IntroductionThe battery architecture for our project had to be carefully considered and chosen. Three types of rechargeable batteries were examined: nickel-metal hydride (NiMH), nickel-cadmium (NiCd), and lithium-ion (Li-Ion). Each type of battery architecture has advantages and disadvantages that needed to be evaluated before choosing which battery type best suits our project. Below is a comparison table of the three types of batteries. Lead acid batteries were not considered for this project as they are relatively heavy and storage for our system could be an issue if lead acid batteries were used. Lead-acid batteries also have the disadvantage of slow charging times of up to 14 hours. Lead acid batteries are better suited for designs with much larger power applications. [1]Nickel-Cadmium (NiCad) [2]NiCad batteries have numerous advantages over other battery architectures available today. NiCad batteries have the ability to be charged quickly and easily even if they have been stored for long periods of time. They have a long life, regardless of the state of charge of the battery. If the batteries are treated badly they are quite forgiving. A big advantage of this type of battery is that it is the most economical type of battery in terms of cost per cycle. NiCad batteries cost about $0.04 per cycle. They are also quite efficient with efficiency ranging from 70 to 90%. However there are major disadvantages to this type of battery architecture. First of all, they have a high self-discharge rate of 20% per month. NiCad has the lowest gravimetric energy density of all battery architectures, at just 45-80 Wh/kg. NiCad batteries can be subject to the memory effect. This occurs when the battery has been co...... half paper ......size of 110-160 Wh/kg.• The nominal voltage of a lithium ion cell is 3.7 V. This is approximately three times that of the nominal voltages of nickel-based chemicals. • The life cycle of a lithium ion battery is relatively good. They generally have a lifespan of over 300 cycles. Typical lifecycle characteristics of lithium-ion batteries can be seen in Figure 1 below. At approximately 500 cycles the battery capacity has reduced to approximately 70%.• Lithium-ion batteries have the highest relative capacity of all three battery types examined at 3.• Lithium-ion batteries do not suffer of the memory effect like chemical nickel batteries. Taking all these advantages into account it was decided that a lithium ion battery would be most suitable for the project. For more information on the advantages and disadvantages of lithium-ion batteries, see section 1.2 of the preliminary report