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From: Kevin McMurtrie
Subject: Re: Does 7808 can charge the car battery lead acid ?
User-Agent: MT-NewsWatcher/3.2 (PPC Mac OS X)
Date: Tue, 17 Dec 2002 07:04:47 GMT
NNTP-Posting-Date: Mon, 16 Dec 2002 23:04:47 PST
In article <3DFEA1B9.38A58933@fanwap.com>, Tong Narak
>I would like to charge car battery at 1A.
>I always park the car for many weeks and it completely dead.
>Does 7808 connect as current regulator at 1A work ?
>one resistor 8 ohm ( 8v / 8 ohm = 1A )
>and one 1.5A 12V transformer.
You want a voltage, not a current, regulator.
You can buy a 13.8V regulated power supply at Radio Shack. Some
electronics stores also sell mini switching power supplies that are
adjustable from 12 to 16 volts. 300mA or more is good.
The voltage you'll want is about 13.8 volts. Do a Google search for
lead acid float charging voltage vs. temperature if the car will in the
cold or heat.
You will need to add a resistor if the regulator doesn't self-limit its
current output. The three-pin regulators and most good switching power
supplies do self-limit.
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