EV batteries degrade two ways at once — calendar aging (time and conditions, whether you drive or not) and cycle aging (use). The habits that matter all attack one of those two, and the list is shorter than the folklore suggests.

What actually wears a pack

State of charge, held over time. High SOC means high cell voltage, and high voltage accelerates the side reactions that consume lithium. The damage isn’t “charging to 100%” — it’s living at 100%, particularly in heat. The practical rule: daily targets of 80–90%, 100% when you need it, don’t park it full for days.

Heat. Both kinds of aging accelerate with temperature — a pack at 100% in a 35°C parking lot is the single worst common scenario. Parking in shade, garage time, and not fast-charging into a heat-soaked battery all help more than most rituals.

Deep cycling. 0→100% cycles wear more than 30→70% cycles of the same total energy — depth of discharge matters at the extremes. In practice, normal use patterns make this a second-order concern; the first-order rules above dominate.

What matters less than reputation suggests

DC fast charging. The scary claim — that fast charging eats packs — survives mostly on first-generation evidence (early air-cooled Leafs lacked the thermal management to cope). Modern liquid-cooled packs, analyzed at fleet scale, show only modest extra degradation from frequent DC use. The BMS tapers power precisely to protect the cells — the taper is the protection working, not failing. Road-trip cadence is nothing to optimize away.

Level 1 vs Level 2. Both are gentle by battery standards — a 0.05 C trickle and a 0.15 C home rate are the same story to a cell. Pick whichever fits your parking, not your anxiety.

The chemistry fork: NMC vs LFP

Half the conflicting advice online resolves to one question — which cathode chemistry your car has:

• NMC / NCA (most long-range trims): the 80% daily target applies. High SOC is the aging accelerant; keep the pack mid-band for daily use.
• LFP (many standard-range trims — base Model 3/Y, some F-150 Lightning and Mach-E variants, much of the Chinese market): a flatter voltage curve and far better tolerance of full charge. Makers including Tesla recommend charging to 100% regularly — partly harmless, partly needed for the BMS to calibrate its SOC estimate on LFP’s flat curve.

Same advice, opposite conclusions — check which battery your specific trim carries before following either.

The habits worth keeping

1. Daily target 80–90% (NMC) or whatever the maker says (LFP — often 100%).
2. 100% when needed, not when parked — fill for the trip, leave soon after.
3. Store at ~50% for weeks-long parking; plugged in with a low target if the car allows scheduled limits.
4. Don’t fear the fast charger — fear the hot parking lot at 100%.
5. Let it calibrate occasionally — a full charge every few weeks keeps the gauge honest.
6. Use preconditioning — a warmed pack charges faster and gentler; navigating to the charger usually triggers it automatically.

None of this needs ritual precision. Packs are warranted for 8 years / ~100k miles in most markets, fleet data shows most lose ~1–2% a year, and the calculator’s honest numbers will tell you when a session is slow for good reasons rather than bad ones. The battery is a tool with care instructions, not an heirloom — follow the short list and spend the worry elsewhere.

Frequently asked questions

Is it bad to charge to 100% every day?

For NMC/NCA packs, sitting at 100% — especially warm — accelerates calendar aging, so daily 80–90% targets are the common recommendation. For LFP packs it's far less harmful: makers like Tesla actually suggest 100% regularly so the BMS can calibrate its estimate. Know which chemistry your trim has.

Does DC fast charging ruin the battery?

The data doesn't support the fear at normal usage. Large-scale analyses (e.g. Recurrent's fleet data) find minimal extra degradation from frequent fast charging on modern packs — thermal management does its job. Sustained extreme use (daily max-rate sessions in heat) is a different story, but road-trip DC is fine.

Is it worse to leave the car at 100% or at 0%?

100% — and it isn't close. Sitting at very low SOC risks deep-discharge damage if the car sits for weeks and keeps losing standby drain; sitting at 100% accelerates aging but can't brick the pack. For storage, ~50% is the right answer.

Do the last few percent matter for battery calibration?

Occasionally, yes — especially for LFP. Charging to 100% every few weeks lets the BMS re-anchor its state-of-charge estimate, which is why your displayed range can drift if you never do it. It's calibration, not conditioning — once in a while, not daily.

Should I worry about battery degradation when buying a used EV?

Worry *measured*, not *feared*. Most modern packs retain 85–95% after 100k miles; the horror stories concentrate in early air-cooled packs (first-gen Leaf, notably). Check the displayed full-charge range against the original spec, get a battery-health report if the maker offers one, and price accordingly.