Featured Dr. Prius Packs Less Than A Year Away?

repairing bad hybrid batteries has nothing to do with replacing with a new pack.

and the decision to replace, repair, sell or scrap should be made based on the mileage and condition of the rest of the car.
either way, your point isn't relative to the thread subject. there is a big market for repair and replacement.

 

Yes, discussed extensively in the professional literature. Here’s a selection:

• Weicker, Lithium-Ion Battery Management: A Systems Approach, 2nd ed., 2020
• Jiang & Zhang, Fundamentals and Applications of Lithium-ion Batteries in Electric Drive Vehicles, 2015
• Santhanagopalan et al., Design and Analysis of Large Lithium-Ion Battery Systems, 2015

Without much more information about Toyota’s battery management systems, as actually implemented, than anything I’ve seen in the open literature, I couldn’t endorse the idea of relying on one to keep an HV battery of an entirely different chemistry within its safe operating envelope.

If I were developing a test program for an HV battery, I’d start with regulatory and consensus standards such as FMVSS 305, SAE J2929, SAE J2964, ISO 6469 Part 1 and Part 3, ISO 12405-4, and UL 2580. I’d also use methods such as fault tree analysis (FTA) and failure mode and effects analysis (FMEA); see, for example, SAE J1739, the AIAG & VDA FMEA Handbook, or for an introduction, Bosch’s booklets No. 14 and No. 15 (PDF) for suppliers.

Having answered two questions, I’d like to ask one: would it be lawful to advertise, sell, or install a Li-ion battery as a retrofit, replacing an original Ni-MH battery, in California or other states that have adopted California’s regulations, without first getting an approval (exemption) from the California Air Resources Board for an aftermarket part? Our emissions tampering law, Cal. Veh. Code § 27156, is very broad, and to avoid surprise certified letters, it might be a good idea to find out CARB’s position before putting a product on the market.

Don’t let all this be too discouraging: I commend the ambition of anyone who would take on a venture like this, and as the owner of a car with a Li-ion battery that may someday need replacing, I’d like for there to be credible alternatives, if only to exert some market pressure on Toyota’s prices for service parts.

At the same time, though: nobody likes crispy Prius.

 

Also confirmed by my own tests in the Prius itself (Gen2). The Prius Gen2 ECU with a lithium pack over the operable range of the vehicle is NOT SAFE. It is pretty easy to make a new Gen-2 ECU that is safe. Gen-3 is much harder but still possible.

I have mentioned this before and been boo-hoo'd. But it isn't my business insurance. I do welcome lithium kits if done properly.

 

It is possible to manufacture lithium battery chemistries (not ion) that follow nimh voltage curves, are tolerant of over/under voltage and cannot light on fire.

The issue is weight/density/shelf life

once a cell of this type fails it becomes an open circuit and bricks the car

 

I have started research and calculation since 2013 and soon realized all the papers and research are nothing if the battery ain't gonna work in real life.

Therefore I spent another 4 years searching for the perfect cells that fit the profile and that's when I started all the crazy testing including sabotage the cells to make them fail purposely while driving the car. Currently 10 packs are being tested all over the world to make sure we don't overlook anything. I'm glad to report all feedback are positive so far.

Most importantly I've waited and waited for the price to drop to a point that it is profitable and sustainable as a small business, without this we are going nowhere

 

When a Gen 2 Prius depletes its OEM HV battery to ~42% SOC, the engine starts so it can charge the battery. What is the actual SOC of the lithium battery when the engine starts? What is the actual SOC of the battery when the car thinks its at 62%? I'm not talking about what is indicated on an app like Dr Prius/Hybrid Assistant/techstream, as they aren't going to be accurate. Am I the only person in this forum that thinks those numbers are important, so you know how much cushion is available for that long downhill, or how much power is still available after a P3190 or a few no-starts? These are questions that should be easily answered, yet it keeps getting ignored. There's no way the techstream values are going to be accurate based on the voltages shown in previous postings. It keeps getting said that these modules have a voltage curve identical to the NiMH modules. Really? Surely, some 3rd party, maybe someone with a boatload of test equipment, could or should be able to test/graph/etc one of these modules and maybe overlay the chart with a newish OEM module? I'd love to see some of these modules actually be put to a test other than a butt-o-meter.

Instead of just driving Ms. Daisey with these packs, put them to the test! Get some input from members on stress tests that could be used.

Run the thing with the cooling fan clogged up for a while and see what it does.

Run the AC until the car engine starts and then immediately turn the car off. That should be about 42% on displayed SOC. Stuff the throttle body full of rags and try to start the car. Make it code out. Then disconnect the 12v battery to reset the codes and do it again! Keep doing it until it won't crank the engine again. Drain that sonofagun. Get a charger and charge it back up and do it again! How many times was it able to crank the engine before being fully depleted? What was techstream showing for SOC after each attempt? This is testing. Someone should have ragged one of these batteries out to within an inch of its life by now instead of just putting miles on it and document it right here, posted in a thread, good or bad.

Do the AC thing again. Except now, remove the battery and use a hobby charger to discharge some modules. What was the mAh remaining in the modules? Do some cycles on them to see what max capacity is.

Do a similar test, except do a gentle force charge until the engine turns itself off. What was the indicated SOC when the engine turned off? Now do some more module discharge measurements. Guess what? Now you have all the info you need. You know what the max capacity is. You know the capacity remaining in the module when the engine starts at indicated ~42%. and you'll know the capacity charged into the module when the engine turns off on the high end. If you take those capacities and compare them with the max capacity, we'll see how close the actual SOC numbers are to the indicated SOC numbers.

 

Of coarse it’s important,
The chemistry chosen has a similar active voltage area as NIMH but can tolerate a much wider charge discharge region. AKA you could theoretically use 100% SOC, which the Prius can’t physically do.

My limited experience with a similar hobby battery lifepo4 was that if I tried to overdischarge voltage instantly hit zero causing a shutdown, as soon as load was removed voltage popped right back up but no current could be drawn
and this (in my case) happened hundreds of times and the battery continued to work albeit likely at reduced capacity.

Ditto on the top end try to overcharge and current instantly drops to zero killing the charge.

I destroyed the batteries over time but they were much older and likely of a different brand/process/chemistry than what is being proposed but probably the same idea, except the Prius is likely not a deadman charge discharge system it does have actual limits.

If the Prius encounters a situation where the battery will not accept current, even as crude as the controls are it will hit an upper limit ditto on the bottom if you hit empty the voltage falls to zero which again even as crude as the Prius is will cause it to not be able to draw further power.

 

@Rmay635703

Your post is exactly why I've been asking this question. One of the testers mentioned that they were now able to drive miles on battery power alone. I don't remember the exact number right now. maybe 3 or 4? That's great! But, not so great if at the end of that ride, when the car thinks it's at 42% but it's really 3% and you have ONE SHOT at starting the engine. That's the concern I have about the voltage curve. Is it causing false high readings in the indicated SOC, and if it is, what margin for error is left?

It's aggravating to me that I've asked several times and the question has not even been acknowledged, much less answered.

 

My guess is they don’t really know beyond theoretical

My main concern would be cells drifting out of balance over time reducing the useable capacity to zero

all we can do is wait and speculate

 

this will be like the covid vaccine. you'll have people asking how soon, others waiting to see how it works, and the anti li-oners

 

I have already tested the pack going on a decline for miles on the 15 south from Apple Valley to Azusa and a traffic jam on the 15 North in which I managed to get the pack down to two bars for the first time and in that traffic the ICE did not come on to charge it at two bars.

Once traffic got moving the pack quickly charged up, oh and the fan did not come on since the temps were so low.

Also being able to drive at 70 MPH on just battery and no ICE is bad nice person!!!



Posted via the PriusChat mobile app.

 

Do your best to gently use the gas pedal and try to use the battery only.

Use EV as much as you can.

Find some mountain area to drive to.

Do your best to find traffic to sit in.

Posted via the PriusChat mobile app.

 

Almost all batteries a consumer can buy have a limited BMS in the pack. They are so cheap and required by law in some places. When you discharge the curve is essentially flat for a long time then drops off a cliff. This is why you NEED to coulomb count to get a reliable measure of SOC of a lithium battery. Sometimes referred as "gas guages" for lithium chemistries. The voltage changes barely at all over 90% of the discharge curve.

As for overcharging the dropping to zero is a function of the BMS. It does the cutoff and charge for you. For most individual cells when you overcharge them, you get some severe lithium plating on the anode. The common safety mechanism for when this happens is the design of the module itself. Most of those pouches you see if properly engineered and designed such that when they are overcharged, it allows for controlled expansion that breaks the battery apart. This is the bulging battery you see in failed electronics. The upside is the battery doesn't burst into flame. Downside is it doesn't work anymore. It's sacrificial. If you have a really robust module design, overcharge can't destroy the module, and then you get thermal runaway. All the lithium cells I have worked with for the auto industry are designed in a way to be as robust as possible with an engineered weak point past the design limits of the BMS. This guarantees (assuming no manufacturing defects in the module itself) that if the BMS fails or an event happens that it can't control (think auto accident) the batteries will self destruct in a way that doesn't combust.

I've worked on lithium packs that are inside some of the formula race cars and they forgo most of the safety aspects for performance. However they can assume it is being driven on a track being monitored and any accident they will extract the driver before the flames kill everyone. Unless you plan on hiring a crew pit to ghost you everywhere you drive... This is a swimmingly terrible idea.

 

I feel like you could have explained this in three sentences but it makes sense.

SM-N986U1 ?

 

Lifepo4 is nearly impossible to ignite

 

In fact quite possibly unpossible

see video of an 8 volt overcharge

https://m.facebook.com/story.php?story_fbid=517586842356668&id=127387328043290&fs=60&focus_composer=0&m_entstream_source=video_home&player_suborigin=entry_point&player_format=permalink