Without getting too technical, the best measure of a lithium-ion battery pack’s performance is its energy capacity, which is measured in watt-hours. To find the watt-hours of a battery pack, multiple the voltage by the amp-hours. For example, the Snow Joe iON18SB 40 V 4.0 Ah 18-inch cordless snow blower runs on a lithium-ion battery that delivers a 160 watt-hour energy capacity (40 V x 4.0 Ah). In comparison, competitor models of cordless tools that also employ a 40 V lithium-ion battery may only be telling you half the story. They cleverly disguise a seemingly “more powerful” battery pack by tacking on a large voltage rating without disclosing the amp-hour rating information, which has been found in some cases to be, at best, only 2.6 amp-hours. A battery with the same voltage rating, but a lower amp-hour rating will have a lower energy capacity, which will significantly impact your cordless tool’s performance. Comparing the Snow Joe Sun Joe EcoSharp 40 V 4.0 Ah lithium-ion battery pack to the 40 V 2.6 Ah competitor lithium-ion battery pack, the EcoSharp battery provides about a 1.6 fold increase in energy capacity (160 watt-hours versus 104 watt-hours). So, when comparing battery packs, it’s not only voltage that matters in terms of cordless tool performance. Know your battery’s amp-hour and watt-hour rating to get a true assessment of what your battery can really do.