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Re: (ET) FW: Diodes
At 02:37 PM 6/3/2008 -0400, RJ Kanary wrote:
Will there be enough forward voltage drop to prevent proper charging of
this battery? {Playing devil's advocate here.<G> }
RJ
Tim Humphrey wrote:
From radio shack pick up Catalog #: 276-1144; which is a two pack of
1N5404 3 amp diodes.
Wire both of these together in parallel in the negative (black) lead with
the band pointing towards the car side. Or in the positive (red) lead
with the band pointing towards the batt pack.
Let me add diodes don't parallel well. The diodes won't have exactly the
same forward drop so the one with the lower drop will take most of the
current, it will heat up more than its companion and as a result it will
carry more current. Repeat until diode fails. Diodes tend to fail short
before fusing so there is a good chance you could end up with one diode as
a short and the other out of circuit.
Now to the power considerations. If the two diodes were to share then at
2.5A each you get about a 0.9V drop or about 2W. At a thermal resistance
of 20 C/W that gives a 40C temperature rise at the junction. That diode
is going to be a bit warm. On the plus side you may drop the voltage enough
that you won't get anywhere near that load current.
Robert
http://www.aeolusdevelopment.com/
From the Divided by a Common Language File (Edited to protect the guilty)
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