Signs Your Device Battery Needs Replacement — Phones, Laptops, Tools, Vacuums

A battery is a consumable component. It's not a defect or manufacturing fault: lithium-ion cells have a limited lifespan, and after 500–1,000 charge-discharge cycles, their capacity noticeably declines. The trouble is that degradation happens gradually, and many people carry on using their device without realising the battery is already operating at its limits — or has even become dangerous.

At the SATER service centre on Silmaču iela 6, we've been replacing batteries for over 30 years. We handle battery replacements in power tools, robot vacuums, cordless vacuums, laptops, and other portable equipment. In this article — a comprehensive list of signs that your battery needs replacing, broken down by device type.

Universal Signs of Battery Degradation

These symptoms are the same across all devices with lithium-ion batteries — from a smartphone to a cordless drill. If you notice at least two, the battery most likely needs replacing.

1. Runtime Has Halved or Worse

The most obvious sign. A laptop that used to last 6 hours now manages 2. A robot vacuum that cleaned the entire flat now stops in the middle of a room. A cordless drill that drove 200 screws on a single charge now barely manages 50.

Lithium-ion batteries are considered worn when their actual capacity drops to 70–80% of the nominal figure. In practice, many people continue using them at 50%, simply charging more often. That's inconvenient but not yet dangerous — provided there are no other symptoms.

2. Slow Charging or Inability to Reach 100%

A worn battery may charge significantly slower than when new — or never reach a full charge at all. You leave your phone on the charger overnight and find it at 87% in the morning. A laptop sits at 94% for hours and goes no further.

This happens because internal resistance has increased. The cells can no longer accept as much energy as before, and the charge controller stops the process early to prevent overheating.

3. Swelling

This is the most dangerous sign. Stop using the device immediately if you notice swelling.

A swollen battery is a lithium-ion cell where gas formation has begun inside due to electrolyte decomposition. The gases cannot escape (the cell is sealed), and pressure inflates the casing.

How it manifests:

• Phone or tablet: the screen lifts from the frame, the case doesn't close flush, the device "rocks" on a flat surface.
• Laptop: the trackpad bulges upward, the case around the battery swells.
• Power tool: the battery pack won't clip onto the tool, the battery housing is distorted.
• Robot vacuum: the battery compartment cover lifts, the robot sits unevenly.

4. Overheating During Charging or Use

Moderate warmth is normal for any battery. But if the device becomes hot to the touch (above 45–50°C — uncomfortable to hold), that's a sign of trouble. Worn cells have higher internal resistance, causing more energy to convert into heat instead of useful work.

Overheating accelerates further degradation — a vicious circle forms: weaker cell → more heat → even weaker cell.

5. Sudden Shutdowns

The device shows 30% charge — then suddenly switches off. After powering back on, it might show 5%, or perhaps 40%. This is a classic sign of a degraded battery: the controller can no longer accurately gauge the real charge level because voltage across the cells is unstable and drops under load.

6. Percentage Jumps

The indicator jumps: 65% one moment, 43% the next, then back to 58%. Or during charging: 80%, 82%, 78%, 85%. This is cell imbalance within the battery pack — different cells have worn at different rates, and the controller cannot compute a reliable average.

Signs by Device Type

Power Tools (Makita, Bosch, DeWalt, Milwaukee)

• Battery "runs out" within the first minutes of use
• Indicator on the battery flashes red immediately after removal from the charger
• Tool loses power gradually, then cuts out abruptly
• Charger flashes an error (rapid blinking) — typically means the charger has detected a cell with abnormal voltage
• Battery gets noticeably hotter than usual during work or charging

Power tool batteries contain 5–10 cells (18650 or 21700). A single "dead" cell is enough for the entire pack to stop working. That's why we offer rebuilds: replacing only the worn cells with new ones, which costs less than buying a brand-new battery pack.

Robot Vacuums (Roborock, Xiaomi, Dreame, Ecovacs, iRobot)

• Robot doesn't make it back to the dock, stopping mid-clean
• Cleaning time has dropped by half or more (was 120 minutes → now 40)
• Robot leaves the dock and returns after 5 minutes
• "Low battery" error or corresponding error code
• Robot won't charge: sits on the dock but indicator doesn't light up

We replace cells with quality Sony, Samsung, or Molicel using spot welding.

Cordless Vacuums (Dyson, Samsung Jet, Philips, Bosch)

• Vacuum runs for 3–5 minutes instead of 30–60
• On maximum power, shuts off almost immediately
• Indicator flashes red immediately after disconnecting from the charger

Laptops

• Only works when plugged in; shuts off instantly when unplugged
• System displays "Replace battery" (Windows) or "Service Battery" (macOS)
• Battery life has dropped to 30–60 minutes
• Case around the battery is deformed (swelling)

You can check your laptop battery's health in software. On Windows: open Command Prompt and run powercfg /batteryreport. On macOS: hold Option and click the battery icon.

When Degradation Is Normal vs Dangerous

Normal Degradation

A lithium-ion battery loses 10–20% of capacity over the first 300–500 cycles — that's normal. With proper use, it retains 80% capacity after 500–800 cycles.

Dangerous Degradation — Act Immediately

• Swelling. Stop using, don't charge, don't puncture. Take it to a service centre.
• Severe overheating (burns your fingers, above 60°C). Stop using immediately.
• Smell. A sweet chemical odour from the device signals electrolyte leakage.
• Device case deformation. If the cover won't close or the screen has lifted — the battery has swollen.
• Device is smoking. Don't attempt to extinguish with water. Place on a non-combustible surface (concrete, tiles), step back.

Emergency Protocol for a Swollen Battery

1. Stop using and charging immediately. Unplug from mains if charging.
2. Don't attempt to remove the battery yourself if it's tightly seated and requires force to extract.
3. Place the device on a non-combustible surface — concrete floor, ceramic tiles, metal tray.
4. Ensure ventilation. Open a window. Gases from a swollen battery are toxic.
5. Take the device to a service centre. We'll safely remove the battery, dispose of it, and fit a new one.
6. Don't put a swollen battery in household waste. Hand it in at proper recycling points (in Riga: Zaļais punkts or electronics retailers).

How to Extend Battery Life

• Don't discharge to zero. Charge when 20–30% remains.
• Don't keep on the charger permanently. For storage, 40–60% is optimal.
• Avoid overheating. Don't leave devices in direct sunlight or a hot car.
• Use the original charger.
• Don't leave unused for months. The battery can enter deep discharge and "die."

Battery Replacement at SATER

The SATER service centre performs battery replacement and rebuilds for power tools, robot vacuums, cordless vacuums, and other portable equipment.

We use only quality cells from proven manufacturers: Sony/Murata, Samsung, LG, Molicel, Panasonic. Spot welding, new BMS where needed.

We've been in Riga since 1993 — over 30 years at the same address, Silmaču iela 6. 186 Google reviews, 4.3★ rating.