 V battery from 12:56 am to 2:44 am. The SOC of the 12 V reached 72% (it was at 51% last night after my experiment posted above). It then continued to charge the 12 V battery until 4:57 am. The final 12 V battery SOC was 73%--the SOC didn't increase very much during these last two hours. This time, the car provided 14.3 V for the 12 V battery the entire time. How many hours does it take to fully charge a 12 V battery? I will have to see what an external battery charger does. Since the car is plugged in all night every night, I don't see why the car shouldn't be able to maintain the 12 V battery at 100% SOC. It seems very strange that 2+ hours of charging each night can't maintain the 12 V battery at 100% SOC. Either the car is not measuring the SOC properly, the battery is not working as expected (although I have not had any problems with the battery), or the engineers don't think it is important to maintain the battery at 100% SOC. I noticed about 5 minutes into my commute this morning the DC to DC converter changed the 12 V setpoint from 14.4 to 13.3 volts, even though the 12 V battery SOC was 73%.

I tried a simple experiment to verify what SOC is measuring. I plugged the car into the 240 V charger with the charger turned off and turned on the car. When I do this, the DC to DC converter is disabled and the entire 12 V power supply to run the car comes from the 12 V battery. The lights, radio, and other accessories in the car consumed 23 amps of power for about 25 minutes. The SOC dropped linearly from 81% to 51% (R^2 = 0.9976, where 1 is perfectly linear). The equation for SOC vs. time was: y = -0.0211x + 80.695, where y is SOC in percent and x is time in seconds. Interpolating (which probably is not accurate), if the SOC were 100%, it would take 100/.0211 = 4739 seconds or 1.32 hours to discharge the battery drawing a current of 23 amps. That means the capacity of the battery is 23*1.32 = 30.2 Ah. The rated battery capacity is 43 Ah. I don't know the actual procedure used to compute battery capacity. At 51% SOC, the car no longer powers the power points after turning off the car. So it definitely recognizes that the 12 V battery is low and is trying to conserve energy. I previously did this unintentionally. The car stopped working after 45 minutes. So extrapolating, the car is completely dead when the SOC is about 25%. I don't intend to repeat this experiment again to determine the actual value.

Note that I have a Fusion Energi. The SOBDM module controls charging of both the High Voltage Battery and the 12 V battery when the car is plugged into the 120 V or 240 V charging station. It decides when and how much to charge each battery. I have it programmed to charge the car starting around 1:00 am when the electric rates are low. This an excerpt from the following document http://www.motorcraftservice.com/vdirs/diagnostics/pdf/OBDSM1303_HEV.pdf. The SOBDM, also known as the Battery Charger Control Module (BCCM), is an air-cooled component that charges both the high voltage battery and the low voltage (12V) battery when the vehicle is not operating and plugged into a (110V or 220V) EVSE. The SOBDM is known as the on-board charger. Its primary function is to coordinate charging operations and convert AC to DC. The SOBDM incorporates an integrated module that communicates with other modules over the HS-CAN, and is located inside the high voltage battery pack electronics compartment.

If you have an ELM 327 scanner and a PC, you can download FORScan to get all the available PID measurements. Go to forscan.org. The latest version of Scan Gauge may also show them. I'm not sure if it is readily available yet. I saw a discussion regarding that at the MyFord Mobile web site recently.

The commute to work is only 15 minutes. The current to the 12 V battery was near zero during the last five minutes. The SOC went from 82% to 85% during the commute. The resolution of the current measurement is only one amp, so I can’t measure fractions of an amp. I will need to continue to monitor the car to see how the SOC gets down to 55%. So far in the past day it is has mostly gone up, from 55% to 85%. A few weeks ago Sunday, I recorded what the car was doing while charging the HVB. The car charged the HVB for about two hours. The SOC of the 12 V battery was 73% at the beginning and 76% at the end. The car maintained 14.5 Volts to the 12 V battery for four minutes. Then dropped the voltage to 13.3 Volts for the remainder of the time. During the first four minutes, the current dropped from 13 amps to 4 amps. The SOC rose from 73% to 74%. After the voltage drop, the current was less than an amp—the car doesn’t show fractions of an amp. The SOC rose to 76% by the end of the two hours. If the car wanted to aggressively increase the SOC of the 12 V battery, it should have maintained the 14.5 V to the 12 V battery the entire time. But it didn’t. I have no idea why yesterday it decided to aggressively increase the SOC from 72% to 85%, but three weeks ago Sunday, it only decided to go from 73% to 76%.

Today, the car seems to prefer 85% SOC for the 12 V battery. This morning, it began charging the HVB at 1:30 am. It immediately charged the 12 V at the same time to 85% SOC. It finished charging the 12 V battery first, but continued to charge the HVB until 3:40 am. When I left this morning, the 12 V battery SOC was down to 82%. I measured the voltage of the 12 V battery to be 12.75 V with no load. Normally, 12.7+ V is considered 100% SOC. Driving to work, it immediately started charging the 12 V with 13 amps of current. The current gradually dropped to less than 1 amp when 85% SOC was reached and the car then continued to maintain that SOC. As soon as I turned the car off, the car immediately drew 23 amps of current from the battery. I only continued to monitor it for a few seconds after that. I suspect that 85% SOC is the max it is going to charge the 12 V battery to. The car seems to be maintaining the 12 V battery correctly.