How to Fix a Power Tool Battery Not Charging
Your drill clicks, the charger blinks, and the battery sits there doing nothing. If your power tool battery is not charging, do not bin it just yet. Most 18V lithium packs in the UK fail for boring, fixable reasons - dirty contacts, a sleeping BMS, or a tired charger - and a ten-minute check can save you ยฃ40 to ยฃ70 on a replacement.
This guide walks through the exact order to diagnose a dead pack safely, what you can clean or reset at home, and when the battery is genuinely done. It covers Makita, Bosch, Ryobi, DeWalt and Einhell 18V systems because the chemistry and chargers are almost identical, even if the plastic is not..
1. Work safe first
Lithium packs store a lot of energy. Do not open the case, puncture, or short the terminals with a screwdriver or foil. If the pack is swollen, hot, smells sweet or chemical, or has cracked housing, stop. Place it on a non-flammable surface outside the workshop and contact your local council's WEEE collection point. For every other case where the pack just will not charge, the steps below are low-risk and tool-free.
Keep spare batteries away from direct sun and radiators while you troubleshoot. A hot pack straight off a job will refuse to charge by design. Let it cool to room temperature - most UK chargers block charging above about 45 degrees.
2. Check the boring stuff: mains, lead, and indicator lights
Start at the wall. UK chargers die quietly more often than batteries do. You will know quickly with a simple swap test.
- Test the socket. Plug a lamp or phone charger into the same socket. UK fused plugs and extension leads with tripped breakers are a classic gotcha. If you are using an extension, plug the charger directly into the wall.
- Look at the lights before you insert the pack. Many Bosch UniversalImpact 18V-60 kits and similar chargers show steady green when mains is present. No light means mains or charger, not battery.
- Insert the pack decisively. Slide it until it clicks. A half-seated Makita or Ryobi pack can sit on the rails without making contact, and the charger will blink as if faulty.
- Read the blink pattern and give it time. A slow red flash often means "charging," a fast red flash or alternating red/green means "fault or too hot/cold." Leave it for 15 minutes. Some packs that have sat flat for months need a pre-charge wake-up before the indicator changes.
If you have two batteries, try the good one in the same charger. If the good one charges, your charger is fine. If neither charges, suspect the charger or the wall circuit. This one swap saves hours and is covered further in our cordless drill battery care guide.
3. Clean the contacts - the fix that works most often
Dust, plaster, and cutting oil build up on the spring terminals inside the pack and the charger. The pack reports a voltage error and the charger refuses to start. You do not need contact spray to fix this.
- Unplug the charger from the wall.
- Remove the pack and look at the flat metal terminals. Brush off loose dust with a dry, soft toothbrush or cotton bud.
- If the terminals look dull or slightly green, gently rub with a dry cotton bud. Do not use wet cleaners, wire wool, or WD-40. A pencil eraser dabbed dry can lift light oxidation - brush away any rubber crumbs after.
- Blow out the charger bay with a quick puff of air. Do not use a workshop air line at close range - the pressure can bend the contacts.
- Re-seat the pack firmly and try again.
4. Waking a deeply discharged pack
Leaving a lithium pack flat for months is the fastest way to trigger its Battery Management System (BMS). The BMS disconnects the cells when voltage drops too low to protect them. The charger then sees 0V and assumes no pack is present, so it never starts.
How to wake it safely without opening the case:
- Extended first charge. Leave the pack on the charger for 30 to 45 minutes even if the light says fault. Some chargers pulse a tiny current and the BMS reconnects after a few minutes.
- Warm then cool cycle. If the pack is very cold from a garden shed in winter, bring it indoors for an hour. If it is warm from use, let it cool fully. Retry.
- Second-charger test. A different charger from the same system sometimes negotiates the handshake better. Borrow one if you can before buying.
If the pack wakes, it may show only one bar initially. Run it lightly in a drill on low speed, then charge fully. Avoid running it completely flat - lithium packs prefer shallow cycles. Our guide to 12V, 18V and 20V cordless batteries explains why shallow cycling triples usable life compared with full-to-empty use.
5. When the charger is the culprit
UK 18V chargers fail in three predictable ways: the DC jack fractures where the lead enters, the fan clogs with workshop dust and overheats, or the internal fuse blows after a surge. Signs of a charger fault are consistent - no packs charge, the indicator stays dark, or it clicks off after a few seconds with any pack.
Checks you can do without tools:
- Feel the charger after ten minutes - warm is normal, hot or rattling is not. Unplug and let it cool.
- Inspect the lead for kinks near the strain relief. UK regulations require fused plugs, so try the charger in a different room on a different circuit.
- Listen for the fan on intelligent chargers. If it never spins and the unit gets hot, the fan is jammed with dust. A soft brush around the vents can free it.
If you need a replacement, buying the same system keeps your batteries useful. A kit that includes two packs and a charger can be cheaper than a single battery. For example, a Makita 18V Cordless Combi Drill with 2 Batteries and Charger often works out as a cost-effective way to refresh charger plus packs in one go if your old charger has gone, while keeping your existing Makita tools running. If you are on Bosch 18V, the Bosch UniversalImpact 18V-60 pack with 2 x 2.0Ah batteries is the same idea - new charger and matched packs that keep your Bosch tools on one system. The same applies to Bosch and Ryobi ecosystems - stay in-system if you have three or more tools on that battery.
6. When the pack is actually tired
Batteries age even on the shelf. A typical UK 18V 2.0Ah to 5.0Ah lithium pack is rated for 300 to 500 full cycles. Timed correctly, that is three to five years for a weekend maker. Gradual runtime loss is normal; sudden zero-charge is not. Replace the pack when you see any of these together:
- It charges to "full" in minutes but dies in minutes under light drilling.
- It gets noticeably warm during a normal charge, or the charger always stops early with a fault light.
- The casing is swollen or does not sit flush in the tool any more.
- You have tried a known-good charger and a known-good battery and isolated the fault to that one pack.
Do not mix a new high-capacity pack with an old tired charger that limps along. A modern charger with proper cut-off protects the new pack's BMS. If you are expanding the system anyway, the Ryobi R18PD3-215GZ ONE+ Combi Drill Starter Kit is a common entry point for makers who want to share the ONE+ battery across drills, sanders and lights - one charger, many tools, fewer packs to maintain. For budget workshop top-ups, the Einhell 18V Cordless Drill Driver kit gives you a spare charger and battery to rotate without breaking the bank.
Recycle the old pack properly. Every UK DIY chain and council tip accepts lithium packs. Tape the terminals with electrical tape, bag it, and drop it at the WEEE bin. Do not put lithium packs in household waste or general recycling.
7. Prevent it next time with a simple routine
The cheapest fix is a habit that stops packs going flat. This is the short version of our full power tool maintenance checklist, focused purely on batteries:
- Store at half charge. If you know you will not use the drill for a month, charge to about two bars, not full. Full storage ages cells faster.
- Top up every 6 to 8 weeks. Even in storage, lithium slowly self-discharges. A quick 15-minute top-up keeps the BMS awake.
- Keep contacts clean and dry. Wipe after dusty jobs and store off concrete floors.
- One charger, one place. Chargers left on damp garage floors or trailing across doorways get damaged leads. Mount it on a shelf or French cleat.
- Label and rotate. Number your packs with a marker and rotate use. Running one pack hard while the other sits flat for a year kills the idle one.
Troubleshooting table: what the lights are telling you
| Charger light | Likely meaning | Try this |
|---|---|---|
| Steady red | Charging normally | Leave for full cycle, check after 45 to 90 minutes |
| Flashing red fast | Fault, hot, cold, or dirty contacts | Clean contacts, cool/warm pack, retry |
| Red to green quickly | Pack already near full or not seating | Reseat firmly, try second pack |
| No light at all | No mains or charger fault | Test socket, try different circuit, inspect lead |
| Alternating red/green | Temperature cut-out | Let pack reach room temperature |
When to call it and replace
Check date codes when buying. A UK retailer moving fresh stock is preferable to a marketplace seller with old inventory - lithium ageing starts at the warehouse. Keep the receipt; most UK tool brands offer two to three years on batteries when registered online.
James writes about power tools, hand tools and workshop setup for MakerUK, helping makers buy the right thing the first time. He has used and broken enough drills and saws to know which specs matter.
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Last reviewed: September 6, 2026 ยท Evidence-based content ยท Contains affiliate links