We know lithium batteries degrade faster when they are charged over 80% and discharged below 20%. Will there be a way to limit charging percentage to a user customizable percentage? It would be especially advantageous if any extra charge over the set amount could be directed to conditioning the cabin, or with V2G, sent to the grid.
The Aptera Forum
To see this working, head to your live site.
Search
Actually, we don't "know" that Li batteries degrade faster when charged above 80% or discharged below 20%. What we know is that automotive traction battery packs, when regularly charged with DC current to 100% of capacity, are more likely to be stressed and will, possibly, lose capacity more quickly than those that are not. Li cells that are allowed to discharge to 0% are likely to undergo internal chemical changes and might not be able to be recharged completely. This is why all automotive traction battery packs have a nominal capacity and an actual capacity: Up to 20% at both the top and bottom of a pack's capacity is "locked-off" by the manufacturer and cannot be accessed by the user. For example, the Li pack in a Honda Clarity PHEV is advertised as being 17 kWh - but only 13 kWh is available for use. Tesla, because of its robust battery chemistry and massive amounts of operating data, has - on several occasions - increased the range of its vehicles by unlocking some of the hidden capacity. Also, if an EV is plugged into a Level 2 EVSE or DC charger, power for cabin conditioning will be drawn from the grid, not from the pack.
I'm no expert, but I do plenty of research. Information from battery university says there is a dramatic increase in cycle life of Li batteries if max charge and discharge rate are reduced as I stated above. interestingly when you say "Actually, we don't "know" that Li batteries degrade faster when charged above 80% or discharged below 20%.", it directly contradicts the entirety of what you said afterward. My point though is that it would be nice to allow owners the option of controlling the max amount of charge their vehicle could receive. a Li battery optimized to stay around the middle of the pack voltage could last much longer than a pack fully charged every night, for example.
@Rex My point in restating YOUR opening sentence was that you named a specific percentage - and that generalization is not true for all EVs: Tesla, for example, recommends a maximum charge of 90% on a regular basis. The figure of 80% has become "common knowledge" based on the experience of the Nissan Leaf (a vehicle that has a history of significant battery degradation - that is less common in EVs with liquid-cooled traction batteries). This "common knowledge" may also have to do with the fact that DC chargers charge most quickly those batteries that have a SOC between 20% and 80%. (You can also find pundits who claim that a Li traction battery should never be charged above 60% - perhaps if one charges to only 30% a battery will last forever...) The simple fact is that all batteries lose capacity over time: The less the pack is stressed, however, the slower it degrades. Right now it seems that only Tesla and Chevy allow drivers to set a maximum SOC percentage while other manufacturers apply other strategies: Larger buffers, automatic cut-offs, driver intervention, etc. I think it's a user-psychology choice: Some manufacturers assume that their drivers will want to fiddle with settings while others are equally certain that their drivers will not. It's also interesting to note that PHEVs - most of which don't accept DC charging - also don't seem to have charging-level prohibitions...
@Kerbe I shouldn't have said 80% you are right. It is well known though that Li batteries loose capacity faster when they are fully charged, and this is why I think it would be great if the max charge level could be user programable.
Programmable charge level would be useful for other reasons. GM's charge limiting feature is called "hilltop reserve" and intended for people who live on top of a hill, to leave room for regenerative braking. And Aptera owners would probably want to leave room for solar charging, e.g. if you only drive a few miles to work and leave the car in an outdoor parking lot all day.
I read that Chevy has changed that in the latest revision of the Bolt and is now calling it by another name.