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diy solar

Are we all getting GRADE B cells??

overkill solar sells 100Ah Frey cells, rated for 2C continuous discharge. that meets my incredibly arbitrary “Grade A” metric.

cells that heat up when discharged faster than 0.5C being EV grade, ok maybe that’s “EV grade” but i expect a lot from cells.

start with a good cell, it’s still going to degrade. “poor quality cells” just start closer to the finish line..

LiFePO4 cells die much faster with higher temperatures, and self-heating from charge or discharge just speeds up to the finish line faster.
 
Most of these EV cells require some type of liquid cooling to meet there high C spec, I read the data sheet for the LF280K and they said .5 normal and like 1c with some type of cooling.
 
Most of these EV cells require some type of liquid cooling to meet there high C spec, I read the data sheet for the LF280K and they said .5 normal and like 1c with some type of cooling.
To be clear, it is the discharge rate that creates the heat and any cell will require cooling to dissipate any heat from hight discharge or charging. Some cells tolerate higher discharge rates better than others.
 
one cell at 0.5C might generate the same amount of heating in Watts as another cell at 2.0C (charge or discharge)

both may need cooling at some point, but one might need cooling at a lower C rate (amperes per ampere hour capacity) than another.

this directly implies an energy inefficiency for cells that self-heat at lower C rates.

energy will be needed to dissipate the self heating and that energy will not be usable for the system.
 
even EV grade tesla NCA (Nickel Cobalt Aluminum Oxide) cells require active liquid cooling when charging very fast.

in fact, the cell is heated to 130°F first, then Fast Charged, and the Heat Pump removes heat to keep the cell at or near 130°F during the >3C charge cycle.

battery cells are very complicated, and it is fun to learn about the various ways they perform in different conditions! :)
 
Doesn't necessarily have to be an active balancer, but something with more than 20mA of passive (or whatever miserably low rating the Daly has).
 
I agree with this part "There is no such thing as A-, A, B+ or whatever fantasy grade people want to come up with. "

May not "It's either pass or fail."

What is pass or fail standards? If it is the EV factory's matching standard, then so-called 'grade B' cells are good cells, they just do not match the main group.

If fail standards is the cell has a quality issue, then EVE should have been bankrupted. This defective rate is too high. According to a report, CATL has a 0.1% defective rate, only 1000 cells have quality issues in 1 million cells.
Currently there are two grades on cells. Grade A(utomotive) and F(ailed automotive testing). The manufacturers are building automotive grade cells because there is a large and steady market for them. We have no way of knowing how those cells failed. Certainly a large portion are perfectly fine for low C rate solar energy storage, but all we know is that they failed testing and were sold for 30% of the cost of cells that passed. Unless the report was published by CATL, it is a guess and could easily be very inaccurate.
 
overkill solar sells 100Ah Frey cells, rated for 2C continuous discharge. that meets my incredibly arbitrary “Grade A” metric.

Frey manufacturers primarily for the mining equipment market, not automotive. At least that is what their website says. Do they need to meet the automotive testing specs set by the Chinese government? I don't know.
 
the common Lifepo4 charge best somewhere between 30 and 40°C.
More like 20 to 30°C. Just so you understand, when we talk about "high C rate", we are talking about charge or discharge rate. 1C means a charge or discharge rate of 100 amps for a 100 amp hour cell. 0.5C means 50 amps, etc. Solar users tend to use low C rates, because nobody wants solar storage that only lasts one or two hours. Automotive C rates tend to be above 1C (at least for charging) because nobody wants to wait more than an hour to recharge their car when on a long trip.
 
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Frey manufacturers primarily for the mining equipment market, not automotive. At least that is what their website says. Do they need to meet the automotive testing specs set by the Chinese government? I don't know.
while simultaneously professing ignorance on the matter,
on my last visit to Jiangsu Frey alibaba page, forklift was also mentioned as a suggested application. got wheels and moves, but i dunno what exact parameters are specified by various vehicle/car/truck manufacturers.

a high performance tesla model 3 can have a 75 kWh battery and 500 kW discharge and 250 kW charge, which translates to nearly 7C discharge and 3.3C charge

but some electric vehicles will have lower C rate. i don't know what a nissan leaf is like.

again this discussion much appreciated ??
 
I have been reading up, apparently thicker plates / waffers = higher discharge but lower capacity.
More numerous wafers / plates = higher capacity / lower discharge.
So It depends on how you design the cell, higher discharge rate or higher capacity, can't have both.

I bet they could make a 100KW model 3 weigh the same but it be with 1c rated cells and will have a slow 0-60 time of probably like 7 secs.
 
So It depends on how you design the cell, higher discharge rate or higher capacity, can't have both.
Yes, and some of that design is the chemistry. I think Lipo may be the most energy dense and high discharge chemistry but also the most volatile. Next is the Nickle, Cobalt combination that Tesla uses in their cells. Cooling is the key to how Tesla manages high charge and discharge rates.
 
I have been reading up, apparently thicker plates / waffers = higher discharge but lower capacity.
More numerous wafers / plates = higher capacity / lower discharge.
So It depends on how you design the cell, higher discharge rate or higher capacity, can't have both.
i think it might be the inverse.
haven't had coffee yet today, to disclaim this assertion.

thicker plates:
more energy stored, but more matter to diffuse through, so slower access to energy

thinner plates:
less energy stored, but less matter to diffuse through, so faster access to energy

some parts of the plate are just for conducting or structural support, only conveying energy, but not storing it.

if the active storing material is thicker, more dense energy storage, slower charge/discharge, but more capacity per volume.

something ratio between storing and non-energy-storing matter.

cheers! eager to be corrected if this is off.
I bet they could make a 100KW model 3 weigh the same but it be with 1c rated cells and will have a slow 0-60 time of probably like 7 secs.
certainly ?
 
The entire Grade A, Grade B etc nomenclature is imprecise and not very useful IMO.
We just kind of wind up with a situation where any cell that doesn't fail basic tests or display visual imperfections gets marketed and traded as "Grade A."

I just want to buy cells which are newly manufactured, unused, and which meet the manufacturers specifications in every way, while lacking any type of defect.
So by your description, 'we' just want to buy Automotive grade cells ?
 
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