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[aprssig] Re: Anyone running APRS on a LCD in a car ?

KC2MMi kc2mmi at verizon.net
Tue Jan 24 18:19:57 UTC 2006


Tim-
 <<This is my next step after replacing the battery. It may be that the charger
in the car is not optimized for the marine deep cycle battery I am using. >>

 You'll find a lot of good information about deep cycle battery use from RV
(recreational vehicle) and marine sources. A couple of small books like "The 12
Volt Bible" commonly available, and tech FAQs from Balmar and some other marine
equipment makers.

 The differences are subtle but critical. A "12 volt" car alternator will vary
but generally never put out more than 14.4V unless the regulator is defective.
That's to prevent boiling batteries dry. Deep cycle batteries are designed to
suck a lot of power for a long time, up to 20% (wet cell) or 25% (AGM) of their
rated capacity amperage, i.e. to be charged at up to a 20A rate for a battery
rated 100AH. On the other hand car batteries--and car alternators--are a matched
pair. The car alternator is designed cheaply for a specific purpose, it puts out
enough voltage and amperage to compensate for the starter draw, and then quickly
cuts back to a near trickle charge so that many hours of operation will not
overcharge the car battery. (Oversimplifying here!) Very different scenario,
many variables and small but important differences beyond that.

The net result is that if you have a deep cycle battery hooked up in parallel to
your car battery, it may take many hours to get properly recharged. And, for
best life it should never be discharged below 30-50% of its capacity.

But since this goes way outside of APRS <G> feel free to follow up via email if
you can't find the goods on the web.





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