Symptoms
- Battery shows full charge in the evening, much lower the next morning
- Battery is dead after weeks of storage without use
- Problem is worse with one particular battery than others
- Battery gets noticeably warm even while just sitting
Likely causes
- CommonBattery pack aging and losing its ability to hold chargeAged cells self-discharge faster than healthy ones, even sitting idle.
- PossibleBattery left attached to a tool with a small parasitic drawRare, but some tool electronics or a stuck switch can slowly draw power even when off.
- PossibleStoring the battery at very high or very low charge for long periodsExtreme states of charge during storage accelerate capacity loss over time.
- PossibleExtreme storage temperatures (hot garage, freezing cold)Both heat and cold accelerate self-discharge and degrade the cells.
- Less commonA failing cell within the pack causing an internal shortThis shows up as unusually fast, consistent charge loss even at rest.
What to do
- Store batteries at moderate room temperature rather than in a hot garage or freezing shed.
- Remove batteries from tools when storing for extended periods, rather than leaving them attached.
- For long-term storage, aim to store at roughly half charge rather than fully charged or fully dead.
- Compare charge loss across multiple batteries if you own more than one, to see if it's one pack or normal for all of them.
- Note if the battery feels warm while just sitting, which can indicate an internal fault.
- If one specific battery consistently loses charge much faster than others under the same conditions, plan to replace it.
Tools and parts
Replacement cordless drill batterySearch: “cordless drill replacement battery pack”
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.