Batteries supply mobile power to robotic systems and have several important criteria to attend to. Battery voltage must be accounted for to interface with all other on board hardware components. Battery capacity (expressed in mAh) will dictate how long the system can run before needing to be recharged. Battery discharge rate is the max amperage the battery can provide at one time without catastrophic failure. In addition, the power density of the battery dictates how much power per unit of mass the battery type can provide.
Lithium Polymer (LiPo) batteries and Lithium Ion batteries offer high energy den- sities and are mass manufactured offering an affordable power solution. Li Ion cells are more energy dense but are limited in their discharge rate, thus to achieve higher current, more cells are necessary. Lithium Polymer are less energy dense, and are more unstable with a higher potential for a lithium battery fire in the case they are mishandled, but have a higher possible discharge rate per cell.
Lipo batteries voltages are correlated to cell count. Higher voltage batteries will have more cells. Battery cells lower in voltage as they are discharged. LiPo batteries have several voltages to consider. The nominal voltage is the battery voltage assumed for documentation. a 1 cell LiPo will be advertised at 3.7 Volts on the side though it can range from 4.2 V to 3 V. The lowest voltage a LiPo can be discharged to is 3.0 V, beneath this voltage the LiPo will be damaged, and can explode. Under normal conditions a Lipo should never drop below 3.2 volts for longevity of the battery. The lower the voltage, the faster the battery discharges so be careful.
The highest voltage the LiPo voltage is the 4.2 V per cell. You don’t have to charge all the way to 4.2 V per cell when using a battery. The storage voltage is the voltage deemed best for long term storage of the battery approximately 3.8 V per cell.
1 Cell LiPo Voltages
| Nominal Voltage | Storage | Lowest | Highest |
|---|---|---|---|
| 3.7 V | 3.8 V | 3.0 V | 4.2 V |