blocking diode

[billi]

Hi

I need to put one or more Blocking Diodes in between the Battery and my windturbine  so no power can  flow towards the turbine and its dump

So am i right that the diode is placed just in line with the positive wire ?   and the threaded connection faces towards battery



Problem is my wire is 70 mm2     and that tiny diode  a bit small , but i could use 3 or 4 in parallel and connect to a bus bar  to achieve  a biger diameter at the connection  

Any ideas

Thanks Billi

[johnrae]

Ideally you should have provided the part number but I can just see the symbol which suggests the cathode is the screwed stud.  However I do not fully understand what you mean when you say battery power goes towards the turbine and its dump.

Could you perhaps provide a sketch of your intent so's a definitive (and hopefully correct) answer can be given.

[billi]

Thanks John

My turbines controller has a dumpelement connected that starts dumping at say 29 volt ,

Also there are 4 kw of PV  but much better controllers that charge with temperatur sensors   and reach  charge voltage upto 31 Volt

I do not want to allow that power from the PV is dumped  there at 29 volt as well at the turbines controller and burn out the 2 kw dumpelement

So thats why the diodes 

Thanks Billi

[johnrae]

Remember that you will lose about 0.7 volts across the diodes so you need to account for that when setting up your turbine charge controller  ie battery + 0.7 volts

[Antman]

Billi

In the diode shown, current will flow from the tag (top right) to the stud (nut) end and johnrae has said.

I am also slightly confused but I think it may result from a typo in the original post.

Did you mean "...so now power power can flow towards the turbine and its dump" or "...so no current can flow towards the turbine and its dump" ? I suspect that the "w" makes a difference which way round the diode is fitted.

I admit to not being involved in wind power but my observation/question would be that if you have two charge sources, one at 29V the other 31V, the 31V will always dominate. Thus the wind will not contibute anything if the PV is generating and holding the batteries at a higher voltage than the wind charge controller will allow.
Also how doe the wind charge  controller sense the battery voltage? It is possible that by blocking the battery with a diode you could also block the voltage sensing on the controller.

Ignore me if I have the wrong end of the stick!

Regards
Antman

[billi]

Hi Antman   you are right  " no Power can flow to the turbine "  is the idea  

I admit to not being involved in wind power but my observation/question would be that if you have two charge sources, one at 29V the other 31V, the 31V will always dominate. Thus the wind will not contibute anything if the PV is generating and holding the batteries at a higher voltage than the wind charge controller will allow.

I do not use the dump element at the wind turbine  , because of this reason  Antman
I have a AC heater that  i  use  and is switched on by my inverter at say 30 Volt and  Wind is then dumped in my house,  as well as some PV   and this holds the Windturbine  as well

But now  i would like to run a GTI (MPPT range 10.5-30 Volt )in parallel with my charge controller  to hopefully increase the performance of the turbine in low wind . And feed that AC 230 Volt into my house directly

But i need that Diode  that the GTI is not feed from the Battery , but the battery clamps the voltage range down to a secure range for the GTI

Something like this here  in the drawing ....





Hope this make sense  

[Antman]

Hi Billi

In the second diagram, the 'triangle' is representing the diode (I assume). Normally the 'point' of the triangle would be the direction of current flow. But confusingly, the arrows point in the opposite direction.
This may be contributing to the confusion and hence the lack of knowledgeable replies - hence why I will bump it again.

In a diode - approximate symbol below but drawing with text characters is not easy so allow some imagination and assume the arrow is formed with the ">" being a steeper angle!....

          |\  |
-------|  >|-------
          |/  |
Anode          Cathode

Current flows this way >>>>>>>>>>
So any voltage applied to the cathode will not appear at the anode terminal.

Hence the confusion in the second drawing.


If I am correct in assuming that you want the wind turbine to charge the batteries but not to be affected by the PV charge controller, then the cathode (arrow tip) of the diode needs to connect to the battery and the anode to the wind turbine busbar.
The first drawing is correct in this respect.

But in doing this, I suspect that the wind turbine will no longer contribute to the battery charging when the solar PV is generating because the 30+ volts across the batteries will reverse bias the diode - meaning it cannot conduct with only 29V coming from the wind genny. So presumably the wind dump load would then have to absorb the entire wind turbine output.

As for connecting the diode, I would parallel 2-3 (depends on rating of what you have) so that the total diode continuous current rating is double your peak wind turbine current (for reliability). Mount copper busbars on insulators and connect the diodes to those so that you also have a stout connection for the cable lugs to bolt onto.

Antman

[billi]

Thank you Antman

But in doing this, I suspect that the wind turbine will no longer contribute to the battery charging when the solar PV is generating because the 30+ volts across the batteries will reverse bias the diode - meaning it cannot conduct with only 29V coming from the wind genny. So presumably the wind dump load would then have to absorb the entire wind turbine output.

As for connecting the diode, I would parallel 2-3 (depends on rating of what you have) so that the total diode continuous current rating is double your peak wind turbine current (for reliability). Mount copper busbars on insulators and connect the diodes to those so that you also have a stout connection for the cable lugs to bolt onto.

Antman

Yeah , i am aware that the dump of the turbine  has to take the power when  voltage higher than ca 29 V  ,  but have other ideas as well

Will built a busbar  for  the diodes

Thanks

[johnrae]

You might also want to consider a charge controller between the turbine and the battery to prevent the possibility of over-charging when it's blowing a 'howler'

[JohnH]

Hi Billi

The diode you have, did this come with the system? I ask because looking at the type letters it looks like a Schottky diode. They have a low forward voltage drop at about 0.2V and hence are used mainly for high speed switching. Their disadvantage is that they have a relatively low reverse voltage and high leakage current.
I don't know if it would be suitable for your application.

JohnH

[billi]

Hi John

No  i have not got the Diodes yet .
Do you have  a better model  ?

[JohnH]

Billi
I would have thought a standard high current metal stud diode would suffice mounted on a heat sink with mica insulators if needed. Depending on the max forward current, the 25F10, 40HF10 or 70HF10 series diodes which are available from Farnell.
JohnH

[fred bloggs]

Billi

I have dozens of Industrial Stud diodes upto 300Amps rating, all gathering dust, therefore if you want a couple of them, PM me and I'll shove them in the post (my good deed for the week-FOC). Tell me the maximum rating (current) you are looking for.

Best Regards

Fred

[billi]

Oh      santa is coming  will PM you 

[fred bloggs]

Hi Billi

  is on its way as per your PM.

Best Regards

Fred