We charge any device that has a battery to 100%. Then we put it in the drawer and we don’t remember it anymore. The next time we need it, we see the battery drain even without it working. It’s strange isn’t it?
Battery draining even without working? That’s why!
Energy does not like to stay in one place. So it moves to achieve balance. Take the simple example of heating and cooling your home. In the winter, you need to constantly add heat as your home releases thermal energy into a cooler environment. And in the summer you have to constantly remove heat and fight energy outside your home.
While we take it for granted, batteries are a small technological miracle. With batteries, we’ve improbably succeeded in creating a system where we can temporarily store electrical energy in a compact container and access it on demand – and it’s mostly stored without escaping into the environment. However, there is an important matter!
Even when your device is completely turned off or the battery is completely disconnected, as is the case with power tool batteries that have been removed from the tool, it is not truly disconnected at an atomic level. The chemical reaction inside the battery continues, although in a much more moderate way than when we actually use the battery.
This continuous low-level activity within the battery now slowly depletes the stored energy. This is called self-discharge. That is, it is an electrical discharge that occurs in the absence of an external load placed on the battery and is unavoidable.
Not all batteries are the same
If you’ve been paying attention to the types of batteries that different devices use and how often they seem to drain when left off the charger for too long, chances are you’ve noticed that not all batteries are the same.
So while they all suffer from the problem of self-discharge as a fundamental side effect of their design, the rate at which they discharge is significantly different.
For example, lithium batteries lose about 2 to 3% of energy per month while nickel metal hydride (NiMH) batteries can lose between 25 to 30%.
Already the acid loses between 4 to 6%.
Lithium-ion batteries are the type of battery most of us have the most experience with. This is the type of battery used in smartphones, smartwatches, tablets, laptops and a wide variety of other consumer electronics. They are also the type of batteries found in electric vehicles.
NiMH batteries are rarely used in consumer electronics, but are often used in power tools because they cost less than lithium-ion batteries.
Although the self-discharge rate is high, there is a low-discharge variant.
How to make batteries lose less charge
You can’t completely stop your batteries from draining, but you can do one simple thing to reduce it: keep them cool.
Whether you’re trying to keep a Li-Ion or NiMH battery charged longer, do your best to keep the battery cool.
Cool within reason, of course. Don’t put your batteries in the freezer, but do everything you can to keep the heat out.