Mini-Solar V.3 – Maybe I Got It Right This Time

I’ve been working on a small battery-based photovoltaic solar-power system for the last, well, 5? 7? years- it’s been a long while. Since I first bought the modules, charge controller and small inverter I’ve been reconfiguring the parts every couple years with hope that it’ll finally “work” and be “done”… but it never has been. Until now? I’ve addressed my biggest issues with the system- location (get it out of my closet), battery size (nice big pack now), and lack of monitoring (nice new Bogart 2020).

The biggest improvement is brought by the box I built to house the batteries and system components. It lives outside the house, so I can finally get my closet back and not worry about acid spills or charging gasses.

The box is actually dual-purpose- it is designed to house the charging cord for the EV Miata so that once I park it in the driveway the charging cord will always be available.

I rewired the system (again) including a fuse and shunt for the Bogart Tri-metric meter. The charge controller and gray box are still from the very fist version of the system.

I also installed new wiring from the panels, using 8/2 tray cable. This replaces 6ga THHN in plastic conduit, which replaced exposed 8ga THHN. I added MC3 leads to the panels and soldered MC3 pigtails to the top end of the tray cable run. Either of the previous wiring solutions would probably have worked OK, but I really wanted to get rid of some of the persistent crappyness in the system. The cable is then connected to the charge controller using a SB 50 connector (and some leftover pink 6ga THHN… it’s not all gone). The 2 L 16 batteries are hooked up with a 200A class T fuse and block. 16/4 tray cable runs inside to power the Tri-metric and another run of 8/2 tray cable runs inside with a SB 50 to power loads. I made a SB-50 -> 3x powerpole pair adapter to break out the power and be able to use powerpoles for distribution.

So far I’ve just been running my computer on my old modified sine wave inverter, which makes everything buzz. I have plans for a DC-DC adapter for my laptop, as well as some direct DC hookups to other lights and things.

The Tri-metric meter is very useful for being able to tell what’s going on with the system, it’s really the confidence gained by that knowledge as well as the security of having the gassy batteries outside that makes me willing to use the system. Which I have been- in fact I’m using it right now to power my computer as I type. On a good day the panels generate far more energy than I need to run just my computer and stereo, I need to find more loads I can transfer over to the system.

It always feels good to “finish” a project (electric Miata? heh. soon, soon).

Posted on March 14, 2010 at 4:41 pm by Henry · Permalink
In: Renewable Energy System

2 Responses

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  1. Written by Greg
    on June 8, 2010 at 8:34 am
    Reply · Permalink

    …and how much did this cost to power a computer and stereo? price per kWh is another issue. economical decisions must be factored into any renewable system. people also need to factor in the life-cycle of the entire system and compare that to a grid network. batteries, controllers, solar panels, they all la small limited lifespan, come from the Earth in one shape or form, processed and manufactured to the product that gets shipped (around the world?) to your place to give you warm fuzzy feelings that you are helping the environment. what is the total carbon footprint of a solar panel? you think silicon or gallium arsenide panels grow out of the ground? harsh chemicals are used in impoverished countries (china and the likes) to build these items with little to no environmental awareness controls. Don’t get me wrong, I am all for being off the grid… at my cottage 400miles away from civilization, but if you live in the city? Stupidly expensive to do for little benefit. EV car? Good for some. Not for everyone.

    • Written by Henry
      on June 8, 2010 at 11:21 am
      Reply · Permalink

      I don’t justify this system financially or really environmentally. (since my parents underwrote the system as a learning experience I have that freedom) I believe it is worthwhile because I’ve learned a lot about design and usage of solar battery based systems from building and using it. It’s nice for when the power goes out- it’s hard to put a price on that really. My utility power is pretty reliable. And just conceptually it’s really cool to charge the electric bike from the solar power. Telling people that the bike is charged with solar power helps complete the picture of the remarkable efficiency of the bike.

      I’m not looking for warm fuzzy feelings about helping the environment. I am aware of the ramifications of the stuff-intensive consumer first-world reality. So, I try to do the best I can- buy as little stuff I don’t need as possible. Try to spend money in the least wasteful ways I can. And until the developed enonomies and nations collapse because of peak oil I’ll continue to buy stuff just like everyone else. I love the industrial, material reality we’ve created- there’s a tangible beauty in well engineered and manufactured stuff that I really appreciate.

      And after the world falls apart I’ll have some electric vehicles and solar panels that I can use, and no plasma TV that I can’t use.

      TL;DR Given the way people buy plasma TVs and cars these days buying solar panels may not actually be good for the environment but in the grand scheme is definitely not out of line. You’re picking the wrong battle.

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