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help me pick out the right type of diode

Jake Hoffman

Nov 27, 2016
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Greetings everybody!

I have large array of SLA batterys wired in parallel to a buss bar. I don't want one battery that drops in voltage severely to be able to drain the other batterys so I am looking for the right diode to isolate them from each other. They are not being charged from this buss bar, only discharged.

How do I find the right diode (type and size) for the job.

Thanks

Jake
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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I cannot imagine any diode circuit that would prevent a bank of paralleled SLA batteries from discharging into one with lower than the average terminal voltages of the remaining batteries. Show us a schematic of what you have in mind before going off on a quest to find "the right diode (type and size) for the job."
 

BobK

Jan 5, 2010
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Hop,

I know he did not say this, but I think he is talking about a diode between the + terminal and the bus bar, so the batteries are paralleled only through the diode, which is a common enough circuit.

The diode needs to handle the full current you expect on the load, and, depending on how high that is, might need to be heatsinked. Schottky diodes are a little better for this since they have a lower voltage drop and therefore dissipate less heat at the same power.

Bob
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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Thanks, Bob. For some reason (senility?) I didn't even think about using isolation diodes in series with each battery. That's a pretty good solution if you don't mind the power waste under load. As you said, the OP needs to know the full load current, and should probably use a Schottky power diode to minimize forward conduction power losses under load. And of course the reverse voltage specification of the diode should exceed the battery terminal voltage. The OP needs to provide more information about battery voltage and maximum load current. Cree makes some high power silicon carbide Schottky diodes, so I would look there first.
 
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