[Joel_Mckay]

Agreed, the study summary needs better explanation to justify the contradiction with dozens of other lab tests. We have several boxes of 21700 cells from various manufacturers (Samsung/Sony/Panasonic) undergoing aging trials for over 2 years now.

All LiIon and LiPol chemistries have shown the following:

1. deep-cycle discharges below 60% full cuts usable charge cycle counts from 8000 to under 2000 uses.

2. high-current discharge or rapid-charging accelerates capacity losses by about 15% a year

3. Internal resistance goes up as dendrite defect shorts damage the cell. Additionally, the self-discharge rates increase as the cell is degraded.

Very surprising if the technique works for all cell chemistries. =3

[gamblor956]

There isn't a contradiction.

This study solely focuses on the very first charge. It doesn't claim that recharging at high currents benefits battery life, only that the first charge at high current forms a larger protective barrier than a first charge at a low current.

Other studies have shown that a larger protective barrier improves lifespan. (See other comments on this thread for more details on the science.)

[Joel_Mckay]

Some early Microchip LiIon chargers did not split the cycle into 3 to 4 stages (pre-prep, CC-prep, and CV rapid charge).

i.e. they would drop into a constant-voltage rapid charge mode assuming the cell was prepped already.

None of these systems showed any sort of increased capacity or longevity. Quite the contrary results, this is why the new study details are rather intriguing. =3

[gamblor956]

The problem was probably the pre prep stage.... that appears to count as the first charge as it is defined in this newer study.

When they say "very first" they mean it very literally.

[Joel_Mckay]

There is a lot of what-ifs in the poorly written press release.

In general, we track the internal resistance (+-0.02ohm for Samsung) of the inventory under both new, charged, discharging, and storage levels. While I don't doubt the Papers results, they need to be clear on the methodology so others can validate it is not BS (common in this area.)

Have a nice day =3

[starky]

Unless you actually work for a cell manufacturer you aren't getting completely fresh cells though. They are talking about the first charge after the jelly roll is sealed into the can. When I would build cells by hand the standard procedure was to do the first couple cycles at 0.01C, record the capacity, and then change them to the charge rate for the experiment.

[Joel_Mckay]

Perhaps, normal practice is already usually to first cycle the cells in the CV charging region a few times to condition them for best capacity. Shipping regulations means Li cells are no longer shipped fully charged anymore even when new from an OEM.

It is fascinating news, and I look forward to more details. =3

[jve]

> deep-cycle discharges below 60% full cuts usable charge cycle counts from 8000 to under 2000 uses.

That is, if you do it single time you are down from 8k to 2k? Or it decreases gradually and 2k is the worst case?

Where can I read about it? Not a paper, but something more down to earth for consumers? That is, for a consumer to know how to properly maintain various devices (phone/car) for longevity?

[magicalhippo]

Keep in mind that for a car, 2000 cycles is still a fair bit. My BEV has a range of 350 km fully charged (highway). At 2000 cycles that's 700000 km.

That said, I previously read studies suggesting to keep the batteries between 30-70% SOC for optimal longevity, though I imagine there's been a lot of research so it might be now outdated.

[Joel_Mckay]

Some older Tesla Models used the Panasonic 21700 cells.

In general, "the battery is the car" for EVs... The bigger the better in my opinion, as it will last longer due to reduced stress on the cells.

Even if people are stressing the vehicle pack, they should still get 5 to 12 years out of the car. Note, some companies hide the expected range loss by over-provisioning capacity.

Best regards, =3

[jajko]

> The bigger the better in my opinion

This is definitely true, recently faced issues with my motorbike battery and oh boy are they fragile and lose charge by themselves quickly compared to bigger car batteries.

Basically I left a few times older (10-15 years) diesel bmw standing whole winter without touching it, started always without any issue (I know not the best idea re fuel in the tank, but it worked).

I did that once to completely new motorbike (honda) with good brand battery but I didn't unplug it, and now battery is permanently damaged and loses full charge in less than 2 days to such levels that it can't start the engine even if those 2 days its completely unplugged.

[Joel_Mckay]

Motorbike Pb AGM batteries are much different in modern vehicles. The prismatic packs often increase the plate surface area to bump cranking amp ratings. Thus, the cells design are thinner and more fragile too. We used these in some equipment at one time, for the extended temperature range.

Tip: if a Pb pack is partially discharged, it is more vulnerable to cold-weather related standby failures. Most people that own boats/heavy-equipment get a plug-in trickle-charger for Pb batteries, as the adapter also helps keep the pack slightly warmed.

Best of luck, =3

[Joel_Mckay]

The problem is there are many different types of Li cells. Some tolerate a wider Safe Operating Area for power output and temperatures.

I don't want to get into the name-and-shame game with other manufacturers. The 3 brands mentioned are generally very good quality, and if you can source new cells without counterfeit/expired nonsense... they will perform as per their app notes.

The cycle limit is a function of whether your charger IC is smart, slow-charge/low-current-discharge, and if your firm uses capacity Boosting (stress costs cycle counts.)

>Or it decreases gradually and 2k is the worst case?

Anecdotally, sensitivity seems somewhat correlated with cell use/age. The more stress, and the faster the cell degrades.

Best of luck, =3

[algo_trader]

> Samsung/Sony/Panasonic

> 1. deep-cycle discharges below 60% full cuts usable charge cycle counts from 8000 to under 2000 uses.

Presumably these are NMC variant?

Major Chinese LFP brands come with 6000K/10K cycle guarantees (but with specific operational parameters). Are these cycle predictions unrealistic ?

catl/eve/etc

[Joel_Mckay]

Yes, China batteries are so good the claims seem impossible... There are good manufacturers like anyplace else, but they are rightly priced accordingly. =3