BEV battery degradation

I use L1 at work and L2 at home, DCFC is something that I would not normally be using. Now, I would use DCFC if I know I'm going to go over my usual range, but I wouldn't make a habit of it.

 

A lot of the battery information comes from what the software in an EV tells us. So I am not surprised (actually gratified) when Tesla releases battery capacity to those living in the path of a hurricane. Just I don't have the same confidence in LG Chem.

If I am feeling generous, LG Chem appears to be 'sand bagging' their batteries. But compared to Tesla batteries, they appear to be weak. As for air cooled Toyota and Nissan batteries, the less said, the better. I've dealt with the 2001-03 Prius batteries and am not amused.

Bob Wilson

 

From my experience the batteries hold up well.It is the effect that cold weather has on EV range that is more of a concern

AAA confirms what Tesla, BMW, Nissan EV owners suspected of cold weather

 

interesting that the much heralded mitsubishi outlander seemed to have the worst degradation compared to average

 

I haven’t had a chance to read this yet, but three notes in general:
1. Most people expect EV/PHEV/Hybrid batteries to degrade like their cellphones, and that’s simply not a realistic comparison. That, for many reasons, such as that cellphone batteries use a very-different chemistry (Lithium polymer rather than LiAlCo, LiMg or related, in EVs), cars are not charged nor emptied as completely as cellphones, and...
2. Most, but sadly not all (looking at you Nissan!), “electrified” Powertrains have active thermal management to keep them from overheating. The P.Prime is “fair” in this regard, in that it does have active thermal management, but using forced-air rather than liquid cooling. That, plus it’s still a fairly-small battery, so forced air can still do a fair job, albeit still not as good as liquid-cooling.
3. Quite a few EVs that do have superb thermal management have gone over 300K miles with only around 20% capacity reduction.

 

with an engine, i expect time longevity, and decent miles with good maintenance.

with a battery, i expect mile longevity and decent time, but they don't seem to like sitting around, which is one negative.
i'm sure they will keep improving though, and engines will probably stagnate in regards to longevity.

in fact, with the ever increasing push for more efficient engines, they might regress a bit.

 

Another consideration here is just the sheer number of charging cycles, even if they are partial.

I tend to “fully” (meaning partially — only up to and down to Toyota’s margins — 15-20%ish depending how you calculate them) two to three times per day, whereas a Tesla is unlikely to be fully charged more than a couple times a week, say.

So, I would probably get longer battery life if I were to drive more in HV, but ... you know, “gas: eeeewww!”

 

BEV, PHEV, hybrid, or regular ICE, my expectation for a personal vehicle is 10-15 years, I am sure most of them will satisfy this without much worry nowadays.

 

Certainly, broadly speaking, any time you can avoid quick charging irlas be better for battery life.

 

Preliminary test results from this morning:

• 240 mi indicated charge - on Mar 2019 Model 3, 15,900 mi, charged at Athens AL. First 20 mi EV showed it is real.
• Tesla warms battery to 51-54 C when fast DC charging but brings temp down to ~30 C

Of course Tesla has a very advanced understanding of their batteries.

Bob Wilson

 

(Oop, make that “Mn,” not “Mg” — manganese. Magnesium is ... a bit different!)

 

Here are some initial temperatures after the Tesla was 'cold soaking' overnight:


Notice the car keeps the battery and electronics in a 'happy place. This is the parasitic load.

This is what happens when driving:

The car is starting to taper the battery cell temperature.

Bob Wilson

 

"tesla stock bear says battery technology is tesla's biggest advantage over competitors:

 

Yes. In general the higher the charge rate the more heat is created. Can be mitigated with the right software and hardware combo.

 

Source: (PDF) Energy Density of Cylindrical Li-Ion Cells: A Comparison of Commercial 18650 to the 21700 Cells

1. The energy content per cell can be higher by ~50% from 21700 compared to 18650. Therefore, for certain applications, less cells have to be built and used to deliver the same amount of energy.
2. The higher energy content on cell level leads to potentially lower effort and costs in the production of 21700 compared to 18650 type cells and their packs. ...

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Rivian claims they can cool the cells by one end more efficiently than Tesla's coolant channel that passes between the cells. Thermal cooling is engineering 'black magic' so I don't have a strong opinion one way or the other. However, I've wondered for a long time if heat-pipe technology could be used in pack construction.

A heat pipe uses the phase change from liquid-to-gas to transport heat away from the hot side. Then the cold side condenses the gas back to a liquid which via capillary action returns to the hot side. No pumps or cooling channels needed as the porous mat covering the hot side handles liquid transport. A whisker fuse coated with an impervious coating would be needed for cell-to-buss. The module/pack would need to be gas and pressure tight.

Bob Wilson

 

Formula E uses a thermal fluid that the battery cells are directly immersed in for cooling. That may be were performance BEVs are heading.