Battery degradation and lifetime

Hello everyone,I am working on a research project where I need to model multiple full calendar-life cycles of a lithium-ion battery within a single SAM simulation.
Conceptually, the goal is simple:

• the battery should degrade from 100 % → 80 % over its lifetime,
• then be replaced,
• and the new battery should again start at 100 % and degrade to 80 %,
• and so on.

What I triedI used the “Cycle and calendar degradation” option, neutralized cycle degradation, and defined a custom calendar degradation curve for each battery type (e.g. 0 → 10 years = 100→80 %).I tried two approaches:(1) Simple calendar degradation for one cycleJust a normal linear calendar curve:
  Then I used “Replace at specified schedule” (year 10) expecting the lifetime state to reset to 100 %.
However, after the first 100→80 % decline, the overall lifetime degradation simply continues downward across the entire project horizon (20–25 years).
It does not restart at 100 % after replacement.(2) Multi-cycle calendar table (“reset points”)I also tested a more explicit multi-cycle calendar table:
  In the calendar-only result series, these resets appear correctly.
But in the final output
“Battery relative capacity to nameplate”,
after the first drop to ~80 %, the value becomes “stuck” around the minimum.
At each replacement event I see only a small bump (e.g. 80 → ~83 %), followed by an immediate fall back to ~80 %.
No true second or third cycle appears.Limitation with “Replace at capacity”I also attempted using “Replace at capacity”, which might more strictly reset the lifetime state, but this option makes the simulation extremely slow at 15-minute resolution (once SoH reaches ~50 %, the model becomes nearly unusable).
For practical purposes, this option is not feasible.My questionIs SAM intended to support multiple physical life cycles (100→80 %, replace, 100→80 %, replace) within a single simulation run?Or is it the intended behavior that
“Battery relative capacity to nameplate”
remains essentially monotonic and reflects only one cumulative degradation curve, even if replacements occur?What I am looking forIs there a simple recommended workflow to achieve the following:

• define replacement years (e.g. year 10 and 20),
• have SAM treat each new battery as starting again at 100 %,
• show a new independent 100→80 % degradation cycle,
• and have this behavior visible in the final SoH output?

Any clarification or recommended practice for modeling multiple full battery life cycles inside SAM would be extremely helpful.Thank you!

Hi Peter,

The attached battery-replacements.sam file contains two PV-Battery / Residential cases that compare the "replace at specified capacity" and "replace at specified schedule" options on the Battery Life page.

The "replace at 80%" case replaces the battery when its capacity degrades to 80%.

 

This results in the battery being replaced three times in the 25-year analysis period:

 

The "replace every 10 years" case replaces the battery every 10 years, regardless of the battery capacity.

 

This option results in two replacements over the 25 years, with the battery degrading to less than 80%:

 

Best regards,
Paul.