A decent Milwaukee or DeWalt battery costs £50-100+. The last thing you want is to kill them through poor storage or bad charging habits. Here's how to get the most life out of your batteries.
How Lithium-Ion Batteries Work (Quick Version)
Modern power tool batteries are lithium-ion (Li-ion). They're better than the old nickel-cadmium (NiCd) batteries in almost every way, but they have different care requirements.
Key things to know:
- They don't have "memory effect" - you don't need to fully discharge them
- They hate extreme temperatures
- They degrade over time even if unused
- They prefer partial charges over full cycles
Charging Best Practices
Do
- Charge before fully dead - Ideally charge when the battery drops to 20-30%
- Let them cool first - Don't charge a hot battery straight after heavy use
- Use the right charger - Always use the manufacturer's charger
- Charge at room temperature - 10-25°C is ideal
Don't
- Run batteries until they cut out - Deep discharge is hard on lithium-ion cells
- Leave on charger forever - Quality chargers stop at 100%, but it's still not ideal
- Charge in extreme cold - Below 5°C can damage cells permanently
- Use fast chargers constantly - They generate more heat
The 20-80 Rule
For maximum lifespan during regular use, try to keep batteries between 20% and 80% charge. This might sound fussy, but it can significantly extend battery life. In practice, this means:
- Don't wait until the tool dies to charge
- Take them off the charger once they're done
- See the storage section below for long-term storage advice
Storage Tips
This is where most people go wrong. How you store batteries matters more than how you charge them.
Temperature
| Storage Temp | Effect |
|---|---|
| 0-10°C | OK short-term, not ideal |
| 10-25°C | Perfect |
| 25-35°C | Acceptable |
| 35°C+ | Accelerates degradation |
Translation: Don't leave batteries in a hot van, cold garage, or sunny windowsill.
Charge Level for Storage
If you're not using a battery for more than a couple of weeks:
- Short-term (2-4 weeks): Any charge level is fine
- Medium-term (1-3 months): Store fully charged, check every 6-8 weeks
- Long-term (3+ months): Store fully charged, check every 6-8 weeks
Why full charge for long-term? Here's something most guides don't mention: some modern batteries have an onboard chip that monitors the cells. That chip draws power from one of the cells even when the battery is sitting in a drawer. Over months, this can drain that single cell below safe voltage - and once one cell dies, the whole battery is toast. Not all batteries have this design, but enough do that it's safer to store them full.
I've lost multiple DeWalt batteries this way. Stored them at 40% thinking I was being clever, came back months later to find them completely dead. Now I store them full and check them regularly - much better results.
The key is checking regularly. Every 6-8 weeks, check the charge level and top up if needed. Set a reminder on your phone if you have to.
Where to Store
- Good: Indoor cupboard, tool drawer, workshop shelf (not near heat sources)
- Bad: Car boot, garden shed in summer, cold garage in winter, direct sunlight
Signs Your Battery is Dying
Batteries don't last forever. Here's how to tell when one is on its way out:
- Shorter runtime - The obvious one
- Won't hold charge - Full charge drains quickly even when not in use
- Gets hot quickly - More heat than usual during light work
- Takes forever to charge - Or won't charge at all
- Swelling - Stop using immediately if the battery looks puffy
What Kills Batteries Fastest
- Heat exposure - Leaving in hot vehicles or near heat sources
- Deep discharge cycles - Regularly running until cutout
- Overcharging - Leaving on cheap chargers indefinitely
- Cold charging - Trying to charge frozen batteries
- Physical damage - Drops and impacts
Brand-Specific Tips
Milwaukee M18
- The batteries have a fuel gauge - use it
- Genuine Milwaukee chargers have temperature management
- Don't mix old and new batteries in dual-battery tools
DeWalt
- XR batteries are more resilient than standard
- The State of Charge indicator is accurate
- Their chargers are good quality
Makita LXT
- Some chargers have "optimum charging" modes - use them
- Star-marked batteries have more advanced protection
- Avoid third-party batteries (protection circuits are often rubbish)
Parkside (Lidl)
- The batteries are decent for the price but less durable
- Don't expect them to last as long as pro brands
- Still follow the same care rules
Quick Maintenance Checklist
Monthly:
- Check battery contacts for dirt - clean with dry cloth if needed
- Inspect for damage or swelling
- Give unused batteries a partial charge
Before Storage:
- Discharge/charge to around 40-50%
- Store somewhere cool and dry
- Keep away from metal objects (short-circuit risk)
After Winter:
- Let cold batteries warm to room temp before charging
- Check charge level before first use
- Clean contacts if dusty
Common Questions
"Can I leave batteries on the charger?"
Quality chargers (Milwaukee, DeWalt, Makita) stop charging at 100% and won't overcharge. But it's still better to remove them once charged. Cheap chargers might not have this protection.
"Should I store batteries in the fridge?"
No. This myth came from old battery chemistry. Lithium-ion batteries don't benefit from cold storage, and condensation when you take them out can cause problems.
"Do third-party batteries work?"
They'll physically fit, but the protection circuits are often poor quality. You risk damaging your tool and the batteries don't last. For occasional use, they're OK. For regular use, stick to genuine.
"How long should batteries last?"
With good care, 3-5 years or 500-1000 charge cycles. Abused batteries might only manage 1-2 years.
The Bottom Line
The single biggest thing you can do for battery life: don't leave them in extreme temperatures. A battery left in a hot van all summer will age faster than years of normal use.
Second most important: don't deep discharge. Charge before the tool dies.
Do those two things and your batteries will last years.
More interested in getting the job done than maintaining tools? We bring all our own equipment - fully charged and ready to go. Call 01392 964094 or get a quote.
Sam Hembury
Sam is the founder of Hembury Contracting, providing professional handyman services across Exeter and Devon. With years of experience in property maintenance, he shares practical tips to help homeowners tackle common tasks.
