Newbie questions about 12v lighting

bostonseven

Hello everyone, it's great to be here and hopefully I'll find the help and advice that I need!

So, as a newbie, I have lots of questions, first ones, are about a 12v setup.

By reading around the forums quite a bit, I figured that I should probably consider adding 12v to a small building, separate from my house, that I use as my office for computer work, instead of using an inverter. The use would be computers, phone/tablet chargers and lighting only. I don't need it, but I like the idea of solar for the sake of it and I'll get solar panels and controller when I feel I'm ready.

I have to start simple, so I have a 3-stage smart charger, a starting/deep cycle battery, a UPS and an inverter (before I decided to consider 12v straight). Solar panels and controller will replace or the charger which will be then used as a backup for any poor charging from the panels.

- I already have a problem figuring out how to hook up the battery and I would love to hear from you, maybe you could explain/show me what are my options.

- I also would like to find out about fuses/breakers and what's the best way to hook up those (close to the battery is the main thing I learned, but better a fuse and switch or a breaker?).

- Switches, breakers, lights are all specific to 12v, but are wires, terminals and fixtures interchangeable (obviously must be kept separate from 110VAC)?

- Should the battery stay outside, maybe in one of those black boxes, even in very cold weather (coming up soon, I'm in Boston)? I know batteries lose a lot in the cold, what can I do about that?

I have a more comprehensive plan for the medium and also planning for the long term, but I want to start getting familiar a little step at a time...

Thanks for any input!

BB.

Re: Newbie questions about 12v lighting

Before you start buying solar RE + Batteries + etc... Get a Kill-a-Watt type meter and measure your loads.

All the calculations start with the loads you need to support (Watts average/peak power, Watt*Hour energy use per day, everyday cycling vs emergency power, etc.).

And with a kill-a-watt meter, you can look at conservation. In general, it is almost always cheaper to conserve than it is to generate the power.

Loads that run 24x7 (such as desk top computers/servers, networks, printers, etc.) are, many times, more expensive to support than running a microwave oven 30 minutes per day:

1,500 watt Microwave * 1/2 hour per day = 750 Watt*Hours per day
250 Watt Computer * 24 hours per day = 6,000 Watt*Hours per day
30 Watt Laptop * 12 hours per day = 360 Watt*Hours per day

So, knowing your loads is the first step. The rest is math and picking hardware that supports your needs.

In general, if the building is within walking distance of the main home--You are (cost wise) better off digging an 18 inch deep trench, putting in a couple of parallel conduits, and pulling AC branch circuit wiring (in one conduit) and networking/phone/cable TV in the other conduit.

You can still do solar--But this will allow you to use the building as a "true office" (with some heating/AC) without the restrictions that solar may place on your operation.

The batteries, if kept above ~40F will work just fine. An insulated box and cycling the batteries will usually keep them warm enough--bury or "berm" earth around them if needed. Charged batteries will not freeze, but they will have less apparent capacity. In general, if everything is done correctly, batteries "like" colder temperatures... They last ~2x longer for every 10C/18F below 25C/77F (i.e., if the batteries average 77F-18F=59F, they will age 1/2 as fast).

Anyway, until you know how many batteries you would need for your application, we are getting a bit ahead of ourselves.

-Bill

bostonseven

Re: Newbie questions about 12v lighting

Thanks a lot, Bill!

I'm sorry for the stupid rookie mistake which is even worse considering that I read so much that I eventually forgot about numbers for loads. I should already be getting a Kill a Watt in a couple of days. I have a pretty good idea of the loads regardless, but I'll wait for the device to double check my math before posting again.

Just to clarify, I don't need the 12v setup as it has 110VAC already, I just want to make the office "green" as much as possible, but in reality, I just like the idea of using the sun! So AC and heat are not an issue. I can decide how big I want to build the system and if I run out of 12v reserves or I don't want to "conserve", I can just switch to the grid.

The batteries, whether one or more (I think 3 should suffice), maybe a problem already. We go below freezing regularly at night, and that's likely until Feb or March. I would probably add low consumption night lights somewhere to have the batteries cycle regularly, if that helps, because there are days when I'm not at the office. Where could I find out more info about insulated boxes?

Thanks so much for your help!

bostonseven

Re: Newbie questions about 12v lighting

Thanks a lot, Bill!

I'm sorry for the stupid rookie mistake which is even worse considering that I read so much that I eventually forgot about numbers for loads. I should already be getting a Kill a Watt in a couple of days. I have a pretty good idea of the loads regardless, but I'll wait for the device to double check my math before posting again.

Just to clarify, I don't need the 12v setup as it has 110VAC already, I just want to make the office "green" as much as possible, but in reality, I just like the idea of using the sun! So AC and heat are not an issue. I can decide how big I want to build the system and if I run out of 12v reserves or I don't want to "conserve", I can just switch to the grid.

The batteries, whether one or more (I think 3 should suffice), maybe a problem already. We go below freezing regularly at night, and that's likely until Feb or March. I would probably add low consumption night lights somewhere to have the batteries cycle regularly, if that helps, because there are days when I'm not at the office. Where could I find out more info about insulated boxes?

Thanks so much for your help!

BB.

Re: Newbie questions about 12v lighting

Not a problem B7,

Energy usage is a highly personal set of choices... We try not to be (too) judgmental--Just figure out what the reader needs and not tell them what we think they need. LOL

The whole Conservation, conservation, conservation thing is not because we are "green", it is because we are "cheap" and this is usually the best bang for the buck. :roll:

-Bill

bostonseven

Re: Newbie questions about 12v lighting

I'm from Europe where resources are always limited (even worse right now), so I perfectly understand the conservation bias. I too like to save where it's reasonable and spend where it's worth it!

I'm here for constructive criticism, so I welcome anybody's useful opinion!

Maybe you missed my last question, so I hope you don't mind me asking again, any info about protecting the batteries from the cold so I can do some research? Already insulated boxes or, even more fun, a "how to" guide or something?

Thanks Bill!

RandomJoe

Re: Newbie questions about 12v lighting

You don't have to worry about freezing a charged battery until *WELL* below freezing. Looking at Trojan's site, they say 92 below zero for a fully charged battery! Even at 40% SOC the freeze point is still 16 F, and you normally try not to go that low unless absolutely necessary.

An insulated box is just that - anything you can put the battery in and insulate it. Many people build one out of wood with a hinged top for access, some have bought a plastic backyard storage bin that was the right size. I'm not sure just what insulation they use (my batteries are in the garage).

On using 12V lights and appliances, there's nothing wrong with that. I assembled a nice collection of 12V lighting when I set up my first system and still use it occasionally but have since switched to using the inverter for everything for the following reasons:

- 12V versions of most things cost considerably more than the equivalent 120V version (e.g. $10-12 for a good 12V CFL vs $1-2 for 120V) It's also much easier to find the 120VAC versions - at just about any store in town. Most 12V stuff I'd have to order in and wait for it.

- Running 12VDC electronics off a solar system may damage the device since the solar system voltage will rise to 15V each day during absorb. Unless they are made for use in cars, most electronics won't give a safe voltage range. Some may work fine (I ran a Linksys cable modem and router straight of the bank for a long time) others may pop some component that's not sized for the higher voltage.

- FINDING 12VDC versions of some things may be tough. Once you need an inverter for one item, you might as well load the inverter up so it's more efficient…

- The resistive losses in the power wiring are ridiculous at 12V! You either run extra large (costlier) wire everywhere, or you put up with the voltage drop (which some devices may not like). You may not be too bothered by this if your building is small. I was starting to run things across the house.

- Switches and outlets for 120VAC are cheaper. (And in my case I just wired existing circuits to a sub panel for the inverter.)

A good inverter nowadays has very low idle power consumption. For your application, it's also easy to just turn the thing completely off when leaving. Just don't get some behemoth 3000W monster when you only have 150W of loads!

Not to say you can't stick with all-12V. I do still have a 12V system for my ham radio bench and even have a 3-outlet lighter socket adapter loaded with car USB adapters for charging the phone and tablets. The ham rigs, scanners, etc are on it too of course. A car stereo on the desk is my office stereo (mostly because it has bluetooth so I can use it as a speakerphone for my cell! ). An RV fluorescent lamp sits on a shelf nearby, it'll light the room reasonably well. And there's even an inverter (Morningstare Suresine 300) connected. The light and inverter rarely get used though, since most of the house is wired to the big Outback inverter in the garage. It's my backup-for-the-backup so to speak…

bostonseven

Re: Newbie questions about 12v lighting

RandomJoe, thanks for the battery info, I should be able to come up with something based on that!

As for the 12v system, I was excited to read about your project until I read that you gave up on that as your main system. However, I decided I am moving forward because it's a very small building, a room basically, maybe 8'x16' and my requirements are for a little lighting and the computer stuff, plus a few chargers. So off 12v I should be able to reduce quite some loss without having to buy too much 12v specific stuff.

Waiting for a Kill-a-Watt for better info to work on then I'll get back to the subject.

Thank you so much for taking the time!

RandomJoe

Re: Newbie questions about 12v lighting

No problem, there are things I still like about running straight 12V systems, just found it easier to use the inverter - and then I upgraded to a (nearly) whole-house system so battery current became an issue at 12V.

When I had the big battery bank wired for 12V, I ran everything (except the 1500W inverter - separately cabled to the batteries) through a few RigRunners:

http://www.westmountainradio.com/rigrunner.php

I had a couple of these anyway since most of my 12V gear was radio-related on the ham bench. A heavy-gauge cable to the input, then change out fuses so they're sized appropriately for each load. I had also settled on Anderson Power Poles for my connectors so kept on with them for the lighting and other devices.

I also had a small desktop computer running straight off 12V, bought a wide-input PicoPSU to run it:

http://www.mini-box.com/M3-ATX-DC-DC-ATX-Automotive-Computer-car-PC-Power-Supply?sc=8&category=981

There are a few different models, some have a very wide DC input others require tighter voltage control. This only runs the computer itself, of course. I never did try getting a 12V monitor but they do sell them. This was a (mostly) headless server that I would ssh into if I needed to do something.

I have a variety of lights. A 16W (2 1-foot 8W tubes) RV fluorescent strip, puts out nice light and the tubes are easy to find. About 1.8A load.

I also bought a couple of (pricey!) 12VDC ballasts for a standard 4-foot fluorescent strip. Uses F32T8 (think that's right) tubes. Have to have a ballast per tube, but that also lets me switch on just one tube if desired. Now, this puts out a *LOT* of light! Around 2.5A per tube.

I have several LED lights, but they are mostly converted work lights and such which tend to use very monochromatic LEDs. Decent light for very low current, but not a pleasing color for daily use! Never did try to get any "good" 12V LED bulbs. I have bought some LED bulbs (for bike headlights) from this place, they have all kinds of bulbs in all kinds of styles and a range of color temps:

http://www.superbrightleds.com


Hope that helps!

bostonseven

Re: Newbie questions about 12v lighting

Awesome, thanks Joe!

Stealth costs coming up, I see, rig runners look great, but they ain't cheap, and there are a lot of other little things that I'm going to need...

Oh well, I can't say I didn't know, also because everything you want to do is like that; it looks simple, then it turns out to be a lot more complex and expensive!

Anyway, I took a look at your website and there's some really cool stuff going on there! I don't understand most of it and I still think it's so cool! Home automation is very interesting and, like you say, you can't beat the feeling you get when everything comes to life at the flick of a switch, especially when you're monitoring from remote!

Thanks again!