Our power distribution system on the DCH (boat) uses two 7.2V NiCd batteries in parallel to provide 7.2 V, thereby offering higher current capacity, to our two drive motors. We use a 3Amp switching regulator to distribute logic level voltage to our circuits. The motors are powered straight from the 7.2 V of the batteries, while the xbee boards are designed to have a 3.3 voltage regulator (for the xbee to run on) and a level shifter to run all of our PICs at 5V.
The project specification required a continous HC operation of at least 8 hours. The HC (controller) uses one 7.2V NiCd battery, which is adequate for 8 hours of operation. One 7.2V NiCd battery is rated at 1500 mA-hr. We measured the current through the battery’s leads and read an average of 74.5mA. This gives us a theoretical operating time of
1500 mA-hr / 74.5mA = 20 hours which is well above the 8 hour requirement of the specification.
We also installed a kill switch to quickly power off the boat motors if necessary. As per datasheet recommendations a 0.1 uF is loacated on the regulated side of the regulators, to smooth voltage ripple from the regulators.