YAPiP - recreating pEEf's approach

YAPiP = Yet Another Plug-in-Prius.

Introduction & Background:

(This is somewhat wordy - but I want to be upfront and (a) provide acknowledgements & (b) describe my "for fun not profit" approach).

I'm about to start on a project to try and recreate pEEf's approach. More accurately, I'd say that I've always wanted to do the complete pack replacement and had planned to use a software based approach. pEEf has already done that - so I'm standing on his shoulders. He's very generously shared some key information and I'm feeling optimistic.

Probably overly optimistic! (But, hey, isn't that how all DIY projects start???).

Go on over and read that thread (and hey I'd recommending just buying his car if you just want the end-result): http://priuschat.com/forums/gen-ii-...-plug-in-hybrid-electric-vehicle-project.html

I plan on documenting my progress here depending on how well the forum approach works for me. If not, I'll move to a blog format. I hope to follow an open-source philosophy - I'm doing this for fun - not profit. If I get this working and you "copy" me - then more power to you! If I get this working and you want my help or my software then chances are if you ask nicely you can just have it - but with no warranty expressed or implied. If you get your own PiP working and you feel that I was helpful then I'll always gladly take a PayPal donation so that I can fund my next "for-fun-not-profit" project. But I won't even entertain taking money for a specific product - with that comes the responsibility for support. Support is fun when it's not required. It can become tiresome otherwise ;-)

If this goes really, really well then I'm toying with the idea of a self-published book. But that's just idle chatter at the moment.

BTW - my day job is Current Motor - Home - so I have access to everything I need (and if you want to go for a 2-wheel EV instead then check us out - OK, I promise that's the only advert I'll post!)

Next post will detail my proposed BOM (bill of materials - no explosives required)

 

OK, as promised here's my proposed high-level BOM:

• Car: Gen 2 Prius - I don't actually have one yet. Anyone have an '04 or '05 for < $10K? Anyone want to take an '03 Ford Focus SVT as trade? Yeah, I didn't think so... I actually have quite a few possibilities from the internet - so I just have to pull the trigger on one. But if anyone knows of a bargain please let me know!
• Pack: 72 x 40Ah GBS cells. That should give me more than enough EV only range for my needs (my guesstimate, based on 250 wh/mile, gives me about 29 miles range using an 80% DoD).
• Charger & BMS
  • option 1: Elkon 2.5kW plus miniBMS
  • option 2: three charger/BMS from our 24 cell bike
• Controller: Atmel AT32UC3C-EK
• Springs: Where can I source stiffer springs? I've got a request in to PIS for just the springs but I can understand if he doesn't want to supply just those. Anyone out there know of a good source?

This pack will give me about the same voltage that pEEf used - his A123 cells have a nominal of 3.3V whereas the GBS's list a nominal of 3.2V (however I'll have far fewer interconnects than pEEf's pack because of a simpler pack topology).

Also, 72 happens to be 3 x 24 and I have access to a reliable supply of excellent 24 cell BMSs. I might go up to as high as 78 cells - depending on packaging and depending on if the higher voltage causes any issue.

If you're going to "play along" with me then you should be able to use pretty much any pack that outputs a nominal voltage around 230V and can supply at least 100A of output current. Also, you'll need to go with your own charger and BMS combo (perhaps the option 1 of an Elcon charger and miniBMS if you're going LiFePO4) - because ours aren't for general sale. If any of you have that Mr. Fusion project or over-unity hydrolysis working just configure it for 230V - 250V of nominal output and you're golden.

The Atmel eval kit is the real find (thanks to my brother! thanks Dave!). It appears to be the ideal development platform for this - even has an on board touch screen. All for only $299. Such a bargain! To program this you'll need a couple of tools. I recommend the AVR Dragon as the hardware programmer (as it also supports JTAG debugging - whereas a simple programmer such as the AVR ISP doesn't do debugging) and using AVR Studio 5 as the IDE (free download). For any coders out there the IDE is built on top of Visual Studio.

Atmel Eval Kit: Atmel Store / Atmel AT32UC3C-EK
Atmel Dragon: Atmel Store / Atmel AVR Dragon

If anyone has any comments, suggestions or questions please let me know.

Step zero: get a darn Prius!
Step one: when the Eval Kit arrives (on Friday) write a CAN packet sniffer application that outputs info to the LCD.

I wouldn't rush out and buy anything yet if I were you - but if all goes well then this should be about the easiest of all the PiP conversions to perform. All of them need a battery pack - so that's a wash between all of them. pEEf's approach involves removing the factory pack, putting in our own pack (it was so nice of Toyota to give us that plastic tray area to use!) and replacing one of the control boxes with one of our own.

Game on!

 

As far as I understand things the PIS "ECM Controller" by Kiettyyyy is doing something similar but not the same. I think it's a read-only device (reading the CAN messages - or possibly using remote frames to request specific PIDs?) that sends signals to the PIS "front board" which allows the "front board" to control the "back board". The "back board" then controls various hardware aspects of the vehicle (by wiring into various I/O lines? - I'm getting very fuzzy at this point).

A better description from Kiettyyyy would be most welcome!

The pEEf approach monitors the CAN bus and also writes it's own messages to the CAN bus. It also separates the engine ECU onto it's own CAN bus. So it acts as a gatekeeper between the main controller (The Hybrid Vehicle Controller or hvController) and the engine controller (or iceController). The controller we're replacing is the battery controller (or bmsController). I'm inventing some terms here as I go (consider it a hybrid of pEEf's terminology (also the official Toyota nomenclature?) and my own abstract model).

So, if I'm understanding it correctly, the PIS control flow looks like this:

1) A combination of hardware inputs and digital input from Kiettyyyy's ECM controller is processed on the front board
2) the front board sends control signals to the back board
3) the back board twiddles some hardware to affect changes in Prius operation
4) Kiettyyyy's controller sees the affects of those changes on the CAN bus.

Whereas the pEEf approach looks like this:

1) Read the CAN bus
2) Replace old messages with new messages

The *BIG* difference (IMO) is that pEEf's is a much higher-level "software only" approach to fooling the Prius into doing what we want. Whereas PIS (and other similar solutions) fool the Prius by overriding some of it's input signals. pEEf's requires no hardware hacking - PIS requires some hardware hacking.

Does that make any sense? At some point I'm going to draw up a diagram to help keep it straight in my head (at which point I will ask pEEf to critique said diagram).

I've been reading up on CAN this evening - getting ready to tackle the job of beginning to passively monitor the CAN frames. Oh what fun!

 

Hi bro! Your secret is safe with me (hint all the gas I save my brother burns...) Oops. Never trust me with a secret.

Yeah, it's a bit too much of a difference to compare. I'm going to be operating at ~240V so @ 100 Amps that's 24kW. You have an 84V system I believe so your Amps will be higher.

In fact the system limit for the Prius is approx 20kW - limited by the DC-DC boost converter (info courtesy of pEEf).

My cells are a touch on the "skinny" side for sustained freeway speed (pEEf reports an approx 100A load at sustained freeway speed).

I may look at those A123 pouch cells - I keep hearing about them. Can you give me a link to a supplier?

 

Yes.

The new "Battery ECU" sits between the main HV ECU and the ICE ECU. Another way of saying that is that we put the ICE ECU on it's own CAN bus and the new ECU creates a bridge between the original bus and this new bus (and that's how it changes the messages).

 

Agreed - this is a Gen 2 only mod - sorry.

However, at the end of pEEf's original post he responds to a similar question by saying:
On the 3rd gen: It's very hackable, maybe even more so. I have looked at it a few times and it should be possible to do many interesting things. Since I don't currently own one, I haven't investigated further.
So, don't give up hope. However, I don't have the budget to buy a Gen 3 - so it's strictly Gen 2 for my project for now...

 

That sounds very doable by taking the same approach as I'm contemplating. Basically the control messages from the HV ECU boil down to "give me this much additional power" or "spin at this RPM" and responding to requests from the ICE to "warmup". So, you'll have no need for the latter messaging and on the former messaging (RPM and Power) it doesn't matter to the HV ECU what's providing the power or doing the spinning (anyone with enough hamsters could also play along).

But my question is "why?" (and if it's just because you want to climb Everest then that's a fine reason).

I used to be a "purist" - I wanted a BEV not a PHEV. After all a PHEV has twice the complexity of a BEV, right? And one of the things I like about BEV's is their relative simplicity - no "warmup", no "NOx" issue, no etc. etc. etc.

However, with current tech, a PHEV suits my needs exactly - most of the time I'll be doing < 40 miles and be on EV only. When I want to do a longer trip then I have "unlimited range". And, here's the kicker, converting a Prius from HEV to PHEV is, IMO, much easier than doing a BEV conversion. It's certainly far less expensive (I can get a PHEV on the road for $15K including the car!)

Put it another way with a 40 mile range PHEV I can cover 100% of my needs and about 90% of those will be covered by EV only. Whereas with a 100 mile range BEV I can cover maybe 95% of my needs - the other 5% I'd have to rent a car. That 5% is no big deal if everything else were equal - but it's not. Also, there is the "range anxiety" issue - or, in my case not so much about anxiety as about a complete lack of planning...

If you want to do a HEV to BEV conversion - go for it! I'm not trying to dissuade you - just describing how I "evolved" on this subject.

 

Sounds good to me. You're right that the Prius makes a great starting point for a BEV conversion.

BTW, I missed the fact that you're in the UK. I'm an ex-pat - I believe it was Oscar Wilde who said "The UK and the US two countries separated by a common language"... I can certainly agree with that sentiment! My folks live in Shrewsbury and I'll be there at the end of June.

 

This is a great report - check out the diagram on page 10 (figure 3.4) - it lists all the parts I'm talking about. And figure 3.7 on page 15 is going to save me a LOT of head scratching...

Woo hoo!