Diversion mode, Blocking diodes, 600 watt heating element

9 Posts
May 25, 2008 11:59 am
Diversion mode, Blocking diodes, 600 watt heating element

Have 2 Krocera 130 watts running threw a Xantrex C-35. It is set for charge control mode. It is a 24 volt system. Run a solar hot water pump 170 watts, Lap top, lamp, Run Boom-box sometimes,it draws alot of watts clock, lights. Will be Adding a 800 watt windmill?? to the system. Starts charging around 10 mph, not much wind around here. Since this system will not run all of the above all night without a low voltage alarm. Would It suffice to add Boom-box and tv converter box @ about 50 watts continuous to counter the dump load of 600 watts or less required for windmill. Have 2 mid-size deep cycle battries, 1500 watt inverter. Will I have to add blocking diodes to the panels when its switched from charge control to diversion mode. Thanks for any advice.
 
Jun 3, 2008 06:09 am
Re: Diversion mode, Blocking diodes, 600 watt heating element

The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift. 
                                            Albert Einstein


I think I understand what you are wanting to know, but may need more information to give better assistance.

One of the things I try to do, but do no always achieve, is to incourage folks to find there own way of understanding.
As an example: There was a time when I had trouble understanding how to wire 3 way - 4 way light switches. All it took was for someone to say, " you can have as many 4 way switches as you want along a hallway, as long as there is a 3 way at each end of the hallway."
Where this may not work for anyone else its all it took for me.
Another example was the understanding of flooded cell lead acid battery. Flipping through the pages of an old high school chemistry text book one day, I read the words, "batteries do not store electricity, they convert electric energy into a chemical energy and store that energy until such time as electricity is needed and then convert chemical energy back into electric energy." After that, no more mystery.
Getting back to the subject.
You have 2 - 130 watt PV modules for a total of 260 watts.
What would be the yearly average of equivlent number of hours of full rated charge?

http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/

I am going to guess 4.
So, 260 multiplied by 4 equals 1040 watts per sunny day.
You have a 24 volt nominal system so this would mean 1040 divided by 24 equals 43 amp hours per sunny day.

Have 2 mid-size deep cycle battries,

This, at best, is vague. You force me to have to guess again. Since your system is 24 volts nominal I can surmise they are 12 volts each and being "mid-size," by your standard, I can only guess there rated amp hour capacity since I don't know you well enough.
I am going to guess 100 amphours at the 20 hour rate.
http://www.criticalthinking.com/company/articles/deductive-reasoning-skills.jsp
Now, onto the load assessment;
1 - hot water pump - 170 watts over a 24 hour period = ?
2 - lap top        -  ?  watts over a 24 hour period = ?
3 - lamp           -  ?  watts over a 24 hour period = ?
4 - boom-box       -  ?  watts over a 24 hour period = ?
5 - clock          -  ?  watts over a 24 hour period = ?
6 - lighting       -  ?  watts over a 24 hour period = ?
7 - TV converter   -  ?  watts over a 24 hour period = ?

I am not even going to guess at all of these but I can tell you that you do not want to use sensitive electronics as a dump load from a wind genny. This is best done with a strictly resistive load. Also the Xantrex C-35 might ether be a charge controller or a load diversion. Not both at the same time. I will have to get back to you on that one after I have had a chance to read its manual. In addition I would recommend a battery monitor such as the Bogart Tri-metric 2020.
http://www.bogartengineering.com/
Can I assume that the wind genny's 800 watts is at top speed just before it self defeats?
http://www.windturbine.ca/waterheat.html
800 divided by 24 equals 33 amps.
After all is said and done, reading and understanding manufacturers product specifcation sheets, installation, and users manuals is of great importance.
I used the analogy once of comparing building an RE system to building a car. You first have to decide what you are going to do with it before you build it. Is it going to be a commuter or an eliminator or something in between?
http://www.kronosport.com/
versus
http://www.nedra.com/
Of course this would possible in a perfect world were we could all just shell out 50 grand like peanuts. If you're like me though, you are building your system gradually and learning as you go. One thing I learned living off grid for over 20 years without any electricity at all was, I can live without any electricity at all.
"What one man can do, another can do."
I've killed my bear, have you?
 
18 Posts
Jun 3, 2008 01:46 pm
Re: Diversion mode, Blocking diodes, 600 watt heating element

This really sounds like one of those questions that you get in a math text book.  If I decipher this right I get that you are going in the red with loads at night (low voltage warning).  The answer here is simple - get a bigger battery.  Your 1500 Watt inverter needs to be fed better, 2 mid-sized batteries just aren't enough.  Consider this 1500W/24v=62.5a - how long will your batteries last under this load?  I have 20kW worth of batteries so I have a little something for the cloudy day.

The C35 charge controller will charge your batteries and then divert excess power (full batt.) from your panel into a dump load (full disclosure - I own one).  But if you have power left to burn (dump) then you are not storing it.

Wind turbines usually come with control panels and dump loads so you should not even need to change the C35.  But I would hold off on a wind genny (not much wind) and get the batteries and maybe another solar panel (or 2) first.

Oh, and No, 150 Watts of electronics does not equal 600 Watts of dump load.
 

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