I just purchased a 2005 Prius. I am highly interested in the PHEV upgrade. Has anyone run into DIY instructions on this? I already have the instructions for the EV switch and I am assuming that the PHEV upgrade uses this in conjunction with the mod.

Also, Has anyone found another source for LiO Potassium batteries other than Valence saphion. I can't seem to find a price for these.

I realize that Edrive systems is coming out with a kit but someone must have published DIY instructions for this.

 

The EV switch is a clip, whereas PHEV is electronics that hack the Prius system. Both have 'E' in their names, but the similarity about ends there. Try again in about five years, three years if you are the optimistic sort.

I am really excited about the possibility too, but it is *way* too early to just jump in, unless you are an EE with special qualifications.

 

I am a manufacturing engineer for an electronics company in SoCal. I have access to a multitude of EE's that show a bit of interest in this as well. Just wondering if there were any open source guys out there that might have published info.

 

I haven't seen any detailed instructions, but you may want to contact the team that has done the hack already, they did a version with lead-acid batteries as well as the lithium ion... The hardest thing I can think of is designing the device (battery ECU hack) that tells the Prius that the battery is full until it gets down to a certain point. From what I understand the car's systems communicate over a CAN (controller area network) interface and standards are publically available for that.

 

Actually from what I have read, it looks like you could just replace the NiMH batteries with the LiO batteries and invoke the EV to make this work in its simplest form. Because of the increased capacity of the LiO batteries and the EV the car would run on battery only under 34 MPH and would have battery assist over 34 MPH. The Prius is designed to not allow the charge to get below 20% or over 80%. If it does then the ICE kicks in regardless of if the EV mode was invoked or not.

I'm sure there is more to it. Edrive has a display on their system that shows system status. This may just be an additional feature to help monitor the system status.

The guys over at Edrive systems are inundated with emails and are no longer replying to them. Why they publish their email address is a question.

 

The reason they feed false data to the car's battery ECU is because the car adjusts the amount of battery assist based on the state of charge, so if the battery is full (80%) it will provide more of the propulsion than if it were at 70 or 60%, thus limiting the amount of work the large battery could do at speeds over 34 MPH.

There may also be some serious discrepancies between what the car is expecting to read as a voltage on the battery and what you have if you use a lithium pack, especially as far as how it's expecting to measure the state of charge, remember the Prius uses other sensors such as multiple temperature probes on the cells to determine the SoC, so there's going to have to be some re-engineering to make it work smoothly.

My preference would be to develop a system that could interact with the NiMH pack by charging it, actually keeping it full until the Lithium pack depleted, then the car would have it's normal pack to maintain once the charger switches off, otherwise the car might try to charge the Lithium pack up to what it thinks is normal operating voltage once you run it down under heavy EV use, thus wasting gas.

 

Most of what you are looking for is over at the Priusplus group.

E-drive are the "professionals", but Priusplus were the not-for-profit amateur group. E-drive could afford the lithium-ions, but Priusplus went for cheaper lead acid batteries - both groups succeeded in making a PHEV Prius. Sadly, the Priusplus ringleaders have closed the forum now as they are too busy with other projects, but the archive is still there and it has a lot of info on potential batteries and of course lots of potential contacts for you.

There is much discussion in the archive of how they overcame the issues of the OEM computer (to cut a long story short, they basically fool it into thinking it still has the old pack and that everything is OK except that the pack is overcharged, so it constantly tries to remove that excess charge by "assisting" at every opportunity). Once some issues of electrical noise were addressed, the project worked quite smoothly.

But as others have said in this thread, this is not an easy project for an individual at the moment! (as far as I can tell no instructions or kit has has yet been made publicly available) Having said that, the more people that try it, the more is learnt!

If you're on a budget, the major stumbling block will be the Valence batteries which are still very expensive, so I'd suggest trying AC propulsion's route of using multiple 18650s Lithium Ions (see here for how its done). By choosing 18650, you get three major advantages over the Valence cells: (i) You can buy them off the shelf! (ii) The Valence are about $1,000 per kWh, but 18650 are about $350 per kWh (so a 9kWh pack as in the Edrive Prius would come in at just over $3,000). (iii) The energy density of 18650s can be about 200 Wh/kg, vs about 100 Wh/kg for the Valence batteries, so the 18650 pack would be about half the weight of the Valence solution. Of course the major downside is the fiddly nature of assembling the pack and trying to tie them all up together with a decent homemade BMS!

Tell us how it goes!