Lithium Prototype Test

Adapt to the competition isn't it?

 

The OEM battery uses 40% of its capacity--it will discharge down to 40% SOC before the car starts the engine to charge, and it will let it get close to 80% driving down a mountain, for instance. When it gets up above 75% or so, the ECU also allows brief electric-only operation above the middle bar on the display.

 

You misunderstand what I'm talking about. The hundreds of times I've had Techstream hooked up while testing a car, it typically controls the battery between ~42 and ~62% SOC. That's the range of normal control. If the car thinks it's controlling a 20% range, but this battery is actually using 80%, how does that correlate. Does it only use 60% normally and the remaining is for cushion? IDK, but one man has the answer.

 

Religious reference?

 

State of charge is one thing and actual voltage in the pack is something different I guess? Wish I better understood how the SOC charge calculation is made because in past few years of this work I think lowest voltage I've seen on a functional pack is 217v and highest is 240's. So I'm thinking that's not the actual capacity / SOC of the battery. Any insight to the difference?

 

Now, if a correlational can be nailed down at which voltage is Typically 42% and which is Typically 62% SOC we can all get closer to being on the same pages.
Ideally, what the high low voltage range used when new - the packs might last that much longer.

 

I was thinking that certainly the builder would have the answer. It would be good information to know. How does the actual battery capacity match up to what the car thinks it is. At some point people are going to have to troubleshoot the car and they're going to use techstream. It's could cause confusion if TS thinks the car is at 50% SOC and it's actually 15% or something.

I see some of the photos above show SOCat 70% plus after installing the battery. If the car is going to try to maintain <60% during normal day to day driving, then it's going to try to discharge the battery a bit. Where does that leave actual SOC?

 

I view these products as catering to different markets, one may edge some sales from the other but I think some “new “ markets will open due to lithium, likely there will be tinkerers that lean forward buying a lithium pack that otherwise wouldn’t be in the market for traditional packs.

 

More batteries out there to keep the Prius on the road, the better.

We actually already have Lithium packs in testing for the newer generations and the older generations as a NiMH replacement. On the newer gen's it is a drop in replacement and you're done. As far as I know, none of those have failed so we aren't publicly selling/testing any. Just quietly collecting miles globally.

For the older generations... I'll answer below this:

The car does not implement a charging algorithm in the conventional sense, but it does overall. It controls/limits the amps going into the battery. The system has very high and low voltage limits. In normal driving, 99.99% of the time a direct lithium conversion has no issues at all. Lithium is cheaper now, it is lower resistance, it's lighter it's a great replacement. Keep the depth of discharge low and you won't wear out the cycles. Drive the car monthly and you won't kill it from memory effect. It is an AWESOME solution. One we've had. But I as an EE refuse to sell it to the public because of that very very small set of corner cases where you can have a thermal event and overall the inverter in the Prius isn't made for those power levels constantly.

There are some cases where the pack voltage can be commanded by the car to go too low, and that's the best case of the worst case scenarios. It just kills the pack life of the new lithium pack by an infinitesimal amount, so small nobody will notice. In the case that the pack is commanded to go too high, you have extreme physical expansion of the cell due to heat. If the cell's geometry gives up first, you might just get an exploded cell and a car that won't go vroom. If the cell holds long enough to combust, then your car doesn't go vroom, it goes up in flames.

On the inverter side since the power isn't being regulated low enough by the NiMH chemistry it is running in a lot more binary mode most of the time. MAX POWER!!!!! MIN POWER.... MAX POWER!!!! etc. This is all within spec, and the Gen-2 inverter topology and super beefy components I believe can handle this on normal days. If you live in a hot/tropical climate I don't think it can. If you look at what Toyota did for the land speed record Prius, they focused on exactly this. The electronic internal guts (to the best of my knowledge, I wasn't there) didn't change but the cooling I believe was upgraded. They also boosted the inverter voltage 50v internally. Because this is Japanese design, I am making an assumption that what is shipped in Gen-2 cars is capable of 50v extra voltage and max power output for lengths of time as long as the thermals are kept under wraps. My own testing shows that the inverter works extra hard with a lithium conversion and that's extra heat and stress on the components. The Gen-2 in my opinion is capable of taking this extra stress in standard climates. However.... The Gen-3 Toyota cheaped out on. They dialed back the engineering on the inverter from super over-engineered to standard consumer product. Squeeze the profit out of the car at the expense of robustness that nobody will ever use.

And THAT is why I haven't marketed or sold my lithium conversion pack without an ECU change, which I have mostly working but will likely never see the light of the day. I applaud these guys for getting something to market. Maybe they have done something internal to their cells that I haven't. Maybe their testing is more extensive than mine and they determined it isn't an issue. This is actually the project I started on in 2007-ish. I was going to make my own Lithium PHEV conversion on the Gen-2. So lots of data gathering. Basically ready to go when the Leaf came out. And then there was no point. I just bought a Leaf instead. Came back and revisited the data as I was starting NPB and could not make it work. I am most likely biased (scarred?) from my work in the auto industry's electronics. You ship a product out to an OEM and it goes in every model of car for 5 years but have 3 failures that are traced back to your product, you get a team of 100 angry Japanese engineers in your lab scrutinizing every design decision and determining if the engineer that designed the part is a failure (inherent design bug), test escape (now you have to fix the test and retest ALL inventory and perhaps recall all products!), or field failure.

Either way, I have no immediate plans to enter the lithium market for Gen-2 or Gen-3. Gen-4 is ready to go.

 

We do not worship the Prius software developer.

 

I can not agree more, that's why we are doing this expensive larger scale testing in different part of the world to make sure we cover all cases!

 

I only worship the software developer from Tesla

 

Wow this is great work. I do hope we don't get any exploding packs lol.
@jacktheripper are you testing in Australia as well??

 

That was one of the concerns why @2k1Toaster our rechargeable battery expert declined to market a similar unit.

Lithium Prototype Test | Page 3 | PriusChat

 

Dr. Prius is based in Southern California so his test packs got a real good work out this past Summer as it got all the way up to 49' Celsius at times...

 

a little correction, for the past 3 summer

 

Seems like a great mod, so when are you able to ship down under!!!

 

I've been told approximately 6 months after decision to order first shipment... That decision could be made at the end of Winter testing...

 

Looks like a nice option for my gen 2...