How to choose the right battery

The design of portable devices is largely determined by the performance of the battery.
The key indicator of the battery is of course the battery life. On the surface, this is just a simple specification, but it involves many factors, including: system load (time of supply at full load current, time of supply at partial circuit or microampere current), power efficiency, system power management, battery type and charging method.
In addition to their special importance, the interaction between these characteristics can enhance or reduce the end user's perception. Generally, when the user starts to notice the battery, things get tricky! Good product design does not require frequent battery replacement (such as TV remote control) or frequent battery charging (electric toothbrush) to make the battery "disappear" from the user's sight. Avoid users paying attention to the battery as much as the function of the device.
Choosing battery chemistry
The interaction between battery and system is an often overlooked issue in design. It is critical to ensure that the battery capacity matches the needs of the system. Common battery types are: alkaline batteries, nickel metal hydride batteries (NiMH) and lithium-ion batteries . They are not interchangeable, and most products have a best choice.
Alkaline Batteries
Alkaline batteries are not rechargeable (a point that has been made repeatedly in recent nightly battery ads), but they have extremely low self-discharge rates and cost (no charger or AC outlet required). For low-power applications, alkaline batteries are a good choice, but they must be used properly and the quiescent or sleep current must be low.
A common design mistake is to focus on operating efficiency and ignore the current consumption in the "off" or "sleep" state. Even tens of μA of current drawn from the battery can lead to frequent battery replacement. Many designs now use soft switching instead of mechanical switches (mechanical switches can completely disconnect the battery), but this design mistake is more common than it was a few years ago. Rechargeable
Batteries
When the load is too large for alkaline batteries, rechargeable batteries are used, which has become the standard for portable products such as laptops, PDAs, and cell phones. Rechargeable batteries should be as "intrusive" to the user as possible, which will promote the product or at least not degrade the product's performance.

There are two choices for rechargeable batteries: nickel metal hydride or lithium ion. Cell Phones Lithium Batteries Charger Circuits
NiMH batteries are less expensive than lithium ion batteries, but this choice becomes sensitive when the product's normal use conditions are unsafe for the battery. This issue is more important for low-cost products that lack complex charging designs, because NiMH batteries are suitable for full charge and full discharge processes. This is suitable for products that often run out of power, such as power tools.
Another application suitable for NiMH batteries is to replace alkaline batteries. When the battery power is exhausted, the battery is removed from the device and recharged by an external charger. This application is more common in digital cameras, but requires frequent user intervention.
Many portable products are different from the above situation. PDAs and cell phones need to be charged regularly, but they only consume power occasionally. These products are best selected for lithium ion batteries. In addition to weight density, this battery has two important advantages: low self-discharge rate and no restrictions on short-term charge-discharge. Consumers do not have to worry about "battery management" issues, which simplifies product use.