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Looking for a Diode

  1. Oct 15, 2014 #1
    Just joined and looking for information on which diode to use to protect a 12V battery charger circuitry connected to a battery. it is charging. Should the mains supply fail ie battery charger has no forward current, the battery may apply voltage and current to the circuitry damaging the LM338 voltage regulator.

    Charge current is max 5A and the trickle charge at 600mA Voltage is 13.8 V

    A friend suggested a 1N5408 but am not sure looking at data sheet.

    Help appreciated.

    Last edited by a moderator: Oct 15, 2014
  2. jcsd
  3. Oct 15, 2014 #2


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    Thread moved and title changed to fit the topic.
    Hylton, I also removed the link to your personal e-mail. I believe it is against the rules to have personal information like this in the main forums. To easy to exploit and all, you know.
  4. Oct 15, 2014 #3
    Tnx Drakkith, all understood.
  5. Oct 15, 2014 #4


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    the 1N540x series are 3 Amp rated

    the usual way to protect a regulator is just to put a 1N4007 from the output of the reg chip to its input
    cathode to output pin. This prevents the voltage output becoming significantly higher than the input voltage

  6. Oct 16, 2014 #5
    Heat will eat you up in this application. 5 amp x 1 volt drop = 5 watts!
    Try this: FMB-G24H
    It's a bit expensive, but it will produce less heat and it's case is insulated so that you can put a dab of petrolatum (vasoline) on it and mount it on most any metal surface to shed the heat.
  7. Oct 17, 2014 #6


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    which is why I suggested the standard protection method so that there isn't a diode inline with the supply :)
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