Battery Comparisons

NiCd vs NiMH vs. LiPo Battery Packs

By Jimmy Fernandez – Systems Engineer

Abstract

In this study, we are researching the best battery pack to use for our Tracked Rover project.  While each of the batteries have their pros and cons, the properties of our chosen battery must satisfy our project requirements.  The choice ultimately comes down to a NiMH battery pack.

Objective

The objective of this study is to determine the best battery pack type for a Tracked Rover.  The main criteria is safety, then capacity and discharge rate.  These packs are the most commonly used battery packs in RC cars and similar applications.  Note that this is a qualitative analysis rather quantitative, this will help narrow battery pack choices to a certain type so that capacity can be determined.

Theory

  • Lithium Polymer – LiPoT-RCB-1013-3__Lithium-Polymer-Battery
    • Pro – Very high capacity, lightweight, good discharge rate
    • Con – More likely to catch on fire if discharged too low or overcharged.  Expands with high levels of static charge.
  • Nickel-Metal Hyrdride – NiMHimage_18264
    • Pro – Higher capacity than NiCd, but lower than LiPo
    • Con – High rate of self-discharge.  Best to recharge before use.  Less environmental impact than NiCd
  • Nickel Cadmium – NiCdnicd
    • Pro – Good discharge rate. Can charge quickly.  Lower internal resistance.
    • Con – Lowest capacity of the three.  Cost more than NiMH

Conclusion

In an effort to be more cost effective while still maintaining the mission length and personnel safety, the best choice is NiMH.  In general, its capacity is large while still being cost-efficient.  LiPo has safety concerns that could be made readily apparent to those who have never worked the battery type.  NiCd in theory does not have the capacity needed while maintaining a cost-effective price-point.

Sources

http://daringrey.com/lipo_nimh_nicd_battery_maintenance.htm

http://www.servocity.com/html/nicad_vs__nimh_batteries.html

http://www.faa.gov/about/office_org/headquarters_offices/ash/ash_programs/hazmat/aircarrier_info/media/Battery_incident_chart.pdf