How long do power tool batteries last?

Runtime per charge

Runtime depends on the energy in the pack and how hard the tool works. Energy is volts times amp hours: an 18 V 5 Ah pack holds 90 watt hours, an 18 V 2 Ah pack 36 watt hours. A drill driving screws uses little power, so a small pack lasts a long time. A circular saw, SDS drill or grinder uses much more.

Compare packs with the battery energy calculator and read volts and amp hours explained.

Lifespan in years and cycles

Lithium-ion cells slowly lose capacity with each charge cycle and with age. Makers do not all publish cycle figures, but tool packs used normally commonly last several years before runtime drops noticeably. A pack used daily on a building site wears faster than one used at weekends.

Capacity fades gradually rather than failing suddenly. When a pack holds noticeably less charge or the charger reports a fault, it is time to replace it.

What wears batteries out

Heat is the main enemy. Charging a hot pack straight after heavy use, leaving packs in a hot van or in direct sun, and running high draw tools continuously all speed up wear. Deep discharge, leaving a pack flat for months, can also damage cells, and the charger may refuse to charge it.

Storing packs fully charged in warm places adds wear too. Cold storage is less harmful, but packs should be warmed before charging; see storing tool batteries in winter.

• Let hot packs cool before charging.
• Do not store packs flat for long periods.
• Avoid hot vans and direct sun.
• Use the maker's charger.

Which batteries last longest?

Quality cells and good battery management matter more than brand names. Packs from established makers have protection circuits that balance cells, prevent over discharge and manage temperature. Larger packs often last more years in practice because each job uses a smaller share of their capacity, so the cells work less hard.

Cheap copy packs may use lower grade cells and weak protection. See how to spot fake Makita and DeWalt tools.

See kits with batteries →

Can you repair or rebuild a battery?

Some services and online guides offer to rebuild packs with new cells. It is risky. Lithium-ion cells store a lot of energy, and poor soldering, mismatched cells or bypassed protection can cause fires. A rebuilt pack may also void the tool warranty. Replacing a worn pack with a genuine one is the safer option.

If a pack is damaged, swollen, has been dropped hard or got wet inside, stop using it and recycle it at a household waste centre that accepts batteries.

Note:Never open, puncture or heat a lithium-ion battery. Charge on a hard surface away from flammable materials, and do not charge unattended overnight.

Checking a battery's health

Many packs have a charge gauge, and some app connected packs show more detail. If the gauge drops fast under light use or the pack gets hot quickly, its capacity has faded. Charger fault lights can also signal a worn or damaged pack; see power tool charger lights flashing.

If a tool stops early but the pack seems fine, the tool itself may be the issue; see cordless drill not working.

Frequently asked questions

How long does a cordless drill battery last on one charge? It depends on pack size and the job. Screwdriving uses little energy; big holes and saws use much more.

How many years do tool batteries last? Commonly several years of normal use, less with heavy daily use or poor storage.

Should I store tool batteries fully charged? For long storage, a partial charge in a cool, dry place is better than full charge in a hot place.

Can I leave batteries on the charger? Follow the maker's advice. Many chargers stop when full, but removing packs when charged is sensible.