Bob999

Thanks. Not what I expected but great information!

Thanks to all who have posted specifics/data. I think it is intuitive that running the A/C puts an additional load on the engine/battery and, all other things equal, would have a negative effect on MPG. What is less clear to me is whether "all other things equal" is the correct construct for most people. In the old days, prior to A/C in cars we drove with the windows open and my understanding is that there is a significant drag penalty compared to driving with all windows closed with a resulting hit on MPG. I think, but don't have data to support this, that driving with open windows in a hybrid like the Prius or CMAX at highway speeds would negatively impact MPG. Only controlled experiments could determine the relative impact of running the A/C vs driving with the windows open but I think this would be the relevant comparison for many people.

From page 281 of the Owner's Manual: Resetting the Oil Life Monitoring SystemNote: Reset the oil life monitoring only after an oil change.1. Turn the ignition key to the on position. Do not start the engine.For vehicles with push-button start, press and hold the start button fortwo seconds without pressing the brake pedal. Do not attempt to startthe engine.2. Press both the accelerator and brake pedals at the same time.3. Keep both pedals fully pressed.4. After three seconds, the Service: Oil reset in prog. message will bedisplayed.5. After 25 seconds, the Service: Oil reset complete message will bedisplayed.6. Release both the accelerator and brake pedals.7. The Service: Oil reset complete message will no longer bedisplayed.8. Rotate the key to the off position.For vehicles with push-button start, press the start button to turn thevehicle off completely.

When the CMAX is shut down the high voltage battery is automatically electrically disconnected by relays. No action by the owner is necessary.

The 12v battery is strictly for the computer, relays, control circuits and some other things like the radio. The CMAX has no conventional starter. Instead one of the motor generators in the transaxle functions as the starter and it is powered by the high voltage battery. "Starting" the CMAX is primarily a process of connecting the high voltage battery via relays powered by the 12v battery. The owners manual has a section addressing medium/long term storage and talks about maintaining the 12 v battery but does not address the high voltage battery. that suggests to me that the high voltage battery discharges very slowly but I suggest you read the section and form your own conclusions.

I agree based on my experience. I have found that the 12v electric outlet shuts off after a period of time but that it reactivates when a door is opened.

EPA mileage testing is done with both heat and A/C OFF. It is done at ~70 F ambient air temperature. The CMAX will run the engine to provide heat when the HVAC is turned on and heat is demanded. If you turn the HVAC off then the engine only runs as necessary to provide power to move the car and/or to charge the battery.

Given it is winter in much of the US I wonder of some of the problems are caused by wearing gloves when trying to use the sensors on the outside door handle. I have never had a problem when I was not wearing gloves.

I agree with the sentiments of Generalbeluga but I think one of the problems is that the owners manual organization is, at least for me, not very straight forward and that the index is also a bit deficient with the result that the new owner has to read the manual cover to cover to find some things. Downloading an electronic version of the Owners Manual so that electronic searches can be done helps a lot given what I see as deficiencies in the Indexing and in the Table of Contents.

Did you check the settings as suggested by JohnTrigger? If not you really should before spending time by going to the dealer. As to the windows all being down--the fact that the car has a "feature" to put them all down strongly suggests someone triggered it with the remote control. I know from personal experience just how easy it is!!!

Yes you can charge the 12v battery from the terminals in the engine compartment. I have done it. Those terminals are directly connected to the 12v battery and connecting a charger there is electrically equivilent to connecting the charger directly to the battery terminals.

With the automatic climate control when heating is indicated the fan won't come on until the engine coolant is warm. You can adjust the left display to show coolant temperature. If that doesn't explain what you are experiencing then the system is probably malfunctioning and a trip to the service department may be in order.

I got the 12.0v after shutting the door but probably before the lights inside the car were totally off. I checked the voltage perhaps 30 minutes later and it registered 12.3v. Not great and probably suggests the battery is a bit degraded but not enough, in my opinion, that it would be replaced. So for now I am just going to occasionally check the voltage. If I have another reason that I have to see the dealer I will raise the matter but other wise I will wait for a more definitive sign of a problem.

I put the Battery Tender back on and this time it indicated full charge within about 2 hours. With the Battery Tender connected the voltage was 12.7v. After disconnecting the Battery Tender, but with no load of any sort the voltage still read 12.7v. But after opening the driver door briefly--which does put a load on the battery while it is open--the voltage dropped to 12.0v. I think I will try a very simple resistive load test tomorrow--The tester simple reads the voltage with a fixed resistive load and gives a good, fair, poor result based on the resulting voltage. One other observation--I got a "normal" voltage at the 12v outlet by the cup holder in the front of the car. This was after the car had been sitting for more than 24 hours and without putting the car in assessary mode or starting it. I didn't expect to get a voltage there based on posts on this site indicating that outlet shut off after a short time after the can is shut down.

No. But I think I will put the Battery Tender back on and include that after the indication of a full charge.

Here are the results of my charging experiment. Recall that when I tested the no load voltage at the connections points in the engine compartment I got ~12V which indicated a state of charge (SOC) of ~50%. So I connected a Battery Tender overnight and this morning the Battery Tender had gone into the anti sulphating mode indicating it now detected full charge. When I checked the voltage with the Battery Tender still connected and powered it was 12.7 v indicating full charge. I then removed the Battery Tender and opened the driver side door briefly to put a very small load on the battery. I then retested the voltage at it was 12.0 v!!!. I also tested the voltage at the power port at the rear after opening the power liftgate and also got 12.0v. I supose I should access the battery and measure the voltage at the battery terminals but haven't done that yet. Overall I am puzzled by the results.

The CCA is a part of the model number--the last three digits and is displayed on the battery. My understanding is that CCA and reserve capacity are correlated--higher CCA generally relates to higher reserve capacity. As a side note as a result of all the discussion about problems I decided to check the state of charge on my CMAX by checking the no load voltage at the connection points in the engine compartment. I should note I have had no problems and frankly I expected to find a fully charged battery. However what I found was ~ 12 volts--indicating a state of charge of about 50%. I have put a Battery Tender on to provide a trickle charge (max 1 amp) and see if the reading increases to indicate a full charge. I will report my findings after the Battery Tender indicates it has completed the charge.

What I find interesting is that the battery specification in the owners manual is for a more robust battery. My car, and by several reports on this site other cars, came with a 390 CCA battery installed at time of delivery. However, the specification for the battery in the manual is for a 500 or 590 CCA battery

A 12v lead acid battery with only 5.5 volts and no load is virtually totally discharged. I hope you load tested the car battery it once you were able to access the rear. I think the reason it doesn't take much to "start" the car with an auxiliary battery is that starting involves powering up the computer and reconnecting the high voltage battery via relays and it doesn't take much power to do that. I think that once the high voltage battery is reconnected it provides 12v power via an electronic device. But the fact that the car has operated normally since at least suggests that the 12v battery was not seriously discharged and causes me to wonder if there is another explanation for the very low voltage reading--perhaps there is a relay or other connection in the 12v circuit that is not making proper contact with the result that normal voltage is not available.

For those cases where the CMAX was dead or "failed to start" but no problem was subsequently found with the 12V battery I have a theory about what the problem might be. I understand that the high voltage battery is electrically disconnected by relays when the car is shut off and that the same relays are activated to connect the high voltage battery when the car is "started". I put started in quotes because the ICE doesn't necessarily start--starting is an electrical powering on process. Based on my experience with other engines I know that the voltage required for a relay to activate varies by the brand of the equipment--for example I have a Deutz diesel where the starter solenoid (relay) won't activate if the voltage drops below 12 volts. I have other engines where the starter will activate well below 12 volts. So my theory is that perhaps some of the relays used by Ford to isolate the high voltage battery may be very sensitive to voltage--if voltage drops they don't work. The voltage drop could be from a slightly discharged 12v battery or could be as a result of a poor connection somewhere in the circuit between the 12v battery and the relay (or in the ground circuit). It could be a combination of both. The fact people are able to "jump" the system with a very small capacity starter battery like the Simple Start is consistent with the theory I have advanced.

There is another thread that says "flakey" behavior can be caused by an undercharged or failing 12v battery which powers essentially all of the accessories.

I am skeptical of the differential pressure theory. To have differential pressure between the inside of the car and the outside of the car while it is sitting in a stationary position all openings would have to be incredibly well sealed--to a degree that I don't believe exists for air intakes for the climate control system to name just one source. However, a well sealed car can make closing a door difficult and a sell sealed car could provide a bit of resistance for that brief moment before air can rush in around the seals when opening a door (or hatchback) so I can see how a very well sealed car could contribute to this issue--particularly if the obstruction detection mechanism is overly sensitive.

The CMAX doesn't have a traditional alternator. As I understand the system the high voltage battery is charged by motor generators located in the transaxle. Then there is an electronic circuit that converts the high voltage power to charge the 12 v battery.

That is not my experience and it is not what is described in the owners manual. Here is what the owners manual says: To open or close using the hands-free liftgate feature (with intelligent access only): 1. Make sure you have an intelligent access transmitter within 3 feet (1 meter) of the liftgate. 2. Raise and lower your leg, moving your foot toward and away from the rear bumper (similar to a kicking motion). The liftgate will power open/close. Note: Allow the power system to open the liftgate. Manually pushing or pulling the liftgate may activate the system’s obstacle detection feature and stops the power operation. I think that a sticking latch/weatherstrip causes the obstacle detection feature to activate and stops operation. Once operation is stopped a second kick will reactivate it--at least for some people as reported in posts here. But as I posted I think the root cause is sticking and, at least for me, application of silicone grease solved the problem.

As I posted here: http://fordcmaxhybridforum.com/index.php?/topic/721-foot-activated-liftgate-two-kicks-to-open/?p=4043 I think the problem is a sticky latch/weather strip. Since I applied the silicone grease the tailgate has worked first time every time.