Update and technical details on my PHEV project

(Note: I'm starting this new thread as all prior project details have been in other threads, and I don't wish to Hijack them any more than I already have.)

I now have full capability with my replacement BMS ECU. I no longer have the original Toyota Pack, Battery ECU, Fan, Ducting, etc, it's all been removed! I kept the top cover of the battery box just to hold up the floor in the back. The new system does everything the original did, such as read battery Voltage, Current, and Temperature, but now is fully controllable by my own software instead of being a fixed "black box" like the original Denso system was. With it I can also do many other things, such as regulate plug-in charging, and even prevent the gas engine from starting/running. It allows me to use EV only at any speed, though the Prius pretty much runs out of EV power at around 70mph. (~20kw power limited by DC-DC boost converter)

Here's my pack:


It's 6.5kwh, and has 72 blocks each containing 12 A123 26650's. Each block has it's own tiny management module with a microcontroller that monitors block temperature, voltage, and has a selectable shunt to allow balancing during charge. The charger is a 3.5kw Brusa NLG4 that's capable of recharging the discharged pack in 2 hours. (when plugged into a 240v outlet, but it will also charge slower on 120v) Here's what the individual cells look like:



The pack as implemented could handle an 840 amp discharge current, so since the Prius really never goes above 100a, I don't need to bother with a complex cooling system like the original pack had. I basically removed 83lbs of Toyota stuff and added in 153lbs of my own, so I only gained 70lbs. The car rides and handles great, with no need for suspension upgrades.

On this new pack, I can run anywhere from 25 miles on the highway to 40 miles in the city in all electric mode using zero fuel. If I leave it in Hybrid mode, but augmenting it by reporting a high SOC I can get amazing mileage and still have better performance than the stock Prius had. This pack has almost no voltage sag compared to the original NiMh pack, and I have a higher voltage, so it really delivers great response!

I took an 80 mile trip to the south bay yesterday. I started off in EV mode and then switched to augmented-hybrid mode once on the highway. I reset the MFD before starting and had a full charge in my pack. I drove normally, (I'm definitely NOT a hypermiler!) with mostly highway miles and the MFD showed 99.9 when I got home, and the pack was at 12% SOC. To me, that's a great improvement, and I didn't have to drive carefully to get it!

My system voltage usually stays around 240 for most of the range, and as I mentioned it sags very little, which allows great response in either EV-only or Hybrid modes. When I'm in EV-only, I don't have to stop and reset to get back into Hybrid. In EV mode, the speed is not limited, and the ICE will not use any fuel, but it also will not provide any help if you floor it. This is a "feature" in that you don't have to have normal Prius EV-Mode anxiety, is it's not coming out of EV mode no matter what, but it also creates a new anxiety by having limited performance. So as of now I do have to disable EV-mode in order to have the ICE available for acceleration, though I hope to have an automatic mixed mode soon with a little more sifting through the CAN frames. Right now all I have to do is tap my "Map" button and it toggles back and forth. I'll probably implement it like Toyota did, but add much more hysteresis for mode change, so you really have to give it substantial pedal before it will burn fuel, that way you can make the best use of the pack.

You may be wondering how did I get this EV mode with no speed limit? I had to totally disconnect the engine ECM from the CAN bus and run it on it's own second CAN bus from my BMS board. The Hybrid (HV) ECU normally asks the Engine ECM for ICE power over the CAN bus, but basically if you prevent these CAN frames from going in, and instead send different frames with a power request of zero, then the Engine will not use fuel. So in hybrid mode I just send the frames as-is, but in EV mode I manipulate the frames to request no ICE power and keep the fuel cut. The HV ECU can then still spin the ICE as needed to lube and protect the transaxle and MG's, but use no fuel, this gives you the best PHEV use scenario, and you are still protecting your valuable hardware under the hood!

You can also block the ICE/Cat warmup cycle by refusing to send the acknowledgment bit when the ECM asks for warmup. This way you can plan your warmup for anytime you like.

So I can develop my fully automatic mixed mode, I have a small remote board sitting in one of my cup holders that allows manual control of many parameters using good old "analog" knobs:



This is a temporary thing, as once I have all the software "dialed-in", I'll take it out. That will leave the otherwise unused Map, Voice, and Phone controls on my Wheel for control of the various modes. (as I mentioned, "Map" enables/disables EV mode, so I can drive w/o taking my hands or eyes off the road)

I hope to have a "terrain anticipation" mode for long trips where you can tell the system when to save charge, and when to empty the pack. So for example when going down a long hill, have it recover as much as it can, then you start the next hill with a nearly full pack to help you back up. Since I have a pack that's over 10 times larger than stock, I might as well make use of it as much as possible.

For instrumentation I have a small 20 x 4 LCD mounted above the rear-view mirror that can display many different parameters. It's effectively a ScanGauge on steroids. It has a selectable bar-graph display on the bottom line (I usually have it set on amps), and updates all parameters at around 10 times per second, so you get much better response than a ScanGauge. All parameter reads are done "passively" which is why I can update them fast. I have a small speaker so it can emit various audio signals, such as for when EV mode is enabled, or when a threshold set for some parameter is exceeded. There are also controls for reading and clearing any DTC's and it will read all of them, whereas the ScanGauge only handles a limited set. Here's a picture:



I'm working on an improved version 2 with a larger graphic LCD that does 192 x 64 pixels. It will allow more bar graphs and variable size fonts, but still be low-cost and relatively simple. The "Holy Grail" would be to interface to the MFD, but the GVIF interface found on the 2008 is tough to generate with low-cost simple electronics.

If the LCD version 2 goes well, I may offer a few prototypes to PC'ers either in kit form, or fully assembled, depending on how busy I am. Anyone interested?

Update: I've created a New Thread for the LCD

This car is now FOR SALE with the system described above!

 

First off, to be clear I'm definitely *not* going to be offering any of the PHEV stuff as a kit, but I might offer the LCD as one. Sounds like you are already working on the Android solution. I carry a Palm Pre at present and love it, but just don't see the allure of interfacing it to the car. Since I already use if for nav and music functions in the car, it's just asking too much of one screen. The STN LCD I'm currently using is readable in bright sun, whereas the phone is likely not, which is another reason to KISS.

Wow, 60ah? That's a lot of battery! That would put you somewhere at 12kwh. I originally considered more than I have now (6.5kwh), but for my typical drive cycle it's just not needed, and then it starts to hurt your hybrid-mode mileage because of weight. (and suspension upgrades are a must)

What's your typical drive cycle like?

 

Agian, sorry to mislead, but I have no intentions of offering the PHEV stuff in any form for sale. The kit I mentioned was from the LCD display.

 

Interesting. They implemented a nice looking graphic LCD, but didn't add any analog functionality! Having the bar-graph is a major part of the usefulness for me, it's essential. If I get time, I'll make a video that shows how this works.

All of the important dynamic data is passively collected, so it's update rate is way faster than most everything out there I've seen. It also makes a big difference in usefulness and readability.

 

I've been asked this quite a few times already, and I *might* do this in the future, but not at this time. I will however share my methods and let people know how it works. But sharing code and schematics puts me in a liability scenario I'd rather not deal with. If someone manages to burn their car down because they tried to build their own PHEV using my designs, I don't want to end up in court. We all know that in the US that's a good possibility! When I was still a teenager, I sold a friend a used car of mine and he added a car stereo improperly and it burnt to the ground. He used that as a basis to not pay me what he owed and I got screwed. Maybe I'm just paranoid now!

I've spent a lot of time digging around on the CAN bus learning this stuff, and I will be happy to share that part. It's also a time thing, as what spare time I don't spend on the car, I am probably here answering questions. Hard to have time to do it all!

 

Yes, the 40's make more sense. I've seen peaks of up to 140A, but that's rare. Generally it will hover around 100A continuous on the highway, but averages less. Of course if you driving on the highway in EV mode, you aren't going to drive much longer than a half hour on a 40ah TS pulling 100a anyway.

Could you even fit a pack of 60's under the floor? (not withstanding suspension upgrades)

Yeah, most of the things we do to our cars are not economically viable. But doing a PHEV is fun and it helps the planet!