Appendix I: Functional Description and Circuitry
101
Battery Wiring
SBE 19plus V2 standard main battery is a series connection of D-cells that
drop into the battery compartment as a cluster of end-to-end stacks, three
batteries each (standard 9-cell battery pack has three stacks). The positive
battery connections are contact areas on double-thick printed circuit disks that
form the internal bulkhead and battery retainer plates. Battery negative
contacts are heavy beryllium-copper springs. The three cell stacks are aligned
by plastic insulated aluminum spacers which also serve as electrical
interconnects. The battery-to-circuit card connection is made by means of a
Molex-type 3-pin pc board connector (JP3 on the power PCB).
The Power PCB contains three series-connected Panasonic BR-2/3A lithium
cells (non-hazardous) which are diode OR’d with the main battery (and
external power source, if used). The back-up lithium supply is capable of
maintaining the buffer and the real-time clock if the main batteries and/or
external power are removed. If the back-up lithium battery voltage (Vlith in
the GetSD or DS response) falls below 7 volts, replace the back-up batteries.
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