Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!usc!zaphod.mps.ohio-state.edu!ncar!umigw!mthvax!wb8foz
From: wb8foz@mthvax.cs.miami.edu (David Lesher)
Newsgroups: sci.electronics
Subject: Re: Why can't I run my radio with the charger plugged in?
Message-ID: <1990Aug30.220304.24565@mthvax.cs.miami.edu>
Date: 30 Aug 90 22:03:04 GMT
References: <1990Aug30.131140.20946@phri.nyu.edu>
Reply-To: wb8foz@mthvax.cs.miami.edu (David Lesher)
Organization: NRK Clinic for habitual NetNews abusers
Lines: 35

In <1990Aug30.131140.20946@phri.nyu.edu> roy@alanine.phri.nyu.edu (Roy Smith) writes:


>	I just bought an ICOM M-11 handheld VHF tranciever.  It comes with
>a removeable NiCd battery pack and a 110V recharger.  The manual says you
>can charge the battery pack while it is still attached to the radio, but
>you should make sure the radio is off because you might damage it.  Can
>anybody think of any good reason why you shouldn't be able to run it while
>plugged in?

Well, it's like this.
Icom wanted a battery that made 14 volts in order to get the
transmitter power up. But they ALSO wanted it to be rechargeable
from a car's (roughly) 13.8 volt source.

So when you plug in the charger, or 13.8 volts to the top of the
radio, a little teeny-tiny relay inside the pack opens and
splits the battery string into two 7 volt strings. THEN two
transistors provide individual charging current regulation to
the strings. There are also about 9 diodes inside there, too.

So with the charger plugged in, you get ~~7 volts from the pack.
The radio is unhappy with this.

When this mess fails, you take apart the pack, and try to fix
it. Then you give up, hardwire the pack to be 14 volts (no
relay) and build a drop-in 14 volt charger. 

You can guess (;,} how I know all of this........

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