I have been test monitoring my 2012 Prius v coolant temp using the Car Scanner app and a bluetooth obd2. What I see is the engine warms up to 195f - 200f maximum temperature while driving. However if I park and leave the car in Ready with the AC on, the engine shuts off as expected and the engine temp will drop to 150f after a period of time, perhaps 10 minutes. In the meantime the hv battery discharges and eventually the engine will start to charge the battery partially, maybe 1/3, taking two or three minutes. During this recharge runtime the engine does not get back up to 195f, in fact it hardly warms at all. So when you start driving again the temp is low and the battery may also be low. Does this behavior seem normal based on anyone’s actual observations?
Yes, this is nominal, because the A/C compressor and fan are significant electrical loads, the A/C fan moves air across the ICE coolant radiator, too, and the ICE is idling, not under any appreciable load, just turning the Motor-Generator, so its temperature does not rise in the same way it would when powering the vehicle at speed.
If you are parked in Ready for long enough to force the engine to recharge, it would be the same amount of energy to charge it three times to 1/3 as it would be to charge it 100% one time. Given an extended idle it might save some energy by reducing the starts three to one. I realize that the system can’t anticipate the amount of “idle” time that may happen but it would seem more charge than 1/3 would be better. Especially since the system routinely keeps it over 75% while driving. However my primary question remains is my vehicle’s parked Ready logic as defined above “normal” per other’s observed experience?
You aren't getting it. Using the gas engine just to charge the battery, at any time and in any way, has built-in losses that you can not overcome. Doing that is inefficient.
Why do you need the engine running? Why do you need to charge the battery while parked? If you really want to keep the engine running, enter maintenance mode. There's no point to the average person to let the gas engine run to solely charge the battery. Just let the Prius do it's it's thing. Sounds like it's working great!
If you use a Scangauge to look at battery state of charge, you'll see it isn't "75%" to "100%"--the system tries to keep battery SOC at 60% and within a range of 40-80%. As it sits without idling, battery charge will drop and when it gets near 40% the engine will turn on and charge it up to mid-to-high 40s, just to keep it from getting too low. It isn't meant to charge it up to its normal 60% or anywhere close to "full" 80% since, as others have noted on this thread, that is very inefficient. The primary function of the battery is to capture braking energy that would otherwise be lost to heat; that's energy you get for "free." If the car will be sitting for a while, it's better to just turn it off.
