beginner needs help with start-up

[jrmadbear]

I want to put up a system and i have a DR 3624 Trace inverter/charger.
i am looking at batteries and i need some help choosing the best setup.
i am a total dummy when it comes to electrical stuff. which battery setup would be the best for a 24 volt system? All things equal would it be better to set up a series of 4-6v or 2-12v. Is there any difference in efficiency, cost and battery life?thanks

[RandomJoe]

I don't think functionally there's any real difference. But if the amp-hour capacity you need exceeds what you can get a single battery in, then you are looking at parallel strings. For a given size, a 12V battery is going to be (roughly) half the AH capacity of a 6V. Too many parallel strings can be troublesome to keep balanced, so it's better to limit how many you have. Thus, going with the 6V batteries reduces that by half. Of course, you can also choose larger batteries to start with as well.

But for beginners just starting out, it is often suggested you try using "golf cart" batteries (Trojan T-105 and the like) because they are good batteries for the application that don't cost a huge amount. It is entirely too easy when starting out to kill your first set of batteries in a variety of ways (overcharging, undercharging, forgetting to add water...) and this limits the financial impact. They are also probably a lot more readily available locally. (This is what I've done, so far I've not killed mine but they haven't been in use for even a year yet...! ) These are 6V roughly 200AH batteries. (Trojans are rated 220AH, I've seen some mention discount-store versions being 180-200AH.)

There are some battery FAQs available if you want to learn more. The one I started out with is http://www.batteryuniversity.com/partone.htm and the hosts of this forum have one as well http://www.windsun.com/Batteries/Battery_FAQ.htm


There are many more questions you need to ask as well, though. You need to determine the loads you will have before you know what size (in amp-hours) your battery bank needs to be to handle it, and you need to know how large your battery bank is going to be before you know how much solar panel (in watts) you will need to properly charge it. (That's just a start! There are a number of others!)

You mention having an inverter/charger. Do you want to install a solar system? Or just a UPS type system? If solar, you will also need a charge controller, will need to know what your solar insolation is (how many hours of "usable" sunlight you get per day, not just how many hours it is light out) which factors in to how much solar panel you need, so on...! There's a lot to it, but it can be fun!

[icarus]

Before you do anything, I suggest you get a really good handle on your expected loads. All other choices come from knowing your loads. I suggest getting a Kill-a-watt meter (~$20) to log your current loads, and extrapolate your future loads.

Tony

[jrmadbear]

Thanks, like i said i am a dummy! Can the kwh data form my elc. Bill be a help with this or do i need the peek load

[GreenPowerManiac]

I think if I had to start over again, I'd choose the highest voltage battery setup possible D/C: 48v or better. Rime or reason for battery voltages is not as important as your loads, like stated. What are you powering ? Higher voltage costs more (inverter) in the beginning and less in the long run (wire sizes & circuits). I'd still suggest some book reading on the subject. There are many out there that are easy to understand without all the science and you don't have to be a "Solar Power for dummies" to understand everything.

[BB.]

Also, be aware that the Trace inverter is long past end-of-life and if it breaks, there is hardly anyone out there that can repair them anymore (and no parts either).

Do not spend any more money until you figure out exactly what it is you want to do.

As Tony says, understanding your loads is the first thing to look at. A kill-a-watt meter and your electric bill is a good place to start.

You will probably find that you are using way to much electricity to really go off grid. Generating off-grid power is expensive... It will probably cost you $1-$2+ per kWhr, and your utility power is $0.10-$0.20 per kWhr--1/10th the price of off-grid power.

So, if you have a 600 kWHr per month power bill--that $60-$120 per month bill will cost you (assuming 20 year system life and buying replacement batteries when needed) will cost you $600-$1,200 per month--much of that is upfront money to install the system in the first place (many tens of thousands of dollars).

Normally, we recommend that people spend money on conservation first (insulation, double pane windows, energy star rated appliances, turning things off, switching from electric stove/hot water to propane and solar thermal, etc.).

Going off grid solar when you have utility power available will never really save any money. If you want emergency power (storms, earthquakes, local utility is unreliable, etc.), generators are good for short/rare outages. And setting up a battery bank, charger+inverter to run the home during frequent outages (people in the Caribbean do this quite often) can be nice too.

Of course, many folks want to experiment with solar RE and build a small system first (a couple hundred watts of solar panels, charge controller, plus a couple of 6 volt golf cart batteries and an Inverter) and play with the system first to understand how to run it and the limitations. Even something like that (enough to run a net book computer, a radio, and a couple small lights off grid) is going to cost around $1,000.

If you want to get a good idea what the major components are and how much they cost, you might wish to browse our host's web store--NAWS.

In the end, understand and define your needs before you take the first step. Your wallet will thank you.

-Bill

[jrmadbear]

Thanks for the 411, I will get a kill-a-watt meter and some books. I think i can do this as I live in a small trailer that is very inefficient yet only uses about 300-350 KWH a month. I will reduce this by upgrading and ajusting my usage.

I lived without electricy For about a year when I let someone live on my property and they ran the bill up and skiped out. That's when I got the inverter and started building a system, but took the easy way out when I got the electricy back on
"for my girlfriend's sake". LOL

I live in the mountians 35 miles out of Albuquerque NM at 6800 ft (plenty of sun).
I am a bit of a "outlaw" and a life long DIY'er and would much rather support the environment than the establishment.

[BB.]

Look at transferring your heating loads from electricity to propane/etc... Solar thermal might be interesting.

If you stick with electricity because propane is expensive/going up in price--You might look at your major energy users (heat/cooling). Replacing with a heat pump system like the Sanyo Mini-Split might be a good conservation measure. Solar thermal for hot water/heating is also a good project for a do-it-yourself type person.

Typically, I would suggest that if you want to go off-grid--that you aim at a maximum of 100 kWhrs per month. Seems to be an achievable level for Off-Grid family home (obviously, lots of work to get energy usage that low).

Take a look at Home Power Magazine for general off-grid/conservation articles.

As always, take everything you read (including here) with a grain of salt. Research first before spending the cash. Prove to yourself that the project makes some sort of economic sense and will be reliable over the long term.

-Bill

[icarus]

350 kwh/month is still ~12 kwh/day. Still a fairly hefty load for a small scale PV system. If this is a battery based system, it is getting to be a real substantial load.

My rule of thumb is that you can take the name plate rating of your PV divide by 2 to account for all the cumulative system loses, multiply that number by the number of hours of "good" sun you can expect on average,, seldom more than 4.

So in your case, if my math is right (never a safe assumption)

6000 watt Pv/2*4=12,000 wh or 12kwh.

To add in a reserve of three days you would need a system ~say 10kw. 10 kw battery based system might run ~$6-10/watt, or $60-100,000

You are also going to need a very large, very expensive battery system, and you have to calculate life span cost of said battery, 5-10 years at best with the kind of loading you are considering.

Now, if you can do everything to conserve, and transfer as much of your energy loads to other sources (gas/propane/heat pump/ solar hot water/solar space heat) so that you can get you use down to say 4 kwh/day, you can see that your system cost(s) drop by 66% making it much more affordable.

Remember, conservation first, followed by more conservation, then a bit more conservation. Then in some order, solar hot water (much cheaper per btu than Pv solar) passive and active solar heat, ground sourced heat pump, or if you use ac a lot, hot water recovery heatpump, and then, consider PV solar.

Tony

[jrmadbear]

Will take that advise!
While I have been researching things I have seen all kinds of DIY kits to build panels, what are your thoughts on this. Can you get a good system with these and is it worth the $. I can't see where they are that much cheaper.