Batteries and Ah explained

Volts, Ah and Wh

The voltage (V) tells you which platform a battery belongs to, such as 12V, 18V or 36V. The capacity in amp-hours (Ah) says how much charge the battery can deliver. So a 2.0 Ah and a 5.0 Ah 18V battery from the same platform fit the same tools.

The energy in a battery is its watt-hours (Wh): volts times amp-hours. An 18 V × 5.0 Ah battery holds 90 Wh; an 18 V × 2.0 Ah battery holds 36 Wh. Wh also lets you compare batteries with different voltages.

What more Ah gets you

At the same voltage, more Ah means more energy, so longer runtime per charge. A larger battery usually contains more cells, which makes it heavier and bigger. You notice that most when working overhead or one-handed.

High-draw tools such as angle grinders, circular saws and lawn mowers benefit most from a large battery. A drill-driver doesn’t need a big pack; a compact battery keeps the tool light and easy to handle.

A battery pack is made of individual lithium-ion cells. Many packs use round cells of the 18650 size; some newer packs use larger 21700 cells or flat pouch cells. The cell type tells you about the construction, but V, Ah and Wh remain the measures to compare.

18V, 20V max, 36V and 40Vmax

A Li-ion cell has a nominal voltage of about 3.6 V. Five cells in series give 18 V nominal and about 20 V when fully charged. That’s why some brands sell the same class in the United States as ‘20V max’; in Europe it says 18V.

Ten cells in series give 36 V nominal, or ‘40Vmax’ fully charged, as with Makita XGT. If a tool on an 18V platform says ‘36V’ or ‘2×18V’, it runs on two 18V batteries at once. Always check which system a battery belongs to.

Charging and storage

Li-ion batteries have no memory effect: you can top them up whenever you like. A fast charger charges quicker, but only within the temperature range in the manual. If a battery is hot from work or ice-cold, let it reach normal temperature first; many chargers wait for this themselves.

Don’t store a battery empty: it slowly discharges further in storage, and a deeply discharged battery can be damaged. For longer storage, manufacturers commonly advise a charge of about 40 to 60 percent, in a cool, dry place. The exact values are in the manual.

Flying and recycling

Under IATA rules, spare lithium batteries may only travel in hand luggage. Up to 100 Wh is allowed; 100 to 160 Wh only with the airline’s approval. An 18 V × 5.0 Ah battery (90 Wh) stays under the limit, 18 V × 6.0 Ah (108 Wh) doesn’t. Check your airline’s rules before you fly.

An empty or broken battery doesn’t belong in household waste. Take it to your municipal recycling centre (genbrugsplads) or to a shop that takes back used batteries.

Comparing kits on ToolRango

With many brands, the letters after the model code tell you which batteries, charger and case come in the kit. ToolRango compares by version: every kit and the bare tool are listed as their own version with their own EAN. So you see straight away which batteries are included.