Can You Use A 6ah Power Tool Battery Instead Of 4ah?

One of the primary factors differentiating rechargeable battery packs sold by a particular power brand is the voltage. Ryobi, for example, has both 18V and 40V battery packs for regular handheld power tools and larger, heavier-duty implements, respectively. In addition to the voltage, though, a secondary factor to be aware of is the ampere hour, or "Ah" for short. If you check power tool batteries on any online storefront, you'll usually see the battery's Ah rating in the product name alongside the voltage.

Considering voltages usually denote completely different, incompatible battery frameworks, it's fair to assume that the same would go for Ah ratings. You might not think that a 6Ah battery would work in the same tool you've been using a 4Ah battery in, for instance. However, Ah ratings are actually different from voltages in that regard. In fact, it's perfectly possible to use a higher or lower-Ah battery interchangeably with another without affecting the actual efficacy and power output of your tool. The only thing that will change is how long the battery can last before you need to recharge it.

A battery's ampere hour rating is a simple way of showing how many amperes of electrical current the battery can generate in a single hour, not unlike the miles per hour rating on your car, or indeed, the Ah on your car's own battery. If a battery has a 4Ah rating, that means it can generate 4 amperes of current in an hour of regular usage. It has nothing to do with the actual strength of the electricity being generated, as that's the voltage's department.

With that in mind, if you wanted to switch from a 4Ah battery on your power tool to a 6Ah battery, it would only benefit you. Since a 6Ah battery has a higher ampere hour, that means it will last longer while under load, lengthening the time you can use it before it needs a recharge.

The only quantifier here is that the 4Ah and 6Ah batteries in question must both be from the same battery system, and have the same voltage. You wouldn't be able to use a 6Ah 18V battery in lieu of a 4Ah 40V battery because the former wouldn't fit into the tool receiver that the latter was using. As long as it safely fits, and you don't mind a little extra weight from the larger pack, a 6Ah battery will work just fine.