[usa2003ardf] Re: Batteries

[Homingin at aol.com]

Non-rechargeable batteries definitely are an option.  One of my sealed 
lead-acids (SLAs) got "flaky" a while back, so I tried using two 6V lantern 
batteries in series in that fox for the last local 2m radio-orienteering session.  
These were "heavy duty" Ray-O-Vac #944, (not alkaline), which I found for about 
three bucks each at the local building supply store.  I think each one is the 
equivalent of four D-cells in one package, and it's certainly easier to solder 
in the spring terminals on a couple of lantern batteries than to find a way to 
install 8 D-cells.  Weight of the two lantern batteries is slightly less than 
a 4 Ah SLA.

The lantern batteries worked great.  After a 4-hour hunt, they were going 
strong.  I just checked the open-circuit terminal voltage of the used pair and 
it's 12.35 V, maybe I can get another hunt or two out of them.

For "important" events in the future, I'll probably use lantern batteries in 
all my foxes, just so I won't worry about another suddenly-flaky SLA.  It 
might even be possible to have a two-day event without needing a marathon charging 
session on the first night.

Regarding recharging, WB6BYU wrote:
<<The simple solution is to float them across a power supply set to 13.8V.  
This doesn't get them to full charge, but you can't hurt them by leaving them 
on too long.>>

Most SLAs are designed for continuous "float" at 13.8, but you can charge 
them at fixed 14.4 volts (with current limiting to about 1C) to get a more 
complete charge if you use care to disconnect the charger when charge is complete.  
That's what I do.

Some SLAs use different chemistry (more calcium?) and will take an even 
higher voltage charge.  Check the Web site for the brand of batteries you're using 
to get specific recommendations for "constant voltage" charging.

Regarding heat sinking, WB6BYU wrote:
<<I think Joe Moell uses the larger ammo boxes and has the whole circuit 
mounted to the lid (which is removable).  You probably could arrange to heat sink 
the radio to the lid and/or box also.

Yes, that's what I did on two meters.  The output transistor studs are 
mounted to the lid.  No heat problems at all, though one could argue that this would 
not be a good scheme if the box were placed out in direct sun.

73,
Joe Moell K0OV