Buy the drill battery for the job you do on a Saturday

Quick answer: If your jobs are shelves, furniture, hinges and pilot holes, buy a 12V kit. If you're building decks, fences or anything with lag screws and big bits, buy 18V/20V. Either way, you're choosing a battery family, not just a drill.

The label is partly marketing

A "20V Max" pack and an "18V" pack are the same animal. Both are five lithium-ion cells wired together. The 20 is the peak voltage right off the charger, and the 18 is the nominal figure under working load. Brands picked different numbers for the box. Don't let it steer you.

The 12V class is three cells. Smaller, lighter, less to push with.

Voltage is roughly how hard the tool can work. Amp-hours (Ah) is how long it can keep going. Multiply them and you get watt-hours, the real size of the tank. A 12V 2.0Ah pack holds about 24 watt-hours. An 18V/20V 5.0Ah pack holds somewhere around 90 to 100. That's a bigger tank, and you carry every ounce of it.

Start with your last five jobs

Write them down. Not the jobs you imagine yourself doing once you own a workshop. The ones you did since last spring.

If it looks like this, buy 12V:

• Assembling a crib, a bookcase, a grill
• Hanging curtain rods, shelves, a mirror
• Pilot holes and driving screws up to a couple of inches
• Cabinet hardware, hinges, outlet covers
• Working in a tight space or over your head

A 12V drill is the one you'll actually pick up. It fits in a drawer, it doesn't tire your wrist, and it won't strip a screw head in half a second because you leaned on a trigger that had too much behind it. For most households, it covers about ninety percent of what gets done.

If it looks like this, buy 18V/20V:

• Building or repairing a deck or fence
• Drilling with spade bits, auger bits or hole saws
• Driving long structural screws
• Mixing paint or thinset with a paddle
• Any weekend project that runs past lunch

Here the 12V runs out of steam. It'll sometimes finish the job, slowly, hot and annoyed, and that's hard on the tool and the pack. The bigger platform is built for sustained load.

The amp-hour mistake

Most people see 5.0Ah or 8.0Ah on a box and assume more is better. It's a trade.

A big pack weighs real pounds. Put it on a drill and hold it over your head to set a ceiling fan box, and by the third hole you'll feel it in your shoulder. A compact 2.0Ah or 3.0Ah pack is far kinder for short jobs, and it charges faster.

Use the big pack where runtime is the problem. A circular saw, a reciprocating saw, a grinder, a day of deck screws. Those tools drink power. A drill pulling pilot holes barely sips.

My rule: a compact pack on the drill, a big pack on whatever eats batteries. Then own two of each size if you can, so one's always charging.

You're choosing a family

This is the decision that matters most, and it gets made on the shelf at the store.

Every major brand runs its own battery platform. DeWalt, Milwaukee, Makita and Ryobi are all common, and a battery from one won't fit another. Buy the drill and you've bought into that line. Next year you'll want an impact driver, a work light, a leaf blower, a saw. If they take the same pack, each one costs less, because you can buy it as a "bare tool" without another battery and charger.

So look past the drill. Check what else the brand makes at 12V and at 18V/20V. Make sure it offers the tools you can see yourself owning. A brand with a great drill and nothing else is a dead end.

One honest caveat. Some brands sell a 12V and an 18V line that don't share batteries at all. Owning both means two chargers and two sets of packs. For many households that's still the right answer, a small drill for the house and a big one for the yard. Just know you're running two families.

Brushless is worth it, up to a point

Brushless motors run cooler and more efficiently, which means more work from each charge and a longer life for the tool. If the price gap is small, take brushless. If it's large and you drill a dozen holes a year, don't sweat it.

Treat the packs like they cost money

They do. A replacement pack can cost as much as a bare tool, so a few habits pay for themselves.

• Don't leave them in a hot truck or a sun-baked shed. Heat is what wears lithium-ion down fastest. The same chemistry is in your phone, and the same logic applies to making your next phone last five years.
• Bring a cold pack inside before charging it. And let a hot one cool off first.
• For long storage, don't leave a pack drained flat or fully pinned. Partway charged, in a dry spot in the house, is the safe place.
• Stop at the cut-off. When the tool slows hard or quits, it's protecting itself. Don't keep hammering the trigger.

When you lend it

Somebody will ask to borrow the drill. Say yes. It's a good neighbor's habit, and you'll want the same favor someday.

But here's the code. If it comes back to you with the battery drained, that's on them. If you borrow one, return it with a charged pack, a clean chuck and a bit or two replaced if you wore them down. Leave it better than you found it. A tool you return sharper is a tool you get to borrow again.

What I'd buy

A homeowner with no big projects planned should buy a 12V drill/driver kit with two compact packs, then stop. If a deck or fence is coming, buy 18V/20V with one compact pack and one large one. Check the brand's other tools first.

And skip the 60V and higher systems for drilling. Those are built for outdoor power equipment and heavy saws, and a drill has no use for them.

Hold the drill in the store if they'll let you. If it feels like something you'd reach for on a Saturday morning, it's the right one.