Which blocking diode to get?

[zcapozzi]

Hi all,

I picked up a diode for blocking the flow of electricity from the battery to the panels at night, and I wanted to make sure that I had an appropriate one. The battery is 12V and the panel is 100W/ 12V. I grabbed a diode with 50V Peak inverse voltage which I would think is more than enough to block my 12 V (or up to 20 if the peak panel to battery flow ever were reversed at night). It's got a 1.6V forward voltage drop and 1A forward current. Max surge current is 30A which again should be more than enough.

Any issues with this setup. And second question, do you really just wire this thing in series between the panel and the battery? I assume it doesn't matter which wire it goes on? Also, if this thing is going to rob me of 1.6 volts when the panel is working, is that really worth blocking the flow of electricity at night. I mean, that's 5-10 percent of my output. Am I really losing that much at night?

Thanks in advance.

[Naptown]

Almost all charge controllers which would be necessary with that panel will have the blocking diode built in and will disconnect from the panel at night

[green]

Also, if this thing is going to rob me of 1.6 volts when the panel is working, is that really worth blocking the flow of electricity at night. I mean, that's 5-10 percent of my output. Am I really losing that much at night?

It's not just about "losing" anything at night, it's about cooking your panel. When a battery is hooked directly to a panel the battery will push electricity through the panel and fry it if the battery is large enough. In a small setup like a landscape light with a small battery and panel, a diode is plenty to control the flow. In a larger system like your 100W panel, a charge controller is necessary not only to control flow from the battery back into the panel but also to make sure the panel doesn't overcharge the battery.

I hope this helps

[Joe_B]

Please post the number of your diode. You want a Schottkey type to minimize forward voltage drop.

[zcapozzi]

Please post the number of your diode. You want a Schottkey type to minimize forward voltage drop.

I didn't realize that the charge controller already has it built in. Probably should have thought of that. I have a Morningstar Sunsaver 10A/12V, which I'm assuming will cover me. If not, the diode is a IN4001 (50V - 1A). But again, I assume the charge controller will handle this for me (anybody want to buy a blocking diode, haha, kidding of course).

Thanks all.

- Zack

[Joe_B]

I think you are all set but just for the groups information, the 1N4001 is not a schottkey type and thus has a 0.6V forward drop. A Schottkey type will typically have half the drop or 0.3V at the same forward current. The issue with schottkeys is that they typically are limited to about 50V reverse voltage where the standard silicon can go up to hundreds of volts in the reverse direction.