My Hymotion: What I've Learned So Far

[Arthur]

I've been trying to find ways around all of the things that cause the ICE (gas engine) to start up. Here's my list of causes:

1) going too fast
2) accelerating too hard
3) traction battery (the NiMH Prius battery) too cold
4) temperature too cold in general
5) Hymotion battery too full?
6) traction battery too full?
7) Hymotion error (13 flashes of red LED)

Some of these are really obvious.

I've found that I have to drive 32 mph (or slower) to stay in EV mode. I generally keep my speed around 30. (It's pretty hard to stay at 32, without occasionally going 32.5!)

I've found that relatively gentle acceleration is enough to stay in EV mode. On a slight uphill grade, MORE gentle is required.

Then, there are the big hills. I live on a fairly steep one. I've found that I can stay in EV all the way up the hill but only if I restrict myself to about 9 mph on the steepest stretches. The trick is adjusting my speed to match the slope as it changes. The other trick is to pull over when someone needs to pass. In some areas, passing is not allowed and there's no shoulder. So, I try to restrict my 9 mph behavior to late at night and use my flashers if I'm feeling really stubborn. :-)

Since I live in New York state (Corning), I have often had to deal with the 0 degree (Celsius) temperature limit for the traction battery. Below this temperature, the Prius doesn't permit EV mode. So far, I havn't found a good solution for this one. Some people have suggested keeping the battery warm with an electric blanket. To avoid running the car's batteries down and to avoid needing an electrical outlet (none available at work), my first attempt was a rechargeable battery-powered blanket, the Chill-Buster. (They don't seem to make them any more, but my wife found one on Ebay.) Unfortunately, it doesn't seem to put out enough heat to do the job. I haven't given up on it yet, but it doesn't seem promising.

By the way, if anybody knows how to monitor the traction battery's temperature with a ScanGauge (on a 2008 Prius), I'd love to know. I tried creating an Xgauge with the codes that someone had posted, but it doesn't display anything. Perhaps it doesn't work on the 2008 model.

I bought an engine block heater through Prius Chat and had my local Toyota dealer install it. However, heating up the engine coolant really doesn't have much effect on whether you can start up in EV mode or stay in EV mode. The traction battery temperature is the limiting factor.

On cold days, using the EBH will definitely improve your initial non-EV mileage, but I'm not sure if I fully understand what results to expect from the interaction of the EBH and the "thermo bottle." For example, if my car has been sitting for a couple days, with the thermo bottle dump cold coolant into the engine and negate most of the effect of the EBH? If anybody understands this, I'd appreciate a better explanation of when and why the bottle dumps and whether this negates the effect of the EBH.

Like others have mentioned, I have noticed that I can use EV mode, even on fairly cold days (in the twenties), if my car is warmed up (not too likely, if you're trying to use EV mode most of the time).

The only useful trick I've found is to completely shut off the heating/air conditioning system. When air is needed to clear the windows, the "defrost/feet" button will often allow you to stay in EV mode (as opposed to the "defrost only" button). Keeping the temperature set lower also helps (not that the temperature matters much, if the engine is cold), but hitting the "OFF" button will give you the best chance of using EV mode.

Here's the confusing thing: Often, even though the temperature seems to be warm enough, my Prius won't go into EV mode when I first start it. At first, I thought it was because the engine (or the battery?) was cold. Gradually, I've come to suspect that it has more to do with the fact that the Hymotion battery is fully charged or is very close to being fully charged. This doesn't always prevent me from going into EV mode. So, it may be some combination of too much charge and too cold a temperature.

If anybody has experienced this or has some understanding of it, I would love to hear it.

The Prius (traction) battery seems to have a similar behavior. If the State of Charge (SOC) gets too high, I get kicked out of EV mode. Every morning, on my way down the hill, I would hear 3 beeps and the engine would start. The ironic thing was that I had figured out how to stay in EV mode on the way UP the hill (go 9 mph) but couldn't keep it in EV on the way DOWN!!! Obviously, it has something to do with exceeding a certain SOC level. When I got my ScanGauge, I found that it kicks me out of EV just before the SOC reaches 80%.

When the SOC gets into the 70's, it seems to increase much faster. I've found that I can stop it from increasing further by shifting into neutral. The SOC actually continues increasing a little bit after I shift into neutral. So, I usually shift when my ScanGauge shows an SOC of about 73% or so. That way, I capture as much braking energy as possible without being forced out of EV mode. After stopping at the bottom of the hill, I shift back into Drive and off I go (still in EV mode)!

The final problem is the 13 flashes of the red LED. Like most other people, I see this occasionally in cold weather. The explanation that others have posted seems to make perfect sense. The battery voltage drops below some threshold if you have to many devices turned on when starting the car. So, I have started turning the heating/air conditioning system (and the headlights and the radio) completely off before turning the car off. This seems to prevent the error.

This error is probably best avoided because it occasionally causes some other problems. Once, I got the error when I was leaving work. I was able to clear it by shutting off the car for several minutes, by I still noticed some strange behavior on the way home. I was going up the hill to my house and noticed that my car was NOT in EV mode, but the engine was also NOT RUNNING! So, I kept going up the hill at 9 mph until I realized that my traction battery was getting very low (and was not being recharged by the Hymotion battery). Very flaky behavior! So, I try to avoid the 13 flashes.

I've probably given the impression that I drive in EV mode most of the time. The reality is that I've been making a lot of highway trips lately and have only had two tanks that were above 60 mpg average (since I had the Hymotion installed in early October).

Today, I am hoping to make my first round-trip from home to work and back (hills and all), without using ANY gas. (By the time I figured out the downhill stuff, it was already cold weather. Today is quite a bit warmer.)

If anyone has any insights into any of the things I've mentioned, I'd love to hear them.

I've probably made it sound like the Hymotion system has a lot of weaknesses. If you're trying to make your Prius be a completely electric car, that's probably true. However, the Hymotion system was never intended to do that. As a plug-in hybrid system, it works great! It provides significantly increased gas mileage in a variety of situations, and I have no regrets about buying it.

[jrmgkia]

Originally Posted by Arthur

I've probably made it sound like the Hymotion system has a lot of weaknesses. If you're trying to make your Prius be a completely electric car, that's probably true. However, the Hymotion system was never intended to do that. As a plug-in hybrid system, it works great! It provides significantly increased gas mileage in a variety of situations, and I have no regrets about buying it.

Arthur thanks for the detailed writeup, every review helps in deciding if this is a good choice for me. I still haven't found anyone with a Hymotion who has a similar commute to mine. I live in a mild CA climate and drive 30 miles on the freeway at ~65mph down to work, where I can plugin for 8hrs during the day. Then I drive the 30 miles back home, I would love to know what kind of mileage I could expect WITHOUT modifying my driving style, I currently get ~45mpg.

[boxer93]

Arthur,
Thanks for stating your experience. 3 points that I would like to add. I know that you try to do a lot of EV. I'm almost the opposite. I like to get the ICE up to temp as soon as I hit the 30+MPH roads. This allows me SHM more often. To me I find this the most efficent work for the L5. I'd rather be getting 99.9+ at 50MPH than 100% EV at 9MPH. Second I am surprised at your mileage. We most likely have similar Temperatures and I'm about to get my worse tank at 73.x MPG (don't forget the electicity used too and Third Grill Block. Not sure if you do or not. Since the ICE works less with the Hymotion every BTU should be saved.
My .03USD
Chris

[PeakOilGarage]

Originally Posted by Arthur

I've found that I have to drive 32 mph (or slower) to stay in EV mode. I generally keep my speed around 30. (It's pretty hard to stay at 32, without occasionally going 32.5!)

That is also my strategy when the engine is cold. 30-31 mph to maintain my EV in the morning. There is a long road with no stoplights about 3 miles into my drive, that is where I normally get it up to 45 mph and go through a warm-up phase.

I also have an early software version that enables me to avoid the CARB mandated warm-up phase. I think you do also if you had an early October install.

Originally Posted by Arthur

I've found that relatively gentle acceleration is enough to stay in EV mode. On a slight uphill grade, MORE gentle is required.

Then, there are the big hills. I live on a fairly steep one. I've found that I can stay in EV all the way up the hill but only if I restrict myself to about 9 mph on the steepest stretches. The trick is adjusting my speed to match the slope as it changes. The other trick is to pull over when someone needs to pass. In some areas, passing is not allowed and there's no shoulder. So, I try to restrict my 9 mph behavior to late at night and use my flashers if I'm feeling really stubborn. :-)

I do exactly the same thing. I have a half mile hill to deal with every day. Great in the morning for regen going down. It sucks in the afternoon coming home. Mine is so steep that I need to keep it at 8 mph to maintain my EV mode all the way up.

Originally Posted by Arthur

Here's the confusing thing: Often, even though the temperature seems to be warm enough, my Prius won't go into EV mode when I first start it. At first, I thought it was because the engine (or the battery?) was cold. Gradually, I've come to suspect that it has more to do with the fact that the Hymotion battery is fully charged or is very close to being fully charged. This doesn't always prevent me from going into EV mode. So, it may be some combination of too much charge and too cold a temperature.

If anybody has experienced this or has some understanding of it, I would love to hear it.

When the engine comes on for the first time after starting the Prius, then the only way to get into pure EV mode is to come to a complete stop after the warm-up phase. After that first engine stop, then you are beyond stage one and can slide in and out of EV mode while driving.

I can start in EV mode right out of the garage with the ICE never coming on at all. But if the ICE is triggered, then I have to let the car warm up to about 115-120 degrees. Then the next full stop of the vehicle will allow me to slide in and out of EV easily while driving.

If you allow the car to warm-up to 157 degrees, then you can maintain 40 mph in EV mode after that.

You only need to get the temp up to that level one time. Even if it cools down to a lower temp, the system is in a stage that will allow 40 mph in EV mode for as long as you have the Hymotion battery power.

Originally Posted by Arthur

The Prius (traction) battery seems to have a similar behavior. If the State of Charge (SOC) gets too high, I get kicked out of EV mode. Every morning, on my way down the hill, I would hear 3 beeps and the engine would start. The ironic thing was that I had figured out how to stay in EV mode on the way UP the hill (go 9 mph) but couldn't keep it in EV on the way DOWN!!! Obviously, it has something to do with exceeding a certain SOC level. When I got my ScanGauge, I found that it kicks me out of EV just before the SOC reaches 80%.

Here is what I do. When I first start my Prius the Hymotion battery is on, headlights and radio are off to avoid any errors. I back out of my garage and start driving in EV mode. I then turn off the Hymotion battery and just maintain the EV mode with the stock Prius NiMH battery. My goal is to drain that NiMH battery down to 5/8 SOC before I start the decline portion of my hill. If I start the downhill portion with 5/8 then by the bottom I am typically at 7/8.

So I am never kicked out of EV mode. So I drive about the first two miles each day with the Hymotion battery being in the off position and maintaining my EV mode the entire distance.

Then I reach a long area with no stop lights that is typically good for my warm-up phase because I can turn on the Hymotion battery, speed up to 45 mph and still average 100+ mpg while the ICE is warming up to an optimal temp for EV use.

Originally Posted by Arthur

This error is probably best avoided because it occasionally causes some other problems. Once, I got the error when I was leaving work. I was able to clear it by shutting off the car for several minutes, by I still noticed some strange behavior on the way home. I was going up the hill to my house and noticed that my car was NOT in EV mode, but the engine was also NOT RUNNING! So, I kept going up the hill at 9 mph until I realized that my traction battery was getting very low (and was not being recharged by the Hymotion battery). Very flaky behavior! So, I try to avoid the 13 flashes.

I have seen that happen also. I knew something was wrong because I was able to go up a steep hill at 20 mph and maintain pure EV mode. Then I noticed that my NiMH battery was REALLY low. It was weird.

Originally Posted by Arthur

I've probably given the impression that I drive in EV mode most of the time. The reality is that I've been making a lot of highway trips lately and have only had two tanks that were above 60 mpg average (since I had the Hymotion installed in early October).

I am surprised by your numbers. Are you driving a lot with your battery empty? I almost never have an empty battery. My current average is 99.9 at 580 miles on the current tank of gas. According to ScanGauge I am averaging about 112 mpg.

[zcat3]

Originally Posted by jrmgkia

Arthur thanks for the detailed writeup, every review helps in deciding if this is a good choice for me. I still haven't found anyone with a Hymotion who has a similar commute to mine. I live in a mild CA climate and drive 30 miles on the freeway at ~65mph down to work, where I can plugin for 8hrs during the day. Then I drive the 30 miles back home, I would love to know what kind of mileage I could expect WITHOUT modifying my driving style, I currently get ~45mpg.

Hey Jason - I resemble that commute. As you may recall, I live in Half Moon Bay. My commute is 28.2 miles to the financial district in San Francisco. I would estimate I am averaging about 85 MPG right now, with a best of 96 MPG for a R/T (charging at my garage in the city) and maybe 110 MPG for a single leg home (my mileage is always better going home). A typical commute so far would be what I expect today - I got 82 MPG coming in and will probably get 90 or so going home for an average for the day of 85 - 90.

I have changed my driving a bit, basically staying close to 60 in the slow lane in the few areas on 280 where it is a slight uphill, and then moving over to the faster lanes and letting in get up to 70 - 75 where the road is a gradual downhill. I would say my change in driving style probably adds 0-5 minutes to my commute each way and maybe 10 MPG per trip.

So with that in mind, and assuming you do not have too many hills (I have 2 pretty steep climbs to make) if you did not change you driving style at all and are getting 45 MPG now, I would expect 75 - 90 for you with the ability to get 95 if you wanted to change your habits a bit.

[Arthur]

Originally Posted by boxer93

I'd rather be getting 99.9+ at 50MPH than 100% EV at 9MPH. Second I am surprised at your mileage. We most likely have similar Temperatures and I'm about to get my worse tank at 73.x MPG (don't forget the electicity used too and Third Grill Block. Not sure if you do or not. Since the ICE works less with the Hymotion every BTU should be saved.
My .03USD
Chris

Chris,

My alternative to EV at 9 mph is not 99.9+ mpg at 50 mph. It's more like 20 mpg at 30-40 mph. Remember that I'm going up a steep hill. Even with the electric motor assisting, the mileage is pretty low. If I spend too much time at 20 mpg, my average mpg takes a pretty big hit.

However, I was oversimplifying a bit. I often go halfway up the hill in EV and then (to avoid blocking traffic) speed up to 30 or 40 mph (non-EV) for the last mile or two. Also, staying in EV doesn't mean I have to go 9 mph the whole way. That's only on the steepest stretches.

The reason I have so few tanks with high mileage is that I rarely go more than a few weeks without some kind of out-of-town trip. So, I rarely finish a whole tank without putting on a bunch of non-Hymotion miles.

I could keep track of the miles separately, but I've been more interested in figuring out how to stay in EV than I have been on tracking my exact mileage.

My other problem is that, currently, I can't charge at work. So, if I need to make multiple trips to town, the second trip home usually ends up being non-Hymotion miles. That drops my average quite a bit.

[Arthur]

Originally Posted by PeakOilGarage

If you allow the car to warm-up to 157 degrees, then you can maintain 40 mph in EV mode after that.

You only need to get the temp up to that level one time. Even if it cools down to a lower temp, the system is in a stage that will allow 40 mph in EV mode for as long as you have the Hymotion battery power.
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Here is what I do. When I first start my Prius the Hymotion battery is on, headlights and radio are off to avoid any errors. I back out of my garage and start driving in EV mode. I then turn off the Hymotion battery and just maintain the EV mode with the stock Prius NiMH battery. My goal is to drain that NiMH battery down to 5/8 SOC before I start the decline portion of my hill. If I start the downhill portion with 5/8 then by the bottom I am typically at 7/8.

So I am never kicked out of EV mode. So I drive about the first two miles each day with the Hymotion battery being in the off position and maintaining my EV mode the entire distance.

Then I reach a long area with no stop lights that is typically good for my warm-up phase because I can turn on the Hymotion battery, speed up to 45 mph and still average 100+ mpg while the ICE is warming up to an optimal temp for EV use.

Are you sure? 40 mph in EV mode? I've never seen that happen. (My commute isn't really long enough to get the engine warmed up very much.) Do you use grill-blocking? Is there anyone who sells grill-blocking material for the Prius? Or, do I have to make something myself? Any suggestions on how to do that would be appreciated.

I've been avoiding switching the Hymotion switch on and off. Have you experienced any problems while doing that? Has anyone else experienced any problems? It does seem like the best way to maximize the capture of braking energy on the way down the hill.

My commute is only about 7 miles each way, mostly on city streets (30 mph speed limit). That's why I tend to stay with EV mode.

I've noticed that, once you get kicked out of EV mode, the only way to get back into EV is to stop the car and turn the power off and back on. I occasionally do that when I accidentally go too fast.

When it's slightly too cold to start the car in EV mode, I sometimes find that driving a block or two, stopping the car, and starting it again will allow you to go into EV mode. When it's really cold, however, you can do that as many times as you want, and you'll never get into EV mode.

[PeakOilGarage]

Originally Posted by Arthur

Are you sure? 40 mph in EV mode? I've never seen that happen.

Go out driving with a full Hymotion battery. Get the Prius up to 40 mph and just put it on cruise control. Monitor RPM and water temp F.

Once the water temp gets up to 155+ degrees F, the car can do EV mode at 40 mph with 0 RPM when there are flat roads. This can be maintained as long as you have Hymotion battery energy.

Originally Posted by Arthur

(My commute isn't really long enough to get the engine warmed up very much.) Do you use grill-blocking? Is there anyone who sells grill-blocking material for the Prius? Or, do I have to make something myself? Any suggestions on how to do that would be appreciated.

I do grill blocking with the pipe insullation foam from Home Depot or Lowes. Cut it in half with a sharp knife, then stuff the grill.

Originally Posted by Arthur

I've been avoiding switching the Hymotion switch on and off. Have you experienced any problems while doing that? Has anyone else experienced any problems? It does seem like the best way to maximize the capture of braking energy on the way down the hill.

No problems for me. I start from my garage in Hymotion EV mode, then turn off the Hymotion battery and drive very gently on flat terrain for about 0.3 miles. This drains my NiMH battery to 5/8 right when I start downhill. By the bottom of the hill I am at 7/8 and never get kicked out of EV mode. Then the next stretch I do my warm-up phase intentionally with the Hymotion battery switched back on. My MPG is 100+ because my speed is about 45 mph.

Then I typically hit a stop light and that allows my Prius to come to a full stop, the ICE goes off and my water temp F is about 115-120 degrees. That allows pure EV mode on and off easily while driving, depending on terrain.

Originally Posted by Arthur

I've noticed that, once you get kicked out of EV mode, the only way to get back into EV is to stop the car and turn the power off and back on. I occasionally do that when I accidentally go too fast.

That is not my experience. I do not need to turn off the car to get back into EV mode. After the first time the ICE comes on, after it is warmed up to 115 degrees F, then the ICE will go off with a complete stop. After that first time coming to a stop (at a light or something), then I can get in and out of EV mode merely based on how I use the gas pedal. If I am at 32 mph or less, I am pure EV. Even if I do bring the ICE briefly, it is easy to get back to EV while moving.

[sidsjiff]

First off -- thanks to all who take the time to report their experiences with the Hymotion, Prius, etc. It's been very helpful for me. Rather than start a new thread, I thought I post here a bit about my experience with the Hymotion, installation, etc.

Install: last week at Galpin Auto Sports, Van Nuys, CA
Based on what I had read here and heard about - I inquired about the low auxillary battery voltage problem. The installers there informed me that my install received the voltage regulator circuit that goes between the 12 v and the Hymotion harness allowing the Hymotion to start properly in cold weather when the voltage drops below 11.5 volts. My Prius is 3.5 years old and presumably the voltage of the auxillary battery would likely have created a problem without this. I have not had a startup problem so far.

My commute: 20 miles each way (30min). Now charging at work and at home. 60% highway 40-65MPH, 40% streets 0-35MPH
Cumulative MPG: 85 MPG (not using ScanGauge yet!)

Few questions:

1) Spare tire
What have you done with yours? Galpin strapped it down on the flatbed surface (above the Hymotion battery). Quite secure, but all the warnings about projectile spare tires during an accident worries me. Any solutions for this problem other than getting AAA Premier?

2) GFCI outlet
As the Hymotion manual suggested, I got 12 gauge 50 foot contractor grade extension cords from Home Depot ($33 each, one for home, one for work). In addition, I purchased GFCI outlet add-on plugs for each location ($12 each). Did others do this as well? Any other suggestions for charging?

3) ICE
I have read with a great deal of interest about techniques to prevent the ICE from engaging or getting it to shutoff. Recently, morning temps have been hovering about 40F and it has been a challenge to keep it off in the morning. But sometimes, even in the warmth of the day, it turns on. A lengthy full stop will usually shut it off, but sometimes my only recourse is turning of the Prius completely. At what ambient temperature is grill-blocking a BAD idea? I wonder if grill-blocking even during our relatively mild winter temperatures here would be worthwhile? Possibly a partial grill-block?

4) Cost
I am very happy to have purchased the Hymotion. I realize I will likely never recover the cost, however, as most know that is not the only reason to do it. At some point, gas prices will rise again and we won't seem so foolhardy. Interestingly, the recent stimulus package includes language that suggests we can recoup at least 10% of the cost as a tax credit:

thomas.loc.gov/home/h1/Recovery_Bill_Div_B.pdf
See page 64, Section 1143 Conversion Kits

That being said, the current price point of $10,395 + tax appears to create a lot of hesitation. What price point would cause this to flip? Or could it be that if the kit were to provide 100 miles of EV driving it would warrant its adoption? Just wondering what people thought of this.

[Arthur]

Originally Posted by sidsjiff

1) Spare tire
What have you done with yours? Galpin strapped it down on the flatbed surface (above the Hymotion battery). Quite secure, but all the warnings about projectile spare tires during an accident worries me. Any solutions for this problem other than getting AAA Premier?

2) GFCI outlet
As the Hymotion manual suggested, I got 12 gauge 50 foot contractor grade extension cords from Home Depot ($33 each, one for home, one for work). In addition, I purchased GFCI outlet add-on plugs for each location ($12 each). Did others do this as well? Any other suggestions for charging?

3) ICE
I have read with a great deal of interest about techniques to prevent the ICE from engaging or getting it to shutoff. Recently, morning temps have been hovering about 40F and it has been a challenge to keep it off in the morning. But sometimes, even in the warmth of the day, it turns on. A lengthy full stop will usually shut it off, but sometimes my only recourse is turning of the Prius completely. At what ambient temperature is grill-blocking a BAD idea? I wonder if grill-blocking even during our relatively mild winter temperatures here would be worthwhile? Possibly a partial grill-block?

I just leave my spare tire strapped down in the back. I pile the grocery bags on top of it. On the rare occasions that I need more space, I take it out and leave it home. The real projectile risk is the tire jack. It doesn't really fit securely under the strap and could do some real damage in an accident.

I don't have a garage. So, I charge my car in the driveway (even in pouring rain). Yes, I have a GFCI outlet. I use a 100-ft, 10-gauge, yellow, Coleman, cold-weather cord. It has a big, round head on it that fits snugly in the car's charging socket, leaving very little room for water to get in.

I'm still struggling with strategies to keep the ICE from coming on. It depends on a lot of things. Last night (at about 10:30), my car went directly into EV mode when I started it up. The temperature was 19 F!! I drove all the way home from work (up a big hill) and the engine never came on. By the time I got home, my ScanGauge was showing that the coolant temperature to be 33 F.

At about 9 pm, I had made a short drive of a mile or two. I think that warmed up the battery enough that it was willing to stay in EV mode for the trip home.

In cold weather, I often notice that I get 3 beeps after driving the car for a block or two. I take that to mean that the battery has warmed itself up enough (just by discharging to run the motor) to allow EV mode. So, I usually just pull over and turn off the car. When I restart, it goes right into EV.