OK... I told myself I wasn't going to post this because it wasn't sure I wanted to hear all the theories about something horribly wrong with my FEH - Buuut... I had a recalibration event last weekend that was very strange indeed. It began as usual, even though I've only recorded 3 events in the 16 months or so that I've owned it. It's pretty unmistakable when it happens. I took pictures of the scan gauge last time it happened as the SOC climbed all the way to 98% before it finally let go to discharge back to normal range. This time the SOC got up to about 88% but I had reached my destination and had to stop. When I restarted, I was in town and only had a few miles to drive and so had to shut it down again before the recalibration finished. On the next short trip the recal finally finished and it started discharging back down to 53%. No big deal right. Well, the next morning when I started it up, the SOC was at 4%. You read that right, four percent! I have never seen or heard of this phenomenon before. What's worse is that the ICE ran normally until I put it in reverse to back out of my garage. Then it revved up to about 2500 and surged several times. I put it back in park and it settled down after that. Put it back in reverse and the drove to the store (about 3 miles). It's been fine ever since that. All this happend between last Saturday afternoon and Sunday Evening.

Has anyone experienced anything similar to that? How could the HV battery get discharged all the way down to 4% overnight with nothing draining it? It was as if there was a dead short that completely zapped the HV battery overnight. It was definitely in the normal range when I got home the night before.

I don't mean to derail this thread. The situation that happened to Don seems somewhat similar.

No lights, no codes, no warnings... Just some strange behavior. It's been very much normal all week ever since.

 

Good idea, made me rethink what happened. I'm positive that I had it in L not N as we were creeping along slowly but continuously.

 

That is strange behavior and I don't have a theory about how the battery could drain overnight to 4%. When you drove away with the low SoC did you have electric assist? IIRC it's disabled below 30 or 35%.

My situation hasn't reoccurred and I have tried to force that scenario again but it always starts the ICE at 40% SoC. But what did happen today on a 35 mile loop of city/highway driving was a jump in mileage to 35.1mpg from my usual 31-32mpg for that loop. I don't see how it could possibly be related but the increase in SG mileage was significant.

I feel somewhat on edge with this vehicle, waiting for the other shoe to fall, another disabling event of some sort like the MECS pump failure.

 

Corey, your FEH does a shutdown procedure when you turn the Key Off. Everything does not shutdown at once by the PCM, but the PCM must be grounded properly to shutdown all the hybrid modules in order. The only way to drain the HV battery with the Key in the Off position is the PCM did not shutdown those modules and they continued to allow the HV battery to supply the 12V battery with a charge through the DC/DC converter. Modules that don't shutdown like the eCVT, HV battery, and those that provide electric power steering, brakes, coolant motors and even the radio continue to drain the batteries.

The 12V battery had enough charge for the relay to start the engine with MG1, and MG1 had enough power to start the engine with the HV battery. After the start of the engine, the HV battery poured juice to the 12V battery and the 12V system further reducing SoC. I bet you had not noticed the SoC level until you shifted into reverse or got that high RPM.

I sort of think you have a dirty ground connection on the 12V battery or the ground to the PCM. That would be the cheapest to fix. If the problem continues, the ignition switch or PCM programming could have a glitch and need to be reflashed.

GaryG

 

You're correct - I didn't notice anything until I put it in reverse and the engine started behaving strangely. That's when I looked at the SOC and saw the 4%. I couldn't believe my eyes. To answer Don's question: The electric assist seemed to be disabled. After I put it back in park, the engine settled down and I let it idle for about 10 seconds before I tried again. Then it was fine. I suspect it might have been nearly stone dead when I first tried it as Gary is alluding to because I didn't look right away. So far I've driven about 100 miles since this goofy thing happened and everything seems normal. I've read some posts about the ground issue... That's a good suggestion Gary. If anything more happens I'll be looking into that for sure.

As for the explanation of how the SOC could have gotten so low overnight, Gary's explanation seems reasonable enough. Sure seems like there would have been some kind of warning though. Something had to be pulling a significant amount of juice after I shut it off.

By the way... Can you help me out with the acronyms please? What is MG1?

 

Sure, MG1 is Motor/Generator 1, mostly referred to as the generator and starter motor. MG2 is the Motor/Generator 2 which is referred to as the Larger Traction Motor. They are both used in the eCVT as motors and generators. MG1 is a motor used to start the engine and a generator being turned by the engine to charge the HV battery up to 53% SoC and higher during a battery recal. MG2 is a motor that turns the wheels in EV mode, and assist engine power during acceleration. MG2 is also a generator driven by the wheels during deceleration and is also used as a brake in regenerative braking up to 60% SoC. MG2 turns in the reverse direction to back-up the vehicle. There is no reverse gear that is powered by the engine, so that's why you got all that stuff with the battery low in reverse.

GaryG

 

Learning all kinds of good stuff here... Thanks Gary. I knew there was no reverse gear so it made sense that things were a little messed up when the battery was sitting at such a low charge. It behaved as if the computer didn't know what to do. I think once the SOC got above... Well... Essentially DEAD, the computer found it's brain again and it settled down. Sure would like to know what caused it though. I hope I don't find out the hard way. I'm going to check the grounding locations for sure.

I was unaware that there are two motors. Where can I find more of the technical system information like this? You must have gained the information from an available source, or do you work for Ford? I enjoy learning how the system works.

 

I don't work for Ford but I've worked on Fords for 45 years. First rebuilding big block engines, then building race engines and racing Fords. I got married and sold my racing equipment in the early '80's and started a family. SUV's and gas prices were going higher, so I made a big change with ordering my first hybrid in December of '04 which was the '05 FWD FEH I recently sold.

I was so impressed with the '05 FEH and hypermiling, I did as much research on the FEH operation I could find. I researched and found the FEH patents, bought all the technical and repair manuals and read all the engineering papers written on the FEH. I've been posting and debating here and learning like you now since 2005. Hypermiling is a hobby of mine and the only way to get better is learning how the FEH works.

The PCM ground for instance came from what I read in the '05 FEH PCM/ED manual. I think it was BillyK that posted first that his HV battery drained while working on the radio with the 12V battery disconnected. I put two and two together with what I read about the module shutdown by the PCM, and figured Billy disconnected the 12V battery before the the PCM shutdown the modules.

My Ford dealer allows me to talk to the Hybrid Techs because they learn from my research and I learn about repairs they are making on the hybrids. I was the first to find out and post about problems with the electronics coolant pumps because the Hybrid Techs told me about the problem and repair attempts they made to fix bad wiring to the motor. My '05 FEH never had a problem with the pump or a need to change the battery blend door or I would changed them myself.

I'm also very impressed with my '09 FEH which has many improvements over my '05 FEH. The first thing I did was purchase the repair manuals when they became available. I compared the '05 and '09 manuals to verify the changes Ford engineers said they improved.

GaryG

 

I appreciate the insights Gary. Based on what you've written here, my best guess at why it discharged like that may have to do with the calibration cycle itself. As in, I think it's very possible that the cycle did not actually finish before I shut it off at the end of my drive. It was definitely still in discharge mode on its way back to 53% when I shut it off. Does this seem like a reasonable theory based on what you know about the recalibration cycle? In the past when I've experienced a recalibration event, I was on a longer drive. The cycle was able to complete all the way through well before I shut it off. It does seem like a malfunction of sorts as you suggested, but if the right conditions existed I have to wonder if the "perfect storm" of logical/conditional events occurred here and the PCM got caught in limbo between logical conditions, effectively leaving the loop open and zapping the HV battery... How's that for a theory?

 

garyg's advice on grounds is good advice. On my oldest car (437,000+) I some years ago started running parallel groundpaths with heavy gauge wires as a result of some funny happenings.

Now with my 06 FEH (117,000+) I'm beginning to wonder if I need to do something similar. Specifically I have now had two occasions where a few miles after a rumbly tumbly dirt road I received a "Check Engine" light. On shutting down and doing a DTC check none were stored. Couldn't find what triggered the lights.

In my experience on shipboard electrical wiring when you see such things the likely culprit is ground circuits.