Types of Batteries

Carbon-zinc batteries (aka zinc chloride, dry cell or "heavy duty") produce 1.6 volts per cell. They are short-lived and prone to leaking. The best advice is to never use them.

Alkaline batteries (alkaline manganese dioxide) produce about 1.58 volts per cell. They are long-lived and less likely to leak than carbon-zinc batteries. When they do leak the electrolyte usually evaporates into crystals that can be simply brushed out of the battery box. Alkaline batteries have a long shelf life and last much longer under use than carbon-zinc batteries. However, they have a fairly high internal resistance compared to nickel-metal hydride batteries and can't be used where very high current is needed.

Lithium batteries (lithium manganese dioxide) produce 3.7 volts per cell and have a very long shelf life (seven years, typically). These are popular for watch batteries and computer clocks.

Zinc-air batteries produce 1.65 volts per cell and have a constant voltage throughout most of their life. They must be sealed when not in use because they self-discharge through oxidation. They are used for hearing aids and other medical devices. Technically, a zinc-air battery is a fuel cell.
Nickel-cadmium (NiCD) batteries produce 1.25 volts per cell. They can be recharged many times and provide high current with light weights. They are also prone to a “memory effect”, where the battery will fail to charge properly after several improper charge/discharge cycles. Nickel-cadmium batteries should be fully discharged before recharging to minimize the memory effect.

Nickel-metal hydride (NiMH) batteries are a direct replacement for nickel-cadmium batteries and are less prone to the memory effect. They have a low internal resistance so can deliver high current. They are often specifically called for in devices that require high current. NiMH batteries tend to self-discharge in about 90 days, even when not in use. However, Low Self-Discharge or "precharged" NiMH batteries will hold up to 80% of their charge over one year.

Lithium ion (LiIon) batteries produce 3.7 volts per cell. They are rechargeable batteries with a high capacity to weight ratio. They are also much less prone to memory effect than either nickel-cadmium or nickel-metal hydride batteries. However, with frequent cycling they can have a life of only 18 months to two years. Computer-controlled charging and discharging can extend the life of Lithium ion batteries. Many lithium ion batteries have microcontroller-operated charge circuitry integrated with the battery.

Lithium ion polymer (LiPo or Li-Poly) batteries produce 4.3 volts per cell. They are a fairly recent development of the lithium ion battery. They are lightweight and don't require a metal casing. They are popular for radio-controlled model cars and aircraft. Lately they have become the battery of choice for many battery powered devices. However, they must be carefully protected from overcharging because they are likely to catch fire or explode. Famous examples were the temporary grounding of the Boeing 787 due to battery fires and the “hoverboard” fires around Christmas of 2015.

Rechargeable Alkaline batteries have the benefits of regular alkaline with the added benefit of rechargeability. They can hold their charge for years where NiCD and NiMH batteries will self-discharge in about 90 days.

Lead-acid batteries produce 2.1 volts per cell. They are rechargeable, provide high current and are not prone to memory effect. However, they are heavy and contain dangerous sulphuric acid electrolyte. For many electronic applications sealed lead-acid batteries or gelled-electrolyte (gel cell) batteries are available.

A battery rated at 1.58 volts delivers 138 milliamperes through a load of 8 ohms. What is the internal resistance of the battery?

Solution: This is nearly identical to the second step of the 'find the mystery resistance' problem on page 57. Using Ohm’s law the total resistance is calculated as 11.5 ohms (using the source voltage of 1.58 volts and the total current of 138 milliamperes, i.e., 1.58 ÷ 0.138 = 11.449). Subtract the load resistance (8 ohms) from the total resistance to find the unknown internal resistance of 3.4 ohms (11.449 - 8 = 3.449).