I wonder how the multiple recharge cycles, especially if partial; i.e. at every station stop, will impact battery life.
Partial recharge cycles are fantastic on lithium. This includes smartphone, laptops, and electric cars using lithium batteries.
Depending on the makeup of the lithium battery -- a lithium battery shallow SoC (
State of Charge) is best. Recharged only to 75% and discharged only to no less than 25%, often lasts 10x longer than a battery charged to 100% and discharged to 0%. So basically you more hours of a battery that way.
It's how lithium battery chemistries tend to be prefer to be handled. The charge computer in some electric cars reserve a charge reserve so 0% actually means 10% or 15% or 25% or some other number. So you only unlock the reserve charge when you badly need to limp to the charge station. It's a method of protecting from deep discharge. And a very common recommendation is to just topoff an electric car to something like 90% except when you're needing to do an out-of-town roadtrip. But it's harder to do with smartphones to interrupt charging before 100%, a kind of a planned obscolescence thing & a human habit to do a full 100% to 0% (Good for nicads, bad for lithium). Even
Teslas will automatically charge-limit (e.g. ~90%) unless you ask it to charge to 100% for the occasional superlong roadtrip -- this is because a 100% charge shortens a battery's durability.
Enhanced versions of
SoC computers / battery mangement systems do this automatically to prolong longevity in valuable batteries like power grid battery farms, electric cars, home-solar lithium batteries, and other extremely expensively large lithium batteries. They
already have this
already in those experimental battery trains too -- to protect the train's battery.
And you can do it too....
There are some
Android apps lets you limit battery charge (e.g. stop charging above 80% or 90%) so you can make your Android battery last literally forever without maintenance... but Apple doesn't have a way to interrupt your iPhone/iPad charging at a desired threshold (e.g. 85%) to minimize battery replacements. If you are lucky to have a 2-day battery in your smartphone, then it is an easy habit. But this could be tough for those who barely make it through a day...
All you have to do is follow two rules (A) Never charge fully every single time, and (B) never discharge fully every single time. And you'll be pleasantly surprised you'll never need to replace your smartphone battery in its lifetime. Even after 2 or 3 years, your battery lasts almost as long as when fully new. Even an 85%-discharge-to-15% is a good range, you still get 70% of capacity, but you'll turn your battery into Methuselah. In some cases, 10x as much partial charge cycles as 100% charge cycle -- e.g.
your lithium battery is much more durable at partial charges, 5000+ cycles of 50%-to-70% recharges, instead of 500 cycles of 100% recharges.
The shallower your depth of cycle in approximately the middle of the range of lithium battery, the better for your lithium battery.
100%-0%-100%-0% = worst total lifetime number of hours out of battery
90%-10%-90%-10% = battery more durable, many more hours
80%-20%-80%-20% = battery even more durable
60%-40%-60%-40% = battery fantastically durable. Even more cradle-to-grave lifetime-hours out of the battery.
That's how lithium behaves, unlike some other battery chemistry.
The range window varies on the exact type of lithium battery chemistry, a few percent off-center. But it's extremely close to center SoC.
With good careful SoC management you can milk a smartphone battery to last for 10 to 15 year life instead of 2 years. There is a 7-year-old Tesla car that
still has 98% battery capacity.
Planned obsolescence & difficulty having all-day phone life -- is part of why it's not easy to shallow-cycle a smartphone battery -- but if you want to keep using a specific $1200 phone in 5 years without battery replacements.... DO IT, shallow-cycle.
(You can make an exception, say, 5% or 10% of the time -- do a full charge/discharge cycle once in a while is OK -- like for those long days away from a power outlet).
Likewise, for battery trains there needs to be healthy excess capacity. Large numbers of shallow charges is fantastic to modern lithium batteries.
This is fundamental Lithium Battery Chemistry 101 that few Laypeople know about.
Very important when dealing with multimillion-dollar lithium battery farms at power substations like those popping up in Australia and elsewhere to smooth wind-power fluctuations.
You want your batteries to last as long as possible -- maintain shallow SoC (State Of Charge) in the goldilocks midrange away from the
lithium-damaging 0%'s and 100%'s.