Voltage vs Amp Hour (V vs Ah) Cordless Garden Tools

In my quest for a new mower, I have been looking into cordless and robotic mower options.

Specs are readily available, but understanding the differences and what these mean in real world use can be a little more complex. So after a trip to my local garden machinery dealer Mower Magic, I am now more enlightened and thought I would share in as easy to understand way as I know how.

We’re all used to seeing electric motors in watts and petrol machines in CC. These are easy to understand, there is one figure and the higher it is, the more power you get. So where does this leave you with a machine running on a battery with 40v and 2Ah?

Voltage (V)

Voltage is fundamentally your engine size / power. This figure directly links to the cutting ability / power of whatever tool you are using. The higher the voltage, the more powerful the tool. There is no direct comparison between cordless power and petrol machines available. However the general perception is that 48v / 56v machines are equivalent to around a 25-35cc petrol engine. Below that, 18v and 24v tools are lightweight with suitable power for the job they’re designed for. Head UP towards 80v and you are getting similar power to a top end 2-stroke engine, or even a typical 4-stroke lawnmower engine.

Amp Hour (Ah)

So if voltage is power, what relevance is Ah? In basic terms, it was explained to me as the size of the ‘fuel tank’. The more Ah’s, the longer the battery lasts. This has no effect on power, but will effect the length of time you can use the tool for. A battery with higher Ah will not only last longer, but also take longer to charge. Large capacity batteries will also weigh a little more. The other consideration is that as larger capacity batteries cost a more, you might prefer to get 2 cheaper lower Ah batteries, rather than one high capacity one so you can have one charging while the other is being used. This way you can get almost continuous use from your tools. Which solution is better really depends on how you use your tools.

Finding The Balance

While in principle more power is going to be better, in reality there are some draw backs. Higher voltages will typically use up an amp of electricity from the battery faster than a lower voltage machine. On the flip side, an under specced tool for the job may struggle and draw a lot of power, while a higher voltage machine will take less strain so it won’t use the power as quickly. There are also different qualities of machine and battery that will effect use and run time.

What spec for me?

I have done a separate post about what power tools might be needed to different jobs around the garden. I have also posted in some examples of recommended cordless machines.

You can read that blog here.