I know little about the mechanics/electronics of regenerative breaking in the PiP. For those with more knowledge, how difficult might if be to capture more energy with more aggressive braking (not talking about regeneration efficiencies here)? The reason for the question is that when there is little or no other traffic on the road, I brake entirely within the vehicle’s ability to capture this energy without using the friction brakes. However, often traffic is such that I must brake more aggressively so as not to create angry tailgaters. For example, if coming up for a turn, instead of coasting then braking slowly, I might come up to the turn faster then have to advance into the friction brakes to safely navigate the turn. With the current PiP, is this a limitation of the size of the regen brake mechanism, limitation of how intense regen the batteries can take in a short period of time, some combination, or something else entirely? Might be nice in the future PiP to be able to capture brake regen more deeply without having to use the friction brakes. And in lots of stop and go driving, this would actually increase fuel ecomony.
The limit on regenerative braking is set to keep the battery within it's capabilities. A higher capacity battery pack could allow more aggressive regen along with longer range, which I feel is more universally desired. Unfortunately Toyota made use of a bigger battery very difficult, otherwise I'd have an HV battery made from cells salvaged from a Leaf and about 40 mile EV range.
Do the PiP and regular Prius have different tolerances to regen depth*? For the Volt and Tesla drivers among us who have also driven the PiP, how does regen depth compare? *By regen depth, this is meant to refer to how aggressively one can brake before transitioning from regen to friction braking
The PiP can do more aggressive regeneration while braking, in part due to the LiIon battery being able to accept a faster charge than the NiMH battery on the standard Prius. Also, on long downhills, there is somewhere to put the energy, whereas on on standard Prius, the battery would be full and the energy will have to be dissipated with engine compression braking or friction brakes.
Ok, so you are saying battery chemistry plays a significant role. What about the total number of cells/battery capacity? If the next gen PiP were to have double the batter capacity and similar chemistry, could we theoretically have deeper regen with braking? Anyone who has driven a Volt and PiP notice a difference?
By all of this rationale then a Tesla ought to never have to engage friction braking, even in very hard braking situations.
It also has to do with the ability of the small MG to convert torque into power. I'd bet the purely electrical decelerative force can't exceed the accelerative force, which we know is pretty limited compared to that of the ICE.
It is actually the bigger MG, #2, doing the regeneration work. But the battery is still the real choke point at about 36 horsepower.
What is exactly the regen braking depth? Is it the limit of the "CHG" bar in the HSI where physical braking begins? This webpage seems to be implying such. Does anyone have a better answer to this?
Along those lines, thinking more battery capacity would also help with big hill and mountain descents. I've noticed that even in cool weather, I'm not able to aggressively brake regen into the battery longer than a minute or so at a time. It seems here the car switches into engine compression braking for a while, probably to protect the battery cells from overheating.
Mine always does this because the battery is full (to the software imposed cap of the SOC gauge, not the true hardware limit), not due to some overheating limit. And I have filled up the battery on many many long mountain descents.
In my case this happens before maximum SOC, when going down high grade long mountain descents and keeping the brake at sustained maximum regeneration. At this rate, the battery starts to recharge very fast (much faster than even a L2 charge). Perhaps for the first 3-5 EV regen miles, the battery fills without incident. Then about every minute (with the car under 62 mph) the EV logo will vanish and no EV regen miles will accumulate. I assume the PiP to be compression braking at this time. This will last for 20+ seconds and automatically go back into regen braking. If I continue to brake at max regen capacity, I probably will not get more than another minute of this before being switched back into compression braking. If I brake lighter, I can stay in regen mode much longer.
Oops, I shouldn't have posted my reply #11 to a PiP thread. Didn't notice that in the 'New Posts' listing. Your observed regen pause happens after my non-PiP has already topped out.
That's pretty much the case. The regen on the Model S is extremely aggressive to the point that it will nearly stop the car even from high speed on a steep downhill. You generally only need the friction brakes to complete the stop. Otherwise you can do the vast majority of your driving with one pedal. That's what a pack that will accept 60kW regen will do for you.
Not that I have ever heard of. Keep in mind that 60kW is just over 1/3 of the theoretical maximum 2C charge rate of the 85kW pack.
