Featured Dr. Prius Packs Less Than A Year Away?

Added my name for the mailing list, not in the market yet for a lithium pack but as soon as the current one fails I will be!

 

H᠎i, it's good to see this is finally on the market!

I'm not in the market at the moment, but I hope you won't mind if I mention a few things I noticed at the web site that would raise questions for me if I were in the market. They might raise questions for others too, and maybe you can find ways to revisit them in ways that would raise fewer questions.

1. In the FAQ, "What is the technical specification of the battery?"
   
   • storage temperature (1 month): -20C ~ +45C
   • storage temperature (3 month): -10C ~ +45C
   
   Where I live, -10C to -20C can be real-life temperatures, not just for "storage", but for normal hopping into the car and going somewhere. What are the operating temperature limits for the battery, and what happens if they are exceeded?
   
2. From the home page:
   
   • Nexcell lithium pack delivers 260Amp peak power compared to 100Amp peak power from stock NiMH battery
   
   Can you clarify any immediate or long-term effects this might have on the 125 amp fuse Toyota uses to protect the battery circuit?
   
3. Also from the home page:
   
   • Nexcell lithium pack maintain an optimal voltage to trick the computer in favor of electric power. Resulting in better fuel economy
   
   Here on PriusChat we spend a certain amount of repetitive effort explaining to newbies the reason why tricking the car into more electric driving generally isn't a win for fuel economy, because of the double tax of conversion losses into and out of the battery.
   
   Perhaps what you are trying to say here is something more specific, and you have a reason why it makes more physical sense in your specific case. It might be helpful to give a little more detail then, so readers can tell what sets it apart from a classic newbie mistake.
   
4. Seeming dissonance:
   
   • From the FAQ: ... testing all around the world in extreme conditions and weather/temperature variances. Some testers race their Prius, some power their home with their Prius. For more detailed information, please visit PriusChat.com [italics mine]
   • From the warranty: Powering high voltage inverter straight from battery pack will void warranty, NO EXCEPTIONS.
   
   It doesn't seem quite cricket in one breath to tout a certain configuration being tested, and in the next breath exclude it unconditionally from the warranty, especially a configuration that doesn't seem abusive on its face. It would be better to mention up front that these testers are doing something excluded in the warranty; it would be better still to explain in the warranty exactly why you consider the configuration abusive, and even better still if you could establish specific guidelines for "plug-out"-type configurations that you would not exclude from warranty.

I hope you find some of these comments useful!

 

Great questions, let me try my best to answer

1. If someone is driving outside of the temperature range, the battery ECU will reduce or even cutoff the power from and to the battery, that's why many prototypes were sent to testers in Sweden, Russia, middle east and northern state, the test all passed with flying color. The LiFePO4 cell we co-developed actually have better temperature tolerance than the Toyota NiMH cell, on top of that the entire Lithium cell is seal, no vent hole, no connectors joints that can leak out or leak in moisture due to temperature difference.

2. Actually our lithium cell can produce peak 400Amp max, 260Amp is a conservative number. It's mostly to show how good the cells are and 125 Amp is basically walking in the park. I know a lot of customers already plan on using these lithium cell on go-kart and EV boat project, can't wait to see what people can do with all these power.

3. I have explain this topic in multiple threads so hear me out again, the lithium has better round trip efficiency at 95~97% compare to NiMH at probabaly around 75%, it means that instead of wasting charging power in heat, lithium actually absorb most of the energy and deliver it back with higher voltage potential. On top of that lithium has 80% usable capacity (compare to NiMH at 40%) means your Gen2 will be much harder to run out of juice again in that long stretch hill. All these contribute to a better fuel economic and match what we see if real world. So far we have only two users saying they are not seeing MPG gain, it turns out these 2 users are basically driving on highway speed 90% of the time and electric motor isn't really helping much in that situation.

4. Very good point and thanks for the great feedback, we should be more specific on how we test and what warranty covered.

Best,
Jack

 

Are you saying that those numbers are capabilities of the pack when used in other projects, but just won't ever be seen when installed in a Prius because the ECUs will keep the current draw within the original limits? Or are you saying that currents of 260 A might sometimes be seen in a Prius using this battery, but you are not concerned what effect that may have on the 125 amp fuse?

 

How many of these retail packs are fielded?

 

Sure, and Pacific Engineering even publishes data on the time-to-blow versus percent overcurrent. I guess I am still wondering whether the number, duration, or amplitude of overcurrent events will be higher with this battery than with the original, and if so, what has been thought about the effect on the fuse of repeated overcurrent events short of blowing on the spot?

 

Doesn't the hybrid controller use a current sensing resistor? The current draw is probably limited by the ECU.

moto g power ?

 

There's a Hall effect current sensor donut. We can speculate about how the consumption is modulated, but I'm hoping jacktheripper has something less speculative.

 

So which is it? Is the "260Amp" touted on the web site a figure that won't really be seen in a Prius because the actual behavior will match the output curve of the NiMH (and, therefore, no new concerns for the fuse, but also nothing really to ooh and aah about)?

Or is it something actually noticeable in a Prius, and therefore possibly worth evaluating for long-term effects on the 125 amp fuse?

 

yes sir, Prius battery ECU won't let the battery drain more than 125 Amp. 115 Amp is the highest I've seen using Dr. Prius App + lithium, again, this is just to show how good the battery cell is.

 

Is it also the case that "Even a NIMH pack will go up over 150amps briefly" (upthread in #66)?

Those statements seem at first incompatible, but is it because of something a difference in timescale, or has there been a mistake?

 

This is false.

 

The numbers are way off. On both sides. I am an EE and have worked with both chemistries a long time. I've already given lots of data before, mostly ignored in this thread. But those values are just way off.

Just think about it for a second. Let's say even 10KW of regen into the pack. You're saying 30% is heat? That's 3000W of heat generation. Prius can do almost 40KW of regen.

NiMH can be charged almost as efficiently as lithium chemistries in many SoC ranges. The bulk of the inefficiencies come from the bidirectional converter which hasn't changed.

Like I said before, I've been here and done this. Both professionally and as a hobby.

 

Wish he would go ahead and implement LiFePO4 tech.

SM-N986U1 ?

 

is that coming next?

 

We can take that as a working number ... 40 kW would be around 150 amps assuming the charge voltage during regen has risen to 270 volts. This could be around the outside extreme regen possible for a short period.

The battery ECU keeps track of the blocks' effective internal resistances as well as their voltages. Values around 19 to 21 milliohms seem to be in the ballpark for good packs. Let's say 20 mΩ.

There are 14 of those blocks (assuming the iconic Gen 2, or the Gen 3 liftback) ✕ 20 mΩ = 0.28 Ω for the pack.

(150 A)² ✕ 0.28 Ω = 6.3 kW of heat generation in a 40 kW regen event. (At a mere 10 kW of regen, because of the quadratic, the heating is only around a sixteenth as much, around 400 W.)

What are the typical effective internal resistances for the lithium packs?