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The goal posts are moving in this argument.
Initially, I said that if you attach a panel to a battery in the dark, nothing happens. You started talking about daylight conditions, as if that answered my darkness statement. I have attached a 12V panel to a 12V battery in the dark, and nothing much happens. Mike said that a diode represents an unacceptable overhead... it does in a 12V system, where it would subtract 1V (or 7%). However, in higher voltage systems, a diode would not cause unreasonable voltage loss.
Now, you've made a implied statement about a higher voltage array (48V) causing reverse bias breakdown of lower voltage panels. I'll admit that panels, like all diodes have a reverse bias breakdown. However, the information I have found, suggests that a single silicon photocell has a reverse breakdown voltage of 60V-35V, which suggests that the maximum voltage recommendations for series-rigged cells of around 1000V, is based around a conservative estimate of the reverse breakdown voltage of a single panel.
Given that panels have bypass diodes, I still haven't figured out what conditions require a blocking diode.
Silicon cells have a typical breakdown voltage of approximately 60V with a minimum of approximately 35V. Gallium arsenide cells have a much lower breakdown voltage, nominally 5V and as low as 1V, and hence are more susceptible to damage. The Advanced "III-V" cells can break down at even lower voltages.
Have you actually done this anecdotal experiment of attaching a panel to 48V?
Initially, I said that if you attach a panel to a battery in the dark, nothing happens. You started talking about daylight conditions, as if that answered my darkness statement. I have attached a 12V panel to a 12V battery in the dark, and nothing much happens. Mike said that a diode represents an unacceptable overhead... it does in a 12V system, where it would subtract 1V (or 7%). However, in higher voltage systems, a diode would not cause unreasonable voltage loss.
Now, you've made a implied statement about a higher voltage array (48V) causing reverse bias breakdown of lower voltage panels. I'll admit that panels, like all diodes have a reverse bias breakdown. However, the information I have found, suggests that a single silicon photocell has a reverse breakdown voltage of 60V-35V, which suggests that the maximum voltage recommendations for series-rigged cells of around 1000V, is based around a conservative estimate of the reverse breakdown voltage of a single panel.
Given that panels have bypass diodes, I still haven't figured out what conditions require a blocking diode.
Silicon cells have a typical breakdown voltage of approximately 60V with a minimum of approximately 35V. Gallium arsenide cells have a much lower breakdown voltage, nominally 5V and as low as 1V, and hence are more susceptible to damage. The Advanced "III-V" cells can break down at even lower voltages.
Have you actually done this anecdotal experiment of attaching a panel to 48V?
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