When looking to buy rechargeable lithium batteries, you see some that are marketed as protected, and some that are not. In this case, depending on manufacturer and price, you might want to know; is a Lithium-ion protection circuit really needed in the batteries I’m looking at buying?
What Does “Protected” Mean Anyway?
It’s actually quite simple.
The protection is in the form of a circuit board which is added to lithium batteries before being wrapped with the distributors label. Its function is to make certain that the rechargeable battery that it’s serving, never over-charges or DIS-charges below a preset level.
Rechargeable lithium batteries (for the most part) provide 3.7 volts of power. When charging, it’s not recommended that the completed charge current exceed 4.2 volts. While being discharged (by using within a device) it’s not recommended that the voltage be allowed to drop below 2.8
Given those limits, it’s the circuit’s job to ensure that the battery is kept of out danger as to the best of its ability.
Is the Danger for Real?
It CAN be. But various elements need to be in place. This article explains how rechargeable lithium batteries like to be treated.
Basically, the circuit is there to shut the battery down when low voltage is detected. In all the lithium cells that I own, I’ve never actually known the circuit to fail. But experts will tell you they have… and do. This is why it’s recommended to periodically check the battery on a voltage meter between uses, and instigate a “fresh” charge if it’s getting close to being shut down by the circuit. I also recommend buying a quality charger (not one that accompanies the purchase of potentially dangerous “cheap” batteries). A name-brand charger will cease charging when the battery voltage gets close to 4.2 This ensures a safe charge, since over-charging is almost worse for the battery, than over-DIScharging!
Does Size Matter (or is it a tight fit)?
Since this is a family site, I’m assuming you’re referring to the length of the battery after the circuit is added. Good question! And in SOME circumstances it does.
The added electronics will stack an extra millimeter or two onto the length of the cell. If being used in LED flashlights, most manufacturers design the tubes to accommodate variable sizes depending on the type of battery used. Where length seems to vary more, is with 18650 batteries. Some users have found some batteries to be a tight fit, both in length and width. I own a couple like that too. But it’s usually only with ONE particular flashlight (for instance). When I switch to a different light, the cell fits perfectly.
What About Unprotected Batteries?
I’m glad you asked! You can certainly opt to buy those if that floats your boat. It’s all a matter of safety. Unprotected cells will work exactly the same way. You just need to be EXTRA careful and be diligent about checking voltage during usage.
As an alternative, this article describes another type of lithium chemistry (IMR) that is not only more commonly found in unprotected form, but is actually safer to use.
Questions about protected Lithium-ion batteries??? Ask away, and you shall receive the best answer possible!
This link features an amazing selection of both protected and unprotected batteries at excellent prices!