NexPower V3 hybrid battery unveil - Sodium-ion battery

Wow, that is big on the accusations, claims and the likewise, without much to back it up ..... When did the Chinese govt start testing products for sale to overseas markets?

T1 Terry

 

With so many different sodium ion (Na+) cell construction methods and manufacturers, the number that are the real deal and the number that are failed production test runs are near impossible to identify one from another.
About the only Sodium ion cell that could be taken on face value as being thoroughly tested, would be CATL, and they don't sell to small enterprises, their second gen products are the cutting edge as far as commercial level production and OEM are taking these as fast as the pass CATL testing procedures, those that failed the testing are available on the open market .... not sure how much faith I'd put in them though, no one says why they failed to meet specs, they just didn't make specifications so were rejected.
Doesn't matter what letter of the alphabet they put on the claimed quality, it either passed CATL specs and went on to the OEM suppliers, or it didn't ........

T1 Terry

 

Maybe you missed all the fun here at priuschat, on the two projects youtube channels and the other projects followers (beta testers) at the insightcentral forum last year (24). As well as the banning frenzy (timed and permanent ) that happened here as a result of all the fun.

@PriusCampers comment about rigorous was referring to the testing Jack has done and published on his youtube channel which you can find by reading the documentation on the projects web site.

 

Why does Nexpower have to survive?

My in house rigorous testing (driving normally for 2 years in CA) caused their $2000+ pack to fail, with the only recourse from the company being the "opportunity" to purchase a $980 sodium replacement. That's $3000+ spent for crossing 1/5 of the life expectancy of a sub-$2000 oem pack.

There are claims being made that sodium is better than lithium and won't fail the same way, but these claims are coming from the same people who made the big lithium claims years ago (yes I was foolish for drinking the koolaid back then).

Additionally, Mudder's videos show that certain design deficiencies that lead to the lithium packs' failures are still present in the new sodium packs.

I can personally say confidently that I would have been better off (money, time and anxiety wise) without Nexpower. I am willing to bet that the overall prius community would've been better off without them too with the reliability of oem replacement packs.

 

Exactly. They never had a convincing story and never answered technical questions from the beginning.

 

I remember jack azausa telling me that Toyota’s bms in the ecu will keeping the lithium battery pack within range. If so, then why does the nimh cells are out of voltage range.

 

Caution, there's at least one recent thread reporting it's harder to find Toyota packs at sub-$2000 prices anymore.

 

The Prius balancing is done per 2 modules, allowing one module to go high and the other to go low, yet still have the same voltage across the BMS measuring points.
Add to that, there are 6 cells in each module, what hope is there if the attempt is to use 12 cells in series to establish the voltage as a comparison to the other 12 cells in series ..... what is supposed to keep each of the 12 cells in the group's voltage the same?

That is the real reason Toyota only use such a small amount of the battery capacity, the balance across the cells in each 12-cell group is an unknown, so they allow a very wide margin of error.

A replacement chemistry battery could use the same technique, but if they used the same safety margin to allow for the out of balance between the cells in each module group, the battery would need to be a much larger capacity and the area available just won't accommodate that .....

A purpose built BMS and dynamic balancing system could be designed and built to make these alternate chemistry batteries function as intended ..... but I doubt anyone would pay the extra to add that, it would more than double the price.

Well worth the cost if the plan was to fit a much bigger capacity battery than the one that fits in the area available at the moment, an additional $2,000 to protect a $10,000 battery pack makes more sense that $2,000 to protect a $2,000 battery pack .....

T1 Terry

 

Toyota is taking heavy advantage of chemistry-specific facts about NiMH. The chemistry has fairly benign behavior under a slight overcharge. A single series string of cells can be kept charging for a while, with the cells that are first to reach full charge simply tolerating a bit of overcharge while others catch up. That strategy definitely doesn't generalize to all battery chemistries.

In my gen 1's later years, I noticed it on several occasions going through such a controlled overcharge cycle. I don't recall catching such a cycle in my gen 3, but I don't know if that is because the programming was revised not to do it, or my gen 3's battery just isn't that old yet.

Toyota's NiMH battery ECU is just a voltage monitor, not a balancer in the sense of being able to direct currents from some cells to others for balancing. Charging current only passes through the whole stack in series.

They can't use that strategy for their Li-ion packs, of course; the battery ECU for those has connections to every cell.

 

I have experienced higher than normal nimh charges but only after a normal full battery sits overnight and ambient temps changed dramatically. This is followed by more regen down a 150 elevation drop in the first mile.

The v then burns off the charge with ev operation up to 35 mph without having to nurse it or force ev. The ev response can be impressive under this condition.

 

its still shocking to me that with all of these voices which sound like they know about Prius HV batteries and how they should perform all the while being critical of the one manufacturere of HV batteries yet... no one else has stepped up to make a battery... Id like to think those with such strong opinions of Jack wouldve gone out and made their own battery. its easy enough to get cells and wire them up right? Yet yall are still singing that OEM is that one true leader song which if you ask me is bland like unseasoned chicken or kool aid that's not sweet.

 

It's not easy to come close to Toyota reliability and years of trouble free hybrid battery lifespan without building and integrating a lithium bms. Which is the whole point of contention from the beginning. Your camp does not understand that critical aspect.

Only Toyota has a lithium bms for gen3 and it was used widely in Europe through 2022 in gen3s.

If I remember right, you had a resource that could modify the Toyota software. Still waiting on that milestone.

In the end, some of us are concerned about unsuspecting members wasting their money on unreliable products.

 

There's a lot of density in this post. Here's some corrections based on what I've read in the forum over the last couple months.

1. Someone else did make a battery. I think their name was newpriusbatteries or 2k1toaster or something similar. They used NiMH round modules. Apparently that guy had many years of experience in the field of automotive battery design and construction. I think I read he only sells to fleets now, rather than dealing with individual DIY drama. Pretty sure I also remember him giving several warnings about trying to make a lithium battery work using NiMH control systems. It's ok though, those warnings were ignored. That's worked out pretty well. I guess some people are choking to death on the well seasoned chicken and sweetened kool-aid. But we'll ignore them and shout them down because they're obviously lying.
2. I think 99.99% of people aren't interested in designing a battery and just want to buy a replacement that's reliable. They have jobs and lives to lead, families to take care of. The majority of people with any experience with rechargeable batteries and any sense whatsoever, realize lithium batteries, or any rechargeable battery won't work long term with a non-matching controller. There's a reason NiMH has an NiMH controller, Lithium has a Lithium controller, NiCD has a NiCD controller, and even a lead acid battery or AGM battery have their own requirements. It's not rocket science.
3. No, it's not easy to just grab a bunch of modules and just wire them up. That's why it's much easier to just use the OEM Toyota design with the correct chemistry, wire harnesses and ecu. It sure has been successful for the last 25 years or so. The last thing I would want to do is market a completely different chemistry battery as a DIY solution, when there are 100,000 different levels of DIY ability. I've seen a LOT of DIY, and the majority of it is beyond sketchy, because people just don't know their limits, especially with electrical stuff. There're some posters on here that act like they're big time battery installers/car workers and many of their posts have made me cringe.
4. Apparently, Jack's lithium design, even after "many years of research", etc, has proven to not be as 'long term' reliable as described, regardless of who has been beating the drum. Sounds like the previous warnings have come to bear.
5. Bland, unseasoned chicken that allows you to confidently get in your car each morning and reliably gets you and your car down the road and home each and every day is a 1000x better than that tasty chicken that leaves you broken down on the side of the road.
6. I guess I just have no courage.

 

They still advertise then for sale from their website.
NewPriusBatteries

 

An engineer has to grok not only the physics (of course), but also a thing or two about production and economics.

An engineer who takes a look and says "you know, there's already a pretty good product in this space being sold for $X by a player whose economies of scale I can't touch, maybe my talents would be better used on some other project" might be not so much less courageous as more selective in what to spend his or her earthly time on.

 

Quoted text is slightly edited for clarity.

The key reason NiMH doesn't require per-cell BMS is that NiMH chemistry has an inherent internal chemical reaction that turns the excess charge energy into heat, WITHOUT overcharging the cell. Specifically, as the cell approaches full charge, the positive electrode begins to generate oxygen gas, which diffuses into the negative electrode where it combines with hydrogen to form water. This exothermic process consumes the excess charge energy without overcharging NiMH cells. The oxygen recombination cycle is non-destructive as long as the cells don't overheat, hence this only works at low charge current (which is why the Prius charges at low current when the pack is nearly full).

This is incorrect. For safety and longevity reasons, both lithium and sodium chemistries require a per-cell BMS.
Lithium and sodium cells do not contain the above oxygen recombination process. Therefore, excess energy causes these cells to overcharge no matter how low the charge current is. This is dangerous because heat and pressure build up inside the cells, which can lead to cell rupture and/or thermal events.

Unfortunately people are always looking for the cheapest possible option. So yes, I agree that at face value customers will gravitate towards a "$2000 lithium battery" versus a "$3000 lithium battery with a BMS", even if the $3000 option is safer and will last longer (because it has a BMS).

For reference, my Honda Insight BMS product is 'only' $1250, but that price includes additional features beyond just the BMS. Notably, it has a built in grid charger, hacks to increase output power, a diagnostic LCD display, etc... removing those extra features would yield a BMS in the ~$700 price range, plus the battery cost.

Why not fit a bigger battery? I designed and sell a 10.4 kWh lithium product that fits in the G1 Insight's OEM battery enclosure (which originally contained a ~0.8 kWh NiMH pack).