One of the things that people do not seem to realize that affects the longevity of rechargeable lithium batteries is the effect that leaving them fully charged has on them. Fully charged lithium batteries typically lose around 5% of their capacity every month that they are left fully charged. If this is not happening, it is likely that the charging systems are not actually fully charging the batteries so that the 1300 pound $40,000 100kwh long range battery is really only being charged to around 80% of its actual capacity to avoid this type of degradation. With proper metering this will eventually be realized by some owners but most will happily tra-la-la along never noticing that their range is much less than advertised. If your EV is not going to be used for a period of time the battery should be discharged to about 50% of its capacity which is typically about 3.8 volts per cell.
And of course leaving lithium rechargeable batteries in a discharged state for an extended period will degrade them faster than leaving them fully charged. But even worse if they are somehow discharged to less than 3.2 volts per cell they will be permanently damaged and likely destroyed. This can also happen to individual cells which are defective or whose connections become damaged or corroded, or the balance charging circuitry goes haywire. I can't tell you how many batteries that I have had to throw away because they became discharged because some type of load from the equipment they were left in took them down too far. Fortunately, many of them were just a few dollars apiece. But some have been much more expensive, but nothing compared to an EV battery.
Another characteristic that most do not seem to realize that fast charging is both risky and hard on lithium rechargeable batteries. The other thing that is hard on these batteries is discharging them at a higher rate than normal. This raises their internal temperature to a point that permanent damage can easily be done. Of course, this is exasperated by hot weather especially when an air conditioner is being used in addition to the normal load. But the most obvious challenge that are likely to cause a problem are trying to drive over mountain passes or towing any type of trailer.
And of course, there is the well known problem that when the temperatures go down the ability of rechargeable lithium batteries to perform to their rated capacity can and will drop to a very small fraction of what one would normally expect. But some people do not realize that if lithium batteries are below 26F and they are not heated back up to a temperature that is above this level that charging can cause permanent damage and they can explode. This is not as much of a problem if they were fully charged before the cold temperatures, but can be devastating if the batteries were discharged and then allowed to freeze. A $40,000 battery can easily be destroyed if not properly warmed before charging. The way this is done in well-designed vehicles and charging system such as that found in a Tesla... is that all the power from the charger is diverted to the heating pads until the battery reaches a safe temperature for charging. Depending on the outside temperature, the temperature of the battery, and the capacity of the charger this may take a considerable amount of time or may not work at all. Systems from other manufacturers which are newer to the game are more likely to be in the "not work at all" category.
I have got to end my post at this point, but the ignorance of most on this subject is actually quite shocking and this often even includes EV owners who I have spoken and conversed with. They typically do not understand the limitations of their vehicle's batteries or how they should be properly treated. If you own an EV you should really spend some time investigating the intricacies of rechargeable batteries. This is also true if you have some type of solar system with rechargeable batteries although those should be some form of lead acid which are much more robust and cheaper for that type of application...
Sorry in advance for the typos.
One of the things that people do not seem to realize that affects the longevity of rechargeable lithium batteries is the effect that leaving them fully charged has on them.
Agreed. Most EV manufacturers recommended topping it off regularly at 80%, going up to only 100% when about to start a long trip to the next charger. You noted this later in your post.
...so that the 1300 pound $40,000 100kwh long range battery...
If I had to replace the battery in my EV it'd cost about $10K (if there was no warranty). Of course my EV isn't a Tesla, which stands for Too Expensive Still Liberals Adore. LOL
...battery is really only being charged to around 80% of its actual capacity to avoid this type of degradation. With proper metering this will eventually be realized by some owners but most will happily tra-la-la along never noticing that their range is much less than advertised. If your EV is not going to be used for a period of time the battery should be discharged to about 50% of its capacity which is typically about 3.8 volts per cell.
Most EV owners I know actually knew this up front before getting their EV. The same for most solar battery owners (though the solar battery specs often encourage charging them fully daily, especially the LifePo4's). The same with discharging to a recommended floor instead of all the way to 0% charge. Most EV owners and solar battery owners know this up front.
Another characteristic that most do not seem to realize that fast charging is both risky and hard on lithium rechargeable batteries.
Actually most EV owners do realize this. The EV forums are littered with discussions on how frequent is too much to charge the EV with Level 3 roadside chargers. Plus there's even discussion on Level 2 home charging speeds (i.e. is it best to charge at a fast rate of about 11kW to get a more efficient AC to DC conversion and thus pull less power from the grid. Or is it better to regularly charge at a slower rate of about 6kW which is less efficient in the AC to DC conversion and thus adds more to the power bill, but is probably less damaging to the EV battery health). For what it's worth I almost always charge my EV at the slowest Level 2 rate for it which is 5.6kW because most of my power is free from solar anyway.
And of course, there is the well known problem that when the temperatures go down the ability of rechargeable lithium batteries to perform to their rated capacity can and will drop to a very small fraction of what one would normally expect.
On that we're in agreement. I'm frankly surprised at how many EV owners who live up north that didn't study this more fully. On the EV forums I see plenty of them who knew about it, but thought they could weather it (pardon the pun) because they were a true believer in saving the planet or whatever. Now they're admitting that if they had known how bad it was they wouldn't have gotten an EV. LOL I don't see that kind of response among the few of us EV and solar owners who go into it with a small government conservative mindset (getting solar and EV to be more energy independent and prepared for the Dims making energy less available and more expensive). Most of the people I interact with who have my small government mindset are people in the south (better climate for solar and EV) who do their homework and make sure it can be efficient for them in the long run.
The LiFePo4 cells both in my e-MTB and starting battery for motorcycle can go way lower than that.
"At the other end of the scale, over-discharging can also cause cell damage. The BMS must disconnect the load if any cells are approaching empty (less than 2.5V). Cells may suffer mild damage below 2.0V, but are usually recoverable. However, cells which get driven to negative voltages are damaged beyond recovery."
Great post, thanks.
Is there any data on charging efficiency/range by latitude and altitude (assuming sun angle and ASL corresponds with average overnight temperatures October-April)?