Rainbow Prius Hybrid Powered by Lithium!

@T1 Terry and @jzchen, I'm not suggesting comparing Jack's new battery to an old or bad NiMH battery. I think we can all agree that would be rather pointless as I would expect a new OEM battery to perform better than my dead one. That's why it would be valuable to compare new packs of both types.

I'm reasonably confident a test can be put together to run the same route during the same time of the day over a period of time and average them out.

And to your point, jzchen, about Jack not wanting to spend money on a NiMH pack just to prove which is better...isn't that what he's asking buyers to do without concrete data?

Do I believe Li is the future? Yes, but NiMH still has its place. Why else would Toyota still be using it, especially for cars in cold weather environments?

 

I thought Jack gave around 12 beta testers out for trial. @jacktheripper Did you charge money for those? (I didn't think so but my mind has been cloudy recently).

EDIT- Of course ignorance is bliss:

"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."

by @jacktheripper 01/20/21 post in another thread....

@VintageGold Guess you missed this thread:

Dr. Prius Packs Less Than A Year Away? | Page 2 | PriusChat

 

Toyota used NiMH because of cost. (My guess). Everything is about cost. Big market like the USA cost competitiveness is everything...

 

Whether he charged testers or not (which I can't imagine he did) isn't the point. The point is, how can anyone claim one is better than the other without a direct comparison by measuring it against a new NiMH pack? Where's the data? At this point, anyone buying one of these batteries is doing it on the word of a small handful of people. And maybe that's OK. Maybe that's all that's needed to encourage people to adopt this new battery.

I don't doubt Jack worked hard on this project - I can see from the length of this thread the time that was put into it.
I don't doubt the testers had positive feedback.
I don't doubt they're good.
I don't doubt they work.

But compared to what? How good are they? How well do they work?

Just show us the data. I'd happily drop $2100+ on a lithium pack if I had concrete evidence that when compared to a NiHM pack they:

• Give better MPG
• Give better range
• Work as well in the cold/heat (I live in UT, it can get well below freezing in the winter and over 100° F in the summer)
• Have a better/as good warranty as Toyota for a NiMH pack

That's all. Doesn't seem like too much to ask to me.

 

Well now you ask fair questions...

 

The LiFeP04 (or LFP for short) are the chemistry of the extended range cells in the "Engineer" set up that was in the car when I bought it. Probably the cells themselves are the cause, but a serious loss of capacity and the stink on electrolyte vapour suggested I needed yo either find better quality cells like Winston, or experiment with a different lithium chemistry ..... so I spent the $$ on buying LTO cells (lithium titanate) to see if the better voltage retention under high load (LFP cells are renowned for voltage sag under high discharge) and the ability to withstand very high charge rates (something LFP doesn't like either because the opposite of voltage sag occurs). The idea is to build a bigger capacity traction battery that can be fast charged at a public charging station as well as handle the high current involved with regen charging.
The original NiMh cells don't enjoy the high current regen charging, but the voltage climbs rapidly and the computer backs off the current if it senses either high cell voltage or rapidly increasing temperature. I just don't knw how this would be achieved using LFP cells, neither terminal is solidly connected to the plates that heat transfer would be a rapid thing. The plate thickness is microns, not millimetres, heat transfer without over heating and oxidising the tab that links the plate to the terminal block isn't really going to happen, the heat rise is after the damage has been done.
I wish Jack all the success that so much effort deserves and I hope he proves me wrong, it's just that the last 10 plus yrs working hands on with LFP and later LYP cells (lithium yttrium ferrous phosphate or LiYFeP04) building hundreds of home power battery pack from individual cells has cost me big $$ to learn the hard truths about the cell structure weaknesses. Prismatic cells can handle the high charge rates better than cylindrical cells because there is a greater area for heat dissipation from the anode and cathode plates, a prismatic cell has a lot of each plate separated by a very thin membrane, cylindrical cells only have one very long sheet of each, tightly wound into a cylindrical shape and that block the inner areas of the plate dispersing its heat, that heat must pass through the other layers that are already heated .....

Enough of the theory ... sorry about that, got carried away

T1 Terry

 

LiFePO4-. "the opposite of voltage sag occurs"

NiMH- "the voltage climbs rapidly"

Therefore the computer backs down on the voltage quickly.

Yes English is my first language.

Thanks for sharing the theory...

 

With the NiMh chemistry, the actual cell temperature can be measured better than the LFP chemistry, so cell or module temp plays a bigger part. The NiMh chemistry can handle a slight over voltage charge, it is the loss of water that causes the capacity loss, with LFP and LYP chemistries, the overheating of the electrolyte causes the higher volatility elements to boil off causing the cell bulging if the pressure valve does not release .... these cells suffer the same dramas as NiMh modules, the release valve plate sticks and far higher pressure is reached before the valve vents ...... this is why these cells must be compressed when in use. The other issue with over heating the LFP or LYP electrolyte, is the coating that occurs on the plate surfaces .... this increases internal resistance and in turn increases the cell balancing problems, but most of all, increased voltage sag under load and over voltage damage when charging.
Charging or discharging LFP and LYP cells relies on cell voltage based control, not module or pack voltage control .... very different to the 12 cells management method used by the Prius BMS ......

T1 Terry

 

Sorry I haven't been on Prius chat for a while. That might be a reference to my posts. I'm fairly certain my stock battery was on its way out, despite being well balanced and conditioned. It's seen a lot of autocross force charging in the heat of Mississippi summer. I noticed a significant increase in my MPG with the lithium pack, but it's not a comparison to a new pack by any means. I'm also thrilled that the pack weighs practically nothing compared to the stock pack. It takes two people to get the stock pack out of the car with some difficulty, while I'm able to pick the lithium pack up by myself and set it exactly where it needs to be. Weight reduction is always appreciated, although I had to play with my coilover height a bit since removing that much weight brought the rear end up about 3/4 inch!

 

I'm all for new products and the discussion of advantages and disadvantages. But I also try to keep it unbiased. ]

Yes, it is fact that lithium can be 50% or more less weight, but do you actually believe what you wrote? This fits right in with the "stock HV battery can only supply 100 amps and this one supplies 300" misinformation that is out there. I don't think I've ever seen any post here about "two guys arrived to install a replacement battery in my car". There are many people on this forum that work by themselves and have pulled dozens or hundreds of these batteries, or more, by themselves with no problems. There are 1000+ times that many people that have done it themselves in their driveway.

Discussion of advantages and disadvantages is great, but let's keep it accurate.

 

That was accurate actually, one person can remove it with ease versus the oem pack where you should not lift it yourself and most if not all have two people take it out.

I have seen silly things like one person using 2x4s as a ramp to get the oem pack out but if it was the lithium pack they wouldnt need the extra stuff to pull it out.

 

One person's silly can be another person's prudent. "Don't depend on your muscles for what your brain can do" can be a rule with long-term advantages.

 

I couldn't get the pack out myself without a ton of effort, they're very heavy. The few times I've had the pack out I've had my wife grab one end while I grab the other to get it in and out of the car without sliding it. I don't have any fancy lifts or trollies in my garage, so that was the method I went with. The weight difference between the lithium pack and the stock pack is enough to make it an easy one person job. I'm not saying it's impossible to get out with one person, I'm saying the lithium pack is so light weight I could lift it off the ground and place it easily in the car with no assistance.

 

Maybe I'm way stronger than I thought, but the OEM NiMH battery seemed light to me. I had anticipated it being heavy and got my brother to come over and help. I said I'd scoot it back far enough for us to grab it. It turned out I had the battery in my hands and out of the car before my brother could walk over and grab it. It's a lot lighter than when I used to lug around my VW Beetle Air-cooled engine by myself, for an example.

But I get the point. The lithium battery is lighter. I'm really excited about this tech and feel like when it's time to change the stock battery on either of my hybrids I will keep this project in mind. The only thing I'm still worried about is the effects of cold. Everything seems to say that LiFePO4 batteries die when charged in freezing temps. And it's freezing here where I live.

 

Greetings.
A theme with LTO has already been created, give a link?
Been using LTO in 12v battery in GEN2 and Prius C for four years.

 

Anyone receive one of the Version 1.5 batteries with 7000mAh cells?

REVVL V+ 5G ?

 

Unsure if @T1 Terry has started that thread yet.

Have you already viewed this thread ? : HV Battery Headway 38120HP LiFePo4 70S pack | PriusChat

HV Battery Headway 38120HP LiFePo4 70S pack | PriusChat
Would be great if you could start a DIY thread for such, including pictures and potential sources/pricing for LTOs.

 

Sorry I've been absent from the forum for a bit, contracted Shingles and spent sometime in hospital trying to save my right eye. Still an unknown but the chances of saving the eye seem better now than before the hospital treatment.

Back on topic. While looking for cells for another project to replace the dangerous LiPo cells that were fitted as original equipment, I stumbled across solder tab LFP 7Ah 32700 cells with a maximum discharge current of 6CA (7Ah x 6CA = 42 amps) so 3 in parallel would provide 126 amps peak current draw, but the recharge of 0.5CA means the regen would still need to be limited to 7.5 amps, no good for a traction battery replacement, but it would make an excellent piggy back battery to increase the traction battery capacity.
This would maintain the peak battery performance on heavy acceleration four times longer and it would also continually drain off that top few bars from the NiMh traction battery while it recharged. Not quite a traction battery replacement, but it would certainly improve the performance of the original NiMh battery.

T1 Terry

 

We have been using LFP cells that have passed there use-by discharge efficiency in electric vehicle use as 12v batteries in all our vehicle, Prius x 2, a Blade Electron V, a Hino Motorhome 4.2ltr diesel, a Mazda 3500 diesel motorhome, a '74 VW Kombi (might be called a transporter over there) a Ford 6.8ltr diesel container carrier/car carrier truck and a Suzuki Jimny 4X4, we just replace the lead acid battery with 4 used LFP cells in series.

The LTO cells are better designed for use where a very high charge rate as well as a very high discharge rate is needed, not particularly temperature effects and rated for over 10,000 cycles, something required in a battery that is deeply discharge and rapidly recharge frequently every time the vehicle is used.

T1 Terry

 

Hi Jack. Did you test these new 7000mAh blades to verify no errors? Nobody seems to have them yet...

REVVL V+ 5G ?