Are we all getting GRADE B cells??

[BatteryStudent]

There are several companies that you can't get their new "Grade A" cells, especially CATL, BYD, GuoXuan, even if you were in China. The greatest cells you can buy are new "Grade B" or "Grade A-".

 

[Miles B]

I have two purchases coming up.. one for a 32 cell house pack. The other for a 160 cell EV conversion. The EV will spend most of its life at or below 1C, maximum draw 1.5C. I'm actually considering the Luyuan $100 cells for both.

I'm anticipating 325km per cycle for the EV, but it will probably rarely see under 50% SOC. I would be lucky to use more than (equivalent to) 50 full charges per year.

The house battery will also likely be a shallow discharge regime most of the year. With ~30kWh capacity and my daily use at 12-15, the solar will mostly keep it topped off. It will be lucky to see 0.3C charge and 0.2C discharge max.

I just don't see the point in the EV grade cells for most of us. It's probably a good idea though to have some spare cells. Not exactly sure how to achieve that.

 

[Alkaline]

There are several companies that you can't get their new "Grade A" cells, especially CATL, BYD, GuoXuan, even if you were in China. The greatest cells you can buy are new "Grade B" or "Grade A-".

Correct Only EVE has an official supply of Grade A cells in the market, yet they also have quite a bit of grade B cells in the market competing with themselves.

But CATL, BYD, Ganfeng all do Not have a grade A channel, if you are buying any of these brands its grade B.

 

[Ampster]

I have two purchases coming up.. one for a 32 cell house pack. The other for a 160 cell EV conversion. The EV will spend most of its life at or below 1C, maximum draw 1.5C. I'm actually considering the Luyuan $100 cells for both.

What size are the Luyuan cells or what will you pack size be for the EV?

I'm anticipating 325km per cycle for the EV, but it will probably rarely see under 50% SOC. I would be lucky to use more than (equivalent to) 50 full charges per year.

EV range will vary but unless it is very light and is driven at speeds below 80 kph on level ground you will be lucky to get 5 km per kWh of battery pack. Using a margin of only using 80 percent of your pack that means a 80 kWh pack.

The house battery will also likely be a shallow discharge regime most of the year. With ~30kWh capacity and my daily use at 12-15, the solar will mostly keep it topped off. It will be lucky to see 0.3C charge and 0.2C discharge max.

That should work fine

I just don't see the point in the EV grade cells for most of us. It's probably a good idea though to have some spare cells. Not exactly sure how to achieve that.

The point of EV grade cells is the discharge rate and the things that happen to cells that fail the automotive grade test. Cell drift caused by poorly matched cells at high discharge rates is just one of those risks.

 

[Sabre36]

These EVE 280 cells were sold to a customer of ours as "A grade", matched etc.... They were so poorly matched his Daly BMS could not keep them in balance..Three cells were pretty well matched the fourth was junk..The seller refused to replace the bad cell and as usual for Aliexpress you have zero rights.. He wound up buying cells from Sunfunk Kits and everything was fine...

 

[turbo6bar]

What size are the Luyuan cells or what will you pack size be for the EV?

EV range will vary but unless it is very light and is driven at speeds below 80 kph on level ground you will be lucky to get 5 km per kWh of battery pack. Using a margin of only using 80 percent of your pack that means a 80 kWh pack.

My Bolt EV gets just over 4 miles/kWh (6.44 km/kWh) for the yearly average. It would dip in the 3.2-3.5 miles/kWh in winter and well over 5 miles/kWh in summer. This is not at interstate speeds, so 5 km/kWh (3.1 miles/kWh) seems awfully conservative. I would definitely be concerned with getting proper lifepo4 cells that can handle peak discharge rate. Most cells talked about here won't like the relatively high discharge rate in a DIY EV, much less a production car. I do believe the 100Ah lifepo4 have much better charge/discharge ability, however.

 

[Ampster]

5 km/kWh (3.1 miles/kWh) seems awfully conservative.

It probably is. I probably applied a derating factor to that and my calculation of pack size.

 

[Alkaline]

LOL... look at the email I just got from Deligreen

Text under the banner:

"
Grade A Brand New

QR code

Studs Terminal

Quality Promise"



Look at the QR code on the cells in the picture it as B on it they could have at least used better pics

 

[lfpinside]

That could be due to some resistance that has crept into your connections somewhere.

Yes, I have experienced the same issue. One cell shoots up to high voltage while charging, and low voltage while discharging.
After inspection, I found that it has a poor connection with the busbar. Then I used some conductor paste on every busbar, the bad cell works as a Grade 5A cell right now.?

 

[Miles B]

What size are the Luyuan cells or what will you pack size be for the EV?

EV range will vary but unless it is very light and is driven at speeds below 80 kph on level ground you will be lucky to get 5 km per kWh of battery pack. Using a margin of only using 80 percent of your pack that means a 80 kWh pack.


That should work fine

The point of EV grade cells is the discharge rate and the things that happen to cells that fail the automotive grade test. Cell drift caused by poorly matched cells at high discharge rates is just one of those risks.

Looking at the 280Ah EVE cells. So around 145kWh. I should've typed 425km, not 325. It's a Chevy truck, and I'm aware that a homebrew system will not see anything like the efficiency of a factory product. Somewhere around 3km per kWh would be a good achievement for me.

I'm hoping to not use the EV grade cells though. The motor I'm looking at is 150kW 100% duty cycle, 250kW max. I anticipate most of the time it will be using under 75kW (0.5C). High discharge rates >0.5C would be either very short duration or very rare. I imagine towing could put the load over 0.75C for minutes at a time, or flooring it could hit a maximum of 1.5C... but you can't go wide open throttle for more than 10 seconds anyway.

I believe the EV grade cells are $150, their others are about $100. That's an $8000 saving, and my number of cycles per year is low, and depth of discharge is very shallow. I'm relying on a huge battery to help me out.

 

[Miles B]

My Bolt EV gets just over 4 miles/kWh (6.44 km/kWh) for the yearly average. It would dip in the 3.2-3.5 miles/kWh in winter and well over 5 miles/kWh in summer. This is not at interstate speeds, so 5 km/kWh (3.1 miles/kWh) seems awfully conservative. I would definitely be concerned with getting proper lifepo4 cells that can handle peak discharge rate. Most cells talked about here won't like the relatively high discharge rate in a DIY EV, much less a production car. I do believe the 100Ah lifepo4 have much better charge/discharge ability, however.

145kWh battery in a Chevy truck... thus the lower mileage and larger battery. Motor is a 150/250kW unit. See my post just before this one for more details.

 

[curiouscarbon]

could come up with a relatively simple model of acceptable load based on cell self heating for 0.5/1.0 C discharge etc, and program the ESC to reduce output gradually until temps get back in range.

excited to hear of your project, please feel free to post more about it on this forum,!

 

[upnorthandpersonal]

The pack has been operating for a year now and is staying well balanced . I charge to 3.45 per cell and never go below 50 percent SOC. I charge at 80 Amps and the discharge rate rarely exceeds 30 Amps.

So, I have 32 cells that have been in operation for two years now. I charge at 50A+ regularly in summer per pack, and my pack often sits full during this time. I tend to go to 3.5V per cell, but don't absorb there. In winter, I take them down close to empty, but not below 2.9V. Summer and winter patterns are very different. In summer, my discharge current can be close to my inverter max output: 50A per pack. After last winter, I checked the first cycle where they would go to 100% state of charge again after many months. All cells are perfectly in balance and there were no runners.
I don't exactly pamper my cells. They can sit in the cold many times where they are discharging (not charging), they never get too hot though. I've had no issues in two years. I'm now entering year three with these, and am about to add another 32 cells - which had a side effect of lowering the charge/discharge current per pack as well.

 

[Warpspeed]

My discussion with Amy at Luyuan a few weeks back was that the A+ grade automotive cells with test certificate were almost double the cost of what she called the otherwise "ordinary" A- cells without the test certificate.

So I figured almost twice as many cells per dollar has to be a bargain, even if some of them are not quite up to the pace, or need to be replaced fairly soon.
Now a vehicle manufacturer cannot take that chance, but I sure can.
Unless more than half of my new cells are unusable, I am definitely in front.
If all of them are down by say 20% in capacity, I still get 160% instead of only 100% guaranteed capacity from the more expensive A+ cells.

So quite happy to own a lot of extra cells for a lot fewer dollars.
For a home installation where space is not an issue for the cells, I am way in front.
If in a few months I have to toss a couple into the wheelie bin, I am still in front.

 

[Don B. Cilly]

Post #9 here:

I ordered A- (minus), I really don't care if I lose a small percentage of capacity.
I mean, almost half price, for the difference, I can assemble another battery, I'm almost certain to gain in capacity, am I not?
It's not as if I'm making it for someone else, and I never discharge past 50% with the much smaller ones I have anyway.

:·)
-

 

[toms]

Literally the million dollar question that will be answered in a few years is: Are we paying 1/2 price for a cell that has 1/3 the lifespan?

I remember well a decade ago plenty of people buying “seconds” thundersky batteries and openly saying they didn’t care if they only lasted five years, because by then everyone will be using a different technology. I know a couple of people that are on their third set of LiFePO4’s since my first pack was commissioned.

These blue EVE cells may tell a different story, certainly plenty of people believe it - i’ll reserve my judgment for another few years.

The thread began asking if we are all getting “B” grade cells. When i first started visiting this forum i got rubbished for stating this - at least now people recognise the vendors have been outright lying to them. Now all is left is to see how good the “B” grade EVE’s are compared to the “B” grade Thundersky’s.

 

[Warpspeed]

I doubt it, they all come down the exact same assembly line initially.
These things are manufactured in vast numbers presumably by a fully automated robot assembly line these days.
Its not like hand assembly by unskilled workers years ago, where Monday morning and Friday afternoon batteries have high expected failure rates.

This practice of testing and grading is very common throughout electrical and electronic manufacturing.
You buy a pressure or temperature sensor and it comes in three grades. +/- 0.5% +/- 2% or +/- 5%. The tight tolerance ones cost maybe ten times as much as the lowest grade. They are EXACTLY the same part and have identical potential reliability.

For a non critical measurement the cheapies will work perfectly well and perfectly reliably.

 

[740GLE]

So, I have 32 cells that have been in operation for two years now. I charge at 50A+ regularly in summer per pack, and my pack often sits full during this time. I tend to go to 3.5V per cell, but don't absorb there. In winter, I take them down close to empty, but not below 2.9V. Summer and winter patterns are very different. In summer, my discharge current can be close to my inverter max output: 50A per pack. After last winter, I checked the first cycle where they would go to 100% state of charge again after many months. All cells are perfectly in balance and there were no runners.
I don't exactly pamper my cells. They can sit in the cold many times where they are discharging (not charging), they never get too hot though. I've had no issues in two years. I'm now entering year three with these, and am about to add another 32 cells - which had a side effect of lowering the charge/discharge current per pack as well.

Biggest question will be will the old cells match in quality/capacity of the new cells recently delivered.

Like fine wines It seems quality comes and goes year to year. Fingers crossed you’re just as happy with the new cells.

 

[upnorthandpersonal]

Biggest question will be will the old cells match in quality/capacity of the new cells recently delivered.

Like fine wines It seems quality comes and goes year to year. Fingers crossed you’re just as happy with the new cells.

If I find the time, I'll capacity test a few so I have a baseline to compare with (also over time).

 

[lfpinside]

I doubt it, they all come down the exact same assembly line initially.
These things are manufactured in vast numbers presumably by a fully automated robot assembly line these days.
Its not like hand assembly by unskilled workers years ago, where Monday morning and Friday afternoon batteries have high expected failure rates.

This practice of testing and grading is very common throughout electrical and electronic manufacturing.
You buy a pressure or temperature sensor and it comes in three grades. +/- 0.5% +/- 2% or +/- 5%. The tight tolerance ones cost maybe ten times as much as the lowest grade. They are EXACTLY the same part and have identical potential reliability.

For a non critical measurement the cheapies will work perfectly well and perfectly reliably.

Yes, it is meaningless to say one cell is grade a or grade b. Grade emerges while grouping cells together. Similar as molecule, gas, and pressure.