Newbie starting out--strictly a hobby project!

System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Been meaning to start my PV project for awhile.

Here's the situation-- I'm here in Southern California, been interested in setting up a small PV system to see how it works and learn about it by getting my hands dirty.

I'm not looking at powering anything at the moment but would love to get a feel for how the stuff works. In a perfect world, I'd ramp up eventually to powering a laptop charger, some CFL lights, then maybe a small PC.

There's no time limit, although I feel that if I don't start, I never will. My primary goal is to put this together in $600-ish chunks. The system should be able to grow without having to completely redesign for a while. This poses a few interesting challenges.

I have: Nothing
Seeking to purchase (very near term):

(1) Kyocera KD215GX-LPU
- Cheap, good $ per watt, and seems like the KD215 has been around a while. If I'm still adding PV panels in 10 years, I want to be able to get ahold of the same panel to match the others.

(1) Outback FlexMax 80
- Seems like it's a great mid-size controller with good monitoring and extremely adaptable to varying battery banks / system voltages.

The questions I have are as follows:
- I'm looking at golf cart batteries to start. Watching Craigslist, or worse-case scenario Sam's Club/Wal-mart. Starting out should I do a 12v or 24v configuration?
- My step-father and father-in-law are both plant maintenance technicians and so I'm hoping to score DC breaker panels from one of them. How do I size/arrange the breakers as the system grows? What role does the 'series fuse rating' on the panel play--if any?
- Wiring from the panel (array) to the CC (/breaker box)--I just need the proper AWG wire with the proper connector on one end, and bare on the other, right? Nothing weird other than the MC2 connector? The CC-to-battery wiring looks straightforward. Looks like I've got around 100 feet from the array to where my CC and breaker panel will be.
- How many KD215GX-LPU's can I add in series before I need to start going in parallel, either due to AWG concern or overloading the front end of the CC? Relevant formulas welcome!

Thanks in advance!
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: Newbie starting out--strictly a hobby project!

    Whoa,, hang on for a minute....
    At a quick glance why, for example would you by a 80 amp charge controller right out of the gate. I am a strong advocate of buying components that you can grow into, but starting with a 80 amp CC is pretty big. 80 amps @ 12 volts would support over 1kw of panels, ~ 4 kw at 48 vdc.

    Before you BUY anything, spend as much time (here and elsewhere) reading and learning all you can about PV. The single, most expensive error folks make is, "ready, fire, aim!"

    I would first read and understand the following: http://www.batteryfaq.org/
    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

    You should start with a reasonable understanding of your loads,, and then realize that all other choices flow from that. Also, understand that a balance between components is very important to maximize efficiency and minimize cost. It is also important to know which components will allow you (within reason) to grow your system over time. For example, batteries of different ages and different sizes shouldn't be mixed together, so battery banks generally don't grow well. Charge controllers have a maximum current threshold so you can get one that is now too big, and add PV to grow into the controller (assuming the battery is big enough) (80 amp flex mate is huge to start with however!)

    Inverters have pretty strict efficiency curves. A huge inverter with little load wastes tons of power for example. Modified Sine wave inverters (MSWs) tend to be cheap, but not very efficient, and some items will not run on them.

    The point here is,, do your homework, and you will avoid making some expensive mistakes. There are some very smart folks here, who have forgotten more about PV than most of us will know. Take advantage of their experience so that you don't have to reinvent a very expensive wheel.

    There are a few "rules"that generally apply to PV. First, most people over estimate the amount of sun they actually can harvest. Second, they tend to underestimate their loads, third these loads will and do grow with time.

    Finally and perhaps most importantly, battery based solar is ~twice as expensive as grid tie for ~1/2 as much out put. It is a great place to start, to learn, but becaue of the added expense/loss of net efficiency you end up getting about 1/2 the power at twice the price,, for a net 4 times the cost of grid tie.

    A general rule of thumb is that a battery based system will yield ~ 53% of name plate, while a grid tie might near ~77%. That said, I actually think a battery based system is net/net less than ~35% just because as the battery becomes fully charged, potential power is lost because there is "no place to put it". This becomes a bit of an uncalculable loss.

    My general rule of thumb for sizing battery base systems is real easy. Take the name plate rating of the PV, divide in half to account for all system loses, then multiply that number by 4 (to represent the AVERAGE hours of good sun per day). That number is what you might reasonably expect to harvest, out the inverter in useable wh/day

    1000wts/2=500*4=2000 wh just for simple example.

    Good luck, welcome to the forum, and feel free to ask away,

    Tony

    A couple of sober second thoughts. After you read the battery faqs you will realize that large batteries need large charging currents,, FLA,s 5-13% for example to stay healthy. Your single panel will put out maybe 13 amps. (12 vdc) One pair of T-105 golf cart batteries wired for 12 vdc is ~225 ah if memory serves, so you would just barely able to come close to the 5% rating. If you went to 24 vdc battery bank, that would require 4 batteries, and you would now have the PV capacity to just barely keep them in float, much less charge them.

    Higher system voltages are (usually) always better, as it allows you to use cheaper wire, with less loss. On the other hand, 24 vdc hardware (inverters etc) might be more costly. You haven't spoken as to how you are going to get the power out of the batteries to power your loads yet.

    T
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #3
    Re: Newbie starting out--strictly a hobby project!

    You are asking the right questions--but to a degree it is much easier to understand if you set your requirements for the load(s) you want to support, then back into designing the Solar RE system to handle them.

    For the "larger" MPPT charge controllers, you can put about 100 VDC maximum worth of Vmp*X panels in series.

    The series protection fuses for panels (and parallel connected battery banks) are to protect the wiring from short circuits anywhere in the wiring being fed by other parallel connected panels/battery banks. Normally, series fuses/breakers are required when three or more panel strings are paralleled (one string and two parallel strings do not need series protection fuses).

    For battery banks, I personally would design for a few parallel battery strings as possible (one to three parallel strings). Lots of parallel strings are expensive to install correctly (wiring, fuses/breaker per string) and require more work to keep watered / monitored for proper sharing of current, mroe difficult to find bad/weak cell or battery, etc. So, if you have a weight/size limitation (stairs, no room for crane/lift)--Instead of a bunch of 12 volt batteries in parallel, look at the 6 volt / 4 volt / and even 2 volt cells -- placing those large AH cells in series to make your 12-48 volt bank.

    As for expanding a system--My two cents would be:
    1. Define/measure loads
    2. Define your solar RE system. There is a "sweet spot" for loads / inverters / charge controllers / charging sources / backup genset and their relative sizes... Too big of batteries--high costs, more charging needed; too low of bank voltage--high currents, large wire, large fuses/breakers, lots of voltage drop issues; wrong inverter wastes energy, does not properly support your loads; usually people get a very large genset which is wasteful of fuel (genset should be ~2x the size of your battery charger AC requirements or so).
    3. First bank, minimum size to support known loads with "cheap" "training wheel" batteries (you have a good chance of early battery death if this is your first system--many of us have done this before :roll:)
    4. There are some very nice/efficient TSW (True Sine Wave inverters) out there... However TSW is not cheap. Some folks have used a smaller TSW for computers, electronic loads, fridge, etc.--And used a cheaper MSW for larger, non-critical, loads (water pumping, power tools).
    5. Install a good battery charger (and backup genset), as needed to ensure batteries will get a good charge (5-13% of 20 Hour bank capacity rule of thumb)
    6. A good charge controller (Morning Star, Xantrex, Outback, etc.) sized to meet your expansion plans (remember, multiple battery charge controllers can be paralleled to the same battery bank)
    7. Add solar panels (and additional charge controllers) as budget permits until your loads are supported per your needs with solar.
    8. In 3-7 years, after first bank fails, then get the bank of your dreams (AGM, flooded cell, etc.).
    The MC-x connectors--For the typical self-install--Buy Male/Female jumper cables and cut them in half to use as transition connectors. I believe that (some/all?) solar panel vendors will not honor warranties if the MC-x connectors are cut off.

    Also, monitoring your system is very important. Some of the newer solar charge controllers have very extensive monitoring functions/options. Some can be connected to a computer, and at least one even has a web server built in.

    I always recommend a Battery Monitor to help ensure that you don't kill the battery bank through inattention. And to measure your loads--Look at a Kill-a-Watt meter... Very neat and also useful just for around the home conservation (find that energy wasting fridge, that TV/Stereo/DVR/Sat Receiver/etc. that draws 20 watts when "turned off", etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Newbie starting out--strictly a hobby project!

    hahahahaha! I knew I'd get that response with the Outback. The thing is so darn cool though and it's the LAST charge controller I'll have to buy for years and years. So I know it's big, but presumably I could toss a whole lot of matched panels its way before I've got to upgrade it.

    1kw of panels--correct me if I'm wrong, but that's only 4-5 of the Kyocera 215w panels... of course that's wired in parallel, which I know better than to do. I'm still trying to wrap my head around input voltage on the CC... 18v panels will serial to 36v or to 54v.
    The flexmax 80 spec sheet says 12vdc@1000w, 24vdc@2000w, 48vdc@4000w, 60vdc@5000w... does that mean that running 3(or 3+3, or 3+3+3) panels in series (i.e. @54w) isn't supported?--I thought it was mainly about amperage? Not necessarily an immediate concern, but would be nice to know.

    The Flexmax has some battery monitoring facility built in, which, again is another reason I'm looking at it to start. Plus the MATE looks like a great addition--I used to do software development for a living, so the RS-232 output looks cool. :)

    Thanks for the heads up, I'll be doing a 6v+6v battery bank to start due to the ready availability of 6v cells. I've read a few dozen times about beginners wrecking their first battery bank, so that'll be my first step :) Good idea about the 2v/4v cells. Once I've got a good handle on how not to screw things up the Surrette 2v cells look killer.

    Another reason I'll stick to 12v then is that I'll be running some small 12v devices to start (ala car-adapter cell phone charger, etc). Provided I've got proper fuse protection inbetween, I can wire that right off the battery bank, correct?

    After I've got some small DC devices working, the next goal would be wiring up a small (I've got a few 100watt car inverters lying around) inverter to power my 60w MacBook power adapter just to charge it.

    After that it's about scaling up, which, of course is a problem for the batteries, but I haven't got a solution to that unfortunately, except saving up for a bitchin battery bank and pulling the trigger on lots of expensive batteries all at the same time. Ouch.

    I've read the 1-3 parallel battery string thing elsewhere. Makes sense. Also the battery monitor thing looks good once I need more than the rudimentary battery voltage monitoring available on the Flexmax.

    Great help so far! I'm fine with making some (costly) mistakes along the way--it's honestly more about learning for me rather than trying to get off-the-grid. That said, there's no way in heckfire I'm attempting a grid-tie system at this juncture. :)

    Thanks for all the help and I'll definitely be back with more questions soon!
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Newbie starting out--strictly a hobby project!

    just a side comment on this,
    "(1) Outback FlexMax 80
    - Seems like it's a great mid-size controller with good monitoring and extremely adaptable to varying battery banks / system voltages."

    if an 80a controller is a midsize then what is a full size?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Newbie starting out--strictly a hobby project!
    niel wrote: »
    just a side comment on this,
    "(1) Outback FlexMax 80
    - Seems like it's a great mid-size controller with good monitoring and extremely adaptable to varying battery banks / system voltages."

    if an 80a controller is a midsize then what is a full size?

    Two FM80's! :p Or even four.

    I can understand the OP going for the FM80; I bought the MX60 way back and haven't regretted it since. The adaptability is excellent. Once bought, you won't likely need another controller even though you may add panels or up the system Voltage. If you have a future target size in mind, getting this controller is a good idea.
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #7
    Re: Newbie starting out--strictly a hobby project!
    esskayexx wrote: »
    Another reason I'll stick to 12v then is that I'll be running some small 12v devices to start (ala car-adapter cell phone charger, etc). Provided I've got proper fuse protection inbetween, I can wire that right off the battery bank, correct?

    you betcha. i charge everything off of 12v including laptops, ebook readers, batteries, run my web server on a laptop direct off the 12v for efficiency reasons. when you have a very small barebones system like you're starting with it makes total sense to stay 12v so you can run things directly off that without inverter or converter conversion losses. i like the idea that I can just buy car powered stuff . just get yourseld a couple (or 1) high quality 12v walljacks and keep your charge loads close to the battery for bigger stuff like running a computer. otherwise just charging low amperage stuff will work fine on longer cable runs.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Newbie starting out--strictly a hobby project!

    There is a fair amount of stuff available for 24 vdc, for the heavy truck, market, as well as construction equipment market.

    Tony
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  • SolarSailor
    SolarSailor Solar Expert Posts: 49 ✭
    #9
    Re: Newbie starting out--strictly a hobby project!
    lamplight wrote: »
    you betcha. i charge everything off of 12v including laptops, ebook readers, batteries, run my web server on a laptop direct off the 12v for efficiency reasons. when you have a very small barebones system like you're starting with it makes total sense to stay 12v so you can run things directly off that without inverter or converter conversion losses. i like the idea that I can just buy car powered stuff . just get yourseld a couple (or 1) high quality 12v walljacks and keep your charge loads close to the battery for bigger stuff like running a computer. otherwise just charging low amperage stuff will work fine on longer cable runs.

    Not to bust the thread here, but can I ask how you're charging laptops with 12V?
    Most laptops/notebooks power supply's are 16v-20v and have the 120V Invertor/Charger to charge batteries. I understood these were fairly sensitive devices, knowing when to stop charging and providing a pure sine wave current.

    Most also have an optional 12V cigarette lighter adaptor for auto use, so I presume that's the route you're going.

    What I don't understand is if this 12V lighter adaptor actually does any conversion (to 16v-20v) or if the notebook internals handle all that. But, to me, directly wiring a 12V battery to the notebook would be a killer.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Newbie starting out--strictly a hobby project!

    We need to point out here a recurring yet often forgotten factor in running 12 Volt devices directly from solar: charging Voltage is 14.2 and equalizing (which should be done with everything disconnected) is 15 Volts. There are times when a "12 Volt" solar electric system will run at Voltages above the expected levels for certain 12 Volt devices. You have to be careful not to exceed the limits.
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #11
    Re: Newbie starting out--strictly a hobby project!
    SolarSailor wrote: »
    Most also have an optional 12V cigarette lighter adaptor for auto use, so I presume that's the route you're going.

    What I don't understand is if this 12V lighter adaptor actually does any conversion (to 16v-20v) or if the notebook internals handle all that. But, to me, directly wiring a 12V battery to the notebook would be a killer.

    yes this is what i do and yes the plugs usually do conversion, thus aren't exactly cheap. I had done measuring in the past and found that the conversion from 12 to 18v was less power than an inverter.
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  • System2
    System2 Posts: 6,290 admin
    #12
    Re: Newbie starting out--strictly a hobby project!

    Another question laying heavily on my mind--

    18v panels... so 2 in series that's 36v... 3 in series is 54v.

    Can the Flexmax 80 do 54v input?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
    Re: Newbie starting out--strictly a hobby project!

    in a nutshell, yes.
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