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From: John Larkin
Subject: Re: Charging a battery from a car battery
Date: Mon, 02 Dec 2002 19:23:36 -0800
Organization: Posted via Supernews, http://www.supernews.com
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On Tue, 03 Dec 2002 00:22:15 -0200, Bruce Douglas
>I am trying to make a battery charger for charging my sealed lead
>batteries from a car on occasions when I am away from mains power.
>I am concerned with limiting the current when a depleted battery is
>put on charge.
>I had been intending to use a LM317 set up as a current regulator but
>am concerned that this will drop the voltage to the battery too much
>(I believe the battery in charge needs to see the full 13.6 or so
>Is there any way to limit the current from the car system without
>dropping the voltage available? Or would I have to boost the car
>voltage first with a switching supply so I could have the voltage
>necessary to use a 317 or series transistor?
A 6-volt light bulb is a nice nonlinear curent-limiting resistor. A
free charge-rate indicator, too.
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