HVB Drain from 45% to 0% While Parked During Workday?

[DrDeke]

I bought a used 2012 Fusion Hybrid about a month ago and had something strange happen when I drove it to and from work this past Friday.

 

[Note: Every time I mention the state-of-charge (SOC) of the high-voltage battery (HVB) in this post, I am referring to the indicator on the dashboard, which I realize indicates the "usable" part of the battery's power, not the true, absolute SOC of the battery.]

 

Everything seemed normal when I drove to work. When I parked the car near the office, the HVB SOC was just under half; probably about 45%. I parked, turned the car off, removed the key from the ignition, locked the car, and walked into my office around 8am. When I got out of work around 5pm and started the car, the dashboard battery indicator was at 0%. The ICE started running as soon as I started the car, and did not stop until the HVB was close to 50% charged. After that, the car drove normally for the rest of the trip home.

 

I drove the car extensively on various trips and errands today and everything seemed normal.

 

I'll be curious to hear if any of you have any idea what might have happened here.

 

Cheers,

DrDeke

[borland]

Same thing happened to me, probably four weeks ago. It was quite a surprise to have the engine start with the ignition key. Same SOC before and after conditions as you. I have a 2010 FFH.

 

I've owned the car for over two years and never experienced a HVB drain like that before. Since then, it hasn't happened again.

 

Also, the HVB battery re-conditioning cycle has only happened once since I've owned the car. That's where it charges to 100% SOC regardless of driving conditions.

 

I was thinking the HVB drain might have been caused by a faulty relay that was stuck on, but is behaving fine since? Initially, I was running out to the garage ever few hours to check the SOC by turning the ignition switch on, however no drain was ever detected. Before this happened, I've always been amazed at how well the HVB maintains the same SOC after several days of not being driven.

 

It would be nice to know why this happened.

[lolder]

I had it happen once at about 74 K miles a few months ago in my 2010. I'm not sure it wasn't a software glitch instead of an actual discharge.

[DrDeke]

Argh! This happened to me again today; exact same situation. Maybe the car is trying to tell me it's a mistake to go to work?

 

I'm off on an ~8 day road trip tomorrow, but after that, I guess it's off to the dealer at least if it happens yet again. (I've only got 63k miles on it, so this should be covered under the hybrid powertrain warranty.)

 

If I have it right, the only potential loads connected to the HV bus are MG1, MG2, the A/C compressor, and the DC/DC converter. I wouldn't expect the MGs or the A/C to pull any power with the key off, but I'm not sure whether the DC/DC converter would operate in a "has HV power, but key is off" state. If that is what's happening, I suppose floating the 12VDC system *might* be able to bring the HVB from 50% to 0% dash-indicated SoC over 8 hours maybe?

 

Ballpark figures here, the Gen1 FFH battery is rated at something like 2.1 kWh actual-full capacity. IIRC, 100% SoC on the dashboard means something like 60% actual SoC, and 0% dashboard is something like 40% actual SoC. So that would leave a 10% "real SoC" difference between dashboard 50% and dashboard 0%. That would amount to 210 Wh of actual power... At 12 V (the output of the DC/DC converter), that would be a current of 17.5 A for one hour, or 2.2 A for 8 hours. Ok, I could maybe buy that; if the HVB relay is stuck closed, and the DC/DC converter continues to operate (although I'm not sure whether it would), I could see it maybe ouputting 2.2 A for 8 hours, between battery charging/floating, whatever loads are still active on the 12 V bus, and conversion losses...

 

I guess I could take a multimeter to the 12V battery terminals the next few times I park the car. What's the nominal full-charge voltage on one of these batteries, something like 12.6V? If that's the case, and I measure it at 13.8+ with the car off, then I guess we've found the problem.

[lolder]

The HVB is about 1.35 Kwh. The level of charge should not change while the car is off The HVB is disconnected while the car is off. Are you certain you are turning car off ( dumb question, I know ). "H" is about 80% SOC and "L" is about 30%.

[DrDeke]

Ehh, no such thing as a dumb question, especially when troubleshooting someone else's problem :). Anyway, yes, the car is definitely off: I turn the key to the off position, remove it from the ignition switch, press the lock button on it, and put it in my pocket. The car appears to shut off normally; the "end of trip" mileage summary shows up on the dashboard, etc.

 

I know the level of charge isn't *supposed* to change while the car is off, but it has done it twice on mine, so I was just kicking around ideas about what kind of fault might cause it, like borland's HVB relay theory. Seems plausible to me, except I'm not sure the DC/DC converter would stay on when the car was "off" even if the HVB relay did fail closed/on...

[lolder]

I think if the HVB relay failed closed, there might be a warning message. That's a bad situation and if I were Ford I would have put in a system to detect it. There are dozens of other monitors for far less important functions. That's just an opinion.

[DrDeke]

I agree; from what I've read about the large number of fault conditions that do cause warning messages, I would have guessed that would trigger one too. It would certainly be easy enough to detect, as well.

[DrDeke]

OK, this is just weird now. I went on vacation for a little over a week - no problems whatsoever. I come back to work yesterday, and today the problem happened again! I guess it's off to the dealer I go tomorrow. This oughtta be "fun" :/ .

[hybridbear]

The BECM monitors the current flow in & out of the HVB. It uses that data to estimate the HVB SOC, based on voltage. But the SOC of a battery can't really be measured until the battery has been at rest for a time. When the car is off, the HVB is disconnected & at rest. Then when the car is turned on again, the BECM can reassess HVB SOC based on voltage. It's common in the Energi to see something like this. If you drive using a large portion of the HVB & then turn the car off, the HVB SOC will usually drop while the car is off. Conversely, if you plug in the car & charge immediately after you have been driving, before the HVB can rest & reset to a lower SOC, until it shows around 95-97% and then stop charging, the HVB will change to showing 100% SOC once the HVB has the chance to rest.

[DrDeke]

I finally caught this happening on video:

 

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

 

My Ford dealer says this is absolutely not normal or correct behavior, but doesn't know what's causing it or what to do about it. They did ask me to show them the video if I managed to catch it happening, so I'll do that tomorrow and see what they say...

[lolder]

I know you didn't do this but part of this is what happens if you leave the car in accessory key position. The various loads in that mode on the 12 v system cause the DC to DC converter to draw the HVB down to the low HVB shutoff point which is considerably lower than the normal low point where the ICE starts. The 12 vdc battery would be dead in that case which was not your situation. You need to leave the car with Ford and get them to fix it under the hybrid warranty. The HVB should be completely disconnected with the key off. The HVB is either discharging internally or there is incorrect sensing. The fact that the car charges to the correct point and operates normally points to a bad HVB. Keep us up to date.

[DrDeke]

Yep, that's what I'm working on. I left it with them for a day, they said they didn't find anything and wondered if I could leave it with them for "a few days." I then left it with them for a week while I was out of town but they still didn't find anything. After that, one of their technicians asked around at a Ford training program he was attending, but said no-one there had ever heard of a problem like this.

 

Next step is to go to the dealer tomorrow and give them a copy of the video and see what they say then :/.

[murphy]

Yep, that's what I'm working on. I left it with them for a day, they said they didn't find anything and wondered if I could leave it with them for "a few days." I then left it with them for a week while I was out of town but they still didn't find anything. After that, one of their technicians asked around at a Ford training program he was attending, but said no-one there had ever heard of a problem like this.

 

Next step is to go to the dealer tomorrow and give them a copy of the video and see what they say then :/.

There is an easy way to prove or disprove that it is a problem with the HVB. Fold down your back seats and there is an access door to the HVB disconnect. Shut the car down normally and then remove the disconnect. That completely isolates the HVB so any loss of charge would have to be from self discharge. When it is time to drive the car again, put the disconnect back in place and start the car normally. If the battery is discharged the problem is in the battery. If the battery is still charged to where it was when the car was shut down then it is in the car. When the car is shut down a contactor opens that does the same thing as pulling the disconnect. If the contactor has failed in the closed postion, that would explain the problem. The only other explanation I can think of is the car is engaging the contactor while the car is off. That should not happen.

[jeff_h]

Next step is to go to the dealer tomorrow and give them a copy of the video and see what they say then :/.

 

I watched the video, and my 2010 FFH did that same thing probably a handful of times (maybe more, don't remember exactly) over the years, which was strange but no malfunction lights ever went off and all was fine afterward. That car currently has about 215k miles now and the HVB is still fine, so I'm curious to see if the dealer can find some type of internally stored error code in your car.

 

But thinking back I think my Prius did that now and then, first time it happened I was upset and said hey where did my charge go???

 

However the best/strangest was in 2014 when we were on a road trip to Florida in her Fusion Energi, we had driven down to FL for a week and so the 20-mile HVB was long long gone and we never plugged in during the week-long vacation - we stopped at Cracker Barrel in SC on the way back and when I started the car again to leave it showed 2 miles of EV range, which I thought was really really strange. But everything drive fine and once we finally got home it charged up fine and no problems, just a really strange occurrence.

 

So again I am curious as to whether they will find something in your car, but from my experience these cars have exhibited seemingly quirkly behavior in the past (like noted above and also the conditioning cycle which makes the ICE charge the HVB to where you think it's going to explode when experienced the first time), so unless some type of warning notice appears I don't worry too much about it when it happens.

[DrDeke]

murphy:

 

That is an excellent idea, thanks! Unless the dealer has some better idea after watching the video, I will propose your plan to them. If I pull the HVB disconnect every time I park the car for 2 or 3 weeks and the problem stops happening, that would definitely seem to isolate the problem to "not the battery pack itself."

 

 

jeff_h:

 

The dealer checked for error codes (as did I, although I think the dealer's equipment might be able to access more codes than mine can) and did not find any codes stored.

 

I do understand that battery SoC estimation is not an exact science, but I don't think that is what's happening here. Going from 40-60% to 0% would be a pretty large gap in estimation, and, if that were happening, I would expect the car to behave oddly either before or after the jump (depending on which state of charge is actually correct). What actually seems to happen is that the car behaves completely normally "before" the jump to zero, and after the jump to zero, the ICE runs constantly until the indicated charge is back around 50% even when conditions would otherwise cause the ICE to shut off. It seems to me that this indicates that the HVB charge was actually low, and that it is actually being significantly recharged by the ICE.

 

The other thing as far as this being a normal glitch goes is that it has happened 8 times in the fewer-than-three months that I've owned the car. That comes out to every one and a half weeks on average, which nobody else seems to be experiencing.

 

 

In general:

 

This is probably stuff that most everyone here already knows, but here is why I am concerned about this problem, beyond just "I don't think the car is supposed to do that":

 

1. The HV battery and many of the other HV components are expensive parts which are, for now, under warranty, but will not remain under warranty forever.

2. Hybrid vehicle HV batteries are designed to be charged and discharged carefully and within strict limits by the vehicle's energy management system. When the dashboard on a hybrid car indicates that the HV battery is at 100% charge, the true state of charge of the battery is considerably less than 100%. Likewise, when the dashboard indicates that the HV battery is at 0% charge, the true state of charge of the HV battery is considerably higher than 0%. Maintaining this narrow range of charge states is one of the reasons that the HV batteries in hybrid vehicles last much longer than a typical cell phone or laptop battery. Discharging a hybrid HV battery beyond its designed-for state of discharge (or under conditions beyond its design specification) can easily do permanent damage to the HV battery which might not become apparent until well after the battery is no longer under warranty.

3. In the 2012 Ford Fusion Hybrid, the HV battery is the *only* power source capable of starting the car's internal combustion engine. This means that if the HV battery is discharged beyond a certain point, the car will not start. If this happens, the car must be towed to a Ford dealer, and most Ford dealers do not have the necessary equipment to recharge a drained HV battery on hand. The Ford dealer will have to request the necessary equipment from Ford corporate (or another dealer), which will cause extended delays and cost me a lot of money for alternate transportation during the delay.

[jeff_h]

The other thing as far as this being a normal glitch goes is that it has happened 8 times in the fewer-than-three months that I've owned the car. That comes out to every one and a half weeks on average, which nobody else seems to be experiencing.

 

Yeah I agree that seems pretty often, hopefully they find a good reason.

[lolder]

In the 2012 I don't think the rear seat folds down easily to reach the disconnect.

[murphy]

It wasn't easy in my 2010 until I read the first responder document and learned how to do it. It was very easy once I knew the procedure.

[borland]

Just to update to my earlier post about experiencing the same HVB drain problem. I haven't experienced any subsequent HVB drains since then with my 2010 FFH.

 

The only problem with my car since is that the 12V battery went dead without any warning. My 12V battery was original equipment, so it lasted almost 6 years. Replaced the 12V battery with another purchased from my local Ford dealer.

[lolder]

It wasn't easy in my 2010 until I read the first responder document and learned how to do it. It was very easy once I knew the procedure.

There are taps to move sideways in the top of the trunk and I don't know if I can see them. I've read that document also.

[DrDeke]

This problem is still unsolved, although the dealer wants me to bring the car in again soon to take another look at it.

 

One suggestion which has been brought up both here and by the dealer is the idea that this may be a measurement or display problem as opposed to an actual battery discharge. I rigged up a camera mount which allows me to drive the car while making a video recording of the dashboard, and I have used the rig to capture videos of me starting and driving the car on two different days on which the HVB drain problem happened. The behavior of the car and dashboard indicator during these drives is, I think, consistent with the theory that the battery has actually been run down, and inconsistent with the measurement/display glitch theory. I post them here for your amusement and in case anything shown in them gives any of you any ideas.

 

Video 1, 2/22/2016:

 

Video 2, 2/27/2016:

[murphy]

When the car is turned off the HVB is isolated when the contactors open. Unless it is self discharging there is no way for it to discharge. Have them check the contactors to see if the contacts have welded in the closed position.

[lolder]

Everything looks normal except the low HVB at start. The temperature bulb Icon switches back to white from green in both videos but that might be normal in cold temperatures. I left the car in accessory mode overnight once and discharged the LVB to dead and the HVB to an even lower point than yours. That was the emergency HVB shutoff point. I had to jump the LVB but then the car started normally from the low HVB and charged normally. I think you'll have to leave it at the dealer. Maybe you'll get a new HVB under warranty.

[borland]

Update to my post #2 of this thread, my 2010 FFH hasn't experienced another similar HVB drain. Only problem on this car that happened subsequent, was the 12V battery went dead and was replaced. That was about 6 weeks after the HVB drain occurance.