Battery stops working after 3 years despite scheduled replacements BESS Marchent

  Hi SAM team,I'm currently modeling a standalone BESS (100 MW / 150 MWh, LFP chemistry) and encountering a persistent issue:
Although I’ve configured battery replacements correctly (tested both “Replace at specified capacity” and “Replace at specified schedule”), the battery consistently stops operating around year 3. After this point:

• No dispatch occurs,
• Battery current and cell voltage flatline,
• Revenue drops to zero,
• Despite replacement being triggered (replacement flag active, cost accounted for).

What I've already tested:

• Replacements set at 70% capacity and every 3 years → same result.
• Battery life model: Cycle and calendar degradation.
• Tried changing to only cycle degradation → still no activity post-replacement.
• Manual replacement cost entered under O&M.
• Energy market and ancillary services configured, system dispatches properly before failure.
• Analyzed hourly outputs: SOC, voltage, capacity all drop and never recover after year 3.
• Cell parameters are valid (e.g. 3.2 V / 320 Ah), system runs perfectly in year 1–3.

It seems like after the first degradation-induced replacement, the battery object exists but doesn’t get reinitialized properly, or the dispatch controller stops sending any commands.My suspicion:This might be an internal issue with how SAM handles re-instantiation of the battery bank after replacement in a standalone configuration. Possibly related to degradation + dispatch interaction.Has anyone encountered this before?
Is there a known bug or workaround for standalone battery systems where replacements are ignored or malfunction after a few years?Happy to share the file and CSV outputs if needed.Thanks a lot!

Hi Christian,

This is a tricky one.

The battery dispatch responds to price and cost escalation (among other things). On the Operating Costs page, operating costs for the system escalate at 2% (in addition to 2% inflation from the Financial Parameters page).

In our tests, changing the escalation rate for "Variable cost by generation" on the Operating Costs page to zero resulted in the battery dispatching over the entire lifetime.

For the front-of-meter (FOM) automated dispatch option (on the Battery Dispatch page), the battery only discharges if ancicipated revenue from electricity sales is greater than the cycle degradation penalty. Given the input assumptions, the dispatch algorithm avoids discharging the battery because it determines that revenues are not sufficient to justify discharging the battery.

Best regards,
Paul.