2nd gen PHEV Prius mkII

[Daox]

Some of you may remember that years ago I installed an Enginer (yes, that is actually spelled correctly) PHEV kit in my 2004 Prius. This was actually a different Prius than I have now as the previous one was totaled by an inattentive driver that I t-boned. When I replaced the car, I never swapped the kit into the new Prius because it frankly never worked that great. I was still working bugs out, and didn't want to deal with it anymore. So, I sold it to another EcoModder.




However, I'm thinking I would like to give the PHEV Prius another try. With finding Battery Hookup, lithium batteries are all too reasonably priced. If you wait for deal you can find cells for as low as $100/kWh! I think building a kit for around $1k could give some decent range, and I don't need a ton for my purposes.

This time I would not go for the Enginer type setup. It just didn't work well and I'm not willing to give it another go. However, there is a pretty snazzy device out there called the BMS plus 2. This BMS plus 2 is a computer that intercepts the CAN signals from the OE BMS ECU and alters them to suit our desires. This allows you to basically run a lithium pack in parallel with the OE nimh pack for additional capacity. It then tricks the SOC to use more assist than it normally would allowing some decent EV mode use, and also providing assist while in normal hybrid mode. I've still got a lot of reading to do on this thing, but thats the general idea in a couple sentences. It’s also basically what Planetaire here on EcoModder uses in his PHEV Prius that is averaging some crazy mileage.

With the BMS plus 2 in place, all you really need to do is wire up a lithium pack in parallel with the OE pack and figure out a way to charge it. This parallel pack splits the current with the OE pack and should make life a lot easier for my OE pack.

The main issue I am having is that the BMS plus 2 is no longer in production. Thankfully, when the designer closed up shop he put out all the info you needed to make your own! So, I have been looking into this. There have been a few people that have made them since. I've been contacting them to see if they have a parts (it does require a custom circuit board) or are willing to make one. Right now I have a guy in Belgium who says he will make and test one for me, or just sell me parts.

[redpoint5]

Sounds fun.

For reference, I'm selling my 2012 PiP for ~$6k. It has 3 kWh usable.

[oil pan 4]

I would like to do something like this on my wife's Hyundai hybrid.
Heck I would just settle for just being able to grid charging the little work boot box sized 2kwh battery.

[vskid3]

Very interesting... It would be nice to spend a couple grand on several kwh of Leaf cells instead of 1.5kwh of NiMH to keep a Prius going.

Originally Posted by Daox

Thankfully, when the designer closed up shop he put out all the info you needed to make your own!

Do you have a link? "BMS plus 2" isn't a very specific search.

[Daox]

Do you have a link? "BMS plus 2" isn't a very specific search.

Haha, it certainly isn't. If you search on priuschat there is info there. Unfortunately the guy's site is down now. The best thread I've found on what it is, how it operates, and any reference info to it is here:

Hybrid Interface 2013

If you're also interested in getting one let me know and maybe we can figure something out. Its not cheap though. The guy from Belgium quoted me:

custom pcb - 25 Euro (~$27 US)
pcb with programmed CPUs (there are two) - 75 Euro (~$81 US)
pcb fully built and tested - 280 Euro (~$302 US)
complete kit, pcb with enclosure and cable - 330 Euro (~$356 US)

These are prices before shipping. I estimate shipping will be at least $30.

I am leaning toward the fully built and tested. I can 3d print an enclosure and make my own cable.

There are a lot of components. I got the parts list and priced out everything from Digikey. The parts without the PCB are $50ish plus a $35 USB programming cable.

[vskid3]

I would be all over that if I had a few kwh of batteries sitting around, but I don't. And like redpoint said, OEM options can be found pretty cheap nowadays, making it difficult to justify financially. I'll just live through your project.

How many kwh of battery do you think you'll be adding?

[Daox]

The current / still in process idea is to use the SPIM08HP cells from battery hookup. These are 8Ah cells. They'll be configured in 56S2P configuration. This should give me about 3.2 kWh of total lithium pack capacity plus the ~1kWh of OE pack capacity. Usable capacity can be controlled by the BMS plus 2 and your charger. I am hoping for about 15 miles of range from the setup. That'll get me around town for most of what I do.

[vskid3]

The way I understand it is that the BMS+ spoofs the SoC causing the car to use more electricity and the two battery packs are directly connected to each other, correct? Do you just have to have the appropriate number of series cells and let lithium's flat discharge curve keep the stock pack in a healthy range? It's too bad there's no way to replace that NiMH brick altogether.

Those cells look like a pretty good deal. They would be great for an e-bike or e-motorcycle. Maybe I'll have to get my e-bike put together again...

[Daox]

Originally Posted by vskid3

The way I understand it is that the BMS+ spoofs the SoC causing the car to use more electricity and the two battery packs are directly connected to each other, correct? Do you just have to have the appropriate number of series cells and let lithium's flat discharge curve keep the stock pack in a healthy range? It's too bad there's no way to replace that NiMH brick altogether.

Yes, that is my general understanding of it.

Planetaire is running 70 series A123 20Ah LiFePo4 cells which should give him a nominal voltage of ~224V, and maximum voltage (while charging) of around 250V. The OE pack at 100% charge should be at 227V (1.35V/cell x 168 cells). So, I just took that and divided by 3.6V and that gives you about 60. I chose 56 just because running the OE pack at max charge voltage sounds a bit harder on it than it could be if I just lowered the pack voltage a little. The BMS plus 2 is faking the SOC anyways, so I might as well run it at a voltage that is a bit more battery friendly.

The BMS plus 2 has several different modes that allow you to do different things. I believe you can completely replace the OE pack with your own, but I am not too interested in that at this point as mine is still good, so I haven't looked into it. I know it has a mode specifically setup to work with the Enginer kit that I used to have. I have no idea what it does though. I still have lots of reading to do on it.

Those cells look like a pretty good deal. They would be great for an e-bike or e-motorcycle. Maybe I'll have to get my e-bike put together again...

I completely agree. Finding a nice easy way to assemble them has been my only issue. It seems a lot of people rivet them or bolt them together. I'm not a big fan of passing 100A through two rivet connections.

[GK13]

This is exactly what I have been wanting to do with my 2019 rav4 hybrid. If you have a source for the controller, I'd be happy to go in on a group buy sort of thing. If its as simple as connecting the controller to the main pack, and adding additional batteries that can be grid charged, that would be a home run. My only caveat is that I do not want to damage my brand new pack in any way or mess with the warranty if it does get damaged.