More interesting cycle life data

[SignatureSolarJames]

reached out and got the actual test sheet by Ganfeng

may answer some questions, every cycle is detailed

48173125-100Ah cycle data.xlsx

1.0循环 48173125-100Ah Cycle 25℃@1C/1C Cycle,充电容量,放电容量,容量保持率 1,101460.0,101851.3,100% 2,101861.9,101810.6,100% 3,101825.6,101740.3,100% 4,101751.1,101682.5,100% 5,101697.2,101642.0,100% 6,101657.2,101597.1,100% 7,101616.7,101559.2,100% 8,101571.8,101485.5,100% 9,101493.7,101401.9,100% 10,101412.2,...

docs.google.com

 

[SignatureSolarJames]

very impressed with this outcome, looks like the 5 year warranty on Lifepower4 was extremely conservative.

 

[wattmatters]

I don't think that is a good analogy since there is nothing wrong with the 2022 car

There are parts of a car which degrade with age, even if not used. Many will sit outside in the weather and sun. Rust is inevitable with ageing, affects some components more than others (e.g. even new exhaust systems can start to rust). Tyres definitely have an age limit and their performance declines with age, rubber components and seals will have aged. The battery is likely to have degraded. Pulley belts also degrade with age. And it has depreciated as well, will have a lower resale value.

 

[EastTexCowboy]

very impressed with this outcome, looks like the 5 year warranty was extremely conservative.

So you're going to extend that to 10 years? Retroactive? ??

 

[SignatureSolarJames]

So you're going to extend that to 10 years? Retroactive? ??

How about you got a 10 year warranty battery for the price of a 5?

the aim of lifepower4 was to make lead batteries stupid cost-wise

 

[Hedges]

reached out and got the actual test sheet by Ganfeng

may answer some questions, every cycle is detailed

48173125-100Ah cycle data.xlsx

1.0循环 48173125-100Ah Cycle 25℃@1C/1C Cycle,充电容量,放电容量,容量保持率 1,101460.0,101851.3,100% 2,101861.9,101810.6,100% 3,101825.6,101740.3,100% 4,101751.1,101682.5,100% 5,101697.2,101642.0,100% 6,101657.2,101597.1,100% 7,101616.7,101559.2,100% 8,101571.8,101485.5,100% 9,101493.7,101401.9,100% 10,101412.2,...

docs.google.com

Graph shows capacity degrades to about 0.8 after 40 cycles??

But last line of table says 4406 cycles and 79% of capacity remaining.

Holding cursor of graph data points in spreadsheet shows correct cycle number, but X-axis "Cycle NO." figures are wrong.

 

[SignatureSolarJames]

Graph shows capacity degrades to about 0.8 after 40 cycles??

But last line of table says 4406 cycles and 79% of capacity remaining.

Holding cursor of graph data points in spreadsheet shows correct cycle number, but X-axis "Cycle NO." figures are wrong.

View attachment 146604

they represent hundreds of cycles

 

[Hedges]

That would agree with the table ...

But where does it say "Hundreds of Cycles"?!

 

[Cal]

Temperature has a large impact on battery capacity. After 240 days of storage, capacity dropped by 5.7% when stored at 45 deg.C and 100% SOC. Not much difference when dropping SOC to 65% (4.9% drop)
https://hal.science/hal-00876555/document

"Fig. 2(a) shows that, after 240 days (8 months) of storage, the capacity increased by 1.8%, 1.07%, and 1% for SOCnom 30%, 65%, and 100%, respectively. Meanwhile, Figs. 2(b) and 2(c) show that the capacity fade is fairly linear as a function of storage time and at a specified temperature, more capacity fade is experienced at higher storage SOC. At 45 °C, after nearly 214 to 247 days of storage, the capacity has decreased by 2.1%, 4.9%, and 5.7% for SOCnom 30%, 65%, and 100%, respectively. This decrease becomes much more substantial for the cells stored at 60°C for which the capacity fade percentages of the cells (~155 to 188 days of aging) are about 18.1%, 23.7%, and 26.9% for SOCnom 30%, 65% and 100%, respectively."

 

[EastTexCowboy]

How about you got a 10 year warranty battery for the price of a 5?

the aim of lifepower4 was to make lead batteries stupid cost-wise

If that was the aim you hit the bullseye. I didn't really expect you to extend the warranty but someone has to give you a hard time. Everyone else on here is always just so nice to you ...

 

[SignatureSolarJames]

If that was the aim you hit the bullseye. I didn't really expect you to extend the warranty but someone has to give you a hard time. Everyone else on here is always just so nice to you ...

much love man

 

[FilterGuy]

And if calender aging doesn't do it the hen pecking some do will get them eventually.
I guess the set and forget isn't good enough. ?

Naw... we tinkerers will rip them out and install the latest and greatest battery chemistry or flux capacitor....and justify it because it will last 30 years!

 

[Vigo]

Great info in here.

I always wondered what happens after 80%, since that seems like such an arbitrary line in the sand that has little relevance to me as a metric. The graph in the first post looked like degradation was very linear until the chart stopped at 80%. Another poster said some cells ‘center cycled’ basically stopped degrading after hitting 80%, which im sure has a limit but is pretty enticing.

I guess im going to cycle my batteries harder. Seems like you are more likely to get the most value out of lifepo4 by cycling deeply and getting the most cycles out of it before some other factor ruins the fun, than by cycling shallowly which doesnt really prevent all manner of ‘unrelated’ failures from screwing up your plan while the cells only have 1000 cycles on them.

 

[sunshine_eggo]

Naw... we tinkerers will rip them out and install the latest and greatest battery chemistry or flux capacitor....and justify it because it will last 30 years!

Pfft... I'll see your flux capacitor and raise you an oscillation overthruster!

 

[sunshine_eggo]

Great info in here.

I always wondered what happens after 80%, since that seems like such an arbitrary line in the sand that has little relevance to me as a metric.

It's a design spec. A battery that has degraded to 80% of rated may not perform its intended function.

What happens?

Increased internal resistance.
Accelerated capacity loss.
Increased likelihood of catastrophic cell failure.

Good chance that they just keep loosing capacity until you decide they don't work for you anymore.

 

[zcskywire2]

Some interesting thoughts on calendar life.

First is on LTO cells, which is ofc not the main focus here. They are basically indestructible on calendar life aging. We have a whole pallet of the original Altairnano 24v 70a cells. They sat untouched for over a decade in storage. We refurbished them when we went to our newer office. All but two of them were still fully charged and read near perfect SoH.



Since it would also benefit the office, I've got approval to test some of the CALB CAM72 and CA series cells we have nib still at the office. These would have been purchased ~2015 for a now discontinued product. Will get back on how toasted or not they are.

 

[Vigo]

It's a design spec. A battery that has degraded to 80% of rated may not perform its intended function.

That’s what i assumed, that it’s something between cell manufacturers and their actual target market (ie not us). It still seems odd that it comes up so much here because that threshold means nothing for home energy storage, but i guess it’s just for lack of a better metric WITH any real data behind it.

One thing ive tried to contextualize it with is that the rate of decline of a lifepo4 AFTER hitting 80%, is probably still better than whats accepted as normal for a brand new lead acid. It may not have much relevance to anyone buying ‘actually new’ cells and never cycling them enough to hit the 80% mark in the first place, but it’s still something i would like to see quantified because i feel like its plausible that a lifepo4 that already has 5000 cycles and is below 80% of capacity might STILL be a better value than new lead acid even at a slightly higher cost.

On an only vaguely related note, as a car guy who has owned about 70 cars so far, ive gradually come to the conclusion that the ‘sweet spot’ for me to buy cars at is around 220k miles. As an auto tech i have my head all the way around the ‘risks’ and can take advantage of the fact that values at that point are depressed by the seller’s ego and paranoia, out of all proportion to the actual functional decline of the vehicle. So my personality type itches to know what happens past 80% even though most people would be ‘thinking about getting a new car’. ?

 

[timselectric]

Pfft... I'll see your flux capacitor and raise you an oscillation overthruster!

Zero point module.
That's game, set, and match. lol

 

[sunshine_eggo]

Zero point module.
That's game, set, and match. lol

Ahem... EXCEPT, we were CLEARLY discussing transportation methods... Had you countered with "Infinite Improbability Drive" I would bend the knee...

While the Zero point module could certainly power quite formidable transportation methods, it is not a transportation method itself.

OH MY GOSH!

 

[wattmatters]

Orac runs my system.