CHAPTER 7 ■ NINE-VOLT BATTERIES
Heavy-duty battery capacity is seriously eroded at higher discharge rates, so the respectable 400 mAh
rating is hideously reduced in power-hungry robots. Older-technology carbon and zinc batteries have a
short shelf life (they self-discharge faster).
Carbon and zinc battery voltage slopes down steadily during use, which decreases the useful battery
life if the device requires a higher voltage. Ironically, the sloping voltage turns out to be useful for predicting
remaining capacity.
Nickel-Cadmium
For environmental reasons, nickel-cadmium (NiCd or NiCad) batteries are not recommended (see Figure 7-14).
Additionally, NiCd batteries have a lower capacity and accept fewer recharges than NiMH batteries. The major
brands no longer make NiCd batteries.
Figure 7-14. Nickel-cadmium rechargeable 9 V battery
e^2 Titanium and Ultra
The top two manufacturers of alkaline batteries have both introduced premium versions of their alkaline
batteries (see Figure 7-15). These enhancements are basically marketing gimmicks. The companies charge a
notably higher price for an unnoticeable change in performance. (Ouch!)