See embedded responses:
You are very knowledgable about the CMax. If you don't mind me asking, where did you get your info from? Have you been talking to Ford engineers that designed the car? Its obvious you have a lot of real world experience with the car.
I am a computer science engineer. I learned to fix things when I was a kid watching my Dad do alot of things. I pretty much am Mr. Fix it around the house and try to do my own work all the time unless I don't have the proper tools to do the job or its too complicated an I don't want to get involved. I have read some stuff about the car, but also figured out other stuff by inspecting the car, not to mention some people on here also gave some valuable information that I could mate with my thoughts and findings.
I am a mechanical engineer and I desing cooling systems for work. I haven't learned much about the CMax, so I only know general information about how things work.
Your advice makes sense and it seems keeping the battery from over heating, or just getting too hot is very important. I have some specific questions that are important to decesion making on how to protect the battery: (this may have been covered in other threads?)
1. How many cooling systems are there for our batteries? Seems there is a charging fan with ductwork and a non-charging fan with ductwork?
There are two systems. The car takes outside air from being the right rear wheel well and pushes that over the charging circuit while plugged in. The charging circuit gets hot and that hot air is exhausted inside the car behind the right rear seat. If you put the seat down and put your fingers between the seat and the plastic and curl them upwards towards the rear you will feel the charging circuit exhaust air. That practically goes under that seat and warms up the car.
2. Where does the cooling air come from, and exhaust out to for our cars. I saw a Ford manual on line that says there are inlets in the rear storage area, not sure where the outlets are. Not sure about either for the charging fan?
The HYB cooling air is taken from inside the car on the left and right vents up high behind the rear seats. That air goes over the HVB and is exhausted under the plastic cover in the back that holds the gas funnel. The exhaust air is on the left side. So the HVB takes air from inside the car and exhausts it back inside the car. It is diffused and is expected to rise out of the left and right lower vents in the hatchback area. Ford engineers decided that the inside of the car must be cooler than outside while in use and the outside of the air (air) must be cooler while charging. So charging air cooling comes from outside, HVB air cooling goes around in circles from the inside. This action actually warms the car up further you can notice it nice and warm in the winter while actively charging.
3. What is the max temp the battery can get to without increasing the natural degredation amount?? How was this determined?
Battery university document on the web talks about that. They suggest that 86F is the max temp the HVB should be. Doesn't mean it doesn't degrade at that temp, but they tell you that hotter batteries degrade quicker and they show graphs of tests done on batteries. A battery that is in a hotter environment will live shorter than one in a cold environment, and the higher the state of charge the worse it is, so the hotter it is, the less the average state of charge needs to be in order to last just as long as a battery in a cooler environment.
4. How much does charging increase the battery temp? How much does heavy power draw while driving increase the battery temp?
Charging can increase the temperature by several degrees, just as heavy power draw on the battery can do the same. But there are a number of factors that affect this. OAT has alot to do with it, as well as the car's cabin inside air temperature. Sometimes if the battery is hot, say 95F, and the OAT is 65F, then you could actually COOL the battery while charging if you leave the windows open to air out the inside so the temp inside the car doesn't warm up from the charging circuit exhaust air as well as the HVB cooling air going around in circles. Sometimes also on a drive home late at night if you roll down all the windows and freeze your butt you can cool the HVB down. Keeping the windows up so it stays warmer in the car definitely stops the HVB from cooling down. Charging on 240v makes more heat than charging on 120v, so that can warm the battery up more as well from hotter exhaust air from the charging circuit as well as a higher negative load (3x more) to charge the battery faster.
Just some more common sense things I assume for EV now mode, which I am guessing is where you are coming from.
Yes but you can also raise the temp of the battery driving in EV later mode too!! To stop or limit that from happening, it is essential that you re-ignite the ICE when it shuts down as soon as practical by tapping the gas pedal. Sometimes say you're driving 55mph in EV later mode, the engine will run, you'll hit a downhill section, it shuts off, then the road levels, and the car tries to stay in EV mode for a mile while drawing 40 amps from the battery to maintain that speed. Until the battery is exhausted (the EV later section), then it restarts the engine and the engine has to charge the battery back up at -20 amps to bring it back to up a useable EV later level. The action of charging and discharging the battery in hybrid mode can and does heat up the battery. Its better to keep the engine running as much as possible to prevent or lessen the charge/discharge yo yo up and down.
-- Keep the interior of the car as cool as possible on a hot day, (without putting more load on the battery) especially while charging. So keep windows rolled down some and park in the shade if possible. (I do this)
-- Go easy on the accelerator to keep power draw low so as not to heat up the battery. (I do this)
-- Let the battery cool off if possible before charging. (I do this at night, not during the day at work)
-- When the outside air temp gets too high, say above 90F then don't charge the car and don't put a heavy load on the battery.
-- The fewer times you charge the battery, the less it will degrade. But it can take a lot of charges by design, so you just want to stay within the "normal" battery charge cycle. What is the normal cycle??? Does Ford say limit charging to once a day?
Every battery has some limit in charge/discharge cycles. You get so many the more you use it the more it wears out over time. That is expected degradation. But you can make it worse by doing the wrong things that we are discussing, hard acceleration, charging in the heat, charging too much, etc. etc. There is no normal cycle so to speak, its all up to you but just remember the more you use it the more it wears. However, you have to use it as the longer it sits the more it wears (time is also a factor but not as much as cycles), and temp is also a factor. At the end of the day it boils down to this. Use the battery where it works best, and use the engine where it works best. Sometimes it makes sense to be on battery 100%, take the country roads to run errands and such, other times it makes sense to start the engine. You will get smarter about those decisions over time. When we all first bought this car in 2013, the goal was to never use the engine for most people. I too would sometimes stop somewhere and recharge the battery so I can go home on battery and not start the engine (when the distance driven is more than the battery could go). Nowadays you still might do some limited thing of this, but gone are the days where you try to burn no gas for 6 months at a time and hop from charger to charger all day long.
--It seems the feeling is Ford fell short on protecting the battery from accelerated loss of capacity due to heat issues. There are so many variables that go into that, I guess I am not surprised. Seems outside temp and whether you roll down the windows or not are major factors.
Ford never ever expected people to use the battery exclusively. There were people on here like Gary who never burned any gas, hopped from charger to charger and then went to the dealer a year later with gas cans and asked them to cyphon the "dealer gas" out of his Cmax so he could put it in his Explorer as he didn't want to start the engine in the Cmax and ruin his lifetime 438 mpg number he had going. Other people bought a 240v charger and fell into the mistake of being able to recharge the car in less than 2 hours and would recharge it several times and day and drive maybe 80 EV miles every day. That didn't work out so well either. In fact 240v charging at home backfired as it allowed people to do alot more in and out on EV errands and overheat the battery. At the end of the day its a small battery in comparison to others so when you load it with 80 amps that alot and it can heat up the battery quickly if you maintain that load like you're trying to climb a hill on the battery and keep your speed up. Cooler OAT and rolling down the windows helps alot, yes. If its 60 outside but you have the windows cracked 1 inch that not nearly as good as rolled down all the way (assuming the HVB is 91F from earlier in the day). If you drive home 1 hour say with the windows rolled up you get home with the battery at 91 or maybe even 93F. But if you drive home 1 hour with the windows rolled down you get home with the HVB at 84F instead. Been there done that.
One last response, I don't have a garage and keep my car outside in the driveway while charging. I charge at night and it is almost always cool, say below 80F. I live on the ocean with nice cool sea breezes. Charging at work is more riskey, partial shade from the building, much hotter day time temps due to no sea breeze.
The best thing you can do is get a scangage so you can monitor the HVB temperature. I didn't have this for 4+ years and only had mine for the last 7 months or so. Knowing that the temperature is at and how its reacting to the way you're driving gives you clues on how to change your behavior to stop the temp rise on the HVB if you find it necessary in that situation. I mean you might not care as much going from 77 to 86, but you care alot more going to 91 to 95F. You may get to work and the temp of the battery on Monday is 89F. You plug it in to charge and find out when you get out that its 95F, or maybe you come out an hour later and find that it has risen to 91F, bells go off in your head and you think forget about this let me disconnect it and burn some gas, there will be another day for the battery later, especially as the weather cools in the winter you welcome the charging as it warms the car some for you so you can drive home on battery with no heat inside (you never want to use EV heat, lots of load on the battery). If you can't live without heat, then you gotta start the engine. But I find it very easy to live without heat in New England, especially with temps 20F or higher its no problem at all for me. Less than 20 it can get a little challenging, but I can get used to it.
Hope this helps!