EMC198 Battery Thoughts 1/2
To:   Emergency Communications Units - Information Bulletin 
To:   Emergency Management Agencies via Internet and Radio 
By:   Auxiliary Communications Service (ACS) of the
      California Governor's Office of Emergency Services
     
EMC198  Battery Thoughts 1/2     Release  8/23/98
     
By Paul Christensen WA6TIL
     
"Providing battery power to equipment is a function of what it is 
used for, where it is located, and what connectors are available. 
Most equipment can accept external power; the down side is the 
need for cables with specific connectors and the correct voltage. 
Where you have a choice, standardize on equipment that can run 
from the same voltages and connectors. Consider current rating, 
size, and durability when selecting connectors. Which connector 
to use can be a subject by itself
     
Rechargable batteries are economical for day-to-day operations, 
and are environmentally friendly, but consider:
     
1. Equipment in operation that is also charging batteries 
dissipates additional heat, which can degrade performance.
     
2. Nickel based rechargables tolerate deep discharging well. Lead 
based rechargables can be adversely affected by deep discharging. 
Auto batteries may be affected if discharged below 75% of their 
total capacity.
     
3. Battery packs that supply 12 volts may not fully charge from a 
car outlet even with the engine running because of diodes or 
other voltage drops within the pack.
     
4. All batteries self-discharge over time. Nickel rechargables 
tend to discharge faster (1 percent per day) so you can't just 
charge them up, and forget them.
     
5. Over charging is detrimental to most rechargable batteries, 
Some chargers prevent overcharging and some rechargable 
batteries are more tolerant of overcharging (NiHm). Lithium 
based batteries have special needs for safe recharging.
     
6. Remember that using a couple of rechargable packs just 
postpones the eventual need for external power, whether by 
recharging or by directly running from an alternate source. 
Multiple rechargable packs can compound battery maintenance 
issues as well as be a useful tool.
     
7. Batteries have internal resistance and the total amount of 
usable energy is less at higher current draws.
     
8. Low temperature typically reduces the available battery power.
     
9. Nickel and Lithium batteries typically can supply more current 
for a given size than Alkaline or Lead
     
10. Alkaline Rechargables seem to be able to supply less current 
than a comparable sized Alkaline disposable.
     
Equipment that can accept both rechargable and disposable AA or 
D batteries can be quite useful because many agencies (private 
and public) stock these sizes of alkaline batteries. The Nickel 
based rechargables provide a slightly lower overall voltage and 
are used for day-to-day operation. A stock of disposables 
(because of their long shelf life) can be kept nearby in case an 
emergency runs longer than your rechargables do."
     
Continues in part 2, next week
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EOM