Hello, for the second time I went a 130 km trip x 2 to my parents. I live in a place with many, many hills and mountains. I try to get everything I can from those. On a descent today, I ended up with a full battery and no way to store more energy, so I had to brake using the discs. My first question is does anybody here got a special technique to increase mpg on roads with long descents ? Second question is, after the battery was full the ICE started, while braking, at a speed lower than 25 mph. Could it be because the electric drive was too hot? Thanks!
If you anticipate that the downgrade will be long enough to fill the battery you ought to use the "B" position with your "gear" selector. That will save your brake linings extra wear and temperature.
So far, no one has told the OP the spacial purpose of 'B mode' and what it does to slow the car and prevent overcharging of the HV battery. jdcollins5's recent explanation in another thread is about as short and good an explanation as I've read of late:
Thats why the Plug in Prius keeps on charging on those long downgrades and in fact is EPA rated 49 mpg hwy instead of 48 the regular Prius hatchback.....
I'm not aware that the EPA test includes any downgrade, or ever tops the traction battery of the regular Prius. Are you sure it is this, and not the higher road speed in electric mode before the ICE is required to spin?
Normally, if I were going down a long hill in the summer time, I would turn on my A/C and set the temperature to the lowest setting. The A/C will consume some of the energy coming in from regen. If you used B mode to slow down the car, some energy will be captured by the battery while the rest will wasted. Rather than wasting that energy, I'd rather use it to cool my car down.
I experience similar challenges as OP, hilly area. To go anywhere in the city I have to go downhill, I get a flat road for about 30 seconds then its pure descending for a mile or 2. I notice instant fuel economy shows fuel use on these descents if the ICE is still in the warmup phase, basically its just idling, doing its warmup thing using fuel while going downhill. I've recently decided to try an experiment which sounds logical to me but please correct me if there is some flaw in my idea. So what i do is use B mode as soon as I start the descent and of course as per usual in B mode fuel is cut to the ICE, but the ICE is still being warmed up because its working as an air pump producing heat, right? After the I finish the descent I switch back to D mode and the ICE will sometimes shutoff, battery level permitting, indicating it is now warmed up. So is this a good idea, better than letting the ICE idle in D mode going down the hill even if the hill is too short to fill the battery using regen?
Just my two cents. I use the Torque app and it shows maximum 83.5% HV Battery charge when driving long grades in the B or D mode and that's it ! Once I reach 83.5 percent it will not charge higher no matter what I do to manipulate this condition. I think Toyota has a maximum charge condition engineered in. The MFD is showing full charge and when app shows upper 60 % range. The road used for the test was a 5 mile downhill with no ups or flats. In B mode it limited charging rate but still charges to 83.5 %.......D just gets to the max charge quicker.
I have a nice descent as well. Coming off a mountain into a valley I use regen to top off the battery and then use the stored battery power to stealth 1 1/2 miles through my neighborhood to my house. My house is on a hill and I get to do a smaller descent in the morning going to work. At the top of the mountain (4 miles from my house) I can zero out the mileage indicator and when I get home I'm reading 90+ mpg or 999 mpg. Really a lot of fun.
Another thing I noticed on my daily hill descents is sometimes the battery level will show 1 bar below full yet act like its at max charge level. I haven't any apps or other indicators to know if it is in fact at 83.5% charge but i'm assuming the battery indicator is not precisely tied to the actual battery state of charge(more of a rough guide) and/or depending on the HV battery temperature the system will limit charge rate to keep it from overheating. Conversely After a long descent and a full indicated battery, the HSD seems to rely more heavily on the ICE for acceleration until the battery cools down. I've only had my prius for about 10 months but this car like no other continues to amaze me with its built in intelligence.
Yes I noticed that too, especially on some extremely abrupt hill in town here, I slow down on 100% charge rate at 20 mph and at some point I see the acceleration coming again even if the display is not showing all bars.
