I currently have two die hard deep cycle rv/marine batteries each of which is 565 cca (how many amp hours is that?). I have two 270 watt industrial grade solar panels I will eventually mount to the top of the rv. I have a cheap charge controller that says to only hook up one panel to it. I Spent a week in Datil, NM with only one panel pointing south and up. With a 500w inverter I was able to run my omega 8008 juicer, laptop, and a few other low voltage charges on iPads, cameras, etc. and keep a charge on both batteries during the day. At night I ran a small light and watched movies on the laptop.
I was told to not allow the charge in the batteries to fall below 11.9 vdc as it will degrade the life of the batteries.
Everything is hooked in parallel for max efficiency at 12vdc.
Eventually,I want to run everything on dc and be rid of the grid.
One question is will I be able to use the existing a/c wiring to run the dc or do I need to run smaller awg to each location I wish to have dc? Another is about the controller: if I hooked the panels in parallel, would that be to much for the charge controller? It seems to me that if they are Hooked in parallel before the controller it should work.
I do plan on acquiring at least a 3000w inverter eventually as well as better batteries.

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Tags: Solar, batteries, charge, controller, dc


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Comment by Fred on January 26, 2015 at 3:38pm
Thank you Gil, I will check that site out.
Ralph, the controller I use now is generic (it just says solar energy), type 201 rated for 20a at 12/24vdc. I do plan to upgrade. The panel I currently use I will post a Photo of the specs for it. I've measured voltage before and after the controller but I've forgotten what they were because everything was working fine. I have a few dc cooling fans from computers and heat sinks but I think I'm going to save and get a good controller.
I've been following Eric on YouTube, Nomadicfanatic, and he just installed a very nice one but did not mention the price...lol.
As of right now, if I were to go out, I know that I am not set up in the correct manner at all. I was using solid wire and then an extension cord wire...but IT WORKED! I was happy with the results.
I plan to use 10awg stranded copper from batteries to the controller and inverter. From there I have not figured out if I wish to tie into the existing circuitry which is 20a ac or just run 20awg from a busbar to different ports. I am learning as I go and I thank you all for your help, support and comments! I do have an understanding of low voltage but when I was a rocket scientist it was mostly all signal wire and inside very small boxes...lol
Ok, I'm going to find and upload that picture for you Ralph. Or maybe I'll just message you with it.
Comment by Ralph Javins on January 25, 2015 at 6:05pm

Good morning, Fred; 

     Before we get to making specific comments, there are some questions: 

     What solar panel charge controller do you have?  The manufacturer name and model number will help. 

     You said that you have two (2) each 270 Watt solar panels.  You did not say what the rated output voltage (Vmax) is for that solar panel at the maximum power point, nor what the "nominal" DC circuit voltage is (12 VDC for example), nor what is the maximum power current output (Imax). 

     The charge controller itself: Usually there will be a specific input voltage range that it is intended to work with, and also a maximum DC Ampere rating that it is intended to handle with normal convection cooling.  It is often possible to raise the maximum current handling capability if the heat sink on the charge controller can be provided with a reliable volume of fan generated cooling air to take away the heat produced.  The main thing is to keep the heat sink temperature below a critical point, and that the additional current and/or power generated by your solar panels is greater than the electrical power used by the fan to provide that needed volume of cooling air for the heat sink.  We can talk about control systems for operating the fan later. 



          Latte Land, Washington 

Comment by Gil Hutcheson on January 25, 2015 at 10:49am

A good resource for Solar info is the Renogy Solar site. They have the formulas for computing the correct size wires from your panels to the charge contorller and from the controller to your battery banks. If you are going to mount the panels on the roof, it is fairly easy to route the cables from the panels to cabin below through the refrigerator chimney. One thing that is important to remember is that low voltage DC requires large wires so as not to lose amps over short runs.

I am currently running a 100 watt Renogy panel with a 30 amp Renogy PWM controller. I only have room for 1 95 amp hour deepcycle battery in my battery compartment. So far, the system has worked well for me with the battery being topped off by noon on sunny days. At that point, we charge whatever needs charging (including friends devices) until the sun is too low in the sky to provide power in float mode any longer.



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