[TrunkCom] 250 heat issue

[Tom Swisher]

STUDIODED@aol.com wrote:

>> The included pack is a NiMh pack, and 500ma would be charging at the C/3
>> rate. I don't recall the exact specs for NiMh batteries, but getting
>> this warm is not a good thing.
> 
> Tom and the group, I remember reading somewhere that the current limiter 
> inside the scanner (there should be one) cuts down the current going to 
> the battery pack to 200ma. I believe Uniden used a 500ma wal-wart to 
> supply enough current to charge the battery WHILE USING the scanner. I'm 
> not sure what the current draw is but I'm sure it's more than the BC-245 
> especially with the BCi25D card installed.

That's right. The scanner has a 5vdc regulator inside; when pumping 12v 
into the thing, all the extra power is dissipated as heat. I don't 
recall if the thing is configured as a constant-current or 
constant-voltage charger, but I suspect it's constant-voltage. I would 
not be surprised if there is a current limiting resistor in there also.

The regulator needs a minimum of about 6.2v to work properly; a 6v 
wallwart would sort of work, but the ideal would be around 6.5 to 7v to 
perform the needed charging with a minimum of heat generation.

Tom WA8PYR
-- 
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Tom Swisher, WA8PYR	     wa8pyr@sbcglobal.net
        "They're not going to catch us...
we're on a mission from God" - Elwood Blues, 1979
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