Question about diodes.


Old 05-28-14, 05:04 AM
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Question about diodes.

Hello Everyone

I have a question about diodes.

I currently have a 100 watt panel and 2 10 watt panels on the roof that supplies my batteries with about 5.6 amps of power currently at peak, we are in winter here, in Summer the amps are around 7.

As I will need to add panels to my set up in the near future, hence my question, as I am not too sure about diodes and their stated amp rating what they can and cannot do.

On my 100 watt panel I have a 10 amp diode. On the 10 watt panels I have 6 amp diodes.

If I was to upgrade the system ie add more panels, would I have to take all the diodes out and replace them with diodes rated at a higher amp rating rating, as the incoming amps rise to say 30 amps or more.

If a diode is rated at say 10 amps is 10 amp the max pass through current or is 10 amp the max current that diode will stop.

Thank you for time and answering my question it is much appreciated
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Old 05-28-14, 05:48 AM
Join Date: Mar 2010
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So long as each panel has its own diode, that diode needs to have an amperes rating at least as great as the maximum number of amperes (pass through current) the panel can supply (plus a safety margin).

Stopping power for a diode is rated as "peak inverse voltage". When the panels are not in the sun and not charging, the battery will try to send power the other way through the panels (and discharge itself). So long as the circuit voltage (battery voltage) is less than the PIV, no current will flow backwards regardless of how many amperes the battery could possibly deliver.

There is also a maximum forward voltage rating. If you expand the system by installing solar panels in series, then you will need to replace diodes with new diodes whose maximum forward voltage is greater than the total voltage in the respective branch of the solar charging circuit. Each component in a circuit needs to be able to handle the maximum circuit voltage which in a system with battery and charger is the maximum charging voltage.

Last edited by AllanJ; 05-28-14 at 06:30 AM.
Old 05-28-14, 07:18 AM
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Dear AllanJ

Thank you very much for a very clear explanation and for your advice. Now that I know what I am looking at I have a better understanding of the diodes that I fitted and what they can and cannot do.

Many thanks


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