Battery dies quickly — diagnostics and rebuild
If your device's battery used to last an hour or more but now drains in just a few minutes or even seconds, the most common causes are natural cell degradation after hundreds of charge cycles, a single weak cell group dragging down the pack voltage, or a device-side fault causing abnormal current draw.
Reduced runtime is almost always caused by capacity loss in the cells after many charge cycles — not by parasitic current draw. Diagnostics measures each cell's voltage, internal resistance, and actual mAh capacity under a calibrated load to determine whether a single group has degraded or whether all cells have aged together. If one cell drops below threshold under load while the others still hold voltage, the BMS shuts the whole pack down — which is why runtime falls out of proportion to overall wear. When the issue really is capacity loss, the fix is to replace the Li-ion cells and recalibrate the BMS so the charge indicator matches actual capacity again. After replacement we run a full charge-discharge cycle test and compare the result with the factory spec. Before any cell swap we also measure the device's own current draw — if that is elevated (worn motor, seized bearing), new cells will only mask the real fault for a short while. All battery work comes with a 6-month warranty. The longer a battery runs in a heavily degraded state, the greater the risk that the remaining cells start failing too and that a damaged cell begins to overheat — so it is worth bringing the pack in as soon as you notice a clear drop in runtime. Early diagnostics often means replacing just one weak group rather than the whole pack.
Likely causes
- Natural cell degradation after 500–800 charge cycles — Lithium-ion cells have a finite cycle life — typically 500 to 800 full cycles depending on cell quality and usage conditions. Beyond this threshold, internal resistance rises, capacity drops, and the battery can no longer deliver factory-spec runtime. This is natural ageing that cannot be prevented but can be resolved by replacing the cells.
- One cell group weak — drags the pack voltage down — In a battery pack, cells are connected in groups. If one group has degraded faster than the rest (due to manufacturing variation or localised overheating), it becomes the weak link. This group discharges faster, and the BMS shuts down the entire battery as soon as the weakest group's voltage drops below the minimum — even if the other groups are still half full. The result is a dramatic reduction in runtime.
- High self-discharge — cell micro-shorts — Degraded cells can develop internal micro-short circuits that cause elevated self-discharge. The battery loses charge even when the device is not in use. The owner notices that a fully charged battery shows only 50–70% the next day. This condition can also be dangerous, as micro-shorts can progress and cause overheating.
- Device draws abnormal current — device fault, not battery — The battery is not always at fault. If the device motor is worn, its bearings are seized, or the electronic control board is faulty, the device may draw two to three times more current than intended. The battery drains quickly but is itself perfectly healthy. We always measure device current draw to rule out this cause before proceeding with battery replacement.
- Temperature damage — stored too hot or too cold — Lithium-ion cells are sensitive to extreme temperatures. Storage in a hot car in summer (above 45°C) or in an unheated garage in winter (below -20°C) can irreversibly damage the internal cell structure, reducing capacity by 20–50% in a single season. Externally the battery looks normal, but its actual capacity has dropped dramatically.
Try this first
- Time the actual runtime and compare it with the manufacturer's specification — if runtime is less than 50% of the rated figure, the battery has degraded.
- Check whether the battery indicator is accurate — sometimes the indicator is uncalibrated and shows 100% even though actual capacity is much lower.
- Try the device in a reduced power mode to compare — if runtime improves significantly, the problem may be on the device side (e.g. a worn motor drawing more current).
- Feel for unusual heat during use — excessive warmth indicates elevated internal resistance or cell degradation.
- Check the device for unusual behaviour — louder motor noise, vibration, or strange sounds may point to a device fault causing excessive current draw.
When to bring it in
If battery runtime has dropped by more than 40–50% compared to the original spec, it is time to bring the pack to SATER. It is especially important if the battery gets very hot during use or charging, if the device suddenly shuts off with 20–30% still showing on the indicator, or if the pack is visibly swollen — a swollen Li-ion pack should not be transported on public transport. We run a full cell-level diagnostic, agree on a cost estimate, and provide a 6-month warranty on all battery work.
Battery replacement warranty: 6 months.
Brands we repair
FAQ
Why customers choose SATER
- Custom-built battery assemblies. We design and assemble packs for the exact device — no 'close enough' substitutes.
- Sony, Samsung, LG, Panasonic, Molicel cells. Only top-tier cells — each one capacity-tested before assembly.
- Batteries for robots, power tools, laptops. We build packs for any device that runs on lithium batteries.
- 30+ years of experience. The service centre has been operating since 1993.
- We serve all of Latvia. Electronics service centre in Riga — we accept devices from anywhere in the country.