The 18650 cell has risen in prominence to become the dominant battery size available. It is used in pretty much every application involving rechargeable cells, from laptops to power banks, if its rechargeable there is a good chance it contains 18650 battery cells.
If you are at all into electronics, repair or just tinkering then you will have seen all the hype around recycling 18650 cells from old electronics and then using them in your projects. We love this movement as even old cells can still be really useful for makers and tinkerers alike. If you are recycling cells however it is important to test them to root out the bad cells. This is where 18650 battery testers come in, in this guide we jump into some of the best 18650 battery testers available online and show you how useful they are.
Best 18650 Battery Tester
This is my favourite tester. It is really easy to use and has a nice bright display. It has a quick test mode that will show the internal resistance of the cell. The internal resistance of a battery can affect a whole range of features such as the charge and discharge rates, the voltage sag under load, and the heat generated internally during charge/discharge. Ideally, anything below 100 mohm on this test would indicate a good cell.
It also has a long test mode which will charge the cell up and then discharge it. Once this is done it displays the capacity of the cell in mAh. This is crucial if you are using recycled 18650 batteries and assembling them into a pack. Knowing the capacity of your cells will enable you to assemble them into balanced packs.
You can also load your cells into this, charge them up, and then use it as a power bank as it does have USB 5V output allowing you to charge your phone or another electronic device.
Here you can see the battery tester results after it has done a full charge and discharge cycle. After doing this the tester will be able to display the capacity of the batteries in mAh as you can see in the image. This is crucial for building balanced battery packs from salvaged 18650 cells. This charger and tester is a great, cheap, way to both charge and test your salvaged cells.
4 different charge current options to choose from (300mA / 500mA / 700mA / 1000mA). 4 slots work independently, you can select and use the three modes 'CHARGE, FAST TEST and NOR TEST' simultaneously.