Battery reuse

• Why batteries get a second life

  A car needs 80–100% capacity; home storage works fine at 50–70%: lower power per kWh, stationary mount, gentler cycling.

• Typical sources

  Batteries from totaled EVs (Nissan Leaf most available), warranty replacements, salvage modules. A Leaf module ~48 V 500+ Wh is the DIY-storage brick.

• What to check when buying

  SOH via LeafSpy/diagnostics, cycle count, no swelling or case damage, intact BMS, module balance.

• Where they're used

  Home storage 5–20 kWh, backup for boilers/servers, street lighting, large projects (stadiums, substations — Nissan/Renault second-life).

• Safety

  Lithium requires a BMS and overcharge/deep-discharge protection. DIY only with a working BMS or external controller; storage outside living spaces without protection.

• Economics

  A used module costs 30–50% of new per kWh; pays back as backup or night-tariff arbitrage. Without BMS data, the price should be scrap-level.

An EV battery 'dies' for the car at ~70% capacity but stays usable in stationary storage for another 5–10 years. Only buy a module with BMS data (SOH, cycle count) — otherwise it's a pig in a poke.