Tesla's Model Y owner's manual says the battery charge rate is decreased when the battery is too cold, when it is nearly full, and when its condition changes with usage and age. Tesla's support page says charging speeds slow as the battery charges, so reaching 100% typically takes significantly longer than reaching 80%. But we could not confirm at what temperature or from what percentage, or by how much, charging slows.
In recent articles we looked at preheating the battery, and at motors. In this article we check, against Tesla's official statements, what changes the speed of charging.
The conclusion: charging speed changes with battery temperature and charge level
Tesla's support page (Supercharging) says this.
"Charging speeds slow as the battery charges, so reaching 100% charge will typically take significantly longer than reaching 80%."
The same page lists factors that change Supercharger charging rates, such as the size and age of the battery pack, state of charge, ambient temperature and vehicle configuration.
When the battery is cold
The Model Y owner's manual (High Voltage Battery Information) says this.
"the Battery charge rate is decreased when the Battery is too cold, the Battery's charge is nearly full, and when the Battery conditions change with usage and age"
So charging slows when the battery is cold, nearly full, or aged. The manual calls these "changes driven by battery physics" and says they may lengthen Supercharging by a few minutes over time.
Why does it slow near full?
The manual only says "battery physics," and gives no detailed reason in this section. In general, lithium-ion batteries are explained as having higher voltage when nearly full, so charging current is reduced to avoid damaging the battery (a general explanation, not confirmed in Tesla materials).
What you can do (from official statements)
- The manual says that using Trip Planner to warm the battery while driving to a Supercharger can minimize charge time (as in the previous article).
- Tesla's support page says that with navigation, the car suggests the charge level needed to reach the next Supercharger, and to reduce congestion the charge limit may be automatically adjusted to 80%. You can raise it manually.
What we could not confirm
- At what temperature charging slows, and by how much.
- From what percentage it starts to slow, and the charging curve for each model.
- By how much an aged battery charges more slowly (the manual says only "a few minutes").
- An official explanation of why charging slows, inside the battery.
From the official statements we can read that "charging a cold battery all the way to full in winter takes the longest." But real numbers should change with the model, the battery's state and the Supercharger's output, and we could not confirm them in this article.
FAQ
Why does Tesla charging slow down partway?
Tesla's support page says charging speeds slow as the battery charges.
Why is charging slow in winter?
The owner's manual says the charge rate is decreased when the battery is too cold. It also says warming the battery beforehand can shorten the time.
How much longer does 100% take than 80%?
The support page says it "typically takes significantly longer." We could not confirm a number of minutes.
Does charging slow as the battery ages?
The owner's manual says that as the battery's condition changes with usage and age, the charge rate is decreased, and Supercharging may take a few minutes longer.
Summary
- Charging speed is lowered when the battery is cold, nearly full, or changed by use and age (Model Y owner's manual).
- Charging slows as the battery charges. Reaching 100% typically takes significantly longer than 80% (Tesla's support page).
- Warming the battery beforehand (Trip Planner) can shorten charging time.
- The temperatures, percentages and amounts of slowdown are unconfirmed.
Next: we will look, in order, at Tesla's charging standard, "NACS" (coming soon).
Sources (checked 2026-10-15)
- Tesla Model Y Owner's Manual, "High Voltage Battery Information" (no date shown): https://www.tesla.com/ownersmanual/modely/en_gb/GUID-7FE78D73-0A17-47C4-B21B-54F641FFAEF4.html
- Tesla Support, "Supercharging" (no date shown): https://www.tesla.com/support/charging/supercharging
This article is for learning about science and technology, and is not investment advice. Facts and the author's interpretation are kept separate. Figures are AI-generated illustrations.