Can You Overcharge a Lithium Battery? What You Should Know to Protect Your Investment.

With the rise of portable electronic devices and cordless power tools, the demand for lithium batteries is ever-growing. These batteries have a high energy density, low self-discharge rate, and long lifespan. However, there is a common question that arises with their use: Can you overcharge a lithium battery? We will answer this question and provide you with important information you need to know about lithium batteries.

Overcharging Lithium Batteries

Despite advancements in durability and longevity, lithium batteries remain sensitive to overcharging. Most lithium  iron phosphate (LiFePO4) batteries have a built-in protection circuit call a Battery Management System (BMS) that will internally disconnect the lithium battery if the programmed voltage threshold is exceeded. The BMS may help prevent overcharging of the battery but this threshold is often much higher than the recommended charging voltage. If you repeatedly charge the battery to this threshold, damage to the lithium cells may occur and battery lifespan will be greatly reduced.

The Importance of Using the Correct Charger

Getting the most effective use out of your lithium battery starts with only charging it with a compatible charger for your batteries' specific chemistry, e.g., LiFePO4, LiPo, etc.. Using a charger that’s not compatible with your battery can cause overcharging, which can lead to damage to the battery or even personal injury. You should always use the charger that is specifically designed for your battery, and never use a charger if you aren’t sure about its compatibility.

Sizing the Charger Properly

While selecting the correct charger for your batteries' chemistry ensures the correct voltage levels, choosing the right amperage of charger is just as critical. Not only to protect your battery investment, but also for safety reasons. The proper charge rate, or amps (A), is determined by the amp-hour (Ah) capacity of the battery. Most LiFePO4 battery manufacturers recommend a charge rate of .3C, or 1/3 of the batteries' Ah rating for longest battery life. LiPo batteries will typically accept up to a 1C charge rate.

Examples:

100Ah LiFePO4 Battery - 100 (Ah) x .3 = Maximum charge rate of 33 amps

5000mAh LiPo Battery - 5000 (mAh) / 1000 = 5Ah  |  5Ah @ 1C = Maximum charge rate of 5 amps

Not only can these recommendations can vary widely between manufactures, but certain batteries may also be designed for much higher acceptable charge rates depending on application. This makes it critical to always consult the manufacturer recommendations for your specific battery to select the correct amperage charger. The increased number of battery lifecycle's you'll get from ding a little match when sizing your charger correctly can pay off many times over in the long run.

Ways To Prevent Overcharging Your Battery

The most important thing you should know about overcharging a lithium battery is how to keep this issue from happening in the first place. One way to avoid overcharging your lithium battery is to use a smart charger. Designed to automatically stop charging your battery once it reaches capacity, these products help you avoid overcharging and extend the lifespan of your battery. All reputable LiFePO4 chargers will charge to a specific voltage and stop automatically to ensure optimal battery performance and lifespan.

Additionally, you should always store your batteries correctly. While LiFePO4 batteries can often be stored at full charge, LiPo batteries should be stored at about 3.7 volts per cell. Always check your battery manufacturers recommendations for proper storage charge level. It’s also recommended that you store lithium batteries in a cool, dry place, away from direct sunlight. Storing your lithium battery in extreme temperatures can reduce its lifespan and cause it to malfunction.

Overcharging a lithium battery can be hazardous and expensive in the long run and at GMI Energy we understand the importance of reliable power sources for all your adventures. Our collection of AGM and lithium batteries include products from top industry brands and you now know the importance of pairing these batteries with the correct type and size of charger. Regardless of the items you need to power your professional or recreational equipment, GMI Energy has you covered.