Path-Q Solar
How can battery degradation change the amount of backup available after several years?
Answer
As usable capacity declines, the battery can provide less energy and shorter runtime, although its maximum power capability may decline differently. The practical effect depends on the loads, reserve settings, degradation rate, temperature, cycling, and whether the system can add or replace storage.
Key points
- Recalculate runtime using projected usable capacity for each future year.
- Check both energy capacity and continuous or surge power requirements.
- High-demand loads may remain power-limited even when sufficient energy remains.
- Designing around essential loads and maintaining a reserve can preserve useful backup longer.
What it depends on
- Battery capacity-retention assumptions
- Load energy and power requirements
- Cycle history and operating temperature
- Warranty, augmentation, and replacement options
Risks and trade-offs
- A system sized only for initial runtime may not meet the same outage objective later.
- Adding storage later may involve compatibility, space, controls, or warranty constraints.
- Reserve settings can protect battery life but reduce immediately available backup.
Information you may need
- Initial usable capacity and power ratings
- Projected capacity by year
- Essential-load runtime calculation
- Warranty and expansion or replacement provisions
Your next step
What to do next
Ask the installer to show initial, mid-life, and end-of-warranty runtime for your essential loads under the same outage assumptions.
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SQ00360