Which dump load regulator

[la7qz]

Hi

My wind turbine has now been up for a few weeks and I find myself for the first time in my 16 years of living afloat in the position of having more energy than I know what to do with. I know that I could easily resolve this issue by installing a 12V refrigerator, but I have thought of a more useful way to use the power. (There's cold beers and good company on land.)

I have decided to install a 12V heating element in the hot water tank and use a dump load regulator to dump power to the heating element. I simply don't have time to build anything from scratch at the moment, so I'm looking for recommendations on which regulator to buy.

I have previously installed a Xantrex C/40 on a customer's boat which seemed to work just fine, but I know some members of this forum have reservations about that particular brand. The wind turbine I'm running at the moment is capable of producing a maximum of around 25-30 A, but typical output is more like 5A most of the time, up to 10-15A in gusts. In addition to the wind turbine, I have 165W worth of PV panels.

I also have another turbine of around the same capacity which I have not installed yet, so I could potentially see output up to 60A in strong winds. I would normally shut down one of the turbines in higher winds. The Xantrex C60 seems a likely candidate, but other suggestions are welcome.

Any hints for sources of 12V immersion heaters would also be very welcome. The best plan might be have a regulator capable of dumping the power from both turbines and install two 12V immersion heaters and disconnect one when only one turbine is in use.

Owen

Yacht Magic

St. Maarten

Netherlands Antilles

[cardamon]

The xantrex c-series and tristar/morningstar line are the two major diversion controllers.  I just bought two c-60's for my wind and pv system, but have not installed them yet.  I havent heard anything negative about either one.  are you using a seperate charge controller for the PV?  You could just use diversion to controll everything if you wanted to utilize excess pv power too.  Here are a few links on 12v elements to get you started:

www.fieldlines.com/story/2005/9/8/0952/24663

www.fieldlines.com/story/2005/11/11/18646/621

Within one of those links, someone said that this was the cheapest 12v element they could find:

http://hydrogenappliances.com/hotwater.html

[cardamon]

there are some comments here on tristar vs. c-series:

http://www.fieldlines.com/story/2008/2/14/22853/4413

[la7qz]

Hi again

Thanks for the replies.

First of all, some info I left out from the first post.

I am not regulating the PV output. While living aboard, with only the PV array, overcharging has never been an issue, so the dump load regulator would be expected to take care of that in addition to the output from the wind turbines.

My batteries configured as follows:

Starter battery: 1x Optima redtop.

I am presently charging it by splitting the output from the PV array between the three battery banks via diodes.

House battery: 4x Trojan T-105 (12V)

Charged from engine, charge splitting diode from PV and the wind turbine.

Electronics battery: 1x D8 Gel battery

Charged from engine and charge splitting diode from PV plus a diode across from the house battery. (I'm aware of the voltage drop across the diode).

(All batteries are also charged when the main engine is running.)

I looked at the 12V immersion heaters and see that they have 300W and 600W models. One of my turbines is permanently installed, the other will be hoisted in the rigging when staying in one place for a longer time, so will not always be used. On high wind days, I will probably shut down one turbine unless my batteries are really low.

My question then is whether to get the 300W or 600W immersion heater. It would seem a good idea to be able to utilise the full output of the two turbines when available, but what about the times I am only running one turbine? And, what do I do when the water in my tank is getting too hot? The water tank is 16 litres (around 4 gallons). My hunch is that it would be better to go for the 300W element and shut down one wind turbine manually on high wind days. Should I go add external dump load resistors in addition to the immersion heater with a thermostat to divert the charge when the water reaches the target temperature. (The engine also heats the water through a coil in the tank, so this may happen even when there is not a lot of energy being diverted.)

Owen

[cardamon]

I seems to me you have the following inputs:

Wind A 30 amps max

solar 14 amps max

wind B 30 (?) amps max

Thus your worst (best?) case scenario would be 74 amps.  Thus you need to be able to divert 74 amps in theory.  So you could go with two 60's or maybe two 45's.  You then size you element so that the max load the controller can see is a littl under the max rating.  That 600w element with 13.5 volts through it will burn up 44 amps.  This is good as it gives you some overhead if using the 60 amp controller.  You might be able to get away with the 45 amp tristar, becasue I think their ratings are continuous.  I think this would violate the NEC though which you may not care about.  now you have 30 amps left to get rid of so it looks like you would need another 600w element and another 45 of 60 amp controller.  There are probably other ways of doing it too.  What I am not sure of is how to prevent you engine from wasting gas by heating water through the diversion controllers.  Maybe the extra load on the alternator is not significant in the sceme of things?

[cardamon]

As for your other question, I dont know if the water getting to hot/boiling is an issue.  Perhaps others with experience heating water can chime in.  My gut is that 900 watts isnt very much when we are talking about heating and boiling water.  Maybe you could get a larger tank?

[elvin1949]

cardamon

 There is not much room on a sailboat for a larger tank.

later

Elvin

[cdog]

I hope someone may comment about the flexcharge controllers, apparently they can handle as many apms as you want to expand to, I am in the market for an upgrade from my c-35 myself, good luck,

Cdog.

[la7qz]

And...

The primary reason for having a hot water tank is to have ... hot water. A larger tank would take longer to heat. The situation where both wind turbines and the PV panels would be charging at full output would be rare indeed. I would not leave the boat for extended periods if high winds were expected without shutting down one or both turbines.

I've had a look at the Flexcharge site and would like to have more information. Unfortunately, the site is not very well laid out. I suppose I'll have to e-mail them.

One point I would like clarification on. Let's say I install regulator and a 600W dump load. Am I correct in assuming that the only thing I will damage if I am producing more than 600W and the batteries are full is the batteries (and any voltage sensitive equipment that is switched on)? In other words, with a 600W dump load, I need to select a regulator capable of dumping 600W?

I believe I am capable of shutting down one of the turbines in high winds long before overcharging would be an issue. It would also be possible to install a relay in parallel with the dumpload to disconnected the PV panels whilst dumping. That would mean only the output from the turbines would need to be dumped.

Owen

[cardamon]

Owen,

Yes your system should be set up so that you cant smoke the diversion controller.  That is the resistance of your dump load is such that, it will not pass more current than your controller can handle.  If more current is available than your dump load can dump with the controller's "throttle" wide open, than you will start overcharging you batteries which now and then is actually a good thing(equalizing) depending on the battery type.

[elvin1949]

Owen

  Check Ghurd's controller kit's. 12 dollars each i think. DavidHK uses them to trigger ssr's to dump

high power.

 Might be worth a look.

later

Elvin

PS---nice boat

[la7qz]

Hi

Would you happen to have a link to this controller? Google didn't return anything sensible.

Owen

[la7qz]

Hi again

I found it, but that raised a new question.

I will be getting a 600W 12V heating element. So - recommendations for an N-fet gate suitable for dumping 600W (or preferably more) would be welcome. I have a couple of nice big heatsinks that would be perfect for the project.

Owen

[ghurd]

I would consider an IGBT or SSR.

Proper planning and design would allow a bank of N-fets to be used on a single load, but it's not what I would do.

I would most probably use a Big bank of low resistance N-fets, with low ohm/high watt ballast resistors.

Partly because all that is here. But I have a lot of IGBTs here too.

That's just what I would do.

[la7qz]

Thanks for your reply Ghurd.

I'm very much a colour by numbers kind of guy when it comes to building electronic stuff, so I'm going to need just a little more help selecting the components. Recommendations of actual components and where to get them would be welcome.

Or...

I may actually have something suitable. I have the bones of a 150A battery charger here. This is where the two big heat sinks I mentioned came from. I have two components marked "NSC 07104G0D 0204", one sitting on each of the heat sinks. Can you (or anyone else) identify these and tell me whether they would be suitable? The charger was dead (toasted transformer), so it is of course possible that they are dead. How do I test them?

Owen

[la7qz]

Oops

Looks like it's "WSC 07104G0D 0204", not "NSC". It's a bit difficult to read because it's partly hidden by the heatsink.

Owen