Simplex Operations and Equipment
Batteries
It is basic to emergency operation that stations have sufficient batteries or other auxiliary power to operate for at least 24 hours.
One amp-hour per watt of RF output power in battery capacity is the minimum recommended. "Barefoot" HT operators need at least a pair of 12-volt, 2ah gel cell batteries, extra NiCd pack, AA battery case, plus a gain antenna such as a telescoping half-wave, "tiger tail" counterpoise, a mobile mag-mount or wind-up J-pole.
Powering a mobile rig from the car battery works OK for only a few hours.
It is wasteful of scarce gasoline in a real emergency to run the engine for 10 minutes out of every hour to keep the battery charged, when there may not be electricity to run the pumps!
A better technical solution is to equip a vehicle with dual batteries and an isolator obtained from a boating or RV supplier so that both batteries are charged by the vehicle alternator, but isolated when discharging.
If the vehicle is not driven regularly, connect solar panels equal to 1.5% to 2% of the battery capacity to maintain the battery banks against self-discharge when the vehicle is idle. If the solar panels don't exceed 2% of battery capacity, they are self-regulating and no charge controller is then needed.
A lower-cost option is to carry a boxed deep cycle battery and automatic, low amperage AC charger such as a Schumacher Electric Mod. SE-I-12S (WalMart, $29).
Despite their popularity, gel cells are not "the answer" because they are not deep cycle and depth of discharge over 25% significantly reduces their life!
They are unusable below -20 degrees C, in the engine compartments of vehicles or other uses subject to temperatures above 50 degrees C. Gel cells must never be charged at over 14 volts or with unregulated current exceeding 1/10 of their capacity. Gel cells larger than 10 amp/hours can be left continually on an automatic, low amperage charger without harm, but should not be allowed to "float" endlessly without shut-off.
For portable operations requiring movement in support of SAR or wildfire suppression, a 15-18ah gel battery such as those used in fire alarm panels and emergency lighting fit in a brief- case or backpack and power a 5w HT, laptop, GPS and TNC all day. Better for extended "portable ops" is a Group UI 33ahAGM battery, used in wheel chairs.
These weigh 25 pounds, fit in a military .50 cal. steel ammunition and run a 25w mobile or laptop, TNC and separate voice and data HTs all day. Two UI's power a dual-band mobile on 10w cross-band repeat for 48 hours. For continuous operation, alternate between two batteries, recharging in 8-hour rotations. If unable to recharge, the primary net control needs a BCI Group 27 (95 ah) battery to go around the clock at 25w with a decent antenna.
Flooded batteries are cheap and plentiful…
However, they must be boxed, stored upright and lose half of their capacity below freezing. Delco-Voyager or GNB-Stowaway sealed-flooded, deep-cycle/RV batteries with recombinant caps give acceptable service at low cost. In Group 27 size they are $79 with a trade-in at Wal-Mart or K-Mart.
Better, for severe service, high vibration, extreme temperature environments are valve regulated AGM batteries used in military or public safety vehicles and by the US Coast Guard.
A Group 27 Concorde Lifeline (65lbs., $199) has aircraft-type cell construction and is UPS shippable from West Marine, (1-800-BOATING). It can power a 100w HF rig through Field Day! Lifeline batteries come in the small U1 size as well as the popular Group 24, 27 and 30 marine sizes and for commercial use to 255 ah.
The usual failure mode of dry NiCds in hand held transceivers is not "memory" effect, but either deep discharge causing cell reversal or diminished capacity caused by excessive charge current or prolonged slow over charging.
Safely charge dry NiCds using rated voltage + 15% to overcome internal resistance, at current equaling 10% of the battery capacity, times ten hours.