BU-415: How to Charge and When to Charge?

Early batteries were reserved for commercial use only, such as telecommunications, signaling, portable lighting and war activities. Today, batteries have become a steady travel companion of the public at large to reach a friend, they allow working outside the confines of four walls, provide entertainment when time permits and enable personal transportation. Best of all, batteries help in missions when people are in need.
Folks are eager to learn more about this wonderful portable energy device and one of the most common questions asked is, “What can I do to prolong the life of my battery?” Table 1 addresses how to care for your batteries to meet their needs. Because of similarities within the different battery families, the table addresses the needs and wants of only the most common systems by keeping in mind that these desires extend to almost all batteries in use.

Keep a battery at a moderate temperature. As food stays fresher when refrigerated, so also does cool temperature protect the battery by reducing internal corrosion, also known as parasitic reactions on the electrolyte and electrodes.
Avoid deep cycling. Each cycle wears the battery down by a small amount and a partial discharge is better than a full discharge. When possible, only apply a full discharge to calibrate a smart battery and to prevent “memory” on nickel-based batteries. Li-ion is maintenance-free and the battery lasts longest when operating between 30 and 80 percent SoC.
Avoid abuse. Like a machine that wears down quicker under strenuous work, so also is a battery stressed by harsh discharges and rapid charges. Use cells that are optimized for the power and energy requirements as per application and increase that pack size to minimize load-related stresses.
Avoid ultra-fast charge. Charge Li-ion Energy Cells at less than 1C (below rated Ah); Power Cells are more rugged and can be charged and discharged at a higher rate. NiCd is the only battery that can be fast charged up to 70 percent SoC without adverse side-effects.
Store Li-ion at partial charge in a cool place. The worst combination is high voltage and elevated temperature. Store Li-ion at approximately 50 percent SoC.

Frequently asked question	Lead acid (Sealed, flooded)	Nickel-based (NiCd and NiMH)	Lithium-ion (Li-ion, polymer)
How should I prepare a new battery?	Battery comes fully charged. Apply a topping* charge.	Charge 14–16h. Priming may be needed to format	Apply a topping charge before use. No priming needed
Can I damage a battery with incorrect use?	Always store battery fully charged.	Battery is robust. New pack will improve with use.	Keep partially charged. Low charge can turn off protection circuit
Do I need to apply a full charge?	Fully charge every few weeks or months. Continuous low charge causes sulfation.	Partial charge is fine	Partial charge better than a full charge
Can I disrupt the charge cycle?	Partial charge causes no harm when applying periodic fully saturated charges.	Repeat charges can cause heat buildup	Partial charge causes no harm
Should I use up all battery energy before charging?	No, deep discharge wears battery down. Charge more often	Apply scheduled discharges only to prevent memory	Deep discharge wears the battery down
Do I have to worry about “memory”?	No, there is no memory	Discharge NiCd every 1–3 months	No memory
How do I calibrate a “smart” battery?	Not applicable	Apply discharge/charge when the fuel gauge gets inaccurate. Repeat every 1–3 months
Can I charge with the device on?	Avoid load if possible	Parasitic load can alter full-charge detection and overcharge battery or cause mini-cycles
Do I remove the battery when full?	Charger switches to float charge	Remove after a few days in charger	Not necessary; charger turns off
How do I store my battery?	Keep cells above 2.10V; topping-charge* every 6 months.	Store in cool place; can be stored fully discharged	Store in cool place partially charged
Does battery heat up on charge?	Gets lukewarm towards end of charge	Warm but must cool down when ready	Must stay cool or slightly warm
How do I charge when cold?	Slow charge (0.1): 0–45°C (32–113°F) Fast charge (0.5–1C): 5–45°C (41–113°F)		Do not charge below freezing
Can I charge at hot temperatures?	Lower threshold by 3mV/°C above 25°C	Battery will not fully charge when hot	Do not charge above 50°C (122°F)
What should I know about chargers?	Charger should float at 2.25–2.30V/cell when ready	Battery should not get too hot and should include temp sensor	Battery must stay cool and no trickle charge when ready

Table 1: Best charging methods
Strenuous demands cannot always be prevented.

* Topping charge is applied on a battery that is in service or storage to maintain full charge and to prevent sulfation on lead acid batteries.

Last Updated: 27-Oct-2021

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Batteries In A Portable World

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