SnowStorm

Our 2013 hybrid (not Energi) is past 246k miles and is doing fine. There are others with similar mileage and no problems. I expect to keep it another 10 years - although it won't get a lot of extra miles. The HVB (high voltage battery) is simply not a problem in these cars.

I thought you could force the ICE to run by pressing (flooring?) the accelerator while parked.

Do you plug it in at night to charge the main hybrid battery? If so, that might keep the 12V charged too (I don't have an Energi so don't know the answer). Otherwise, you should be able to connect the tender to the two posts under the hood (driver's side) where you jump-start if the 12V is dead.

Well, I keep seeing this complaint about the turning radius but even after 245,000 miles and almost ten years I could hardly care less. I'm not even sure I would have ever noticed it if I hadn't read about it on this forum. We all have different things that annoy us and different driving/parking situations but for most folks it shouldn't be a significant issue. I sure wouldn't let it rule out selecting a C-Max over another car.

I don't have an Energi model and have no experience with the TCU but here are my thoughts based on the understanding that the car has a 12V battery drain problem somewhere. There could be a drain somewhere else - replacing the TCU wouldn't help. The dealer may not know about it, simply sees that the TCU is out of date so says you should replace it. You should find out exactly what is happening with the 12V battery over time. Get a voltmeter and a jump starter (the small lithium-ion ones are great). Use the 12V "jump-start" posts under the hood on the driver's side. (You can also plug the voltmeter into the 12V jack in the back since it doesn't turn off.) When the car is ON (Ready-To-Run), you should have over 13VDC - the 12V battery is being charged by the DC-DC converter. When the car is OFF the voltage will be below about 12.8 volts. Check the voltage with the car OFF, first in the evening and again in the morning. If there is a drain, it will go down a lot. A 12V battery is considered fully discharged at 10.5 volts but it might go a lot lower than that and the car will still turn ON. I've seen mine down around 4 volts! Of course at that point you have to use the jump starter. You should have the 12V battery load tested and replaced if it fails. (Be sure the mechanic knows how to reset the battery age counter.) You still need to perform the above step or you may end up eventually ruining the new battery. Repeated discharges of the battery to a low level will damage it. Can't the TCU be simply unplugged if it is the culprit? I understand its no good anyway with 3G dead. You can also get the Forscan software and a compatible OBDII adapter and investigate lots of codes and issues that way if you want to get into the guts of everything. I would think using a trickle charger should also keep you operational but still keep the jump-starter in the car when away from home.

These cars are fantastic in winter - you'll waste money staying with ICE. As mentioned, ICE only runs as needed to keep you warm, not generate gobs of extra heat to dump into the environment. We got caught in a snowstorm in Wyoming, spent the whole night 'sleeping' in the car, stayed very comfortable and only used about 0.7 gallons. The ICE only runs about a minute out of ten. its wonderful. Seat heaters are a great help too - try and find one with that option. Use recirculate as much as possible (when humidity isn't too high to fog things up). Its true that gas mileage goes down in winter but with an ICE car its "down" all year!

Interesting, as that appears to be the problem with the early transmissions with transfer shaft failures. Mine failed, I tore down the old tranny and what appeared to be a pressed on ring had slipped which then allowed the shaft to move sideways causing the problems. My 'pet' theory was that a software glitch caused a severe jolt after a long down hill run using engine braking and that jolt drove the ring out of place. (It was quite an awful noise when it happened.) Or, it was a design or manufacturing problem. I suppose any of these could be aggravated by too much heat but I would doubt that heat is the root problem - if at all. I think there are a number of posts where folks have tracked transmission temps under various conditions. You can certainly get the data with Forscan. For me, I'll never use engine braking again!

Slight correction: the transfer shaft is directly geared to the differential so only turns when the car is moving. When sitting still with the ICE running, the only things spinning are the planetary gears and one of the electric motors (and I guess the oil pump) so your sound would be from one of those. If yours is truly out of fluid, its more likely due to a leak as described in TSB 15-0174. Read about it here. Maybe fill it with fluid and see what happens - see where the leak is???

Forget about that plug on top. I used the check plug hole on the side as described here. Turn the wheels full left then reach in front of the left tire, pull up a mud flap and you can see it. A bit cumbersome but not that hard.

What happens when you try the link? It still seems to work for me. It should go to: https://ford.oemdtc.com/1696/15b04-12-volt-battery-test-and-module-software-update-2013-2014-ford-c-max

If it hasn't been done (I doubt it), see if your dealer can perform CSP 15B04 - read it here. It seemed to clear up dead 12v battery problems for a lot of us years back. It does sound like you may be having overnight 12V battery drain issues. A good (or new!) battery can be drained beyond full discharge (below 10.5 volts) when the problem occurs. I once saw mine down around 4 volts! You can charge it back up and it may load test OK but keep doing it and the battery is progressively degraded. What happens when you try and start the car depends on how low it went. If it only went down to maybe 8 volts (?) it might still start with you unaware of what happened. Or you might have some errors. At some point the car won't start and has to be jumped. You might get a cheap voltmeter and plug it in the 12v jack in the back (it doesn't turn off). Check it often and see what is going on.

In my opinion, the compressor always sounds noisy from outside the car.

If it hasn't been done (I doubt it), see if your dealer can perform CSP 15B04 - read it here. It seemed to clear up dead 12v battery problems for a lot of us years back.

Here's my answer to oldbeyondmeasure's post about charge efficiency. I did not include charging efficiency - I haven't taken any measurements. 70% seems quite low but I did see an undocumented article saying efficiency could vary between 70 and 90 percent. Another article here references an EPA document that indicates the charge efficency for a Tesla Model Y at 88%. That would make my cost about 3.4 cents per mile. You should see if you can get lower electricity rates at night - so called time-of-use charges.

This topic is for discussion of charging efficiency, that is, the total energy needed to charge versus that used to run the car (energy out of the battery).

We recently sold the camping trailer so the SUV is next. The Y can tow 3500 pounds so that will handle the occasional tow of a utility trailer and small boat. C-Max is at 246k miles - still doing great (except for that long dead audio problem). The Y is fantastic on efficiency with a lifetime average (at over 7k miles) of 235 watt-hrs / mile. I'm sure 9 years of hybrid driving has helped! Charging at home costs 3 cents / mile and there's a free level 2 charger I can conveniently use long enough for about 300 or so free miles per month. Conversely, Tesla's chargers, though fast and super easy to use, cost 3 times home charging (one I found is 2X, others 4x or more) but we'll rarely need them. Its the first car I've had with "traffic aware" cruise and I love it, all the way to a stop. And, BTW, once engaged, you can scroll the cruise speed all the way down to 0 in 1 mph increments! Yes, you can "cruise" along at 1 mph. Not sure what its good for but fun to try out! Then there's Autosteer. Keep a hand on the wheel (at least every 30 seconds!), continue to watch the road like always and the car does the steering. Even on narrow 2 lane roads with patches of new pavement without lines it is amazingly capable. It may sound like its not that valuable since you still have to watch all the time (like manual steering) but after hours of driving you are less tired. It removes a lot of mental and physical tension. Like a lot of things, you have to get used to it but I now use it 90% of the time. The touchscreen user interface is not a favorite for sure (in fact, a lot of screen design details are down right awful) but you don't get a choice so I put up with it. It is a lot easier when Autosteer is active and there are a ton of voice commands as well. The big screen, though, is great for satellite view of navigation! Then, of course, you have acceleration! I don't even have the "boost" option but a short punch on the accelerator can cause a passenger to have an "expletive deleted" moment! Silky smooth power is really fun to drive!

Who did the diagnosis? 13k sound about twice what it should be. My 2013 failed about 4 years ago and I was quoted 7k by my dealer for a new transmission with 3 year warranty. Now, I think, they have a repair kit (?) which lowers the cost. I bought a used one from a wrecking yard, had them ship it to my dealer and they installed it - less then $3500 total. I wouldn't say it is "normal" but there have been quite a few failures - various mileages. Read the CSP here. Of course I really don't know if this CSP corresponds to your problem. Its hard to say how urgent it is. I think mine had "failed" (faint whirring sound under only certain specific conditions) tens of thousands of miles before it wore a hole in the housing and started losing fluid. It was urgent then! My car is at 246k miles now with 70k+ miles on the replacement tranny.

I too would try to jump start it. If possible, check the voltage first, just for information. NOTE! The positive post is just to the right of the brake fluid reservoir and should have a red cover with a + sign on it. The post itself is thick metal bent into a sort of flat C shape. NOTE! The negative post is the hex shaped one and is in front of the positive one and lower down. Saying the "plug in battery was junk" may only mean the car had a reduced range in EV mode. It originally had about a 20 mile range but many people have reported reduced range with age and miles. As I understand, its still a great car just driving it like a normal hybrid and forgetting about the plug-in feature. Of course, if the High Voltage Battery (HVB) is not functional at all, you have a bigger problem.

Louis, it is likely that your car needs to have CSP 15B04 done on it (assuming it was never done) - read about it here. See if you can get a dealer to do it, though I suppose you will have to pay for it now. Many of us had this problem years back and this CSP seemed to fix most everyone's problem. Your 12V battery will also need to be replaced, I expect, since the repeated discharges to a very low voltage damage the battery. I doubt that sitting for 3 months is the root cause.

What did you use to check for codes? Its my understanding that using Forscan can find codes that other methods won't (I suppose, more Ford specific ones). Should you find codes associated with a particular module, you might try unplugging/re-plugging its connectors a couple of times. AGM batteries require a different charging profile so yours may not be getting maintained properly. I suggest checking the voltage occasionally to see how it is doing. Of course this check must be done before turning the car on because the HVB and DC-DC converter will start charging the 12V battery at that point.

Some questions about your problem: How many miles on the car? Does the pitch or volume change with engine speed? You can set the My View screen to show RPM. Does the pitch or volume change with car speed? Does the pitch or volume change with load (pressing or letting off the accelerator) while driving at about 35 mph? Is the sound present while sitting still but with the engine running? You can force it to run in Park by pressing the accelerator. Is there any sign of transmission fluid leaking? Has the fluid level been checked? You might want to post a recording of the sound. Oops - I didn't see stolenmoments post before I posted - that may be it.

Nice. Hybrid cars have the potential to make an incredible back-up and portable power source.

BTW, there isn't a "hot line" (singular). Both sides of the HV battery are un-grounded "hot" lines. Both lines are monitored for resistance to ground - IIRC, you can read the values in Forscan. Again, nothing like a 12V car battery! Great video. This guy can give you quite an education on hybrid stuff.

The answer to this thread's title is NO. I wouldn't think of trying this even though (sorry to say all this) I'm a professionally licensed engineer with a Masters Degree in EE and decades of engineering work experience including years with VFDs operating at twice the voltage and many times the power. These hybrid car systems are nothing like working with a couple of 12V lead-acid batteries in series or parallel. Theoretically, most anything is "possible" but this one isn't feasible - too many unknowns, too much complexity and too great a danger to both you and the car. Much simpler, safer, and likely cheaper to get a used Leaf or Volt.

A few more comments: A "Ford Dealer" is not Ford, and certainly not Ford Engineering. Of course Ford isn't perfect, but we shouldn't transfer distrust for a lousy dealer to Ford. You could change the transmission fluid every 10k miles and it would have no effect on whether your transmission fails (as we are discussing). It has nothing to do with "normal wear" and nothing to do with the bearings. The failure appears to happen as a catastrophic, abrupt event where a ring (I suspect it is friction fit) on the transfer shaft slips which then allows the shaft to shift back and forth allowing gears to hit each other or rub against the housing. In my case the corners of all teeth on one gear were sheared off, groves were worn in the housing (as pictured by Ford) and the end of the shaft eventually wore a hole through the housing. The bearings were still amazingly good. This problem has nothing to do with the prior condition of the fluid. What we feel good about doing is often based on what we've heard and how we interpret it, not engineering data. Personally, anyone can change fluid as they like, but for other folks reading this forum, we shouldn't suggest that deviating from the published schedule is recommended or will provide longer life.