Living on top of a hill

Your profile mentions a 2004, but you also mention charging timers and posted in the Plug-In section. I am going to assume you have a 2010 or later Prius Plugin and your profile is out of date.

Yes, you are filling up the battery, so the ICE comes on the waste the energy. Your best bet would be to not fully charge before you go down that hill. Or while going down the hill, consume lots of power with the AC or defrost or something. The first is your best bet. The second is a silly workaround that just wastes power.

The other option is to stop regenerating power from your braking. You can do this by switching into neutral. This will use your friction brakes, but they will wear out much faster. Also when in neutral, the engine will not start or stop, it will stay in the mode it is in.

One scenario would be you are in neutral at some speed below 62mph with the engine off. You remain in neutral and the car accelerates to a speed above 62mph. You are now overrevving the MG's. If not in neutral, the engine would have started and the MG's would counterrotate to provide the correct rpms to not blow up one of your MGs. This cannot happen because you are in neutral.

The other worst case scenario is you are in neutral with the engine off and your traction pack's SOC falls below the 40% low threshold. Normally the engine would startup and recharge to keep it at a minimum of 40%. In your case with the engine off, it could continue to discharge. Perhaps long slow grade with AC on or something, no regen. Once you reach the 12% to 15% mark not only have you damaged your pack slightly you have discharged the pack so much that it will no longer be able to spin the engine and start. Luckily with the PiP, you can recharge the pack and be on your way. In a non-PiP, you would be stranded until Toyota flies in the special HV pack charger.

 

That would be my advice. If I were in that situation I would start at the top of my hill with only about 1 or 2 miles of EV range left and see how much charge I had built up at the bottom. Then I would use that to estimate how early I should cut off the charging using the PiP's built-in timer.

 

I have the same situation. I go down a small hill in the morning after leaving the house and if I'm not careful, the ICE will start when the battery gets too full.

I think your best bet is to coast (in D) as much as you can.. a good gauge for me is to coast until I'm about 0.2 miles of the original EV range estimate you left the house with. So if you leave the house with 12.0, for example, you're probably safe regenerating up to about 11.8 before the ICE starts up. These are the figures I've been working with lately, your numbers may be different. If you try this out, you'll probably figure out in a day or two when you should stop regenerating. Once you reach that point, then put it in N and coast the rest of the way, applying brakes as needed.

You could try to time your charge so you leave the house with a less-than-full battery, but personally, I think thats too much to think about in the morning. You could also, as you said, drive around the block a couple of times, but I think that's a waste of time too.

 

I _would_ suggest charging first thing in the evening when you get home, not morning, and letting a little electricity "bleed" overnight. But my experience with lithiums is that the amount of bleed, overnight in temperate climates, would be negligible. Just don't charge fully.

 

I also live on top of a hill, and was concerned that my engine was coming on shortly after leaving home. I read that when fully charged the PiP will spin the ICE to get rid of excess energy since the battery is full. The good news is that this isn't using any gas! It's just free-spinning the engine from my understanding.

So while leaving your battery a bit short of full would be best for maximizing energy generation, it may be impractical to set up a timer to do this. For me I just ignore the engine sound and my gas consumption hasn't been impacted.

 

This is definitely not true.. at least not in the case of the OP. Once the ICE starts up it will go through the whole cold-start/warm-up process.

 

You aren't going to lose enough charge overnight to matter much. Plus it is best to not leave the battery at full charge for long.

Mike

 

Plus it is still a waste of energy.

 

I live on the top of a hill. Have several alternative routes I can take to the bottom. Luckily they are all about the same length. However, two of the routes allw me to run along the contour of the hill before descending into town. I use ~.3-.5 EV miles on the contour and regan .3 EV miles on the descent. By the time I reach the bottom I am pretty darn close to a full charge.

 

Just be very careful when approaching 100kph. You do not want to overrev and burn out an MG to save a penny worth of fuel. If you are going to coast in neutral keep it well below the limit. Remember the car is Japanese. So the 62mph threshold is really 100kph threshold. So if you want to almost redline it, do so with the car in KPH not MPH and only run up to 99KPH (61.5MPH).

 

re: engine free-spinning when battery is full and not using gas:

Thanks much for the correction. I'll do a better job of checking my sources before posting next time. Do you have a link to more information on the cold-start/warm-up process? I'll dig around the FAQs. I do notice this happening to me. When the engine comes on, it seems to want to run for a couple minutes before it will turn off. I wonder how much gas it takes to go through one cold-start/warm-up cycle.

I'm still learning so much! Two weeks in on PiP ownership, and I can't seem to get fully off the gas. I'm doing about 1 gallon for every 200 miles; and getting a little frustrated. Only a little though...I LOVE this car.

 

Through a small sample of our community here, usbseawolf2000 concluded that a warm-up cycle uses 4 ounces of gas. If you dig through the forum, you'll see he makes reference to "2 large eggs" worth of gas a few times

There is a whole lot of information, especially if you're not coming from a different model Prius. I cant even imagine how many hours I spent here, especially prior to my purchase.

You're not doing so bad though at ~200 MPG. Some of us add our fill-up data to ukr2's spreadsheet, which you can see here:

Google Docs

 

How would exceeding 100 kph in "N"over rev the MG? Are you saying the MG stays in gear when the driveline is in neutral but it disconnects when driving with the ICE when running at higher speeds?
I also live at the top of a hill and usually switch into neutral as I approach the max range numbers I had when starting.
I should mention that I normally run in EV mode at speeds between 65 and 70 MPH during my short commute because my freeway entrance is near the bottom of the hill where I live and since the ICE is normally stone cold when I get to the bottom of the hill it would be stupid to allow the ICE to start at the bottom of the hill and then accelerate to freeway speeds cold.
Considering all of the safety features designed to protect the driveline, the simple fact that the system lets me accelerate past 65 MPH and maintain speeds around 70 MPH if the SOC allows it, tells me the 62 kph limit was just a figure quoted to make the corporate lawyers happy because it is closer to the actual speed you can get under average conditions as opposed to what some can achieve under ideal conditions part of the time.

 

All of the drive components are always mechanically connected. At somewhere near 62MPH (100KPH), the ICE will turn on to keep the speed difference between the component connect to the wheel and the component connected to the ICE within its mechanical limits. At this time, you are still in "EV" mode. The EV car icon on the display will change from filled-in to just an outline. The ICE is producing very little power and consuming very little gasoline in this mode. When you are in Neutral, the ICE cannot turn on, so you risk wrecking the Power Split Device by going above this speed.

 

Well, I did my first "fill up" today to figure out if my estimates match reality.

317.4 miles
2.27 gallons

So my gallon every 200 miles was way off. I'm burning a gallon every 139.82 miles just from the multitude of 4 oz "warm ups". If it's happening 3 times per day, over 20 days, I guess that's possible. (128oz per gallon) And there were a few oz spent for legitimate engine starts (but I'm trying to be 100% electric...so these are extremely rare).

I'm working on some method to automatically stop my charge short of 100% so that this doesn't happen anymore on the way down the hill. Unfortunately I haven't figured out how to read the charge while the car is charging in an automated fashion; and I can't really sit in my garage several times per day watching the charge level. I can only read ODBII while car is ON. I may have to wire some sort of sensor directly to the battery...but that sounds like a warranty voiding situation.




I would kill for a "never ever start the engine" button. Obviously regular EV cars figure out some way to burn off excess energy in this situation, I wonder why Toyota forces the engine spin.

 

How about "City" mode in European models? It isn't "never ever start the engine", but it is "you really have to try hard to start the engine". It is designed for "emission free" zones in some European cities.

 

Verrrry interesting! Now I need to find a European owner that lives on the top of a hill and ask them if they have this issue in City mode. Then see if there is some way to add a City mode button...not very likely...but who knows.

 

Tracksyde had a great potential solution for this problem:

So if I had a device that watched for the amperage drop, then that would probably be right around 98% or so. If it cut off there, I would be set...and it would probably gain the 2% on the way down the hill. If there was a switch on the device that said "98%" and "100%" you could select the appropriate one if you happen to be driving UP the hill instead. Now I just have to figure out how to build such a device