Specifications

A very common type of rechargeable battery is the lead acid battery. It is used in

a variety of applications, including marine and automotive use. As such, it is a

mature technology, and the charging technology is not complex and is also well

understood. It is the oldest type of rechargeable technology, and is a proven

technology.

As such, concerns of its reliability during operation either when new or after some

time are not of great importance. Compared to other technologies, it is the

cheapest (if compared for each unit of capacity). However, there are several

disadvantages which may make this battery a poor choice for the portable unit.

The primary issue is with its unique charging needs. Lead acid batteries need a

significant amount of time to charge. While the portable unit may be connected to

the base unit to charge for a fair amount of time, it has a high probability of not

being connected for the up to 16 hours required by a lead acid battery. In

addition, as the device may be left with a battery in a low charge or no charge

state, a lead acid battery will experience additional problems due to this. Deep

discharging or being stored at a no/low charge state can damage the battery and

make future recharging difficult, if not impossible.

In addition, due to its low energy density compared to other options, it is the

largest of the options (dimensioned and shown in Figure 2.11.5-1), and also the

heaviest. Neither is optimal for a device which concentrates on portability. Also,

the number of recharge cycles is limited, which means limited life. Due to the

variety of environments the portable device will be used in, the battery must be

able to perform adequately in low temperature. The performance of lead-acid

batteries in cold weather is considered to be low. Lastly, the lead-acid content of

this battery is very environmentally unfriendly.

Figure 2.11.5-1: A 6V lead acid battery. Reproduced with permission from