If you’ve ever looked under a ThinkPad T480 and wondered why it has a removable battery and an internal one, you’re not alone.
Lenovo designed the T480 with a dual-battery system so you can extend runtime and (in many cases) swap the external pack without shutting down.
- Internal battery = built-in pack inside the laptop (typically 24Wh). It’s the “backup/bridge” battery and is not meant for quick swaps.
- External battery = removable pack at the rear/bottom (available in different capacities). It’s the battery you can replace or upgrade in seconds.
1) What is the internal battery on a T480?
The internal battery sits inside the chassis, under the bottom cover. On most T480 configurations it’s a smaller pack
designed to keep the laptop running briefly when you remove the external battery, and to provide a bit of extra runtime.
Because it’s internal, replacing it is a “service-style” job: you remove the bottom cover, disconnect the battery, and install the new one.
It’s still very doable, but it’s not something you swap during a workday like the external pack.
When the internal battery is the problem
- The laptop shuts off instantly when you remove the external battery (even if it “should” stay on).
- Battery wear is high on “Battery 1” in Windows battery reports (depending on how your system labels packs).
- Runtime is short even with a known-good external battery.
Safety tip: If you plan to open the bottom cover, shut down the laptop and follow Lenovo’s service guidance (including disabling the built-in battery in BIOS where applicable).
2) What is the external battery on a T480?
The external battery is the removable pack that slides and locks into the rear underside of the laptop.
This is the one most people replace first because it’s quick, tool-free, and it’s also the battery you can “upgrade” by choosing a higher capacity.
Lenovo offered the T480 with multiple external battery capacities, so two T480 owners can have very different real-world runtime
even if the laptops look almost identical from the top.
When the external battery is the problem
- Battery percentage drops quickly (especially under load) or jumps around.
- The laptop works fine on AC power but dies unusually fast on battery.
- You see obvious swelling, fitment issues, or the pack won’t latch properly (stop using it immediately).
Tip: If you want more runtime, upgrading the external battery capacity usually gives the biggest improvement per dollar.
3) How the dual-battery “bridge” helps (hot-swap concept)
The whole point of the T480’s dual-battery design is flexibility:
the laptop can run from the internal pack for a short time while you remove and replace the external pack.
In practice, this means you can often swap the external battery without losing your work—especially if the internal pack still has charge.
Think of the internal battery as a buffer and the external battery as your main “swappable fuel tank.”
If you travel, work in the field, or simply hate being tied to an outlet, this is one of the most useful ThinkPad features of that era.
4) Internal vs external: side-by-side comparison
| Feature | Internal Battery (Integrated) | External Battery (Removable) |
|---|---|---|
| Location | Inside the chassis (under bottom cover) | Rear/bottom of laptop (slides in/out) |
| Replacement difficulty | Moderate (requires opening the laptop) | Easy (tool-free swap) |
| Main purpose | Bridge/backup + some extra runtime | Main runtime + upgrade path (higher Wh options) |
| Capacity options | Typically fixed on the T480 platform | Multiple capacities depending on the pack |
| Best time to replace | When bridge behavior fails or wear is high | First choice when runtime is poor |
| What you’ll notice when it fails | Shutdown when external is removed; reduced total runtime | Fast drain; sudden drops; poor unplugged runtime |
5) Which battery should you replace first?
For most T480 owners, the best order is:
- Replace/upgrade the external battery first (fastest install and biggest runtime gain).
- Replace the internal battery next if you still have short runtime or the “bridge” behavior doesn’t work.
If your laptop turns off immediately when you remove the external battery (even at a decent charge level), the internal pack is a prime suspect.
6) How to identify what you have (and what’s failing)
A) Check the physical pack
- External battery: remove it and read the label (model/FRU/type/capacity are usually printed there).
- Internal battery: you’ll typically see it listed in software tools even without opening the laptop.
B) Use a battery report (Windows)
- On Windows, you can generate a battery report and compare Design Capacity vs Full Charge Capacity.
- If one battery shows dramatically lower full charge capacity than its design capacity, that’s the pack that’s worn.
C) Watch the behavior during discharge
- If the laptop behaves unpredictably when one battery hits low percentage, the weak pack may be triggering early shutdown.
- If runtime is fine on AC but collapses quickly on battery, start with the external pack.
7) FAQ
Can a T480 run with only the external battery?
Yes—many users run the T480 with an external battery installed and rely on it as the main pack. Just remember: without a healthy internal battery,
you lose the “bridge” safety net during swaps.
Can a T480 run with only the internal battery?
In most cases, yes, but runtime will be much shorter. The internal pack is not designed to be your only long-duration power source.
Does the T480 support different external battery sizes?
Yes. Different external packs exist with different capacities. The easiest way to choose correctly is to read the part number/capacity printed on your original battery label before buying.