solar help

[caddyshack]

hi,
just bought s/hand 20 watt solar panel. i need a blocking diode to combat reverse charge when dark ??. been in to radio shack shop and they say not heard of blocking diode, i explained what it was for, but assistant,though helpfull,not that technical. he thought it may be a rectifier diode ?? but not sure. can anyone help with info, please.

tom

 

[biggirafe]

this is the one I used
NEW 12V 7A SOLAR PANEL CHARGE REGULATOR CONTROLLER 84W on eBay (end time 01-Feb-10 15:01:32 GMT)

Cheap n cheerful but does the job

 

[Kontiki]

You need the charge controller which should have a blocking diode built into it. This will also prevent overcharging but I think it would be unlikely with a 20 watt panel unless we get shed loads of sun

 

[ubuntu1]

If your not sure then pop into Maplin as they sell what you need, (charge controller)

 

[Deleted member 8180]

Go to Maplin. You need a schottky diode aka blocking diode. Around 6amp. Cost you £1.50 max. I'm assuming you have a charge controller... you need one of these to keep your battery safe, most of them have a blocking diode built in. The diode stops your batteries discharging through the panel at night.

 

[jamiemumt]

By nature a diode in general "is" a block diode. It will only allow current to run in one direction, so any diode will do the job "providing its large enough to take the load.
Looks like you got the info for the one you need in the replies anyway.
Jim.

 

[Channa]

Time for me to get my unsheathed probes out perhaps

It will never work when I get me hands on it ...lifetime guarantee

Come on I has to start somewhere

Channa

 

[Deleted member 8180]

Diodes stop current flowing in one direction but at a cost - typicallly a diode will absorb around 0.7volts (forward voltage) which is significant in a 12v system. Schottky diodes have a much lower forward voltage, making the system more efficient. (I only know this 'cos I had to research for my wind/ solar setup).

 

[cntopsolar]

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Lily

 

[Nosha]

EVERY diode blocks i.e. only flows one way! So all you need is a diode that will handle the 20w max that will flow so you'll need a 2amp diode - remember that some diodes 'absorb' more power/voltage than others so you won't get the full 20w any more!!

I would suggest you run a multi-meter in line with it, then stick the panel in a box/dark and see what if any backwards current flows... as others have said you may not need one!