The world is battery powered!
Batteries are everywhere in our lives. Every piece of electronics from cell phones to remote control toys to leaf blowers depend on them to make our lives more convenient every day. When it comes to users who depend on these technologies, they care about 2 things:
How long is it going to last?
How strong is it?
Many people have studied the first question and the battery manufacturers proudly post their longevity claims on the front of their packaging. However the second question is a bit more elusive. There's lots of clever marketing used to reassure the buyer that the battery has the power to do the job. Words like "heavy duty", "plus", "power", "max" and other buzz words tell you that the battery is up to the challenge of whatever you stick it in and the commercials speak to our emotions by showing firefighters using batteries of a specific brand in their lifesaving flashlights but under all the shiny paint, which battery is the most powerful? The manufacturer's certainly not going to tell you if they fall a little shy of their competitor.
Normally this question isn't really an issue however. Every piece of electronics out there will tell you very explicitly what sort of battery to use. If the battery isn't proprietary, then the type of generic battery needed will be mentioned somewhere, if not on the battery cover itself then somewhere in the documentation. For this reason, most people never have a problem. Still, every AA, every 9V and every D cell falls on a spectrum of quality, usually tied to price in some way, so even if the battery you buy is sure to work, is it going to work well or is it going to be worked so hard that it dies in half the time?
Why is battery current important?
Suppose you aren't just buying a replacement battery for your favourite gadget. Suppose you need one for your Arduino project, your university thesis or the LED Christmas sweater you made yourself with a blinking Rudolf nose. Whatever it is you're doing that that battery maker didn't expect you to do, you want to know if the battery is going to handle the load you have in store for it. That's why current is important.
Unlike voltage ratings or mAh ratings, current (how many amps will flow from the battery) tells you the battery's strength. The more current the battery can supply, the beefier the load can be. Lithium batteries, which are all the rage these days, may claim to keep your phone running for a week on a single charge but can the same battery run a motor in a toy car for more than 10 seconds? This is the sort of information you just can't find on the internet. Try as you might, there just aren't any resources out there telling you how much current this or that battery can supply to your project. That is... until now.
Let's have a look at our contestants!
For this test, I'll be looking at 9V batteries only. I chose the 9V form factor because it's compact, has a relatively high voltage and therefore is convenient to use in portable projects where small size and high power are desirable. This makes 9V batteries flexible to use for a variety of different tasks. In this test we'll be looking at:
1) Panasonic Super Heavy Duty Power (Carbon Zinc non-rechargeable), $1
2) Panasonic Alkaline Plus Power (Alkaline non-rechargeable), $2
3) Energizer Ultimate Lithium (Lithium non-rechargeable), $9
4) Energizer Recharge (Nickel Metal Hydride rechargeable), $11.50
5) Duracell (Alkaline non-rechargeable), $5.50
6) Energizer Max (Alkaline non-rechargeable), $4.25
The test setup
In order to measure the maximum current each 9v battery can supply, we need to short-circuit them. This is dangerous so don't do it. That's why I've done it for you. Once short circuited, the voltage will drop and the current will rise. We need to measure both values to get a sense of how strong the battery is, although current alone will speak volumes regarding what the battery can do.
In order to measure voltage you could simply use a multimeter and probe the 2 terminals of the battery but I'm going to do 1 better and use an oscilloscope to track the voltage as a function of time. I'm also going to be measuring current vs time but since you can't measure current directly with a scope, I'm going to pass the current through a hall effect sensor, which will detect the magnetic field generated in the wire and report back a voltage that can be translated into current later on. So my scope will have 2 lines on it representing voltage and current respectively. The voltage probe will be connected to the battery terminals, while the current probe will be connected to the output pin of the hall effect sensor. The battery itself will simply be short circuited so it will have no load, other than its own internal resistance. This may not be how you plan to load your battery but knowing how much current it CAN supply will give set the bar for you so you know which battery is right for you.
So! Let's get to it!
The video contains details too numerous for the scope of this article but I recommend having a look, as all information regarding the batteries tested, the setup, the time-lapse footage of the tests themselves, the post-test discussion, the raw data pulled from the graphs and the final ranking and conclusions are there. Below is a summary of the key metrics for each battery:
Peak Current: 2A
Sustained Current: 1.28A
Duration: 200 seconds
Peak Current: 2A
Sustained Current: 1.28A
Duration: 200 seconds
Peak Current: 1.9A
Sustained Current: 1.2A
Duration: 160 seconds
Peak Current: 3.6A
Sustained Current: 3A
Duration: 30 seconds
Peak Current: 0.5A
Sustained Current: 0.4A
Duration: >4 minutes
Peak Current: 4A
Sustained Current: 0.11A
Duration: Until end of experiment
As you can see from the results, the Lithium and Ni-MH produced the highest peak currents but due to their short duration, they would only be useful to you if you only needed a few seconds of performance from the battery. They are also kind of expensive so if you are on a budget, these batteries may not be the best choice.
On the other hand, the Energizer Max and Duracell alkalines produced modest current numbers and are not cost-prohibitive so they would be well suited for a project where 1.28A is enough for your needs.
The real surprise was the Panasonic Alkaline since it's almost as good as the name brand alkalines but is significantly cheaper. Again, if you don't need that extra 0.08A for the extra 40 seconds, go with this one since it's more cost-effective.
The Carbon Zinc battery isn't a suitable chemistry for high drain applications but it is very cost effective and reliable so if you only need 400-500 mA, you could make do with this battery for very little cost incurred.
Where do we go from here?
If you look at the waveforms in the video you'll notice that no single battery is a clear winner across the board. Each one has something advantageous to offer the customer so picking the right one for your project will require more than a simple ranking. However, armed with this test data, you now have everything you need to make that decision conscientiously. The other articles out there discussing battery capacity will go well with this one in giving you the entire picture so whether you're after brute strength or long life, now you know the facts!
I'm not sponsered by any of these brands and I did this test for the sheer scientific curiosity. In the future I may tackle the next obvious target... AA batteries. Until then, have fun and stay safe :)