PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

Light
Light Registered Users Posts: 5 ✭
in Off Grid Solar & Battery Systems #1
First post. ;)

Thanks everyone for all the contributions. Been learning quite a bit here and much more to learn.

Just a quick profile:
At this time do not have my own property; planning ahead.
Would like to plan a complete off-grid setup. To use the term loosely, possibly shooting for a 2kW system.
Fairly frugal already in my life in regards to power use (no tv, no microwave, plan on propane heating and possibly propane fridge, things of this nature).
Plan on a well & rainwater harvesting.

Can only buy a couple more items at this time.

Certainly it's best to already be at the property you plan to setup a solar system on and have already calculated usage.
Already came across 2 items for a nice deal and considering their decent nature, figured to build from these.
Maybe not best to be taking the "piece together" approach, but hey, already have them and best to start somewhere than not at all.

The 2 items I already own, new:
Xantrex ProWatt SW2000 Inverter
Morningstar TriStar 60A PWM Controller.

No panels, no batteries, no wires, nothing.

Yes, I know, the inverter is more geared towards RV/Marine/Trucking use but I can't see why it wouldn't work for a frugal, small, off-grid house.
Others have already been successful doing so.
Besides, I already have it, and can't buy another.


The heart of this post is to ask about 12v / 24v.

The basics, that on a 24v system, a controller will permit more wattage based simply on Ohm's law.

With that 60A controller, at 24v, could get much closer to the desired 2kW vs being on a 12v setup.
(Max solar input: 12 volt: 800 Watts / 24 volt: 1600 Watts / 48 volt: 3200 Watts)


The hitch is that the inverter indicates a ~12v input. :(

Therefore, the key question is, any way around this using these 2 components already owned?

Considering that I do not have all the other components, and considering that I can actually do a 24v setup, would be key to know for further buying and contemplation of the system.


Next is to start gathering the batteries over the months.

Definitely looking to avoid paying shipping fees for these heavy items, and on a budget, therefore contemplating possible places like walmart, sears, lowe's, etc. Not sure.

Now heading off to read the forum to see what others have to say about department store batteries. ;)

Thank you for your time and any help. :)
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

    Welcome to the forum.

    Let me give you the short form answer: no.

    In long form, your inverter (already purchased) runs off 12 VDC. Therefore your system Voltage is fixed at 12. You can't run a 12 Volt inverter from a 24 Volt battery bank. Well, you can - but not by any practical means.

    Now the good news. If this is the charge controller you've got http://www.solar-electric.com/tr60amp12244.html then it will charge a 12 Volt battery bank fine. What it will not do is down-convert a higher nominal array Voltage for use with that 12 Volt bank. Only the MPPT type controllers can manage that bit of magic.

    So what you're looking at on a 12 Volt system is:
    60 Amps @ 14.2 Volts charging = 852 Watts - typically a 1000 Watt array.

    Don't confuse array size with inverter capacity. The inverter can supply up to 2 kW of power regardless of the array size, as it runs off batteries. The array recharges the batteries, and there you get in to the ever-confusing Watt hours.

    What you could expect is up to 600 Amp hours of battery. 50% of that would be the most you could use, so you have the potential of 300 * 12 = 3600 Watt hours.

    What you could expect to harvest with that array is 852 Watts * the hours of equivalent good sun (usually 4) or about 3400 Watt hours. Not too far off.

    Remember the inverter will not be using or supplying 2 kW all the time (we hope). It can supply up to 2000 Watts at once.

    Clearer? Or more confusing?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

    Don't " gather batteries over the next few months". Wait and buy them all at once. Barreled of different ages don't play well together, and absent a proper charging regime they will quickly degrade.

    Tony
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  • Paul54
    Paul54 Registered Users Posts: 18 ✭
    #4
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

    No easy way to use the 12 volt inverter in a 24 volt system. You can rewire your battery bank each time you use the inverter, and then wire it back for 24 volts for charging. This won't help you much as the real problem is if you try to draw the full 2,000 watts AC out of the inverter, you will be pulling around 200 Amps DC at 12 volts DC. That will take some very large wire.

    A couple of suggestions. Since you already have the inverter, build a small 12 volt system for now. You can expand to 24 volts later. Your charge controller will be good for a much bigger system down the road, since it can switch from 12, 24, or 48 volts. As far as how many panels and batteries, you can calculate that based on your predicted loads, or if money is an issue, figure out what you can afford in panels and batteries and let that dictate how much load you can power.

    Expanding latter with panels you buy now can be a problem. As you build bigger strings or paralleled sets of panels they work best if all are closely matched.

    I hope I don't open too big of a can of worms by discussing department store batteries. I'm sure you will find lots of opinions. I think for a starter system they are a good idea. There is a lot to learn about using and maintaining battery banks. You don't want to screw up thousands of dollars of high end batteries while learning. That being said, my favorites are the Everstart 29 or Maxx 29 marine batteries from Walmart. They are NOT deep cycle batteries and really need to be pampered to get any kind of long term use out of them. They are about $70 to $80 each for the 125 Amp Hour model 29s. If any one is interested, I finally got a spec sheet from Johnson Controls with details on charging voltages, absorb times, float and EQ settings, etc. Of course the tech said that the batteries are not designed for deep cycle use and they can't endorse them in that application. I have one pair of them in parallel on a small system that gets used daily. They have been running for about a year now with no noticble loss in performance. Keep reading this and other forums. There is tons of good info on how to size, use and care for batteries.

    You really can't expand on batteries further down the road. They need to be the same model, type, and age for best results. If you build bigger later you really don't want to mix old and new batteries. So plan on all new ones if you expand.
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  • Light
    Light Registered Users Posts: 5 ✭
    #5
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

    Wow, what a great forum! Very helpful replies and all within just hours of starting the thread! Thanks!

    Of course, as this project is still in much infancy, there are many things up in the air. Quite thankfully, it is just a baby project compared to the "big guys".

    The posts are a great help. Now I have some things to digest.

    Cariboocoot, yes, that is the controller I have.
    Am I reading you clear in that technically, I can wire into the controller a 24v solar array (to pull more watts) and it will charge into a 12v bank? Or is that some sort of magic work?
    Yes, I had been looking to squeeze of course as much as I can out of these 2 initial components, but what matters most is being sensible and practical.
    Yet, if it is an option, then it's an option.

    Also, when it comes down to the actual implementation, getting the system finally up, I may find that I don't need so much, and running a complete 12v system (maxing the controller), as large a battery bank as I can go, may be enough.
    Again, I don't do the tv, microwave, A/C, very little, if no use of a freezer nor fridge, small amount of powered tool use, etc.


    As well, could also get another one of those controllers & more panels afterwards, if need be.

    Tony, yes, after I posted, did some searching; there's a post about long term storage of batteries and it looks as if no such thing really exists. :( And especially that I wouldn't be around to be charging them.

    Also makes sense about getting panels of the same batch at the same time, so can't really piece that together now either.

    It's just a shame because by the time I can save up and get around to buying these things at the time of the system implementation, well, I may not be able to afford them due to commodity price increases, or the saved money spent on other things, or who knows what will be going on by then. Thinking realistically probably up to 2 years from now.

    I suppose a decent question would be, is there anything else I can buy at this time based on this sort of unknown future system?
    Recently bought a Kill-A-Watt meter, so that is an example of an item not so particular to system design or shelf-life.

    Very happy a resource such as this forum exists especially in a field that naturally will become more and more in demand and a field in which is not as complicated as designing a circuit board with programmable EEPROMs, but can be a bit head-dizzying at times.
    There will be more and more newbies coming along and it's a great place here for them to learn and ask, such as my first thread here.

    Thanks!
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #6
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

    You've got some time, and it sounds like you've been deal shopping (I do it too!) I'd post the inverter in Craigslist, in boats and auto, and repost it until your close, then if I had no action I'd throw it on Ebay and sell it. I think anything over 1000 watts of array and you'll want to go with 24 volts.

    Next your going to look for land, buy a compass! I found only 1 in 10 properties where solar was viable and less that it was easy, with out taking down lots of trees and/or putting the array very high. Take into account the contour of the land and the proximaty of you house and array. I wanted a naturally shaded house and an array within 50 feet. It took a while to find it but I did, Only had to take down one good sized cedar for the cabin.

    On batteries, i'd much rather you purchased 6 volt golf cart batteries to build your system, generally they aren't available at Wally world, your nearest Sam's club or Costco, they run @$75 and at Sam's club a $15 core charge, typically they will take any auto battery as a core, so you might collect some dead auto batteries now.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?
    Light wrote: »
    Cariboocoot, yes, that is the controller I have.
    Am I reading you clear in that technically, I can wire into the controller a 24v solar array (to pull more watts) and it will charge into a 12v bank? Or is that some sort of magic work?
    Yes, I had been looking to squeeze of course as much as I can out of these 2 initial components, but what matters most is being sensible and practical.
    Yet, if it is an option, then it's an option.

    No, this is exactly what a PWM controller can not do. PWM controllers have to have the same nominal array Voltage as nominal system Voltage. If you connect a higher Voltage array, the extra power potential is essentially lost.

    A 2 kW 12 Volt inverter is fine, so long as you don't habitually run it near its output limit.
    I have a 3.6 kW inverter, and most of the time its output is less than 500 Watts. But if everything has to be on at once, I need that massive capacity. Mine is 24 Volt, so the DC current is not a big consideration even at full output.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #8
    Re: PROWatt SW2000 12v Inverter & TriStar 60A Controller. 24v System Possible?

    While a 12 volt system is fine, if your serious about a 2000 watt array, take into consideration that you will already need another 60 A charge controller, likely more $ than you'd loose selling off the inverter and buying a 24 volt version.

    Of course if yor needs are small enough, you might not need more than a 1000 watt array, at 2000 watts with a reasonable battery bank, good exposure, I wouldn't hesitate to expect to run a fridge. What kind of electric watthours are you consuming monthly now.

    Where is this located?

    I skipped over that golf cart batteries are about the smallest of the mass produced, flooded, deep cycle batteries. I've been waiting for mine to die, they made it 3 hours of running the A/C at night along with the small fridge and tv, during a hot spell late last month, but after 5 1/2 years they are ready to be replaced. Set of 4 purchased at Sam's club.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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