Charging EV portion of the battery going down mountains

After reading a page on battery operations for Li-Ion this is correct, NiMH works with more trickle charging where Li-Ion drops off its charge acceptance voltage at various stages during its charge cycle. The charging circuit needs to recognize this cutoffs and properly account for them to protect the overall battery. There is some additional resistance and heat given off as a battery gets closer to full but this is only about 5C delta according to the document I read. And now I have read more about the battery than I want to know, so I am going to go read something useless about politics or something so I can feel dumb again .

 

The title of this this thread is a bit misleading. There are not two different physical sections in the traction battery for HV vs EV. It is all one big battery (with lots and lots of cells, organized into modules). The hybrid software manages it in two different ways. When the charge get down to around 20% or so, or you set HV mode, it manages the battery like a standard Prius, in hybrid mode. When the state of charge is higher and you are in EV mode, it manages it as a big traction battery. Separate HV and EV "partitions" are a convenient fiction created by the hybrid software. When we talk about 80% charged, we are talking about the state of charge of the single traction battery. All of the energy going into or out of the battery effects the whole battery.

Early prototypes of the first generation plug-in DID have real separate HV and EV batteries, but by the time production started, they had changed to the single battery design. Sometimes people come across old documentation referring to the two-battery design, and think that is how it is now.

 

I got 42 miles in EV mode going down a mountain. 1. I did not exceed the speed limit while on EV(65mph). 2. No heat or AC. 3. Saved 4 mi of EV range at the beginning of the trip by switching to HV mode. 4. At the top of the mountain I switched back to EV, with 4 mi of EV range remaining. 5. I used B mode exclusively when going down hill to maintain my speed and recover as much energy as possible. Elevation drop should have been between 3000 and 4000 ft. End of 160 mi trip was 58.9 mpg. Some of the HV was done at 75. YMMV.

 

Is it still the case that using B mode while in EV mode is exactly equivalent to lightly pressing the brake pedal? In other words, it just steps up the regeneration over what it is if you just take your foot off the throttle.