Greetings and some questions - Solar Generator

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Krus8r
Krus8r Registered Users Posts: 9 ✭
in Solar Beginners Corner #1
Greetings! I am new to the forum and wanted to say “hello”. Also, I wanted to get some input on a recent project I am building. It is a portable solar “generator”.

It all started when I was thinking of buying a gas powered generator to provide emergency backup power to my home as well as being portable to take up north to my mountain cabin. I decided that I did not want a noisy gasoline powered generator, rather a quiet battery-based inverter system that could be recharged by the sun, thus started my research and overall project.

Here is a list of my components:
- Kyocera KC85TS ( 2 panels, 12V, chosen for their specific frame size required for mounting on my trailer)
- Xantrex Freedom SW2000 inverter
- Trojan T-105 batteries (6 batteries to be wired series-parallel for 12V input to inverter)
- Morningstar MPPT SunSaver (15A charge controller)
- 250A Class T fuse and holder

Questions:
1.) Which is the optimal configuration to wire the solar panels: series (24V) or parallel (12V)? The cable length will be fairly short (~3 feet each). In parallel I was planning on fusing each panel at 7.5 amps.

2.) I was thinking about making my own combiner box to provide the ability in the future to add a couple standalone panels. I know I would have to upgrade the charge controller. Otherwise, I assume I don’t need a combiner box for just 2 panels no matter the config (series or parallel).

3.) The batteries are going to sit in the same physical trailer enclosure; however, I built an enclosed battery box for them with a three inch inlet and outlet for airflow. Do I need to use a small fan to push more air or will natural convection work well enough to exhaust battery fumes?

4.) As I understand it, a setup like this would typically require 4/0 conductor from batteries to inverter. I have a real short run (about 1 foot from batteries to inverter) with the entire conductor length (series connections, etc.) only for the whole system only 5 feet. Would 2/0 work for this shorter length?

Thanks for any insight. It has been an enjoyable project even if I have made some mistakes ;)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Greetings and some questions - Solar Generator

    Welcome to the forum.

    Now, shall I be rudely blunt? I'd ask: "What kind of generator were you thinking of getting to recharge those batteries, because those panels aren't going to do it."

    Let's have a look at what we'll call Problem #1.
    The batteries you've selected are great. In the configuration you want, that will be 12 Volts and 675 Amp hours. That's the number that causes trouble. In order to have Trojan's recommended 10% peak charge current, you'd need this:
    67.5 Amps @ 14.2 Volts = 958.5 Watts, less a "typical" 77% derating = 1244 Watt array.

    Pretty awful, eh?

    Now let's look at it from the right design starting point: what amount of power consumption do you anticipate? If you can get a reasonable number for daily Watt hours of use you can more correctly size your battery bank and come up with the right amount of panel to recharge it.

    Look at one set of T105's: 225 Amp hours @ 50% maximum DOD is 112.5 Amp hours @ 12 Volts: 1350 Watt hours. To recharge it you'd need 22.5 Amps @ 14.2 Volts = 319.5 Watts or 415 Watt array.

    As you can see, that doesn't fit with the 15 Amp charge controller.

    And people here will tell you flat out that the generator will give you much more Watt per dollar, and that the little ones like the Honda EU2000i are very, very quiet.

    But if you want to spend your money right, you've got to know your loads.
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  • ronc89021
    ronc89021 Registered Users Posts: 9 ✭
    #3
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    Re: Greetings and some questions - Solar Generator

    Very cool idea! I hope you can make it work!
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  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #4
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    Re: Greetings and some questions - Solar Generator

    Xantrex already makes a product called the Powerhub 1800 that is referred by many as a "solar generator" Only 2 or 4 batts, but otherwise a nice package along your lines and no doubt less expensive.
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  • Krus8r
    Krus8r Registered Users Posts: 9 ✭
    #5
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    Re: Greetings and some questions - Solar Generator
    solarix wrote: »
    Xantrex already makes a product called the Powerhub 1800 that is referred by many as a "solar generator" Only 2 or 4 batts, but otherwise a nice package along your lines and no doubt less expensive.

    Yes, I saw that. It is modified sine wave though. Nice little unit nonetheless.
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  • Krus8r
    Krus8r Registered Users Posts: 9 ✭
    #6
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    Re: Greetings and some questions - Solar Generator
    Cariboocoot wrote: »
    Welcome to the forum.

    Now, shall I be rudely blunt?

    Not rude at all. I like straight talk ;)

    Thanks for your feedback. It is clear the mobile nature and form factor of this device poses a challenge for adding enough panels. I will need to get some standalone panels and upgrade the charge controller.
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  • System2
    System2 Posts: 6,290 admin
    #7
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    Re: Greetings and some questions - Solar Generator

    Hi Krus8r,

    A solar generator is the perfect technology for emergency backup power and powering off the grid structures like your cabin. An example of a great, already built product that I am particularly fond of is the SolMan, made locally in northern California. This all-in-one integrated unit can deliver up to 1200 watts of AC power and 12 volts of DC power. The design includes a 135 watt photovoltaic panel, three 100 amp/hour deep cycle sealed batteries, a solar charge controller, a watt Meter, a 1500 watt inverter/charger, and external AC/DC plugs, all contained in a light, easily transportable two-wheel cart. It’s an extremely affordable model made out of long-lasting and environmentally friendly aluminum, not plastic. Here is their website: http://www.sol-solutions.com/.

    Whatever you decide to do, good luck with your solar generator adventures, and I hope you find or build something that works perfectly for your needs!
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  • Krus8r
    Krus8r Registered Users Posts: 9 ✭
    #8
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    Re: Greetings and some questions - Solar Generator

    Ok, I have finally finished building this thing. Here are some pictures (See below/attached). Based on the feedback I received here I upgraded the CC to an Outback FM80. That worked well because it allowed me to power a vent fan as well as have the needed capacity to attached another 1000W of panels (which have now been pre-wired with breakers). They will simply be standalone or mounted on my garage roof.

    I am still in the process of wiring a transfer switch into my electrical panel to isolate the circuits that I want to move "off grid".

    Attachment not found.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #9
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    Re: Greetings and some questions - Solar Generator

    One of those units advertises 480 amp hours at the 1 hour rate, As a solar novice I am used to seeing quotes at the 20 hour rate. What does this 1 hr translate to?

    SolarChick22 wrote: »
    Hi Krus8r,

    A solar generator is the perfect technology for emergency backup power and powering off the grid structures like your cabin. An example of a great, already built product that I am particularly fond of is the SolMan, made locally in northern California. This all-in-one integrated unit can deliver up to 1200 watts of AC power and 12 volts of DC power. The design includes a 135 watt photovoltaic panel, three 100 amp/hour deep cycle sealed batteries, a solar charge controller, a watt Meter, a 1500 watt inverter/charger, and external AC/DC plugs, all contained in a light, easily transportable two-wheel cart. It’s an extremely affordable model made out of long-lasting and environmentally friendly aluminum, not plastic. Here is their website: http://www.sol-solutions.com/.

    Whatever you decide to do, good luck with your solar generator adventures, and I hope you find or build something that works perfectly for your needs!
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  • TheBackRoads
    TheBackRoads Solar Expert Posts: 274 ✭✭
    #10
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    Re: Greetings and some questions - Solar Generator

    Neat looking setup Krus8r! How frustrating was that wiring to do in that tight space?!
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  • Krus8r
    Krus8r Registered Users Posts: 9 ✭
    #11
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    Re: Greetings and some questions - Solar Generator
    TheBackRoads wrote: »
    Neat looking setup Krus8r! How frustrating was that wiring to do in that tight space?!

    Thanks. Not too frustrating just hard on the low back bending over, especially lifting the batteries in and out so many times...
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