Questions for Toyota Prius owners.

I'm learning about the gen I and gen II Prius. I would like to hear from Prius's owners. Thanks in advance.

I have a lot of questions, but let's begin with a few basic ones.

1) How involved is it to add the EV Mode button to a Prius sold in the USA?
2) Once the EV Mode is enabled what is the top speed (on flat) before the ICE kick in? 34mph?
3) How far can it go in EV mode when the battery is fully charged?
4) What is the LVC threshold for the ICE to kick in?
5) What are the highest and lowest voltages of the stock NiMh pack you have seen on your Prius?

SamTexas said:

I'm learning about the gen I and gen II Prius. I would like to hear from Prius's owners. Thanks in advance.

I have a lot of questions, but let's begin with a few basic ones.

1) How involved is it to add the EV Mode button to a Prius sold in the USA?
2) Once the EV Mode is enabled what is the top speed (on flat) before the ICE kick in? 34mph?
3) How far can it go in EV mode when the battery is fully charged?
4) What is the LVC threshold for the ICE to kick in?
5) What are the highest and lowest voltages of the stock NiMh pack you have seen on your Prius?

Click to expand...

Not what you asked, but here is some info on the latest generation Prius, which has the EV Mode button, along with "Power" and "Eco". I always drive in Eco, and my GF in Normal (the default mode if no buttons are pushed and it wasn't shut off in Eco) mode. We get roughly the same fuel economy, with me slightly edging her out in warm weather, and getting somewhat better economy in cold weather.

Top speed: 26 MPH is the cutoff for EV Mode. It will also cut off for too much throttle, low charge, and engine cooling off, often lying about the exact reason and calling it "excessive speed." It will sometimes cut off for no apparent reason at all, calling it "excessive speed." HOWEVER: in Eco mode at least, the car will run in EV mode with no speed limit (that I've found) as long as the engine is hot, the battery pack has enough charge, and you keep the throttle opening below the EV mode cutoff on the bar graph. I've gotten ours up to 45MPH with the engine off this way, and 55 should be easy on a downhill run. I've also driven it several miles - mostly downhill or level road - in Eco mode with the engine off. For this reason I only use EV mode in parking lots and to move the car without starting the engine, if it's still warmed up. If "LVC" is voltage as measured by the stacked bar icon, then EV mode cuts off in all 'official' modes when it drops below 2 bars. IOW the pack won't drop below two bars if the car is on and the engine is working.

there's some sites/threads in this search page that mgiht be the info you're after; i'm naot famialir enouhg with the prius to judge
http://www.google.com/search?q=ecomodder+prius+ev+mode

Thanks LeftieBiker.

More questions for gen 1 and gen 2 Prius owners:

6) What is the highest observed discharge current from the NiMh battery on your Prius? And highest charge current?

SamTexas said:

I have a lot of questions, but let's begin with a few basic ones.

1) How involved is it to add the EV Mode button to a Prius sold in the USA?
2) Once the EV Mode is enabled what is the top speed (on flat) before the ICE kick in? 34mph?
3) How far can it go in EV mode when the battery is fully charged?
4) What is the LVC threshold for the ICE to kick in?
5) What are the highest and lowest voltages of the stock NiMh pack you have seen on your Prius?

Click to expand...

1. Not very, there are kits. Just a couple wires to the ECUs behind the glovebox.
2. Yes. "kill switch" style EV-mode is good for 52? 55? at that point the MG1 speed is at its physical limit and the car can't travel faster without spinning the ICE
3. Depends how you drive. Pack is very small capacity.
4. Not sure. Depends on the circumstances.
5. Gen2: 150-275? Ballpark.
6. About 100 amps.

I believe the most useful way to think about the powertrain design is that the battery is part of the transmission system. The car is not designed or optimized to EVER run in a charge-depleting mode. The pack is just a short term buffer. In normal driving the SOC stays within about 1/3 of the indicated range- the only situations which cause deeper cycling than that are hills (full charge after decent), stop and go traffic (full depletion due to very low speeds), and sitting in P with climate control on (cycling).

I'm sure you can find lots more accurate and detailed technical information on PriusChat or one of the several enthusiast websites for this car, the car has quite a large following of technical-minded people, tons of info to be found. These answers are just what I remember off the top of my head from back when I was paying attention to it, now I usually just drive it.

Thank you acuteaero.

I have spent considerable time on the sites you mentioned. Yes there were some relevant info, but detailed technical they are not. Unfortunately, like most things published on the net, they are heavy on form and light on function.

Don't use the E.V button, I really use it if I need to reverse in the yard or when stopped at lights etc. The reason is you will use up the charge and the engine will have to be on a lot more to charge back up the battery.

The trick with the Prius is to learn when and how to use the energy in the battery and hitting the E.V button at slow speeds is the most inefficient way to use that energy.

Tricks like pulse and glide where you back off the throttle and gently push until there is no energy flowing anywhere on the display, when you get used to it you will know what mode you are in just by the feel of the car, I've driven mine for 45,000 miles in the last 2 years. But using pulse and glide at speeds up to 44 mph at decents in the road, you will be surprised the distance you can make it roll, this isn't the same as hitting neutral as doing that will cause the ICE to kick in.

The other mode where you back off the throttle and gently push until energy only flows from the battery, this is the most efficient way of using the power. This works where there is a slight descent in the road, going down gentle hills etc where the motor doesn't have sufficient power to drive the car but it will keep the momentum going, this works surprisingly well.

Economy suffers in winter, but this time I have F rated winter tyres but even so I can get a good 58 mpg imp or 48.29 US. per tank When I got the car it had winter tyres on it and I even drove them in summer but averaged 64 mpg in summer with those tyres on (53.28 US) I can't wait to try it with proper fuel efficient tyres.

My old 2003 Audi A4 Multitronic diesel Auto managed only 48 imp mpg per tank or 39.96 US mpg. But I miss the punch of a diesel, the lack of torque in the prius means the engine is stressed a fair bit. The MK III has a much better engine. When you got a full battery the torque is better. But still the whack of a turbo diesel is great.

I drove the Leaf at xmas and loved the punch in that, I'd love one.

Sorry I couldn't answer all your technical questions, but I hope that was of some use!

Thanks.

My plan (just a plan at this time, no imminent implementation) is to replace the stock NiMh pack with consumer Lithium Cobalt 18650 cells. The replacement lithium pack will have at least 3 times the capacity (energy content) of the stock pack. The idea is to be able to run short trips (5 to 10 miles) without firing up the gasoline engine.

To replace the stock pack, I need to know its operating parameters, its behaviors so I can mimic them with the new pack. That was supposed to be a relatively straight forward task or so I thought.

SamTexas said:

Thanks.

My plan (just a plan at this time, no imminent implementation) is to replace the stock NiMh pack with consumer Lithium Cobalt 18650 cells. The replacement lithium pack will have at least 3 times the capacity (energy content) of the stock pack. The idea is to be able to run short trips (5 to 10 miles) without firing up the gasoline engine.

To replace the stock pack, I need to know its operating parameters, its behaviors so I can mimic them with the new pack. That was supposed to be a relatively straight forward task or so I thought.

Click to expand...

Ah gotcha now,

I think I read all that on the Prius forum if you look around the Prius II mods, there are guys converting Prius, but I don't think it's worth it as it's not very efficient, though most use inverters to charge the stock pack some do replace it altogether.

I wouldn't have thought it safe to use Li cobalt though ?

I would only use the packs that have been tested to work with the prius, BMS seems to be the biggest problem last time I checked but maybe they sorted that now.

I thought about doing that but it would be very expensive and getting stuff shipped here would just make it even more un economical. I'd rather put that money into a new/2nd hand leaf. Which I think you'd be better off waiting for as you get them way cheaper over there than here.

Actually the biggest saving I could make would be to convert to LPG as it costs half what petrol does here.

I agree with you about efficiency, especially with the current DIY approach for the Prius. The current DIY method (if I understand correctly) is to "parallel" the stock pack with a external lithium pack. It's not true parallel, because the lithium pack is used to charge the stock pack. And that's the inefficiency.

My approach (not even sure if it's feasible) is to replace the stock pack.

I think you're thinking about the danger of RC LiCo (HobbyKing LiPo and the likes). I'm talking about consumer LiCo (laptop, cell phone, gps, Tesla, etc ...)

SamTexas said:

I agree with you about efficiency, especially with the current DIY approach for the Prius. The current DIY method (if I understand correctly) is to "parallel" the stock pack with a external lithium pack. It's not true parallel, because the lithium pack is used to charge the stock pack. And that's the inefficiency.

My approach (not even sure if it's feasible) is to replace the stock pack.

I think you're thinking about the danger of RC LiCo (HobbyKing LiPo and the likes). I'm talking about consumer LiCo (laptop, cell phone, gps, Tesla, etc ...)

Click to expand...

I think people remove the stock pack if installing a Lithium pack when hacking the ECU for more than 30 mph.

The ones who use the inverter method leave the stock pack connected and just top it up off the lithium pack and still can only do 30 mph max in e.v mode.

LiCo I thought would be just as dangerous ? Tesla cool their pack.

Even hacking the ECU the prius won't have a lot of power and many people are not happy with the end result. But if you can get the batteries cheap enough it would be an interesting project.

o00scorpion00o said:

I think people remove the stock pack if installing a Lithium pack when hacking the ECU for more than 30 mph.

Click to expand...

I recall seeing this, but again I could not find the specific details. If you happen to know the link off-hand, let me know.

>>>LiCo I thought would be just as dangerous ? Tesla cool their pack.
Yes, Tesla cool their pack. But that's because they do 3.65C for performance. I have no plan to exceed 1C. This is a Prius after all.

>>>Even hacking the ECU the prius won't have a lot of power and many people are not happy with the end result. But if you can get the batteries cheap enough it would be an interesting project.
Yes, I'm aware of this fact. Still, given the opportunity I'd like to give it a try. But I won't do anything until I have a much better understanding of how the stock NiMh pack functions.

You might find some useful information here.

http://priuschat.com/threads/md-tech-phev-conversion-kit.119469/

If you do this, start a thread, I'll be very interested.

SamTexas said:

Thanks.

My plan (just a plan at this time, no imminent implementation) is to replace the stock NiMh pack with consumer Lithium Cobalt 18650 cells. The replacement lithium pack will have at least 3 times the capacity (energy content) of the stock pack. The idea is to be able to run short trips (5 to 10 miles) without firing up the gasoline engine.

To replace the stock pack, I need to know its operating parameters, its behaviors so I can mimic them with the new pack. That was supposed to be a relatively straight forward task or so I thought.

Click to expand...

You don't mention an external charger. You're really going to need one, because otherwise if you try to use most if the capacity of the new pack, it will end up staying at the bottom. If you wait and use it pnly when the ICE and braking system can fully charge it, you will get little use from it - maybe one trip a week, if you're lucky. So plan on making this a Plug-in hybrid, not a Non-plugin with a big battery pack. I'm guessing you are planning that, but you never know...

Yes, the charger is part of the plan. It was not mentioned because I didn't have an issue with it (not yet anyway).

Have you found any information yet Sam ?

Thanks for asking. No. I have not found any additional meaningful technical data. The same thing is repeated (copied or slightly modified) over and over from one site to the next. I'm loosing interest. May be the real solution is beyond the DIY realm. I definitely don't have the resources to do a thorough reverse engineering job.

Check this out.

http://diy.pluginsupply.com/system-overview/img_2033.jpg.php

It shows the way it can connect, but It doesn't say how you hack the ECU for more than 30 mph ? maybe it's in there somewhere.

10kw/hr that actually sounds interesting. 10,500 USD ready to install (me arse) By the time it got over here and I'd probably get stung for import tax, might not be worth it. 10 kw/h would be useful. That's almost half the usable kw/h of the Leaf !

HI Sam,

Check out this thread on priuschat.

http://priuschat.com/threads/plug-in-supply-diy.105157/

Quote.
PIS sell a "ECM assembly" as listed in the price list for DIY. I have no idea what it looks like. I believe this is the part which allows EV at high speed (lot greater than 85kph) by enabling and disabling the ICE. Since there is no bridge on the Canbus I then assume that they somehow manipulate the ECM or maybe replace it with one which has been reprogrammed for a PIS kit. With this ECM assembly there is no need to stop and cycle the power to enable the ICE like the old PIS kit used to do by using a simple fuel cut switch followed by a instant clearing of the DTC. The new PIS kit is a lot more sophisticated than the old one. I guess that the ECM assembly is also the part that allows the Prius to discharge 200amps (10kwh PIS kit only) into MG2 instead of the maximum of 125 amps on a standard Prius. A good reason to get a 10kwh PIS kit instead of a 4kwh PIS kit.
End Quote.

Very interesting.

Thanks.

I've spent three years in Gen II Prius land. In the beginning I was just like a lot of people and had ideas of making it more electric. Now it is just a daily driver and I've stopped messing with it.

IMHO, the Prius is a very poor candidate for doing anything beyond adding some kWh and running in the 52 mph mode. Consider that Plug-in Supply, Enginer, they have been working on this problem for several years. Some commercial and DIY implementations are clearly better than others. Some cars go at freeway speeds in full EV, while at least one burned up in a thermal runaway charging event. Probably the best DIY conversion was by pEEf, freeway speeds with in pure EV, and he has since bought a Leaf. He wasn't able to post the fine details of his conversion due to threat of lawsuit from one of thesbigger players in the PHEV space.

The stock NiMH battery has 168 cells serially, organized into 14 blocks of 12 cells each for battery management. The first thing you have to decide is whether to replace the pack completely. If you do that, you need to reproduce the battery ECU with your own CAN bus unit. The ideal case integrates a BMS for the replacement pack with a CAN bus spoofer to replace the battery ECU.

If you put a pack in parallel with the stock pack, then there is a limitation on the amount of extra current that can be delivered, about 14 amps, if you connect downstream of the current sensor inside the battery case. If you connect upstream, not only is it a little dangerous, since the connection is live even with the car off, but also the battery ECU gets confused real quick.

Operating extremes of the stock pack is about 180 - 300 V at 100 amps of boost/regen respectively.

Unless you have a PhD in CAN bus, it is really difficult to make progress, unless you pay big bucks to get a kit and the corresponding intellectual property that solves all of the battery ECU, HV ECU, ECM, etc problems.

seilerts said:

Probably the best DIY conversion was by pEEf, freeway speeds with in pure EV, and he has since bought a Leaf. He wasn't able to post the fine details of his conversion due to threat of lawsuit from one of thesbigger players in the PHEV space.

Click to expand...

May be that explains the lack of real technical data on the net.

Well I certainly don't have a "PhD in CAN bus". Thanks for the input. I think I'm going to look for another project to keep me busy.

Aren't there companies in California who sell PHEV Prius kits that use SLA batteries? Maybe you could make a deal with them to get the kit minus the batteries?

SamTexas said:

seilerts said:

Probably the best DIY conversion was by pEEf, freeway speeds with in pure EV, and he has since bought a Leaf. He wasn't able to post the fine details of his conversion due to threat of lawsuit from one of thesbigger players in the PHEV space.

Click to expand...

May be that explains the lack of real technical data on the net.

Well I certainly don't have a "PhD in CAN bus". Thanks for the input. I think I'm going to look for another project to keep me busy.

Click to expand...

I have run into this problem a few times and it is quite frustrating..Wonder what that 1st amendment is for or any amendment at this point..I am not looking to start a political argument by any means just fed up. :x :x