BEAR 1 & 2 Batteries

BEAR-1 APRS System Battery

For the APRS system battery we had hoped to use 2 high output Lithium cells with a weight of only 3.9 ounces, however we were unable to locate any in time. Since our payload was very small and weight was not a big issue, we simply used 5 "C" size Duracell's weighing 12.6 ounces.

After the BEAR-1 flight I located some high output Lithium cells and now know why they are not more commonly used or stocked. Try $36.00 each! Using these cells, the APRS battery pack will cost $72.00 per flight. Add another 2 cells of even higher capacity (and cost) for the cross band repeater and it is clear that we will not be using lithium batteries.

Bear-2 APRS System Battery

An operational life test was performed using a 7.5 volt battery pack consisting of 5 Duracell standard "AA" cells. This battery pack lasted for 3 hours and 35 minutes before dropping to 5.15 volts during transmit. Even though the telemetry analog data was no longer accurate after this time, the tracker continued to transmit position reports until the battery voltage fell to 4.05 volts after 25 hours of operation. (Note: At 4.05 volts the RF output power is very low, however the tracker was still being received by a digipeater 10 miles away.)

BEAR-2 APRS Tracker, 7.5 Volt, 2.85 Amp-Hour
Five (5) Duracell "AA" Cell Battery Pack Performance
Initial Open Circuit Voltage 8.20 volts
Initial Voltage with 63 ma load (idle current) 7.76 volts

The BEAR-2 APRS system will use a 9.0 volt battery pack consisting of six (6) Duracell Ultra "AA" cells. The "Ultra" cells have the same 2.85 amp/hour rating as the standard copper top cells, but have a lower internal impedance which will allow them to operate longer before reaching the 5.15 volt level. To further extend the operational life of the APRS tracker, a 6th cell has been added to the battery pack to provide an additional 1.5 volts to the total battery voltage. This will allow each cell to discharge further before the total battery voltage drops to 5.15 volts. During initial transmissions this 9 volt 6 cell battery provides 8.5 volts on transmit (giving us an RF output power of 5 watts).

Based on the results of the Duracell standard "AA" 5 cell battery operational life test, little will be gained by doing an operational life test on the Duracell Ultra "AA" 6 cell battery. We are confident that either battery would provide sufficient operating time to complete the recovery of the BEAR package. The total operational life of the Duracell Ultra "AA" 6 cell battery will be determined during and after the flight of BEAR-2. Check back for the results which will be posted here.

BEAR-2 APRS Tracker, 9 Volt, 2.85 Amp-Hour
Six (6) Duracell Ultra "AA" Cell Battery Pack Performance
Initial Open Circuit Voltage 9.40 volts
Initial Voltage with 63 ma load (idle current) 9.25 volts
Initial Voltage with 1.6 amp transmitter load (4.5 watts) 8.10 volts
after 1 hour 7.40 volts
after 2 hours 6.40 volts
after 3 hours 5.90 volts
Last BEAR-2 transmission was at 4 hrs and 15 minutes.
No telemetry data is available for battery voltage at that time.

Bear-2 Cross-Band Repeater Battery

The BEAR-2 cross-band repeater will use a 9.0 volt battery pack consisting of six (6) Duracell "C" cells. These cells have a 7.8 amp-hour rating. The initial RF output power will be about 2.7 watts.

BEAR-2 Cross-Band Repeater, 9 Volt, 7.8 Amp-Hour
Six (6) Duracell "C" Cell Battery Pack Performance
Initial Open Circuit Voltage 9.55 volts
Initial Voltage with 54 ma load (receiver squelched) 9.30 volts
Initial Voltage with 0.97 amp load (transmitting - 2.7 watts) 8.30 volts



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