The need for and how to create a Solar dump

[NorthPacific]

Hi,

Sort of missed the boat on this one. I am actually storm bound waiting my chance to jump off to the South Pacific. I built a solar 200watt and four winds 2 which can generate at max 20amps so in perfect conditions 40amps.

System works great I used a Tristar 45 controller.

I unfortunately did not build in a diversion. Read about hooking it up to the 120v water heater as a dump? How have others created a "dump" for too much power!

In my defence I did follow the manual which gives 2 options one with a dump the other without.

Cheers Steve

[NahanniV]

You don't need a dump load for solar.

Some wind generators need a dump load for overspeed protection, but your four winds II has a mechanical (centrifugal) governer, so you should be OK.

Have a great trip !

JM.

[noelex 77]

Solar panels can be switched off without harm. So solar regulators rapidly switch the solar panels on and off to maintain the desired battery voltage.

Wind generators cannot employ this method of regulation. If the load is disconnected from a wind generator it speeds up. They need a dump regulator which converts the excess energy to heat maintaining the load on the wind generator.

Some regulators will do both. Solar regulators can be wired to incorporate a dump load, but the most common solution is a separate regulator for solar and wind. As the regulation type is different for solar and wind this is usually the most practical solution and also provides redundancy.

[djmarchand]

Nolex is right. Solar and wind generators are entirely different animals and need different controller strategies. Unless I have missed something, one controller can't handle both types of charging sources.

But if you need a dump, either use an inverter and dump your excess amps into the water heater or with no inverter replace your 120V electric element in your water heater with a 12V one.

[Jim Cate]

Originally Posted by djmarchand

But if you need a dump, either use an inverter and dump your excess amps into the water heater or with no inverter replace your 120V electric element in your water heater with a 12V one.

I suspect that one could simply put the 12 V output of the wind gen into a 120 V heating element in the water tank. Would not make very much hot water, but would keep a load on the generator. Air-X and others simply short circuit the output to shut down the turbine. Seems to work pretty well for me.

Jim

[NahanniV]

Originally Posted by Jim Cate

I suspect that one could simply put the 12 V output of the wind gen into a 120 V heating element in the water tank. Would not make very much hot water, but would keep a load on the generator. Air-X and others simply short circuit the output to shut down the turbine. Seems to work pretty well for me.

Jim

NO ! Common but incorrect thinking. A 120V 1500W element will not work as a dump load for 12V; lower wattage elements would be worse.
The resistance of the element is too high, not enough current will flow to slow the wind generator.

As stated by Djmarchand you need to switch to a special 12v element if you want to do this.

[NahanniV]

Originally Posted by djmarchand

.....use an inverter and dump your excess amps into the water heater.....

I have seen this suggested in a few threads lately; Sounds easy, inverters are cheap, but will it actually work ? Will the inverter handle being continually cycled on and off. And, what happens if the water gets hot enough for the thermostat to turn off (perhaps engine is running too).

I'd like to hear from someone who has actually done this ????

JM.

[NorthPacific]

The way I have it rigged at the moment is that the fourwinds has a simple switch that I can turn on and off. In the off position it is disconnected to the controller. The controller I use is a Trimetric 45, iris designed to control both wind gens and solar combinations.

So far down the coast it has worked fine. Ironic that I was concerned about not producing enough electricity! My monitor is a morning star and tells you everything including your horoscope lol. I can see not leaving the wind gen running when the boat is unattended but the battery bank is large for a small boat as we have fridge and water maker and radar and ais and computers ssb etc.

I am open to suggestions but hope I do not have to redo my brilliant work lol. With engine solar and wind going the regulator never lets the batteries go over 14.7volts. I have had no gassing problems and the batteries never get below 12. 7 volts. Unless I turn on the inverter and forget to unplug the electric heater. Now that drains a battery bank real quick.

So thanks for the advice, if I create a dump what should it be? Maybe I should wait and see if I get into a problem of producing too much power?

[Jim Cate]

Originally Posted by NahanniV

NO ! Common but incorrect thinking. A 120V 1500W element will not work as a dump load for 12V; lower wattage elements would be worse.
The resistance of the element is too high, not enough current will flow to slow the wind generator.

As stated by Djmarchand you need to switch to a special 12v element if you want to do this.

I wonder... do you know what the cold resistance of such elements might be? I think they are wound with nichrome or such wire, and the R changes considerably as they reach working temperature.

Remember that if it succeeds in slowing down the turbine, it does not have to dissipate much power. All we are trying to do here is keep the speed of the turbine down to some reasonable value. If I had such an element around I would give it a try, but alas, we don't even have a calorifier on board.

Cheers,

Jim

[sailinglegend]

Originally Posted by NorthPacific

....Maybe I should wait and see if I get into a problem of producing too much power?

Many owners say that by lunchtime their solar has fully charged their batteries and wonder how they can make use of their "Excess Power". I would suggest that for MOST of them their batteries are not fully charged. Check out this forum for the "Charging Gotcha" to understand how you can be confused by little green lights, battery monitors or especially the charge controller telling you that it has dropped to Float mode. In Float the batteries may be only charged to 85-90% of full capacity, and charging at a low "Float" voltage there may not be enough hours left in the day to get the batteries back to 100%. Failure to recharge fully every 2-3 weeks will kill batteries.

[NorthPacific]

The Fourwinds is old school. The original controller has transistors! It has an air brake so that it can not be pushed past about 2o knots. Real simple. Took it apart replaced bearings and brushes. $40 just like new. 2 blades and very very quite

The tower cost more. But it does produce.

The controller and monitor is as recommended by an off grid RV guy in Montana. ( I was referred from this site)
http://handybobsolar.wordpress.com/t...ging-puzzle-2/

So no flashing lights, you program and set the parameters and if you wish can hook up to your computer. His big thing was that so many people kill expensive batteries by not charging them high enough. So far he has been proven right.

Early days I know. But when you add all the electronic stuff on the boat it is hard to see when I would get to the point of having to dump battery power. Started using the SSB and the amount it sucks is scary!

Anyway we are again storm bound listening to the bloody wind from the south tonight. I am not using the wind generator tonight lol

If anyone is interested we have a blog of our escape from the snow.
www.SouthPacificEngagement.com
Hopefully the pics will soon show Sailing rather than motor boating :-)

[monte]

Or a -12/120 volt water heater element - contains 2 loops of heating wire coils. Three style and adaptors fit all makes and models of U.S. built tanks. Makes it possible to heat water with shore power or gen set and to provide a divert load for a wind generator. One loop at 300 watts DC, other loop at 500 watts AC, so it will take 2-3 times longer to make hot water with shore power.
KISS Charge Control System
or
charge controller – svHotwire - 727-943-0424 | svHotWire