Lithium replacement pack nearing market. Sounds great

Nintendo says not to use rechargable batteries in my Gamboys but rather to use only Alkiline, Yet I do use NiMH AA's and haven't had a problem, going on 30 years now.

Just throwing something in without checking specs would be wrong. But here there's been a lot of work doing the math.

The NiMH cells have a nominal voltage of 1.2V with a dead zero capacity at around 1V and are fully charged at around 1.5V. But they have a high internal resistance so they can be charged at a much higher voltage and discharged to a lower voltage as long as the voltage sag is being justified by a high current. Once the current starts to change at those voltages the BMS knows the battery is nearing it's "full" or "empty" or should I say about 35% to 75%

Now the LiFePO4 cells do act like an entirely different animal. But look at them block per block, or better yet, as an entire battery. The stock NiMH battery will reach as high as 258.1V when charging and can drop down to as low as 174.7V when discharging. Now with the high resistance NiMH cells, that voltage will have a lot of sag in it that goes away as soon as the current is cut, so resting voltage will be much different.

But with high current LiFePO4 cells things change. Put 70 cells in there and the usual max voltage it can handle for the absolue maximum life is 3.6V or 252V for 70 cells. But that can be pushed up to as high as 4V per cell, or 280V total. So the Prius will put out up to (but not always this high) 258.1V, or 6.1V more that typical or 0.09V per cell if perfectly balanced. That's still well within range and works great for the constant voltage charging characteristics of the LiFePO4 battery. The difference is that the sag may be different. But it doesn't really matter because they'd have to be pretty well out of balance for one to pass the 4V threshold.

Now discharging the same 70 cell LiFePO4 replacement and the lowest possible voltages will be 174.7V. Now the Nexcell specs apparently say that you don't want to go below 2.8V per cell, or 196V for the whole battery. But although 174.7V would put each cell at 2.5V, which is still considered ok for LiFePO4 cells, that would also entail a lot of sag, so the standing voltage would likely be much higher.

As a result from the cells fitting into the charging and discharging characteristics of the NiMH Prius BMS, the LiFePO4 cells never are overchaged, undercharged or overpowered in any way. The tests point to the LiFePO4 cells as staying within about 10 to 90% of their capacity, which should extend their life quite well as those extremes of 10% and 90% would hardly ever be reached do to the way the BMS works in a Prius. It is true that the LiFePO4 cells have a higher current rating and therefor have less voltage sag, but they also have a wider voltage change between empty and full which not only gives you a greater percentage of the capacity used but also reduces losses in the battery itself which is both more efficient and creates less heat.

As long as the cells are kept within spec, it doesn't matter what battery they are replacing. LiFePO4's have now long been used as a lead acid replacement with many saying they work way better as a 12V battery than a lead acid one does. Try watching Will Prowse on YouTube for an example. The only exception is that LiFePO4 batteries normally don't like the freezing cold.

 

I'd like it to not need to be connected to the grid. Now if I can insulate the battery (or batteries) and use the battery's own power to heat itself, that might work. Although that could be sketchy if the battery drained too much.

A couple ideas. One would be to install this stuff around the battery and under some sort of insulation: Insulation that STORES energy! | Phase Change Materials - YouTube. If I heard her right, it has the heat storing capacity of 12 inches of concrete but looks like it's only half an inch thick. That way I could heat it somehow when the car is on and it would help keep the battery warm over night.

Another thing would be to add a gasoline fired water heater like this: Heater Webasto Thermo Top Evo VW Bus T5 T6 Petrol 7E0898008 7E0819008J | eBay and route some tubing so it heats both the engine and the battery (or batteries) somehow. Although putting that diesel (or petrol) air heater in the battery cooling duct could make it heat the battery (and cabin) together.

Again, this is for the days when the battery is too cold. That's not going to be every day. But I'd hate for a cold day and day without electricity be the same day.

I see...

 

Very much depends on the lithium chemistry used. The only safe ones are LFP/LYP and LTO, all the other will explode into flame if pushed into over voltage or under voltage.

LFP/LYP can't handle the high charge rates required for regen braking and discharge rates for high torque acceleration that the LTO and NiMh can handle ... yes they will short term, but the cycle life really suffers.
I'd love to see a genuine 1C discharge capacity test on a 5 yr old LFP/LYP battery pack ..... I doubt the result would do much for sales though.
I've been working with big capacity LFP and LYP battery packs for over 11 yrs now .... not model plane batteries but the real thing and I know what the chemistry is capable of and what it isn't ...... only under charging and under discharging will save an LFP/LYP cell from high current charging/discharging from suffering high/low voltage damage resulting in lost capacity .... ask anyone who has done a DIY EV build using LFP/LYP cells.

T1 Terry

 

I think you're overthinking this... You don't need to keep the battery "warm" and you don't need to keep the car running and the interior of the car itself is more than enough insulation. You simply need to study up on heated clothing systems and make use of those components to keep the battery up near 15' F, when it gets to -40' F out. That's not going to require that much energy and a small separate auxiliary battery would allow you to not have the car on. And again, we're talking about an emergency back up system that will rarely be used. Also you want something that's not going to interfere with how the battery pack cools itself during hottest parts of Summer. Fortunately, ProjectLithium packs have no need for much cooling even in 120' F degree heat in Southern California after many years of testing.

 

Although LTO batteries are the king of power density of electrochemical batteries, I don't think putting NiMH cells on the same level as them and LFP cells on a way low level as being true. LTO's are based on LFP cells with a twist that creates a better nano structure that facilitates high charge and discharge currents at the expense of cell voltage and energy density. According to some charts, they may even have less energy density potential than NiMH cells.

The thing is that there are NiMH cells and there are NiMH cells. There are LiFePO4 cells, and there are LiFePO4 cells. Some NiMH cells can hardly put out a fraction of a C. They don't come near LTO's in terms of power. But low power NiMH cells usually have very low self-discharge characteristics. The hybrid level NiMH cells are much more powerful, at the expense of having a high self-discharge rate.

Something similar happens to LFP's. As said before, LTO's are similar to LFP's. I read somewhere that some even consider LTO's a variation of LFP's. Lumping all LFP's as low power is not a fair comparison. So far degradation on the LithiumProject LFP cells shows a 10-year life expectancy under extreme conditions that would likely kill the NiMH cells in a much shorter time.

Maybe I am overthinking this and direct heating is definitely the most efficient. But have you ever got into a vehicle that your breath immediately freezes to the windshield making it impossible to see? And sure, you can scrape it off, but you won't be able to see in less than a block distance of driving. I've worked outside in temps as low as -52°F and didn't think it was too cold for me. But keeping the glass clean is important for safety. Which is why I'd prefer a system that keeps the block warm as well. The stock OEM block heater hasn't been enough for me. Many days the engine is just barely in the 30's and there can be days driving around to and from work, school and store that it never reaches 130°F.

 

The passive technology to keep Lithium cells at an optimal temperature during charge and discharge cycles was invented and commercialized years ago by a researcher at the Illinois Institute of Technology.
Very simple and uses no external energy relying instead on elementary thermodynamic principles of thermal phase change to store and release heat.Temperature excursions during charge and discharge degrade Lithium cells and cause premature failure.
see PCC Technology | AllCell Technologies

 

From what I've heard, once temps get down to -10' F or lower it's really hard to breathe and function and unless it's an emergency you shouldn't be outside in the first place. And granted you may boast about how these extreme temps don't bother you, but that sounds like someone who isn't taking the risk seriously enough and may well take too big of a risk at some point and get themself killed. But then again, maybe it's just a regional thing? As in out here in the PNW nobody has an umbrella because it rains so often, so maybe there's something similar with the thinking in the coldest city in the lower 48?

 

I've never heard of there being a cold enough temperature that a person shouldn't be outside, at least from people around here. People here and their kids work and play in the snow at any temperature. You'll see people out ice fishing, ice skating, skiing, sleding etc. at -30°F. The only fears are hypothermia and frostbite, although admittedly the cold dry air can be hard on the lungs "if you breath through your mouth and not your nose." But the solution is to just dress for the weather. With enough clothes I can lay out on the ground and watch the clouds go by and be plenty warm even at -40°F.

But that's here. Where my wife is from people seem supersticious about the cold. They think that every type of sickness, from the flu to canker soars to Bell's paulsy, are all the result of stepping out into the "cold." And I put "cold" in parenthesis because to them, cold is 65°F. Here, people and their kids go out in short sleeves at 30°F. Down there, I get yeld at for not putting on a sweater when it's 60°F outside.

 

-10°F is child’s play healthy people. Usual winter temp excursion in Chicago in December or January.
-50°F is a problem without proper precautions in places like Fairbanks where steel tools become brittle as well.

 

Yea... In Southern California people freak out when it gets below 60' F and up here in the PNW where we have temps around 45' F for 8 months of the year people freak out when it gets down below freezing. Of course when it comes to rain... Nobody is ever very concerned about getting wet and you never see an umbrella, but we also sell more sunglasses than other parts of the country because when you can go weeks without needing sunglasses you tend to lose track of where they went since you last used them.

 

Back to the topic, well sort of, simply heating the engine water would not be enough to stop the freezing cold inside the vehicle, so the water pumping through the heat exchanger would need to go through the heater core and then on to the engine and the normal feed to the heater core from the engine would go to the heat exchanger inlet.
The climate control would need to be permanently powered when the heating is required so this might be too much for the battery pack, even doubled in capacity, to supply over night ...... so not plugging into the mains may not be an option. The plus side would be the battery pack would be fully charged the next time you wanted to use it.
The only other option would be to leave the car in running mode so it started up when the battery went flat, but then you could block off the radiator with newspaper to hold the heat in and just let the engine run to keep the inside warm enough to save the battery pack .... or a combination of the two ......
As far as the amount of power say a diesel air heater uses, a 100Ah 12v LYP battery would be plenty .... but that is a genuine 100Ah, not the smoke and mirrors method of the drop in battery sellers use .... as in, the capacity discharge rate is C2 not C20 and there is no 20% margin being added ..... those using the C20 and 20% safety margin claiming only 80% of an LFP/LYP battery can be used, are actually selling 50Ah genuine capacity lithium batteries, not 100Ah .....

Just as an explanation of what LYP chemistry is, Winston Batteries are the only manufacturer who can use the Lithium Yttrium Ferrous Phosphate chemistry because Winston Chung was the person who developed it.
Winston Chung was the person who rescued Thundersky batteries from oblivion when they had a very poor reputation in regards to quality, then had a falling out with management and opened his own manufacturing plant. Thundersky tried to buy the exclusive rights for the LYP chemistry but failed and eventually sold the Thundersky name to Winston Chung and became Sinopoly.
Winston Batteries now sell LFP cells under the Thundersky label and LYP cells under the Winston label .....
LYP have a better low temp operating range, faster charging, longer cycle life and better load v voltage drop capability

T1 Terry

 

Anybody tried a lithium battery from Braille in Sarasota?

 

That is the next hurdle. There is an EE who left Tesla to start his own company to recycle batteries from EV, to cell phones to computer waste. Millions of batteries in the world that he buys. Takes apart and rebuild new batteries are the ingredients have been “refreshed “ lithium etc etc. I don’t know much about the tech but there is a market for it for sure as we rely more on batteries for all tech communication and EVS now. And the plant is in NV in the desert I believe where they can store the old batteries on pallets 100’ apart from each other to avoid the fire combustion issues. Volatility is the new nut to crack as nobody wants a fire.

 

:lol: Battery fires aren't restricted to the lithium chemistry, lead acid were known to catch fire ... well explode first, then start the fire that way, NiMh certainly do, there is a photo on another thread on this forum where my Prius NiMh pack went up in flames from over charging ... insurance wrote it off but I bought it back.
I believe there are lithium chemistry battery recyclers here in Australia as well, some just munch them up and separate from there, others are actually stripping the plates out to reprocess them and avoid the contamination of the very valuable lithium compounds ....

T1 Terry

 

Which is why connecting the last jumper cable clamp to the chasis of the car away from the battery is a good idea so you don't get any sparks nearby it. Sulfuric acid sprayed from a lead acid battery explosion is not a good thing and definitely could cause a fire. At my work we use sulfuric acid and it is nasty stuff.

 

So, what's the answer then, can I buy these for my car if I live in MN? Coldest day in the last 3 years was -28F.

 

Here's what the website says:

 

Isaac's post says it all, you would need a battery heater that at least kept the cells at 0*C (32*F) when stored and around 10*C when charging or under load.
The LTO chemistry is a bit more forgiving with a range of -50*C to 65*C but the storage temp is -20*C to 45*C for 1 mth or less and -20*C to 20*C for 1 yr.
The LYP Winston cells are better at the high temp, charging or discharging between -45*C and 85*C and no storage temp listed.
-28*F is roughly -34*C, so they could still be charged without a heater pad under them.

T1 Terry

 

True, but I think someone wanting the Project Lithium Nexcell LiFePO4 batteries is looking for a drop-in replacement. If you could make a drop-in LTO pack, I'd be all ears.

 

:lol: I'm still building the 55Ah LTO pack, but once that is sorted I will look into it to see if it is feasible as far as supply and price.
I have already enquired and 9Ah cells are available that would fit in the space available, building the enclosure so the air cooling was available might take a bit if the cells don't easily fit inside the existing steel battery shell.
Maybe I'll just do a DIY instruction thing, I could Crowd Fund it maybe, to cover the costs ..... something for the future

T1 Terry

T1 Terry