Over the last few months I have noticed that my 2006 has had much less regenerative braking capacity. At first I though it was due to the colder weather but as we have warmed up around here, it still seems to be doing it.

Kind of hard to describe so bear with me but after having the car (plus my '05 FEH) for 9 years, I can tell when something isn't quite right. Hoping some of the long-time owners, or the technical types, my have an idea what is happening. So, here are the details:

1. No codes showing up when I do the on-dash diagnostics (holding the odometer reset button at start-up).
2. Maybe a slight decrease in fuel efficiency. Hard to tell though.
3. When I decelerate by braking, the Charge/Assist needle deflects to charge only slightly. When I decelerate by using "L", the needle deflects only slightly. Combining the two does not change this.
4. Braking or even coasting (in gear) while in EV mode will almost always cause the ICE to fire back up.
5. Braking or coasting in gear on even a slight down-grade will make the engine rev to 3k or higher.
6. Sometimes when braking or coasting in gear will feel like the car is in neutral with absolutely no regeneration going on. I never coast in neutral but this is what it feels like.
7. If I use the dash diagnostics I can see the charge rate to go as high as about 14 amps.
8. There does not appear to be any decrease in how far I can go EV.

Any thoughts? Feels to me like the battery has decreased capacity or something and can't take a charge like it used to. But other than this, it seems perfectly normal. I still have about a year left on my Extended Service Plan so if something is wrong, I will get it repaired. But, if I go into the dealer and say "it just doesn't seem right", they will charge me an hours labor and tell me all is well.

Thanks for the help.

Ray

 

Hi Ray

Sounds like you may have a HV battery going bad. Have you had a battery recalibration lately? Also, have you drained the battery near 32% or at least 40% lately?

When I ran out of gas on I-95, my '05 battery drained below 32% before I got to an off-ramp and to a parking lot to stop. After adding gas and restarting it, MG1 was charging the battery so fast, the battery would not accept any regen till the battery got to a higher SOC.

Also, is your A/C cooling your battery properly? That will also cause limiting charging and not cause a code. A long trip may be in order to flush out the issue. You may find you get a "Stop Safely Now" code so the dealer can identify the problem. Take a few pictures of the warning and OD if you do.

I'll continue to give it some thinking, so keep us informed.

Gary

 

2. Any problem with the hybrid system should cause a loss of fuel efficiency. Otherwise the system could have been set up to begin with the way yours is now.

3. The deflection of the charge indicator during braking should vary depending on how hard you brake. Using "L" will never show more than a modest amount of charging, but should be more than "slight".

4. This is not normal.

5. This doesn't seem normal either.

6. I agree, this doesn't sound right.

8. By itself, would indicate there's no problem.

Gary's suggestions of a problem either with the hybrid battery pack cells or temperature regulation sound like good places to start. There's all those issues with the blend door actuator etc. But beyond that it sounds like some sort of a controller, sensor or computer problem.

 

Thanks guys. I am going to keep watching it for a while and try to document exactly what it is doing. I did check the A/C last night and it blasted very cold air so I can at least rule that out. Supposed to be 80° tomorrow so maybe have a chance to see if the rear A/C is working.

To be continued....

 

I agree that #8 would kinda indicate that the battery cells themselves are probably fine.
It almost sounds like a brake related thing, maybe even tone ring. If you have a scan gauge, program the MxD and MxC xgauges. If the MxD is always pretty high, then the battery is probably fine. If the MxC continually drops and then rises but always drops when braking, then you most likely have a brake issue. If you have a 4WD FEH then maybe an issue there.

BTW I saw on the escape-city site that the instrument cluster thing only looks for instrument cluster trouble codes, not anything else.

 

Does it behave that way first thing in the morning after sitting overnight?
Pay really close attention to this.
Your battery should be at ambient temperature after sitting 12 hours.
My battery shows signs of age in the form of increased internal resistance.
This means my battery is starting to get hot. Fast.

It is not unusual for my battery to rise 20 degrees F in 10 minutes of city driving. So much so that the AC turns on for battery cooling on a 50 degree day. The freon evaporator in the rear air duct cools to 40 degrees (F).

With increased temperatures internally above 95F the current allowed for regen drops off about 2% per degree above this.

In a parked car in the sun the internal Temperature can be 120 to 140 degrees.
Regen can be dialed down because you have backup brakes.
There is no alternative to propel the car especially at low speeds so you get assist and EV until you hit a critical Point somewhere above 140 deg.

 

One day since I posted last, after descending a long grade with the engine spinning about 3k the whole way down, the STOP SAFELY NOW warning came on. I stopped and shut the car down and restarted it. It has been acting much better since. Still not getting as much regen as I think I should be getting but more than I had been.

My current tank after about 400 miles is 36.9 and that 400 miles includes a 210 mile round trip to western Massachusetts (over lots of hills) and four days of running around the base (all short trips, never going EV). I guess I can't complain about that.

The A/C is working fine. I heard the rear fan running today. Maybe it was nothing, maybe it fixed itself. But, if the HV battery is going to STB, I hope it does it soon before my warranty expires next summer. :-)

Maybe one day I should get a scangauge and learn how to program it...

Thanks for all the ideas.

 

I have noticed that the longer I drive, the more often the ICE cycles.

Starting to see the decreased regen happening more often now. Enough so that I am starting to think the big battery is starting to go. I still get pretty good EV distance but if I try to coast at all in EV, even a few seconds will make the ICE fire up. On a grade, it is almost instant.

And now that the weather has gotten to where it should for this time of year, I have noticed my mileage drop. I blame some of it on my commute distance dropping from 25 to 12 miles and not having enough time/distance to make up the cold start condition but the car spends more time on gas than it should in these temps. My current tank is 36.5 after 220 miles when it would normally be 39+ under these weather conditions.

Time for a trip to AutoZone for a SGII it appears.

 

Can you tell if the A/C is running a lot to cool the pack?
With a SG its easy but you could also hear the compressor under the hood cycle and hear the electric fans come on...

Like I said, my nearly 10 year old battery raises about 2 degrees F every regen brake from 40 MPH to zero. I have confirmed fans are working OK.

A/C will opportunity cool (if you have the cabin A/C on) at any HV battery temp above 72 degrees. The compressor will kick on for the battery even if the cabin settings are off at anything above 86 degrees, but you still get EV mode.

At any battery temp above 96 degrees you lose EV mode ability until the pack drops below 86 degrees.

 

Thanks John. I am picking up a SGII this week and going to learn to program it so I can better see what is going on. My mileage on this tank has, well, tanked compared to where it should be for the weather and my driving patterns. I do believe it is HV battery related. Thankfully I still have a year on the 10/150 warranty AND still have the extended warranty on it. I just want to be well informed before going to the dealer to avoid the inevitable "seems okay" conversation.