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Make a battery last: test, store, recycle

Most batteries are replaced earlier than necessary, and a meaningful share of the replacements fail early for avoidable reasons — a parasitic drain, a charger left on the wrong profile, or months of storage at half charge.

Test before you replace

Three checks, in order. First, resting voltage after an hour off charge: 12.6-12.8V is healthy for lead-acid, 12.4V is about half charged, below 12.0V is discharged. Second, a load test — a proper carbon-pile or conductance tester gives a pass/fail against the battery's CCA rating. Third, a charging-system check: 13.8-14.6V across the terminals with the engine running. If that is low, the battery is a symptom, not the fault.

For lithium, voltage is nearly useless as a state-of-charge indicator. Use the BMS app or a shunt meter.

Storage that doesn't cost you a battery

Lead-acid: store charged (12.6V+), cool, and top up every 6-8 weeks. A battery left at 50% for months sulfates and loses permanent capacity.
Lithium: store around 50-60% charge, above freezing, and disconnect the BMS load. Don't leave it at 100% in a hot garage for months.
Any chemistry: disconnect the negative terminal if the equipment has a parasitic draw — clocks and alarms will flatten a good battery in weeks.

Charging profiles, briefly

Flooded lead-acid wants 14.4-14.8V absorption with occasional equalisation. AGM wants 14.4-14.6V and no equalisation. LiFePO4 wants 14.2-14.6V, no equalisation, and no charging below 0°C. Using a flooded profile on AGM dries the electrolyte; using a lead-acid equalise cycle on lithium trips the BMS at best, damages cells at worst.

Recycling: lead-acid is the most recycled consumer product in the US — most retailers take the old one at the counter and many pay a core charge back. Lithium must go to a household hazardous waste facility or a specialist recycler; never into curbside recycling, where a punctured cell is a genuine fire risk in the truck.

Shipping reality

Batteries are regulated dangerous goods. Flooded lead-acid ships with restrictions, lithium above certain watt-hour thresholds requires UN38.3 testing and carrier approval, and many sellers simply will not ship either. That is why local purchase remains normal for car batteries, and why online battery prices vary so much between sellers.