What the Ah number means
Amp-hours indicate how much electrical charge a battery can store. Within the same voltage family and similar cell design, a higher Ah rating generally means longer runtime. It also usually means more cells, added weight, a larger housing, and a higher price.
Capacity is not voltage
Voltage and amp-hours describe different things. Voltage relates to electrical potential; amp-hours relate to capacity. Watt-hours—volts multiplied by amp-hours—provide a broader energy comparison, but tool compatibility still depends on the manufacturer’s battery system.
Why some packs produce more output
Cell size, cell arrangement, temperature management, electronics, and internal resistance affect how well a pack supplies current under load. Two batteries with similar capacity can behave differently on a demanding saw. Look for the tool maker’s recommended pack rather than judging only by Ah.
Match the pack to the tool
A large pack can make a compact driver tiring and poorly balanced. A very small pack may run a grinder briefly or limit performance under heavy load. Many owners benefit from a mix: lighter packs for handheld fastening and larger packs for continuous cutting or high-draw equipment.
Protect battery life
Avoid storing packs fully discharged, keep contacts clean and dry, and follow the manufacturer’s temperature limits for charging and use. Stop when the tool or battery repeatedly overheats. Use the correct charger and inspect damaged packs before putting them back into service.