ICE comes on anyway

So why did you say starting made sense, when I was not in charge mode?

 

Regen = Brakes

Charge = Engine

 

I suspect we're just having some semantics issues here...

In EV mode, regen occurs both during light to moderate braking, AND during plain old deceleration (ie, letting your foot off the accelerator) while in 'D' mode. Put it in 'B' mode and let off, and the car decelerates even faster, since more regeneration is taking place. Engine-on charge mode is a whole separate thing.

When in EV mode, and the battery has room to accept charge, either type of regen should add charge to it, and the ICE should not come on. That's how my Prime worked the first 7 months I owned it, but not how it's worked this last month.

 

One thing I've been wondering about lately is, if ICE-on during EV tends to happen when the ambient temperature is around 50F, why it didn't happen to me last fall.

I'm wondering if it had to do with my garage temps. In the fall my garage's thermal mass/Geo warmth meant the car was warmer than the air I was traveling in when I left the house. For example the car might have been 65F when I headed out into 50F weather. Now in the spring, the garage and car are about 50F when I head out into 50F weather - maybe that combination is necessary for the ICE-on event to occur. If so, I suspect I won't see any ICE-on events as things warm up further this spring.

 

Looks like when it is warm, ICE would be less likely to turn on, maybe I am wrong.

BTW, I had battery full this morning, close to 50F, no AC no defroster. I was not surprised than ICE was on when I drove out (pretty steep down hills for 0.7 mils which adds 1.2 mils of electricity). Then I driove for a few miles, the EV range was reduced from full 33 miles to 27 mils, and ICE was on again with another steep down hill on freeway.

It is really annoying. I would rather use the brake pad instead to let ICE to finish the warm cycle as I don't plan to use it at all for the whole day.

 

So I'm not sure if a case such as (see my example below) has been discussed or is related to anything in the previous 50 pages of posts, but what about:

1. Car parked outside. Start car at any time of day or night.
2. Cold outside temperature, oh, let's say, below 30F.
3. EV capacity could be anywhere between 1% and 100%.
4. While driving, or just after starting the car, switch to HV. Let the car complete its warm-up cycle as you drive like normal in town traffic, highway, whatever.
5. Drive to a place where you may want to do some regen. Let's say that it's descending a hill or slowly approaching a traffic light.

Here's what I notice.
If you are descending a short hill and you ride the brake to regen about 30-60 amps for about 8 seconds, then the engine kicks on while you are still doing regen.

Notes:
1. Battery capacity is nowhere near full.
2. This behavior does not occur when it's warm outside, e.g., 65F.
3. Also, the current to the battery drops to about 20 amps, so presumably the rest of the braking causes energy loss between the engine and friction braking, thus wearing out the pads.
4. Though I am in HV mode, if I switch back to EV mode, and do the descent anyway, the engine still kicks on at the same time that the engine would have kicked on if I stayed in HV mode.

Why does the engine have to come on? Why can't I just regen 60 amps to the battery and have the engine stay off, either in HV or EV mode in this situation? Why is it temperature dependent? Where is this situation clarified in the manual? I couldn't find this clarification.

 

I can only imagine that, being the traction battery cold soaked, in order to protect the battery, HSD limits the regen current dissipating kinetic energy through ICE.

 

Here's a wild and crazy idea:
The car could use the friction brakes.


iPhone ?

 

But then we'll have another 50 pages of posts about how the car could have used the engine because the engine will never wear out, uses just a few cents of gas and would therefore save money over having to have a brake job every so often...

 

Well obviously I am, since if I push the brakes more when the engine switches on downhill, the RPM stays around 960, yet the battery current won't go past 20 amps. What really annoys me is how much it is a problem on the Prime ($33K), yet on my Prius c ($24K), when I had it, was a lot less frequent, since the engine would be less likely to turn on once braking downhill in the cold.

Yes I agree, iPhone.

 

Yes I want to use break pads instead of engine to break!

 

I just started monitoring with a scangauge. I have a '17 Prime Advance. The SOC on said about 82% after a full charge. Does it ever read closer to 100%?

 

It shouldn't. That buffer is for battery longevity. Avoiding a full charge and full discharge is how the system is programmed.

Here's what that looks like using the HybridAssistant app...

 

Thanks!

 

A follow-up - I haven't had an ICE-on incident of this sort since that one in late winter/early spring. Curious to see if it happens again next spring...

Posted via the PriusChat mobile app.

 

or this fall.

 

I'll be surprised to see it happen in the fall (see previous posts theorizing why not), as it didn't last fall.

Posted via the PriusChat mobile app.

 

gotcha.

 

So, just when I thought that I, and my car, were immune to the ice comes on anyway syndrome, something really odd happened yesterday.

Temperature was 70 F. in evening. Charged to full 100% at night. Next morning was 75 degrees. Started car to get to work and ICE is instant, and stays on. Never an "EV" on the dash. I tried switching EV>HV and HV>EV and back, several times - no change. Stays in HV. No hills, no electrical accessory usage other than radio (no AC/heat/defrost/fan/cruise control).

I parked the car halfway to work, and shut it off. Waited 30 seconds and turned it back on. Indicated 36.9 miles. Started in EV and stayed there.

One thing different is that I'd never seen 100% charge indicate 37 miles before. That was at least 2 miles more than normal. And I can't think that 75 degrees was too out of range from charging the night before at 70 degrees.

What might cause EV to not be the default?

 

Our BMW i3-REx insists on running the engine after 60 days. I suspect our Prime have a similar time limit before the engine has to run. If nothing else to lubricate the moving parts.

Bob Wilson