Date: 16 Nov 88 16:47:25 GMT x-------------- CUT HERE --------------------------------------x - 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 - x-------------- CUT HERE --------------------------------------x Bob Parnass AJ9S, AT&T Bell Laboratories - att!ihuxz!parnass - (312)979-5414