[TrunkCom] 250 heat issue

[Tom Swisher]

TOES1976@aol.com wrote:
> If any of you are having trouble with your 250s heating up, I would suggest 
> calling Uniden.  They shouldn't do that.  Uniden might have gotten wrong 
> chargers.  500mah instead of 200/300mah.  Unless 500mah is needed for power 
> only with the digital card installed.

The pre-production model I did an early review on for National 
Communications also came with the 500ma wall wart.

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.

 From the Maha NiMh Q&A Page:

A1: If you have a slow charger or wall adapter:

Maha NiMH battery packs will work with slow charger/wall adapter, or any 
charging method with a charging rate less than C/10 or 1/10 of battery 
capacity. Batteries can be continuously overcharged, at C/10 or lower 
charge rate. This battery also has chemical built-in reverse polarity 
protection. Also observe the following while using a wall adapter:

     * If the wall charger / trickle charger goes through the radio, be 
sure the radio is OFF during the charging.

     * If the wall charger goes DIRECTLY to the battery pack, please 
also administer the following:

           o The charge current must be less than 1/10 of the battery 
capacity. (i.e.: If your battery pack is 1800mAh, then the maximum 
charge current must not exceed 180mA)
           o The polarity of the charger connector is the same as 
labeled on the battery pack casing, or charging socket protective rubber.

While some of the info is specific to Maha NiMh packs, NiMh batteries 
themselves are pretty much the same. There's enough info there to point 
out that 500ma is most definitely more than 1/10 the battery capacity. 
Way too much. Guess I'll be building a current limiter to knock it back 
to 100 or 150ma to keep the temperature down and allow a continuous 
trickle charge.

Tom WA8PYR
-- 
-------------------------------------------------
Tom Swisher, WA8PYR	     wa8pyr@sbcglobal.net
        "They're not going to catch us...
we're on a mission from God" - Elwood Blues, 1979
  WA8PYR Radio & More - http://www.qsl.net/wa8pyr