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1993-01-14
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- 1 -
BATTERY CONSUMPTION OF THE
UNIDEN/BEARCAT 200XLT SCANNER
by Bob Parnass, AJ9S
The Uniden/Bearcat 100XLT and 200XLT scanners are the
first portable scanners with enclosed, slide on battery
packs. Some 200XLT owners don't get the battery life
they expect. They report having to recharge the slide on
NiCd (Nickel Cadmium) battery pack after as few as only
3-1/2 hours of operation. Owners expect the battery pack
to last longer, at least the 5 hours mentioned in the
documentation supplied with the radio.
Much has been written about NiCd battery characteristics
and charging in general. This article will not rehash
general NiCd charging techniques. Rather, we will
analyze the current consumption of the Uniden/Bearcat
200XLT scanner, and make recommendations specific to that
radio.
BP-200 Battery Pack
The BP-200 battery case contains six Sanyo 600 mAh NiCd
cells soldered in series configuration and wrapped in
heat shrunk plastic. This pack furnishes 7.2 VDC to the
radio. A charging regulator circuit and a light emitting
diode are also contained within the battery case.
In contrast to the Yaesu FT-23R 2 meter walkie-talkie,
which is supplied with a wall-mounted charger, the 200XLT
wall-mount unit is actually a 12 VDC power supply. Since
the BP-200 regulator circuitry is contained within the
battery case, 200XLT owners cannot easily opt for rapid
or trickle chargers.
Measurements and Their Implications
The 200XLT's current drain was measured under several
conditions, and a graph appears later in this paper.
Tests show that the 200XLT consumes more current on
higher bands than it does on lower bands. For instance,
listening on the 870 MHz band takes 13 mA more current
compared with the vhf-lo band.
Measurements indicate that 200XLT current consumption is
independent of scanning, searching, or manual modes, pro-
vided the scanning or searching is within the same band.
This implies:
- 2 -
o If you must monitor 870 MHz frequencies for a pro-
longed period, it is more "battery-wise" to scan a
mixture of 870 MHz and low band channels.
Several factors can contribute to "shortened" battery
life. Shortened recharge intervals will be needed if
using the radio with the volume control at a loud set-
ting. In portable receivers, the audio amplifier stage
generally consumes more current than any other stage.
The 200XLT has a more powerful, cleaner audio output
stage than do other portable scanners.
The factory supplied earphone is inconvenient and uncom-
fortable, but test results prove:
o Using the earphone decreases current consumption.
Using an earphone saves about 14 mA indoors, and about 50
mA in noisy situations where one might have the volume
control set at maximum.
When using an earphone with the test radio, the best
volume control setting was at the 10 o'clock position,
versus 12 o'clock when using the internal speaker.
Listening to "busy" channels generally consumes more
current than listening to infrequently used channels.
One surprising exception, borne out by test results, is
that:
o When using an earphone (at 10 o'clock volume set-
ting), listening to busy channels actually consumes
less current than when the 200XLT is fully squel-
ched!
Improper battery charging can require the battery be
charged more often than normal. If the battery indicator
on the 200XLT's panel flashes, charge the battery pack
for a full 16 hours. Test results showed:
o The low battery indicator flashes when battery vol-
tage falls to 7.2 volts or less.
The 200 memory channels in the 200XLT are backed up by a
capacitor kept charged by the NiCd battery pack. Current
is required to retain the memory information, even when
the radio is turned off.
How much battery drain is due to maintaining the memory
information? To answer this question, the author
measured the current required to backup the memory in the
- 3 -
200XLT. A Fluke 8024B digital multimeter indicated that:
o The 200XLT draws about 0.50 mA with the power
switched off.
The six cell Sanyo NiCd pack is rated for 600 mAh capa-
city. If the batteries were perfect, and had infinite
shelf life, the memory backup would drain a fully charged
battery flat in 50 days:
600 mAh / 0.50 mA = 1200 hours
= 50 days
But no NiCd battery is perfect -- all have a finite shelf
life. NiCd batteries will discharge by themselves,
through spontaneous chemical decomposition, even when not
connected to a load. The General Electric Company indi-
cates that the average NiCd will lose about 1% of its
capacity per day at 70 degrees F.
The author developed a discrete time computer simulation
which shows that:
o The cumulative effects of self discharge, combined
with 0.50 mA drain due to memory backup, will
deplete a fully charged 200XLT battery pack in about
40 days.
A plot of the predicted daily decrease in battery capa-
city appears elsewhere in this article. The plot indi-
cates that:
o To get the most use between recharges, charge your
200XLT right before using it. If you charge your
200XLT battery, but then leave it in a drawer for a
week, you will have already lost 20% of the opera-
ting time before the next recharge is required.
Average self discharge at 100 degrees is about double (2%
per day) the discharge at 70 degrees, which is a good
reason to avoid storing NiCd batteries in a warm automo-
bile. At 100 degrees, it only takes about 34 days to
deplete the 200XLT battery.
These Recommendations Can
Work For You
By using his 200XLT right after charging its battery for
16 hours, Mr. Ron Smithberg reported he is now getting
6-1/2 hours use on a charge instead of the 3-1/2 hours he
- 4 -
got previously.
References
1. Parnass, Bob, AJ9S, "Uniden/Bearcat 200XLT Scanner
Review," RCMA Newsletter. October 1988.
2. Nickel-Cadmium Battery Application Engineering
Handbook, Second Edition, General Electric Company,
Battery Business Department. P.O. Box 861,
Gainesville, FL 32602. Copyright 1975. pp 7-14,
7-15.
For further information on NiCd batteries, see:
- The ARRL Handbook for the Radio Amateur, 65th Edi-
tion. The American Radio Relay League, Newington,
CT. Copyright 1988. ISBN 0-87259-065-8. pp 6-25,
6-26, 6-27, 6-28.
- Meyer, Budd, K2PMA, "Charge It! Your NiCad, That
Is," QST, March 1977. pp 29-31.
- Meyer, Budd, K2PMA, "Nickel-Cadmium Pandemonium,"
QST, March 1982. pp 32-34.
- 5 -
______________________________________________________
| Additional Current Consumed by Uniden/Bearcat 200XLT|
| Per Band Over VHF-lo Band |
| |
| Band Additional Current (mA) |
|_____________________________________________________|
| VHF-hi 1 |
| UHF 5 |
| 870 13 |
|_____________________________________________________|
_________________________________________________________________________
| Uniden/Bearcat 200XLT Scanner Current Consumption |
| Measured Under Various Operating Conditions |
| |
|Condition Measured Current Consumption (mA) |
|___________________________|___________________________________________|
|sqlch closed vhf-lo | 49 *************** |
|sqlch closed vhf-hi | 50 *************** |
|sqlch closed uhf | 54 **************** |
|sqlch closed 870 | 62 ******************* |
| | |
|sqlch open 10oclock vhf-lo | 48 *************** |
|sqlch open 10oclock vhf-hi | 49 *************** |
|sqlch open 10oclock uhf | 53 **************** |
|sqlch open 10oclock 870 | 61 ******************* |
| | |
|sqlch open 11oclock vhf-lo | 57 ***************** |
|sqlch open 11oclock vhf-hi | 58 ****************** |
|sqlch open 11oclock uhf | 61 ******************* |
|sqlch open 11oclock 870 | 69 ********************* |
| | |
|sqlch open 12oclock vhf-lo | 64 ******************** |
|sqlch open 12oclock vhf-hi | 65 ******************** |
|sqlch open 12oclock uhf | 68 ********************* |
|sqlch open 12oclock 870 | 76 *********************** |
| | |
|sqlch open full vol vhf-lo | 99 ****************************** |
|sqlch open full vol vhf-hi | 100 ******************************* |
|sqlch open full vol vhf-uhf| 104 ******************************** |
|sqlch open full vol vhf-870| 112 ***********************************|
|___________________________|___________________________________________|
- 6 -
_______________________________________________________
| Predicted Shelf Life of Uniden/Bearcat BP-200 Battery|
| Battery Pack While Connected to 200XLT Scanner |
| |
| Day % of Original Capacity Remaining At End of Day |
|____|_________________________________________________|
| 1 | 97% *********************************** |
| 2 | 94% ********************************* |
| 3 | 91% ******************************** |
| 4 | 88% ******************************* |
| 5 | 85% ****************************** |
| 6 | 83% ***************************** |
| 7 | 80% **************************** |
| 8 | 77% *************************** |
| 9 | 74% ************************** |
| 10 | 72% ************************* |
| 11 | 69% ************************ |
| 12 | 66% *********************** |
| 13 | 64% *********************** |
| 14 | 61% ********************** |
| 15 | 58% ******************** |
| 16 | 56% ******************** |
| 17 | 53% ******************* |
| 18 | 51% ****************** |
| 19 | 48% ***************** |
| 20 | 46% **************** |
| 21 | 43% *************** |
| 22 | 41% ************** |
| 23 | 38% ************* |
| 24 | 36% ************ |
| 25 | 34% ************ |
| 26 | 31% *********** |
| 27 | 29% ********** |
| 28 | 27% ********* |
| 29 | 25% ********* |
| 30 | 22% ******* |
| 31 | 20% ******* |
| 32 | 18% ****** |
| 33 | 16% ***** |
| 34 | 14% ***** |
| 35 | 12% **** |
| 36 | 10% *** |
| 37 | 7% ** |
| 38 | 5% * |
| 39 | 3% * |
| 40 | 1% |
|____|_________________________________________________|
- 7 -
Computer model based on these assumptions:
1. A new battery, fully charged to 600 milliampere-
hour capacity at start of day 1.
2. Continuous drain of 0.50 mA to retain 200XLT
memory.
3. Ambient temperature 70 degrees F.
- 8 -
