Battery chemistry & storage
Enter your starting charge level, storage duration, and storage temperature. See how much charge each chemistry loses just sitting idle.
How it works
Step 1
Storing at a lower starting charge, often around 50%, is a common way to reduce stress on the cells during long idle periods. The state of health calculator is a useful check before and after a long storage stretch.
Step 2
An unconditioned shed or attic runs warmer than a climate-controlled space, which speeds up self-discharge.
Step 3
Letting a lithium battery sit at very low charge for extended periods can risk permanent damage. The calendar aging calculator covers the separate, permanent aging effect that happens alongside self-discharge.
Self-discharge is charge that leaks away over time and comes right back the moment you plug in a charger, while calendar aging is a slow, permanent loss of maximum capacity that no amount of charging can reverse. A battery can score well on one and still be a concern on the other, a distinction NREL's energy storage research treats as two separate idle-state loss mechanisms, which is why the calendar aging calculator is worth checking alongside this tool for any battery in long-term storage.
LFP, NMC, sodium-ion, and saltwater batteries all have inherently low self-discharge rates thanks to stable electrode chemistry, typically losing only 2% to 3% of charge a month at room temperature. That's a major practical advantage over older lead acid technology for anything left unused for weeks or months at a time, exactly the scenario the seasonal cabin battery storage over winter tool is built around.
A flow battery's energy lives in liquid electrolyte tanks rather than a charged solid electrode, so it largely avoids the chemical side reactions that cause self-discharge in other battery types. For a cabin, boat, or RV battery that sits unused for months at a time, that near-zero self-discharge is a genuine practical edge covered further in the flow battery vs lithium comparison, and it also means less recovery time needed before the backup runtime estimator's numbers apply at full strength after a long idle stretch.
If your battery will sit idle for extended stretches as its primary use case, the best chemistry for backup only use comparison weighs self-discharge alongside the other factors that matter most for that scenario. This same idle-loss consideration factors into how the DOE's Office of Electricity evaluates storage system readiness for infrequent backup applications.
Questions
Self-discharge is temporary charge loss that comes back the moment you recharge the battery, while calendar aging is permanent capacity loss that recharging can't fix. A battery can have a full self-discharge recovery and still be slowly losing maximum capacity in the background from calendar aging.
An LFP battery starting at 100% and stored for 6 months at moderate temperature typically retains around 86% state of charge, while lead acid under the same conditions can drop to roughly 74%. A flow battery barely loses any charge at all over the same period, often retaining 99% or more.
A flow battery stores its energy in electrolyte tanks separate from the reaction stack, so the charged electrolyte doesn't undergo the same slow self-discharge reactions that happen inside a solid-state lithium or lead acid cell. This makes flow batteries unusually well suited to long-term seasonal storage.
Yes. Warmer storage temperatures accelerate self-discharge across all chemistries, while cooler storage slows it down. This calculator applies a rough multiplier for warm, moderate, and cool storage conditions to reflect that relationship.