21700 VS AA Battery

Series vs Parallel Applications: NMC Lithium 21700 Battery vs Alkaline AA Battery

Comparison Items	NMC Lithium 21700 Battery	Alkaline AA Battery
Single Cell Voltage	3.6V / 3.7V	1.5V
Typical Series Pack	3S ≈ 11.1V 4S ≈ 14.8V 10S ≈ 36V 13S ≈ 48V 20S ≈ 72V	8S ≈ 12V 20S ≈ 30V 32S ≈ 48V
Parallel Expansion	Capacity scalable to tens/hundreds of Ah. suitable for Scooters, and Solar ESS.	Limited. requires many cells in parallel, bulky. rarely used for large packs.
Application Features	Few cells in series achieve common system voltages. parallel adds high energy and current.	Needs many in series for higher voltage. parallel is inefficient for large capacity.
Typical Applications	Scooters, Balancing Scooter, E-Bikes, E-Rickshaw, Ride on Car for Kids, Power Banks, Portable Power Stations, Flashlights, Headlamps, 3C Digital Products, Portable Fans, Mini Turbo Fans, Mini WiFi Router, and Solar ESS	Appliance controller, flashlights, toys, small appliances

21700 vs AA Battery About Charging

21700 battery (NMC Lithium-ion)

The 21700 battery has a standard charging C-rate of 0.2C.
0.5C is the common charging rate (fully charged in ≈2.5 hours).
1C is fast charging (fully charged in ≈1.5 hours).
>2C is considered super fast charging. Requires professional factory for special customization, can't be applied to ordinary 21700 battery and carries risks, the Joinsun is customizable.
The 21700 battery's charging factor ≈1.2.

AA battery (AA NiMH battery)

The AA rechargeable NiMH battery has a standard charging C-rate of 0.1C (fully charged >10 hours).
0.2C~0.3C is the common charging rate (fully charged ≈5 hours).
0.5C~1C is fast charging (fully charged ≈1~3 hours). Requires charger support with ΔV detection and temperature control, otherwise it may easily overcharge and cause damage.
>1C, Rarely used, high risk, requires specially designed cells and chargers for support. The NiMH AA battery's charging factor ≈1.4.

Difference in Charging Methods: 21700 vs AA

NMC Lithium-ion 21700 battery: Does not support trickle charging, can only be charged with constant current / constant voltage (CC/CV).
NiMH AA battery: Supports trickle charging (TC).

NOTES:
(1) Alkaline AA battery are not rechargeable, the alkaline AA battery is primary (non-rechargeable) battery.
(2) NiMH AA battery are rechargeable.
(3) All batteries have overvoltage protection. Charging beyond their maximum voltage tolerance can directly cause battery hazards. In addition, they also have overcurrent protection, charging above their maximum current tolerance is not allowed.
(4) ΔV detection is a commonly used full-charge detection method for NiMH or NiCd batteries.
A) Principle
When a NiMH/NiCd battery is approaching full charge, its voltage first rises to a peak and then slightly drops.
ΔV is the difference between this peak voltage and the subsequent voltage drop.
The charger monitors ΔV to determine whether the battery is fully charged, and automatically stops charging or switches to trickle charge mode.
B) Features
Prevents overcharging and prolongs battery life.
Only applicable to NiMH/NiCd batteries. Lithium-ion batteries do not use ΔV detection, they use CC/CV (Constant Current / Constant Voltage) charging instead.
(5) TC Trickle Charging is a method of charging a battery with a very low current continuously, intended to maintain the battery at full charge without causing damage.
Principle: When the battery is nearly full, a small current (typically 0.03C~0.05C) is used to top up the charge. The current is very low and does not overcharge the battery.
Must use a charger that supports trickle charging, ordinary fast chargers cannot be used as trickle.
(6) CC/CV stands for Constant Current / Constant Voltage. It is the most common charging method for lithium-ion batteries (e.g., 21700 battery, 18650 battery).
A) Constant Current (CC) Stage:
The battery is charged from a low state of charge with a constant current (e.g., 0.5C, 1C).
The voltage gradually rises until it reaches the battery’s nominal full-charge voltage (e.g., 4.2V).
B) Constant Voltage (CV) Stage:
Once the battery voltage reaches the set value, the charger maintains constant voltage.
The charging current gradually decreases until it reaches the termination current (typically ≈0.05C), at which point charging is complete.
C) Features:
High safety: prevents overcharge and overcurrent.
Wide applicability: suitable for NMC lithium-ion, LiFePO4 (LFP) Lithium-ion, and other rechargeable batteries.
Automatic stop: the charger automatically stops when the current drops to the termination level, no trickle charging is needed.

Where i can find the high quality 21700 battery?

Joinsun has extensive experience in battery manufacturing and has successfully developed 5500mAh 3C 21700 battery (NMC Lithium). You are welcome to reach out to the Joinsun sales team for detailed information on pricing and technical documents.