Tiny House Tools: Power Tool Batteries

When you decide to cut the cord for the first time and go cordless on your power tools, there are a many choices that can be deceiving. Believe it or not, most of the choices are based around the cordless battery that the tool comes with. If you want to change your battery less and have enough power for the job, consult the following essential guide to power tool batteries.

When I started working for Dan, I told him that I did not own even one cordless tool. My reason being is that cordless tools never seemed to be as powerful as corded tools and the battery life never seemed to be that good. “Times have changed,” Dan told me. On our next trip to the Home Depot, I found out just how much.

Power Tool Batteries – NiCad vs. Lithium Ion

NiCad power tool batteries are older and are being phased out for good reason. NiCads are noticeably heavier and they will discharge if they are left without being used. They also have “memory,” which means that your battery will charge less and less the older it gets and will lose charge faster based on usage. In other words, if you don’t use it, you lose it. Lithium Ion power tool batteries are lighter, hold their charge while lying dormant and don’t lose power as they get older. It is crazy to think that they still make NiCads at this point.

power tools batteries - 12v battery

12V Lithium Ion Battery

Voltage and Amp Hours Values

What really determines the “power” or “life” of a battery really doesn’t have anything to do with the type of battery, it has to do with the size. This is pretty straight forward: the bigger the voltage the stronger the tool is going to be.  The bigger the amp hours, the longer it is going to run.

When it comes to voltage there are really three values that you will see often. 9.6, 12 and 18/20 volts (you will also see 40v and 60v for lawn equipment). The only difference between the 18v and 20v is marketing. If you see an 18v it is nominal voltage (voltage under load) and if you see 20v its maximum voltage (voltage not under load), but they are both the exact same. If you are getting ready to build a home and considering tools, steer clear of the 9.6v and the 12v. The 18/20 is sturdier and will get you through the project more smoothly.

power tool batteries - 3, 4, and 5 Ah batteries

3, 4, and 5 Ah batteries, all the same size

Amp Hours are a big deciding factor on what the price of the battery and typically hard to find as most brands don’t normally advertise it. You will normally find 1.3Ah, 1.5Ah, 2Ah, 3Ah, 4Ah, and 5Ah. Many cheaper power tools that come out on special sales are accompanied by a very short battery life. Some companies even go as far as to not label the Amp Hours at all and will actually make you do the math. Simply divide the Watt Hours by the Volts to figure out how many Amp Hours you technically have.

Power Tool Batteries - Amp Hour rating difficult

Amp Hour (Ah) rating can be difficult to find

How Many Batteries Do I Need?

If you are working with a decent amped battery you can probably get away with just one extra. But, if you have multiple tools that take batteries best to have one for each tool and then one extra as well.

Beware of the Deals

Make sure you keep this all in mind when you look at Black Friday / Memorial Day / Father’s Day ads. Many companies will be giving you a great tool and then a tiny battery to go along with it.

READ MORE: The Ultimate Tiny House Tool Guide


Ah is unmarked and must be calculated. This Ryobi battery is a small 1.33 Ah

How many cordless tools do you have? Do you have issues with battery life? Any suggestions? Let me know in the comments below.

6 thoughts on “Tiny House Tools: Power Tool Batteries

  1. Jim said:

    What can i do with my old 12 volt DeWalt tool set? The tools are in good shape, but the batteries are crap. Can you upgrade batteries to better ones for the older tool sets?

    • Tom Bastek said:

      Hey Jim!
      Dewalt does make converters for their batteries, but I am just not sure if they make them for the 12v tools. You may be better off replacing the tool altogether.

    • earl colby pottinger said:

      I took apart the batteries and ran an external cable to connected to my big 12 volt marine battery.

  2. Karen McCoy said:

    Thanks for this info! This makes sense!
    My dad, before he died, complained a lot about batteries and got really frustrated with them! He left behind many nice looking power tools with crappy batteries.
    Can I purchase good batteries to revive his power tools?

    • Tom Bastek said:

      Hey Karen!
      You should research the manufacturer as they might make a converter from NiCad to Lithium Ion. If not,m you can still buy new NiCad batteries, but you will face the same problems.

  3. I’ve been working with tool for a while and never thought about dividing watt hours by volts to determine the battery’s amp hours. In fact, I worked in a wood shop and never, ever heard any one mention this. Great tip!

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