How do I look after a cordless vacuum battery so it lasts?

Cordless vacuum batteries are treated differently from tool batteries because they live differently. A drill pack sits off the charger in a box; a vacuum pack sits on a wall dock, on charge, in a hallway or a garage, permanently. Held at full charge and at a temperature above about 25 degrees, a lithium cell ages measurably faster than one sitting at half charge in a cupboard. That is the mechanism behind almost every cordless vacuum that will not do the house any more after three years.

Safety

What you'll need

• The machine's manual, to see whether the pack is user-replaceable (optional)
• Somewhere at normal room temperature to dock or store it

Step by step

1. Work out whether your pack is removable before anything else.Some models take a clip-out pack you can replace in a minute and can buy a spare of. Others have a sealed pack that needs a service or a partial strip-down. It changes both how you care for it and what happens when it fails, so it is worth knowing on day one.
2. Move the dock somewhere at normal room temperature.A cold garage or an unheated utility room in winter, and a sunny conservatory or a spot above a radiator in summer, both age the cells faster than use does. A hallway cupboard is better than either. This is the single change most people could make and do not.
3. Do not leave it sitting at 100 percent for weeks on end.If the machine is used most days, docking is fine — it cycles. If it goes weeks between uses, take it off the dock and leave the pack at roughly half charge, then top it up before use. Some newer models have a storage or battery-care mode that does this for you.
4. Stop running it to a dead stop as routine.Finishing a room and putting it back on charge is fine. Repeatedly running until the machine cuts out stresses the cells at their lowest state of charge, which is where lithium chemistry is least happy.
5. Use boost or max only where the floor needs it.Boost typically doubles or triples the current draw and can cut a 40-minute quoted run time to 6 or 8 minutes. Use standard for hard floors and open carpet, and boost for a rug, a stair or a spill. This alone transforms how far one charge goes.
6. Keep the filters and brush bar clear, because they cost battery too.A restricted machine works the motor harder for less pickup, and the battery pays for it. A clogged filter reduces the effective run time as well as the suction, so filter maintenance is battery maintenance.
7. Let it cool before charging after a long hard run.A pack that is warm to the touch is best left twenty minutes. Good chargers refuse until it cools, which is protection rather than a fault. Charging a hot lithium pack is the fastest way to age it.
8. Judge whether it is the battery by the shape of the failure.Gradually shorter run time over years is normal ageing. A sudden drop to a few minutes, a machine that cuts out under load while still showing charge, or one that will not charge past a certain point, all point at a failing pack rather than a failing motor.
9. Replace the pack rather than the machine where you can.For a machine that is otherwise fine, a genuine replacement pack is usually a fraction of a new vacuum. Buy the manufacturer's pack or a reputable equivalent with proper cell protection — this is the wrong place to save money.
10. Recycle the old pack properly.Battery recycling point, retailer take-back or a household waste recycling centre. Never the household bin. Tape the terminals before transporting it.

Tips

• If you can buy a second pack, do. Two packs each doing half the cycles both last longer than one pack doing all of them, and you can do the whole house in one go.
• Charge to full before a big clean rather than keeping it topped up at 100 percent all week. The pack spends less time at the state of charge that ages it.
• A pack that is hot rather than warm after a normal run is a warning, not a quirk. Stop using it and have it looked at.
• Note the date you fitted a replacement pack somewhere. It makes the next repair-or-replace decision an evidenced one.

Common mistakes

• Docking the machine permanently in a cold garage — Cold reduces available power immediately and cold charging damages cells. Combined with sitting at full charge, it is the worst storage condition a lithium pack can have.
• Buying an unbranded replacement pack to save money — Cell quality and protection circuitry are where the saving comes from, and both are what stop a lithium pack failing dangerously. This is a documented fire risk, not a theoretical one.
• Vacuuming the whole house in boost — It triples the draw for a marginal gain on most floors, and it is the single reason people believe their machine's run time was overstated.

If it doesn't work

Questions people ask