How to Charge and When to Charge

How to Charge and When to Charge

Date: 2021-5-28

Batteries have unique needs and Table 1 explains how to satisfy these desires based of common batteries. Because of similarities within the battery family, we only list lead, nickel and lithium systems. Although chemistry has its own requirements, there are common denominators that affect the life of all batteries. These are:

·       Keep a moderate temperature. As food stays fresher when refrigerated, so also does cool temperature retard battery corrosion, a life-robbing adversary of any battery.
 

·       Control discharge. Each cycle wears the battery down by a small amount. A partial discharge before charge is better than a full discharge. Apply a deliberate full discharge only to calibrate a smart battery and to prevent “memory” on a nickel-based pack.
 

·       Avoid abuse. Like a machine that is exposed to strenuous work, a battery wears down more quickly if discharged harshly and if force-charged with high currents. Strenuous demands cannot always be prevented, but the user has the choice of selecting the right battery size, keeping the temperature moderate and following life-extending service guidelines.

Batteries for the electric powertrain have changed the philosophy of battery manufacturers from designing packs for maximum energy density, as demanded by the consumer market, to focusing on optimal safety and longevity. Batteries on the road are exposed to extreme environmental hazards; they must perform at maximum duty under severe heat, cold, shock and vibration. Storing energy of several kilowatts, batteries for the electric powertrain can be dangerous if stressed beyond normal conditions. Furthermore, vehicular batteries are expensive and must last for the life of the car.

Pampering a battery to achieve an extended service life, as is sometimes possible with a laptop or cell phone pack, is more difficult with a large battery in a vehicle that must deliver high load currents on command and is exposed to freezing temperatures in the winter and blistering summer conditions. The user has limited control as to the care and attention of the battery. This task is passed over to an intelligent battery management system (BMS), which takes over the command and does the supervising. The BMS assumes the duties of a lead commander who must make sure that the troops in a large army are well organized and that all soldiers are marching in the same direction.

While a battery in a portable device can have its own personality and occasionally slack off, this liberty does not exist in a large battery system where all members must be of equal strength. Managing fading and failing cells as the battery ages is a complex issue that the BMS must address effectively. Monitoring and eventual replacing the cells or battery groups is far more complex than getting a new pack for a portable device when the old one becomes a nuisance.

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 topping charge	Charge 14–16h. Priming may be needed	Apply a topping before use. No priming needed
Can I damage a battery with incorrect use?	Yes, do not store partially charged, keep fully charged	Battery is robust and the performance will improve with use	Keep some charge. Low charge can turn off protection circuit
Do I need to apply a full charge?	Yes, partial charge causes sulfation,	Partial charge is fine	Partial charge better than a full charge
Can I disrupt a charge cycle?	Yes, partial charge causes no harm	Interruptions 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?	Some UPS systems simultaneous charge and deliver current.	It's best to turn the device off during charge; parasitic load can alter full-charge detection and overcharge battery or cause mini-cycles
Must I remove the battery when full?	Depends on charger; needs correct float V	Remove after a few days in charger	Not necessary; charger turns off
How do I store my battery?	Keep cells above 2.10V, charge every 6 months	Store in cool place; a total discharge causes no harm	Store in cool place partially charged, do not fully drain
Is the battery allowed to heat up during charge?	Battery may get lukewarm towards the end of charge	Battery gets warm but must cool down on ready	Battery may get lukewarm towards the end of charge
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?	Above 25°C, lower threshold by 3mV/°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; should include temp sensor	Battery must stay cool; no trickle charge when ready

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

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