Battery Health 101 · 1 / 9 · The idea
How an EV battery actually ages
Batteries don't fail.
They age.
Not suddenly, and not randomly — in six specific, measurable ways.
Aging is a process you can read
2 / 9 · The misconception
What people expect
Phone battery
- Fails suddenly
- Opaque — no warning
- Just replace it
What actually happens
Traction battery
- Fades gradually
- Follows a curve
- Measurable, manageable
Degradation is a curve, not a cliff
3 / 9 · The six mechanisms
Capacity fade
less range over time
Impedance growth
rising resistance
Lithium plating
cold, fast charging
SEI growth
protective layer thickens
Thermal stress
heat accelerates all
Cycle vs calendar
use and time
Six mechanisms, working at once
4 / 9 · Mechanism 1 — capacity fade
A steady, predictable loss — a little less usable capacity each year.
Capacity fade — the slow slide toward 80%
5 / 9 · Mechanism 2 — impedance growth
Internal resistancerising
Resistance rises quietly — power sags and heat builds well before range looks bad.
Impedance growth — power fades first
6 / 9 · Mechanism 3 — lithium plating
❄️
Cold pack
low temperature
+
→
⚠️
Metallic lithium
permanent · unsafe
The reason smart systems throttle charging when the battery is cold.
Lithium plating — cold, fast, permanent
7 / 9 · Mechanism 4 — thermal stress
As a rule of thumb, aging roughly doubles for every ~8–10°C of added heat.
Heat accelerates everything
8 / 9 · Mechanism 5 & 6 — two clocks
🔄
Cycle aging
From use
Every charge and discharge wears the pack a little. More cycles, more wear.
📅
Calendar aging
From time
Age and temperature degrade a pack even when it's parked. Time never stops.
Real-world aging is always both at once — which is why a parked battery still ages.
9 / 9 · The takeaway
Six mechanisms. One score.
CareStar™ models all six to predict a battery's future — the engine inside EVCare.
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