Too BIG of a dump load possible??

[ralph5]

I have searched the board for a while now and it was easy to learn:

what a dump load does, and results of too small of a dump load.

My conclusion is that a dump load needs to hand all the power the wind turbine will produce plus some.

My question is, Can i choose too big of a dump load? If so what is the result of too big of a dump load? For example: Would a 24 volt 600 watt water heater be too much for a 24 volt 25 watt wind turbine for example?

I haven't found an answer for this.

Are there other factors involved without getting too complicated? (I'm a beginner with wind turbine in progress)

[DamonHD]

Too large a dumpload will likely overload components upstream of it (between it and the turbine), burning them out.

Rgds

Damon

[Flux]

Yes and no!. Partly depends on the way it operates. If it is a simple switched on/off load then You may be dealing with excessive currents for the size of battery if you go far too big.

If it is common pwm you will put severe loads on the pwm controller and if it survives then you may end up with a lot of nasty RF interference from the high current spikes.

Within moderation it doesn't matter as long as you don't go crazy. As long as your controller could handle it your proposed 600W should be possible with a decent sized battery but you wouldn't expect low capacity batteries to handle that sort of current.

With a small system although it may be tempting to reclaim heat it really will have so little effect that you might as well not do it and use a suitable air cooled resistor instead. 25W in a resistor will burn your fingers and you have to mount it carefully to avoid fire risk but in terms of heating forget it.

Flux

[ralph5]

To sum things up?

1. A dump load needs to be able to dump all power generated from turbine?
   
2. Not exceed the rating of the dump controller?
   
3. and not over draw from the batteries?
   
   

note: I don't care about heat, just want to match up an easy reliable dump load.

[TomW]

Ralph;

I would say  you have it. Only thing I would add is in statement #1 "turbine" could be "sources" in case you have solar or whatever.  

Good luck with it.

Tom

[kurt]

if you are using a pwm diversion controller like the trace C series or Morningstar Tristar controller then you absolutely cannot go over the max rating of the charge controller with your dump load or you will fry the controller. the max dump load rating can be found in there respective instruction manuals.    

[Capt Slog]

I'm using one of Ghurds dump controllers..

http://ghurd.info/

Due to inexperience and wanting to err on the side of caution, I put in extra FETs in parallel (three in total) and have them powering a huge dump.  It's capable of dumping 18amps!  You can see it here...

http://www.fieldlines.com/story/2007/8/30/8538/81113

In comparison to my set-up, it's laughable really but as I said at the time, I'd rather have it running cool than hot.  I built for caution and it wasn't a lot of extra trouble to do that at the time.

In terms of operation, it seems to be fine.  The dump light flashes, and in that time it's dumped what it needed to dump and then gets on with it.  Occasionally, these flashes will be come at around 4-5 a second.  This is my first, so I've nothing to compare it to, but as far as I concerned it works perfectly.

[WineGuy]

I'm slightly confused.

I noticed mentions of battery size in the dump load conversation.

I was under the assumption that the dump load bypassed the batteries when they were "full". This way all of the power from the "source" went to the load. Am I missing something?

I may be answering my own question here, but I have noticed two different ways of connecting the controller; inline between the source and batteries, and "off to the side" of the batteries so the source never gets fully disconnected. In the second scenario, the batteries are still in the circuit. Does the dump load pull power from the source, batteries, or both?

[TomW]

Guy;

The dump load dumps from the batteries not the turbine.

The reasons for this I leave to others to explain.

Tom