IntroductionThe battery architecture of our project had to be carefully studied and chosen. Three types of rechargeable batteries were studied: Nickel-Metal-Hydride (NiMH), Nickel-Cadmium (NiCd) and Lithium-ion (Li-Ion). Each type of battery architecture has advantages and disadvantages that we had to weigh before choosing the type of battery that would best suit our project. A comparison table of the three types of batteries is available below. Lead acid batteries were not considered for this project as they are relatively heavy and storage of our system may be an issue if lead acid batteries were used. Lead-acid batteries also have the disadvantage of slow charging times, up to 14 hours. Lead acid batteries are more suitable for projects with much larger power applications. [1] Nickel–Cadmium (NiCad) [2] NiCad batteries have several advantages over other battery architectures available today. NiCad batteries have the ability to be charged simply and quickly even if they have been stored for long periods of time. They have a long shelf life regardless of the battery's state of charge. If the batteries are treated poorly, they will be quite forgiving. One of the big advantages of this type of battery is that it is the cheapest type of battery in terms of cost per cycle. NiCad batteries cost around $0.04 per cycle. They are also quite efficient with an efficiency ranging from 70 to 90%. However, this type of battery architecture has big drawbacks. First, they have a significant self-discharge rate of 20%/month. NiCad has the lowest gravimetric energy density of all battery architectures, only 45-80 Wh/kg. NiCad batteries may be subject to the memory effect. This occurs when the battery has been reduced to 110-160Wh/kg. • The nominal voltage of a lithium-ion cell is 3.7 V. This is approximately three times that of the nominal voltages of lithium-based chemicals. nickel. • The life cycle of a lithium-ion battery is relatively good. They generally have a lifespan of over 300 cycles. Typical life cycle characteristics of lithium-ion batteries can be seen in Figure 1 below. At approximately 500 cycles, battery capacities have been reduced to approximately 70%.• Li-ion batteries have the highest relative capacity of the three battery types examined at 3.• Li-ion batteries do not suffer from memory effect like nickel chemistry batteries do. Considering all of these benefits, it was decided that a lithium-ion battery would be best suited for the project. For more information on the advantages and disadvantages of lithium-ion batteries, see section 1.2 of the preliminary report.