4 ms·

what is 'state of charge swing'?

• hwillis 7y ago
  I think it is referring to the fact that it is ubiquitous to leave some amount of reserve so that the battery is never fully charged (100% SoC) or discharged (0% SoC). This formulation is capable of going the full 0-100%, while most formulations will last significantly longer if they don't do that.[1] In that graph, charging to 75% and discharging to 25% gives you about 3x more life than from 25%-100%. NB that most li-ion cells are rated for 300-1000 cycles at 100% Depth of Discharge. Reducing the DoD to 90% or 80% will get you thousands or tens of thousands of cycles, although it is abnormal to actually measure that long. A charge-discharge cycle at .1 C (the former standard) takes 20 hours. [1]: https://batteryuniversity.com/_img/content/DST-cycles-web2.jpg https://batteryuniversity.com/_img/content/DST-cycles-web2.j...
  • FooHentai 7y ago
    24kw leaf battery is an example of this with user stats seemingly bearing it out. Charge it to 80% each time, you can expect 3000 cycles before it's spent (drops below 85% of original capacity). If you charge to 100% each time, you'll only get 1000 cycles. 3-4 years versus 8-10 years use makes a big difference.
    • taneq 7y ago
      The 85% capacity benchmark seems pretty arbitrary to me. I'd imagine most owners very rarely use more than 85% of their range (or at least, could avoid doing so easily) at which point 85% isn't "needs expensive battery replacement", it's just "slightly less range buffer". I imagine in 20 years' time we'll see plenty of old beaters, student cars etc. with 50% or less range that are still quite happily driving around.
      • drcross 7y ago
        That's already the case, you can pick up 2013 Nissan Leafs with very small batteries for small money. They're used for commute cars or grocery pickup.