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Fwd: Re: Re: Kenwood D7



>Date: Wed, 11 Sep 2002 14:30:50 -0800
>To: Bob Bruninga <bruninga@usna.edu>
>From: "Edward R. Cole" <al7eb@ptialaska.net>
>Subject: Re: [amsat-bb] Re: Kenwood D7
>
>My two cents:
>
>I find that many folks are not careful of Nicad charging...i.e. they run
the radio for an hour an then plug it back into the charger.  This will
lead to the famous "memory" condition where the battery will only discharge
that far.  Best to run the battery until fully discharged (1.0 v/cell)
before re-charging.  I maintain 120 commercial VHF hand held radios with a
battery inventory of 250.  Batteries are charged about every two weeks (or
less) and reconditioned around four times/year (fully discharged and
recharged using a reverse voltage pulse procedure).  The reconditioner
breaks up gas bubble build-up on the cells which interferes with charging.
Using this policy I get nearly three years usage from these 1100 mAH
Nicads.  Any battery that tests below 90% full capacity is recycled!
>
>My predecessor placed the batteries into desk chargers full-time so they
were always full-charged and ready for deployment...average life was under
six months!   So roughly 120 x $60/battery =  $7,200/year!  My replacement
cost now runs at ~30/year (= $1,800).  {since I buy in quantities >25, I
get around a 25% discounted price} 
>
>My biggest challenge it to get my folks (who are not electronic techs) to
take a spare battery!  The next chalenge is to get them to return the
batteries...They squirrel them away somewhere and months later wonder why
they went flat!  My experience is a Nicad's shelf-life is two-weeks max (if
fully charged).  New batteries may last longer but after a few discharge
cycles that is all they will hold!
>
>I believe most radio mfrs scale the battery size to provide eight-hours
usuage (per the 10% Tx/ 90% stby-RX rule).
>
>73, Ed - AL7EB
>
>At 04:36 PM 9/11/02 -0400, you wrote:
>>On Wed, 11 Sep 2002, Bruce Bostwick wrote about running the D7 for 7 Hrs:
>>
>>> > Band A draws about 35 mA, and band B about 55 mA and the TNC about 10
>>> > mA. WIth both bands running thats 90 mA and for a 600 mA battery, that
>>> > works out to about 6.6 hours.  8 AM to 3 PM is about 7 hours.  Looks
>>> > like your battery is right on spec...
>>>
>>> Depends on which type of battery it is.  If... it's a NiCd pack ... then
>>> not all of that 600mAh is going to be usable by the radio, because at
>>> some point the battery voltage will go below cutoff for that unit and
>>> the remaining charge will be unusable.
>>
>>The 600 mAH rating is determined by the point at which the voltage
>>drops below 1.1v per cell (maybe its 1.2, I don't remember for sure) when
>>discharged at the 0.1C rate, but the  radio will also work down to that
>>cell voltage too, and the dischrage of 90 mA is close to the 0.1C rate so
>>if the battery is rated at 600 mAH then it should produce 600 usable maH.
>>
>>Thats when you should turn off the radio.  One should never try to run a
>>NiCd down to get the very last bit of charge out of it (below 1 volt per
>>cell) or you will be ruining the cells in the long term...
>>
>>Bob
>>
>>
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