Choosing a Diode for 12V Battery Charger: Tips and Recommendations

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When selecting a diode for a 12V battery charger, it's crucial to protect the circuitry from reverse voltage that could damage components like the LM338 voltage regulator. The 1N5408 diode was suggested, but it is rated for only 3 amps, which may not be sufficient for a maximum charge current of 5A. A common protection method involves using a 1N4007 diode from the output to the input of the regulator to prevent excessive voltage. Additionally, heat management is essential, as a 5A load can generate significant heat; alternatives like the FMB-G24H diode can help reduce this issue. Proper diode selection and heat management are key to ensuring the longevity and reliability of the battery charger circuit.
Hylton Conacher
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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.

Regards
Hylton
 
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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.
 
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Drakkith said:
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.

Tnx Drakkith, all understood.
 
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

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

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