|
|
|
|
|
Saturday, January 11, 2003
BC250D Battery Charging "Problem" [Source: David Sterrett] (Originally posted to the UnidenBC250D Yahoo! Group)  EVERY portable scanner that I have owned does NOT have any overcharge protection and I've owned many over the years. My gut feeling is the BC250D is no different from how Uniden has done things before.The battery charge circuit in all but a few handheld scanners is simply a power resistor in series between the AC adapter input and the battery pack (constant voltage method). The few exceptions are the old BC200xlt and BC250xlt where the charger plugs into the battery pack and charge current is limited using a linear voltage regulator wired up to operate as a current regulator (constant current method). Both of these battery charging circuits work fine for NiCd and NiMH charging at the standard 14-16 hour rate. It's the old simple low-tech force-feed approach to charging the battery pack. The two drawbacks are that the circuit doesn't have any way to automatically turn off when the battery is fully charged and some power is dissipated in the charging circuit as heat. It's inefficient but it works. It's simplest, lowest cost, and most reliable of battery charging circuits. I received my BC250D yesterday (Friday 1/10) and I've noticed the same thing where the radio appears to get a bit warm during charging. I've already used mine enough to need charging. The heat produced appears to be from the low-tech battery charge circuit in the radio, not the battery pack heating up. The warning in the owner's manual about overcharging is also a clue that it uses a simple "dumb" charging circuit. The standard 14-16 hour rate is the fastest that the battery can be safely charged without needing circuitry to automatically turn off the charge circuit. However, it is recommended that the charge time not exceed 24-48 hours to avoid the long-term effects of cooking the battery. The 14-16 hour figure comes from the fact that the charge time is actually based on a 10-hour charge rate (C/10), assuming the energy conversion is 100% efficient. But given that the energy conversion is less than 100% (actually somewhere around 67%), the intentional 40-60% overcharge is added to ensure that all cells in the battery pack are fully charged and charged evenly. Like others have said, overcharging once in a while won't cook the battery pack, but don't make a habit of it. Just be aware of it and don't worry about it. With cell phones and other portable equipment all having "smart" battery charging circuits, you would think that Uniden would have used a smarter battery charge circuit. It would be nice to have the battery pack rapid charge to 80% in 2-3 hours, and then automatically go into a low current "trickle" charge mode to top off the charge. In the trickle charge mode, the charging can be left on for days, even weeks and months without damaging the battery pack. It looks like Uniden chose the simple low-tech approach, probably because this is how they've done it before and they may be under a lot of pressure to hold the line on costs. Stop worrying and enjoy the BC250D! David Sterrett Nashua, NH Ham callsign = N1DAS GMRS callsign = KAE9013 Sunday, January 05, 2003
Ventura County's Newest American LaFrance Eagle Pumper [Source: American LaFrance]  The addition of this Eagle places 15 total American LaFrance units in service with Ventura County. Truck Specifications: Chassis – Eagle 134” Flat Roof, 4-door Aluminum Cab Wheelbase - 175” Travel Height – 114” Travel Length – 28’-6” Seating Capacity – 6-Person Front Axle / Susp. – Meritor FL-943, Taperleaf Spring rated @ 18,000 lbs. Rear Axle / Susp. – Meritor RS-23-161, Flatleaf Spring rated @ 24,000 lbs. Engine – Detroit Diesel Series 60 rated @ 430 HP, 1550 lb/ft. Transmission – Allison HD-4060P 5-speed Automatic Fire Pump – Waterous CSU single-stage 1500 GPM Booster Tank –UPF 500 Water & 30 Foam Polypropylene Gauges – Class 1 & Fire Commander Body Material – Extruded Aluminum Compartment Configuration – Side Mount Controls, LH/RH Highsides Lighting – Code3 Strobe and Halogen, (2) Churchville 70W Floods Additional – Foam Pro-2001 |