Do Higher Ah Power Tool Batteries Take Longer To Charge?

So you finally decided to start building a collection of cordless power tools for your home improvement and DIY projects. As you start shopping around, you'll quickly notice that it's not just the tools that come in a variety, but the batteries do too. Power tool batteries are available in different capacities, measured in amp hours or Ah. Most major power tool brands offer anywhere from 1.5Ah to 12Ah.

As the capacity increases, the battery's runtime and power also improves. That means you can run a tool longer and get more power when you use a bigger Ah like a 6Ah pack instead of a smaller Ah like a 2Ah battery. But other than the runtime and power, the capacity of the battery affects one other thing: its charging time. A higher Ah on a power tool battery means it will take longer to charge compared to a lower Ah pack.

This is largely because the bigger-capacity batteries have just that — big capacities. They can store more energy and release more energy. So when it's time to replenish the depleted charge, it isn't as quick. It's just like how filling a jug takes more time than filling a cup. There are, however, some tips and tricks you can apply to speed up the charging time for higher Ah power tool batteries.

A power tool battery's charging time is primarily dependent on two factors: its amp-hour (Ah) rating and the charger's output current. Since you can't change the Ah rating, the only other way to top up your higher Ah power tool batteries faster is by going with a charger with higher current.

Fortunately, some major power tool brands make fast chargers for their power tool batteries. For instance, Milwaukee has the Super Charger and Rapid Charger, on top of its standard charger. Its Super Charger features a max output of 18A, while its Rapid Charger delivers a maximum of 6A. Between the Milwaukee Super Charger and Rapid Charger, the former can charge the 12Ah pack nearly three times as fast. It only takes 45 minutes for the 12Ah battery to reach 100% on the Super Charger, but you'll have to wait 130 minutes on the Rapid Charger.

If, however, your power tool brand doesn't offer fast chargers, you can still help speed up the charging process by making sure the area you're charging in is around room temperature. This is the best condition for charging Li-ion batteries. Charging a Li-ion battery in extreme cold (below 41°F or 5°C) will only extend the charging time. And if you try charging in extreme heat (above 122°F or 50°C), your charger might not even work at all.

If you don't have a fast charger and are already charging the power tool battery at room temperature, there's generally nothing more you can do. The charging time of power tool batteries with a higher Ah is fixed for the most part. Just wait for the pack to top off and use a spare in the meantime.