Featured Discussion: NexPower V3 Sodium-ion Battery Announcement

You seem concerned that I might become destitute if Jack and I end up in court. Thank you for your concern. However, you need not worry about my well being.

Can't wait for my legal team to cross examine you.

So far the answer is 'no'.
They often advise me not to post as much as I do.
However, they don't mind reading my missives for a fee...
...and I don't mind paying them to do so (hi legal team).

 

FYI: @mudder is aware that this response was written to @TMR-JWAP.

You should educate yourself regarding California's "notice of appearance" laws.
I would likely end up flying out to CA maybe once or twice.
Of course my attorneys would spend time soaking up the sun.

This is of course if I choose California as the venue. I probably would, which just goes to show how little I care about the distance. California is a better venue from a legal perspective, hence that's where I'd bring this hypothetical case.

In your hypothetical, I'd probably just buy a condo and a car in California.

You seem to think I have to beg everyone for everything, or at least you use that word a lot.
You have fundamental misunderstandings regarding how the legal system works.
If this case made it to court, the actual trial would be at most hours long.
You also forget that I'm retired, and so I have as much time as needed to burn.
You also forget that I presently do not intend to take Jack to court.

Are you referring to the part where you're getting cross examined and throw out every wildcard you can surmise?
I would like to advise Jack's legal team that putting @AzusaPrius on the stand is not going to help their case.

This is unlikely.

 

Bless your heart.

 

Here's the cell discharge curve for the prototype NexPower cell I'm evaluating:

The following assumptions are based on the Gen3 Prius allowing regen up to 250 volts, and assist down to 210 volts.

Overall the pack has ~837 Wh usable energy in the Prius, compared to 2228 Wh measured from 3.94 to 1.50 volts. That means the V3 sodium pack only uses ~37% of the total pack energy from full(Prius) to empty(Prius). In other words, ~63% of the total capacity is unusable.

 

I found a whole lot more, too...
...waiting on Jack to answer my questions (see above post) before discussing more.

 

I'm tired of wasting my time replying to your posts.
It's easier than invalidating your each and every baseless claim.

So it would be a one day event? Earlier you said it would take forever.

Using capital letters MUST make you correct. I HAVE LOST ALREADY!
Can't wait for Jack to serve me. The discovery (this is a legal term) is going to be amazing.

 

Here are the as-found voltages on the 'left' module:


There's a 144 mAh delta between the most-full (+15.7 mV) and most-empty (-7.3 mV) cells!

 

More feedback on the prototype unit I've inspected:

The "BMS" is nearly identical to the V1 unit I reviewed previously. Specifically, there is no supervisory control method... still just using a voltage comparator fixed to ~3.52 volts. When active, each individual discharge resistor pulls ~120 mA (sinking into a 33 ohm load).

Fortunately the Signal Soother circuitry isn't present on the V3 hardware. Good riddance. However, there's still no per-cell knowledge anywhere in the system.

Airflow isn't stellar, and is non-uniform due to cells just being glued together. Specifically, there's no mechanical member that separates the cells. The V3 announcement video shows what I'm talking about @7:34. Here's a screen grab showing how close the cells are in their model:


In addition to poor airflow, this close spacing (some cells are actually touching) poses a short circuit risk, as cells with different voltage potential are only separated by a couple layers of heat shrink. Wearing through the heat shrink is possible due to lacking mechanical support which could lead to rubbing. I would like to see more space, and also mechanical support members between cells. There's certainly room inside for this, as both sides are stuffed with foam (probably to force airflow through the small gaps between cells).

The "BMS" wires route directly over unmeasured cells... there's an effort made to place kapton tape between the wire and the cell, but there are sharp radii between the wires and cylinder corners. I'd like to see the wires routed elsewhere. I can actually see the wear from whatever is pushing against the outer enclosure when installed in the car.

The cell terminals are still soldered.
The busbars are still too thin.

With the pack initially resting at 228.4 volts, charging at 10 amps immediately raises pack voltage to 233.1 volts.
Therefore, total pack ESR(charging) is 470 mOhm. This is a single data point, but we can still predict the general heat generation inside the pack under load. For example, discharging at 125 amps will theoretically self-heat the pack at an astonishing 7.3 kW! That's ~105 watts heat generated inside each cell under heavy assist. Not great.

Notes:
-ESR is non-linear, and will increase as current increases. In other words, my 10 amp test is erring in NexPower's favor.
-My ESR measurement includes all QTY70 cells, plus all interconnects. I subtracted out the 1.24 mOhm fuse I placed between the modules... because I like fuses.
-I don't actually know the Prius' peak assist and regen current values. However, my understanding is the gen3 Prius' electric motor can deliver 27 kW... I assume it can do that when Vpack = 240 volts, which is the value I used in the above calculation. Again, this (probably) errs in NexPower's favor.

 

I'm done discussing potential legal matters for now, and will ignore further correspondence regarding said topic. If Jack wishes to serve me, he has my contact info. I will of course publicly disclose any such legal complaint as soon as I receive it. Until then, let's focus on the technical merits.

They certainly do. My prototype unit is less than three months old. I would certainly hope that the final design was mostly locked in that close to release.

Counterpoint: If Jack's latest V3 hardware is better than my prototype, it would make sense that Jack would want me to review that hardware instead. I can only review the product that's in front of me. If @jacktheripper agrees to send me new hardware (that I will pay for), I will review it instead. Information wants to be free. I am just the messenger.