The motor is powered by a battery consisting of 24 sub-C size (2.2Ah)
nickel-metal-hydride (NiMH) cells. NiMH was chosen over nickel-cadmium (NiCd) due to it's
greater energy density. The major disadvantage of NiMH cells is that they have a higher
internal resistance than the low-resistance NiCd cells usually used in this application.
As a result, both the charging and discharging currents must be kept lower than with NiCd
cells.
A battery consisting of 8 AA size (1.2Ah) NiMH cells is used for the computers and
electronics. This battery is regulated to 5.0V by a Texas Instruments TL780-05C regulator.
The regulator is attached to a big heat sink because it gets pretty warm. This provides
power to the PC/104 computer. The compass and RS-232 boards receive power from the PC/104
board, and the HC11 board receives power from the RS-232 board. The other components
receive power from the HC11 board.
A battery of 4 AAA size (0.55Ah) NiMH cells powers the receiver and servos.
The Panasonic battery pack that came in the transmitter has failed due to a bad cell, so
we have replaced it with some standard NiCd cells (0.65Ah).
All of our batteries are provided by Energizer.
We are using an Astro Flight model 212D digital peak charger to charge the battery packs.
Information on our battery packs is presented in the first table, and a comparison of
various cells we considered in the second table. Battery pack weight includes wires and
connectors.
| Pack | Desc | V | mAh | oz | Wh | Wh/lb |
| Motor Pack | 24 x subC | 28.8 | 2200 | 48.8 | 63.36 | 21 |
| Servo Pack | 4 x AAA | 4.8 | 550 | 2.0 | 2.64 | 21 |
| Electronics Pack | 8 x AA | 9.6 | 1200 | 7.6 | 11.52 | 24 |
| TYPE | Desc | Manuf/Part | V | mAh | oz | in3 | Wh | Wh/lb | Wh/in3 |
| NiMH | SubC | Ever/EMP2200Cs | 1.2 | 2200 | 2.0 | 0.97 | 2.64 | 21 | 2.7 |
| NiMH | AA | Ever/EMH1200AA | 1.2 | 1200 | 0.9 | 0.48 | 1.44 | 26 | 3.0 |
| NiMH | AAA | Ever/EMH550AAA | 1.2 | 550 | 0.4? | 0.22 | 0.66 | 26 | 3.0 |
| NiCd | C | Ever/CH35 | 1.2 | 1800 | 2.0 | 1.64 | 2.16 | 17 | 1.3 |
| NiCd | AA | Ever/CH15 | 1.2 | 650 | 0.8 | 0.51 | 0.78 | 16 | 1.5 |
| NiMH | Big Flat | Ever/NI1020 | 12 | 3500 | 20.9 | 16.0 | 42.0 | 32 | 2.6 |
| NiMH | Big Flat | Ever/NI1030 | 10.8 | 3500 | 17? | 16? | 37.8 | 36 | 2.4 |
| Li+ | Big Flat | Ever/NI2020 | 10.8 | 4050 | 15.6 | 16.4 | 43.7 | 45 | 2.7 |
| NiCd | VCR large | Ever/CCM2460 | 6.0 | 1800 | 9.9 | 9.8 | 10.8 | 17 | 1.1 |
| NiCd | VCR std | Ever/CM1060 | 6.0 | 1200 | 5.5 | 4.59 | 7.20 | 21 | 1.6 |
| NiCd | VCR large | Ever/CM4160 | 6.0 | 2400 | 10.6 | 9.26 | 14.4 | 22 | 1.6 |
| NiCd | VCR large | Ever/CV2096 | 9.6 | 1800 | 16.3 | 20.9 | 17.3 | 17 | 0.83 |
| NiCd | VCR std | Ever/CC1096 | 9.6 | 1200 | 11.8 | 11.5 | 16 |
Back to Avigator
Revised 8/13/99