Arizona Emergency Net - Maricopa

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This site currently includes recordings from 2010-2012

AEN-MAR

Every Monday night, the Arizona Emergency Net – Maricopa meets on 2 meters FM for training and exercise in the public service communication arts. We focus on preparation and readiness for public service – be it scheduled events like bike races or drills, or emergencies such as storm damage or terrorist attacks. Someone has to be ready. This net is dedicated to addressing that challenge. The Arizona Emergency Net – Maricopa also activates during threats or emergencies affecting Maricopa County

12-6-2010 - Field Power - Part 1: Batteries - AK7RB

24-12-2010

The topic was " FIELD POWER - PART 1: BATTERIES"

We had 32 stations that participated in the net. We checked in by the battery power and capacity. 11 station had more than 10AH battery capacity. 15 additional stations were using battery power, and 5 were using AC power. The majority of battery operated stations were using LED flashlights as their light source.
We started with a discussion of what amp hours (AH), milli-amp hours (mAH) and watt hours (WH) means when referring to battery capacity. mAH is the same as AH/1000. If you radio pulled `X' amps average, and your battery had a capacity of "Y" AH, your battery life (to a full discharge) is Y/X hours.
For example, a radio drawing an average of 150 mA, using a 1500 mAH battery would last 1500/150 hours, or 10 hours. To convert WH to AH, Divide by the battery voltage.
We also discussed that most rechargeable batteries don't respond well to being fully discharged, so a more conservative estimate is a battery life of half the rated capacity.
We talked about the different battery chemistries being used. 2 stations used AGM, 5 used sealed lead acid, 3 used lithium ion, 6 used nickel metal hydride, 2 used Alkaline. Two new battery chemistries were in use, Nickel Zinc and Lithium ferrous phosphate.
Correct charging was discussed. Be sure to use a charger matched to the size and chemistry of your battery. Explosion, fire, or damage could result if the wrong charger is used.
We discussed estimating how long your battery will last in a typical net situation. The estimate we use is to have six 30 second transmissions per hour (for a total of 3 minutes), and receiving for the remaining 57 minutes. Assuming an active net, there is no idle time. So, from your owner's manual, look up the average transmit and receive currents for your radio (TX and RX), then use the following equation to calculate the current that would be used in 1 hour:
TX * 3minutes/60minutes + RX * 57minutes/60minutes = radios AH requirements
For example, a Yaesu FT60 has a TX current is 1.5A at 5 Watts, and a RX current of 0.125A, so the radio uses 1.5*3/60+.125*57/60 = .194A of current in an hour, or 194mAH.
A spread sheet on the website www.aen-mar.org/files titled AEN-MAR Battery and Charger Sizing Utilities.xls lets you plug in numbers for your radios to calculate battery needs and how long your radio will last in given situations.
Additional web sites with battery information are:
http://batteryuniversity.com/ and an article titled "Batteries in a portable world" at http://www.buchmann.ca/part1.asp

I want to thank Mark, W7AYU, for volunteering as Alternate Net Control.

The topic next week is "Field Power part 2 – after batteries". Net control will be Andrew KF7CCC, with alternate net control Mark, W7AYU.

73's AK7RB
Kelly
Net Control

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